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<h1 class="titlefont">FFmpeg Filters Documentation</h1>
<hr>
<a name="SEC_Top"></a>
<a name="SEC_Contents"></a>
<h1>Table of Contents</h1>
<div class="contents">
<ul class="no-bullet">
<li><a name="toc-Description" href="#Description">1 Description</a></li>
<li><a name="toc-Filtering-Introduction" href="#Filtering-Introduction">2 Filtering Introduction</a></li>
<li><a name="toc-graph2dot" href="#graph2dot">3 graph2dot</a></li>
<li><a name="toc-Filtergraph-description" href="#Filtergraph-description">4 Filtergraph description</a>
<ul class="no-bullet">
<li><a name="toc-Filtergraph-syntax-1" href="#Filtergraph-syntax-1">4.1 Filtergraph syntax</a></li>
<li><a name="toc-Notes-on-filtergraph-escaping" href="#Notes-on-filtergraph-escaping">4.2 Notes on filtergraph escaping</a></li>
</ul></li>
<li><a name="toc-Audio-Filters" href="#Audio-Filters">5 Audio Filters</a>
<ul class="no-bullet">
<li><a name="toc-aconvert" href="#aconvert">5.1 aconvert</a></li>
<li><a name="toc-aformat" href="#aformat">5.2 aformat</a></li>
<li><a name="toc-amerge" href="#amerge">5.3 amerge</a></li>
<li><a name="toc-amix" href="#amix">5.4 amix</a></li>
<li><a name="toc-anull" href="#anull">5.5 anull</a></li>
<li><a name="toc-apad" href="#apad">5.6 apad</a></li>
<li><a name="toc-aresample-1" href="#aresample-1">5.7 aresample</a></li>
<li><a name="toc-asetnsamples" href="#asetnsamples">5.8 asetnsamples</a></li>
<li><a name="toc-ashowinfo" href="#ashowinfo">5.9 ashowinfo</a></li>
<li><a name="toc-asplit" href="#asplit">5.10 asplit</a></li>
<li><a name="toc-astreamsync" href="#astreamsync">5.11 astreamsync</a></li>
<li><a name="toc-atempo" href="#atempo">5.12 atempo</a></li>
<li><a name="toc-earwax" href="#earwax">5.13 earwax</a></li>
<li><a name="toc-pan" href="#pan">5.14 pan</a>
<ul class="no-bullet">
<li><a name="toc-Mixing-examples" href="#Mixing-examples">5.14.1 Mixing examples</a></li>
<li><a name="toc-Remapping-examples" href="#Remapping-examples">5.14.2 Remapping examples</a></li>
</ul></li>
<li><a name="toc-silencedetect" href="#silencedetect">5.15 silencedetect</a></li>
<li><a name="toc-asyncts" href="#asyncts">5.16 asyncts</a></li>
<li><a name="toc-channelsplit" href="#channelsplit">5.17 channelsplit</a></li>
<li><a name="toc-channelmap" href="#channelmap">5.18 channelmap</a></li>
<li><a name="toc-join" href="#join">5.19 join</a></li>
<li><a name="toc-resample" href="#resample">5.20 resample</a></li>
<li><a name="toc-volume" href="#volume">5.21 volume</a>
<ul class="no-bullet">
<li><a name="toc-Examples" href="#Examples">5.21.1 Examples</a></li>
</ul></li>
<li><a name="toc-volumedetect" href="#volumedetect">5.22 volumedetect</a></li>
</ul></li>
<li><a name="toc-Audio-Sources" href="#Audio-Sources">6 Audio Sources</a>
<ul class="no-bullet">
<li><a name="toc-abuffer-1" href="#abuffer-1">6.1 abuffer</a></li>
<li><a name="toc-aevalsrc" href="#aevalsrc">6.2 aevalsrc</a>
<ul class="no-bullet">
<li><a name="toc-Examples-16" href="#Examples-16">6.2.1 Examples</a></li>
</ul></li>
<li><a name="toc-anullsrc" href="#anullsrc">6.3 anullsrc</a></li>
<li><a name="toc-abuffer" href="#abuffer">6.4 abuffer</a></li>
<li><a name="toc-flite" href="#flite">6.5 flite</a>
<ul class="no-bullet">
<li><a name="toc-Examples-13" href="#Examples-13">6.5.1 Examples</a></li>
</ul>
</li>
</ul></li>
<li><a name="toc-Audio-Sinks" href="#Audio-Sinks">7 Audio Sinks</a>
<ul class="no-bullet">
<li><a name="toc-abuffersink-1" href="#abuffersink-1">7.1 abuffersink</a></li>
<li><a name="toc-anullsink" href="#anullsink">7.2 anullsink</a></li>
<li><a name="toc-abuffersink" href="#abuffersink">7.3 abuffersink</a></li>
</ul></li>
<li><a name="toc-Video-Filters" href="#Video-Filters">8 Video Filters</a>
<ul class="no-bullet">
<li><a name="toc-alphaextract" href="#alphaextract">8.1 alphaextract</a></li>
<li><a name="toc-alphamerge" href="#alphamerge">8.2 alphamerge</a></li>
<li><a name="toc-ass" href="#ass">8.3 ass</a></li>
<li><a name="toc-bbox" href="#bbox">8.4 bbox</a></li>
<li><a name="toc-blackdetect" href="#blackdetect">8.5 blackdetect</a></li>
<li><a name="toc-blackframe" href="#blackframe">8.6 blackframe</a></li>
<li><a name="toc-boxblur" href="#boxblur">8.7 boxblur</a></li>
<li><a name="toc-colormatrix" href="#colormatrix">8.8 colormatrix</a></li>
<li><a name="toc-copy" href="#copy">8.9 copy</a></li>
<li><a name="toc-crop" href="#crop">8.10 crop</a>
<ul class="no-bullet">
<li><a name="toc-Examples-11" href="#Examples-11">8.10.1 Examples</a></li>
</ul></li>
<li><a name="toc-cropdetect" href="#cropdetect">8.11 cropdetect</a></li>
<li><a name="toc-decimate" href="#decimate">8.12 decimate</a></li>
<li><a name="toc-delogo" href="#delogo">8.13 delogo</a></li>
<li><a name="toc-deshake" href="#deshake">8.14 deshake</a></li>
<li><a name="toc-drawbox" href="#drawbox">8.15 drawbox</a></li>
<li><a name="toc-drawtext-1" href="#drawtext-1">8.16 drawtext</a>
<ul class="no-bullet">
<li><a name="toc-Syntax" href="#Syntax">8.16.1 Syntax</a></li>
<li><a name="toc-Text-expansion" href="#Text-expansion">8.16.2 Text expansion</a></li>
<li><a name="toc-Examples-1" href="#Examples-1">8.16.3 Examples</a></li>
</ul></li>
<li><a name="toc-edgedetect" href="#edgedetect">8.17 edgedetect</a></li>
<li><a name="toc-fade" href="#fade">8.18 fade</a></li>
<li><a name="toc-field" href="#field">8.19 field</a></li>
<li><a name="toc-fieldorder" href="#fieldorder">8.20 fieldorder</a></li>
<li><a name="toc-fifo" href="#fifo">8.21 fifo</a></li>
<li><a name="toc-format" href="#format">8.22 format</a></li>
<li><a name="toc-fps" href="#fps">8.23 fps</a></li>
<li><a name="toc-framestep" href="#framestep">8.24 framestep</a></li>
<li><a name="toc-frei0r-1" href="#frei0r-1">8.25 frei0r</a></li>
<li><a name="toc-geq" href="#geq">8.26 geq</a></li>
<li><a name="toc-gradfun" href="#gradfun">8.27 gradfun</a>
<ul class="no-bullet">
<li><a name="toc-Examples-9" href="#Examples-9">8.27.1 Examples</a></li>
</ul></li>
<li><a name="toc-hflip" href="#hflip">8.28 hflip</a></li>
<li><a name="toc-histeq" href="#histeq">8.29 histeq</a></li>
<li><a name="toc-hqdn3d" href="#hqdn3d">8.30 hqdn3d</a></li>
<li><a name="toc-hue" href="#hue">8.31 hue</a>
<ul class="no-bullet">
<li><a name="toc-Commands" href="#Commands">8.31.1 Commands</a></li>
</ul></li>
<li><a name="toc-idet" href="#idet">8.32 idet</a></li>
<li><a name="toc-kerndeint" href="#kerndeint">8.33 kerndeint</a>
<ul class="no-bullet">
<li><a name="toc-Examples-15" href="#Examples-15">8.33.1 Examples</a></li>
</ul></li>
<li><a name="toc-lut_002c-lutrgb_002c-lutyuv" href="#lut_002c-lutrgb_002c-lutyuv">8.34 lut, lutrgb, lutyuv</a></li>
<li><a name="toc-mp" href="#mp">8.35 mp</a></li>
<li><a name="toc-negate" href="#negate">8.36 negate</a></li>
<li><a name="toc-noformat" href="#noformat">8.37 noformat</a></li>
<li><a name="toc-null" href="#null">8.38 null</a></li>
<li><a name="toc-ocv" href="#ocv">8.39 ocv</a>
<ul class="no-bullet">
<li><a name="toc-dilate-1" href="#dilate-1">8.39.1 dilate</a></li>
<li><a name="toc-erode" href="#erode">8.39.2 erode</a></li>
<li><a name="toc-smooth" href="#smooth">8.39.3 smooth</a></li>
</ul></li>
<li><a name="toc-overlay-1" href="#overlay-1">8.40 overlay</a>
<ul class="no-bullet">
<li><a name="toc-Examples-7" href="#Examples-7">8.40.1 Examples</a></li>
</ul></li>
<li><a name="toc-pad" href="#pad">8.41 pad</a>
<ul class="no-bullet">
<li><a name="toc-Examples-8" href="#Examples-8">8.41.1 Examples</a></li>
</ul></li>
<li><a name="toc-pixdesctest" href="#pixdesctest">8.42 pixdesctest</a></li>
<li><a name="toc-pp" href="#pp">8.43 pp</a>
<ul class="no-bullet">
<li><a name="toc-Examples-3" href="#Examples-3">8.43.1 Examples</a></li>
</ul></li>
<li><a name="toc-removelogo" href="#removelogo">8.44 removelogo</a></li>
<li><a name="toc-scale" href="#scale">8.45 scale</a>
<ul class="no-bullet">
<li><a name="toc-Examples-6" href="#Examples-6">8.45.1 Examples</a></li>
</ul></li>
<li><a name="toc-setdar_002c-setsar" href="#setdar_002c-setsar">8.46 setdar, setsar</a></li>
<li><a name="toc-setfield" href="#setfield">8.47 setfield</a></li>
<li><a name="toc-showinfo" href="#showinfo">8.48 showinfo</a></li>
<li><a name="toc-smartblur" href="#smartblur">8.49 smartblur</a></li>
<li><a name="toc-subtitles-1" href="#subtitles-1">8.50 subtitles</a></li>
<li><a name="toc-split" href="#split">8.51 split</a></li>
<li><a name="toc-super2xsai" href="#super2xsai">8.52 super2xsai</a></li>
<li><a name="toc-swapuv" href="#swapuv">8.53 swapuv</a></li>
<li><a name="toc-thumbnail" href="#thumbnail">8.54 thumbnail</a></li>
<li><a name="toc-tile" href="#tile">8.55 tile</a></li>
<li><a name="toc-tinterlace" href="#tinterlace">8.56 tinterlace</a></li>
<li><a name="toc-transpose" href="#transpose">8.57 transpose</a></li>
<li><a name="toc-unsharp" href="#unsharp">8.58 unsharp</a></li>
<li><a name="toc-vflip" href="#vflip">8.59 vflip</a></li>
<li><a name="toc-yadif" href="#yadif">8.60 yadif</a></li>
</ul></li>
<li><a name="toc-Video-Sources" href="#Video-Sources">9 Video Sources</a>
<ul class="no-bullet">
<li><a name="toc-buffer" href="#buffer">9.1 buffer</a></li>
<li><a name="toc-cellauto" href="#cellauto">9.2 cellauto</a>
<ul class="no-bullet">
<li><a name="toc-Examples-10" href="#Examples-10">9.2.1 Examples</a></li>
</ul></li>
<li><a name="toc-mandelbrot" href="#mandelbrot">9.3 mandelbrot</a></li>
<li><a name="toc-mptestsrc" href="#mptestsrc">9.4 mptestsrc</a></li>
<li><a name="toc-frei0r_005fsrc" href="#frei0r_005fsrc">9.5 frei0r_src</a></li>
<li><a name="toc-life" href="#life">9.6 life</a>
<ul class="no-bullet">
<li><a name="toc-Examples-12" href="#Examples-12">9.6.1 Examples</a></li>
</ul></li>
<li><a name="toc-color_002c-nullsrc_002c-rgbtestsrc_002c-smptebars_002c-testsrc" href="#color_002c-nullsrc_002c-rgbtestsrc_002c-smptebars_002c-testsrc">9.7 color, nullsrc, rgbtestsrc, smptebars, testsrc</a></li>
</ul></li>
<li><a name="toc-Video-Sinks" href="#Video-Sinks">10 Video Sinks</a>
<ul class="no-bullet">
<li><a name="toc-buffersink" href="#buffersink">10.1 buffersink</a></li>
<li><a name="toc-nullsink" href="#nullsink">10.2 nullsink</a></li>
</ul></li>
<li><a name="toc-Multimedia-Filters" href="#Multimedia-Filters">11 Multimedia Filters</a>
<ul class="no-bullet">
<li><a name="toc-aselect_002c-select" href="#aselect_002c-select">11.1 aselect, select</a>
<ul class="no-bullet">
<li><a name="toc-Examples-4" href="#Examples-4">11.1.1 Examples</a></li>
</ul></li>
<li><a name="toc-asendcmd_002c-sendcmd" href="#asendcmd_002c-sendcmd">11.2 asendcmd, sendcmd</a>
<ul class="no-bullet">
<li><a name="toc-Commands-syntax" href="#Commands-syntax">11.2.1 Commands syntax</a></li>
<li><a name="toc-Examples-2" href="#Examples-2">11.2.2 Examples</a></li>
</ul></li>
<li><a name="toc-asetpts_002c-setpts" href="#asetpts_002c-setpts">11.3 asetpts, setpts</a>
<ul class="no-bullet">
<li><a name="toc-Examples-5" href="#Examples-5">11.3.1 Examples</a></li>
</ul></li>
<li><a name="toc-ebur128" href="#ebur128">11.4 ebur128</a></li>
<li><a name="toc-settb_002c-asettb" href="#settb_002c-asettb">11.5 settb, asettb</a>
<ul class="no-bullet">
<li><a name="toc-Examples-14" href="#Examples-14">11.5.1 Examples</a></li>
</ul></li>
<li><a name="toc-concat" href="#concat">11.6 concat</a></li>
<li><a name="toc-showspectrum" href="#showspectrum">11.7 showspectrum</a></li>
<li><a name="toc-showwaves" href="#showwaves">11.8 showwaves</a></li>
</ul></li>
<li><a name="toc-Multimedia-Sources" href="#Multimedia-Sources">12 Multimedia Sources</a>
<ul class="no-bullet">
<li><a name="toc-amovie" href="#amovie">12.1 amovie</a></li>
<li><a name="toc-movie-1" href="#movie-1">12.2 movie</a></li>
</ul></li>
<li><a name="toc-See-Also" href="#See-Also">13 See Also</a></li>
<li><a name="toc-Authors" href="#Authors">14 Authors</a></li>
</ul>
</div>
<hr size="6">
<a name="Description"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Description">1 Description</a></h1>
<p>This document describes filters, sources, and sinks provided by the
libavfilter library.
</p>
<a name="Filtering-Introduction"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Filtering-Introduction">2 Filtering Introduction</a></h1>
<p>Filtering in FFmpeg is enabled through the libavfilter library.
</p>
<p>In libavfilter, it is possible for filters to have multiple inputs and
multiple outputs.
To illustrate the sorts of things that are possible, we can
use a complex filter graph. For example, the following one:
</p>
<div class="example">
<pre class="example">input --> split ---------------------> overlay --> output
| ^
| |
+-----> crop --> vflip -------+
</pre></div>
<p>splits the stream in two streams, sends one stream through the crop filter
and the vflip filter before merging it back with the other stream by
overlaying it on top. You can use the following command to achieve this:
</p>
<div class="example">
<pre class="example">ffmpeg -i input -vf "[in] split [T1], [T2] overlay=0:H/2 [out]; [T1] crop=iw:ih/2:0:ih/2, vflip [T2]" output
</pre></div>
<p>The result will be that in output the top half of the video is mirrored
onto the bottom half.
</p>
<p>Filters are loaded using the <var>-vf</var> or <var>-af</var> option passed to
<code>ffmpeg</code> or to <code>ffplay</code>. Filters in the same linear
chain are separated by commas. In our example, <var>split,
overlay</var> are in one linear chain, and <var>crop, vflip</var> are in
another. The points where the linear chains join are labeled by names
enclosed in square brackets. In our example, that is <var>[T1]</var> and
<var>[T2]</var>. The special labels <var>[in]</var> and <var>[out]</var> are the points
where video is input and output.
</p>
<p>Some filters take in input a list of parameters: they are specified
after the filter name and an equal sign, and are separated from each other
by a colon.
</p>
<p>There exist so-called <var>source filters</var> that do not have an
audio/video input, and <var>sink filters</var> that will not have audio/video
output.
</p>
<a name="graph2dot"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-graph2dot">3 graph2dot</a></h1>
<p>The ‘<tt>graph2dot</tt>’ program included in the FFmpeg ‘<tt>tools</tt>’
directory can be used to parse a filter graph description and issue a
corresponding textual representation in the dot language.
</p>
<p>Invoke the command:
</p><div class="example">
<pre class="example">graph2dot -h
</pre></div>
<p>to see how to use ‘<tt>graph2dot</tt>’.
</p>
<p>You can then pass the dot description to the ‘<tt>dot</tt>’ program (from
the graphviz suite of programs) and obtain a graphical representation
of the filter graph.
</p>
<p>For example the sequence of commands:
</p><div class="example">
<pre class="example">echo <var>GRAPH_DESCRIPTION</var> | \
tools/graph2dot -o graph.tmp && \
dot -Tpng graph.tmp -o graph.png && \
display graph.png
</pre></div>
<p>can be used to create and display an image representing the graph
described by the <var>GRAPH_DESCRIPTION</var> string. Note that this string must be
a complete self-contained graph, with its inputs and outputs explicitly defined.
For example if your command line is of the form:
</p><div class="example">
<pre class="example">ffmpeg -i infile -vf scale=640:360 outfile
</pre></div>
<p>your <var>GRAPH_DESCRIPTION</var> string will need to be of the form:
</p><div class="example">
<pre class="example">nullsrc,scale=640:360,nullsink
</pre></div>
<p>you may also need to set the <var>nullsrc</var> parameters and add a <var>format</var>
filter in order to simulate a specific input file.
</p>
<a name="Filtergraph-description"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Filtergraph-description">4 Filtergraph description</a></h1>
<p>A filtergraph is a directed graph of connected filters. It can contain
cycles, and there can be multiple links between a pair of
filters. Each link has one input pad on one side connecting it to one
filter from which it takes its input, and one output pad on the other
side connecting it to the one filter accepting its output.
</p>
<p>Each filter in a filtergraph is an instance of a filter class
registered in the application, which defines the features and the
number of input and output pads of the filter.
</p>
<p>A filter with no input pads is called a "source", a filter with no
output pads is called a "sink".
</p>
<p><a name="Filtergraph-syntax"></a>
</p><a name="Filtergraph-syntax-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-Filtergraph-syntax-1">4.1 Filtergraph syntax</a></h2>
<p>A filtergraph can be represented using a textual representation, which is
recognized by the ‘<samp>-filter</samp>’/‘<samp>-vf</samp>’ and ‘<samp>-filter_complex</samp>’
options in <code>ffmpeg</code> and ‘<samp>-vf</samp>’ in <code>ffplay</code>, and by the
<code>avfilter_graph_parse()</code>/<code>avfilter_graph_parse2()</code> function defined in
‘<tt>libavfilter/avfiltergraph.h</tt>’.
</p>
<p>A filterchain consists of a sequence of connected filters, each one
connected to the previous one in the sequence. A filterchain is
represented by a list of ","-separated filter descriptions.
</p>
<p>A filtergraph consists of a sequence of filterchains. A sequence of
filterchains is represented by a list of ";"-separated filterchain
descriptions.
</p>
<p>A filter is represented by a string of the form:
[<var>in_link_1</var>]...[<var>in_link_N</var>]<var>filter_name</var>=<var>arguments</var>[<var>out_link_1</var>]...[<var>out_link_M</var>]
</p>
<p><var>filter_name</var> is the name of the filter class of which the
described filter is an instance of, and has to be the name of one of
the filter classes registered in the program.
The name of the filter class is optionally followed by a string
"=<var>arguments</var>".
</p>
<p><var>arguments</var> is a string which contains the parameters used to
initialize the filter instance, and are described in the filter
descriptions below.
</p>
<p>The list of arguments can be quoted using the character "’" as initial
and ending mark, and the character ’\’ for escaping the characters
within the quoted text; otherwise the argument string is considered
terminated when the next special character (belonging to the set
"[]=;,") is encountered.
</p>
<p>The name and arguments of the filter are optionally preceded and
followed by a list of link labels.
A link label allows to name a link and associate it to a filter output
or input pad. The preceding labels <var>in_link_1</var>
... <var>in_link_N</var>, are associated to the filter input pads,
the following labels <var>out_link_1</var> ... <var>out_link_M</var>, are
associated to the output pads.
</p>
<p>When two link labels with the same name are found in the
filtergraph, a link between the corresponding input and output pad is
created.
</p>
<p>If an output pad is not labelled, it is linked by default to the first
unlabelled input pad of the next filter in the filterchain.
For example in the filterchain:
</p><div class="example">
<pre class="example">nullsrc, split[L1], [L2]overlay, nullsink
</pre></div>
<p>the split filter instance has two output pads, and the overlay filter
instance two input pads. The first output pad of split is labelled
"L1", the first input pad of overlay is labelled "L2", and the second
output pad of split is linked to the second input pad of overlay,
which are both unlabelled.
</p>
<p>In a complete filterchain all the unlabelled filter input and output
pads must be connected. A filtergraph is considered valid if all the
filter input and output pads of all the filterchains are connected.
</p>
<p>Libavfilter will automatically insert scale filters where format
conversion is required. It is possible to specify swscale flags
for those automatically inserted scalers by prepending
<code>sws_flags=<var>flags</var>;</code>
to the filtergraph description.
</p>
<p>Follows a BNF description for the filtergraph syntax:
</p><div class="example">
<pre class="example"><var>NAME</var> ::= sequence of alphanumeric characters and '_'
<var>LINKLABEL</var> ::= "[" <var>NAME</var> "]"
<var>LINKLABELS</var> ::= <var>LINKLABEL</var> [<var>LINKLABELS</var>]
<var>FILTER_ARGUMENTS</var> ::= sequence of chars (eventually quoted)
<var>FILTER</var> ::= [<var>LINKLABELS</var>] <var>NAME</var> ["=" <var>FILTER_ARGUMENTS</var>] [<var>LINKLABELS</var>]
<var>FILTERCHAIN</var> ::= <var>FILTER</var> [,<var>FILTERCHAIN</var>]
<var>FILTERGRAPH</var> ::= [sws_flags=<var>flags</var>;] <var>FILTERCHAIN</var> [;<var>FILTERGRAPH</var>]
</pre></div>
<a name="Notes-on-filtergraph-escaping"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-Notes-on-filtergraph-escaping">4.2 Notes on filtergraph escaping</a></h2>
<p>Some filter arguments require the use of special characters, typically
<code>:</code> to separate key=value pairs in a named options list. In this
case the user should perform a first level escaping when specifying
the filter arguments. For example, consider the following literal
string to be embedded in the <a href="#drawtext">drawtext</a> filter arguments:
</p><div class="example">
<pre class="example">this is a 'string': may contain one, or more, special characters
</pre></div>
<p>Since <code>:</code> is special for the filter arguments syntax, it needs to
be escaped, so you get:
</p><div class="example">
<pre class="example">text=this is a \'string\'\: may contain one, or more, special characters
</pre></div>
<p>A second level of escaping is required when embedding the filter
arguments in a filtergraph description, in order to escape all the
filtergraph special characters. Thus the example above becomes:
</p><div class="example">
<pre class="example">drawtext=text=this is a \\\'string\\\'\\: may contain one\, or more\, special characters
</pre></div>
<p>Finally an additional level of escaping may be needed when writing the
filtergraph description in a shell command, which depends on the
escaping rules of the adopted shell. For example, assuming that
<code>\</code> is special and needs to be escaped with another <code>\</code>, the
previous string will finally result in:
</p><div class="example">
<pre class="example">-vf "drawtext=text=this is a \\\\\\'string\\\\\\'\\\\: may contain one\\, or more\\, special characters"
</pre></div>
<p>Sometimes, it might be more convenient to employ quoting in place of
escaping. For example the string:
</p><div class="example">
<pre class="example">Caesar: tu quoque, Brute, fili mi
</pre></div>
<p>Can be quoted in the filter arguments as:
</p><div class="example">
<pre class="example">text='Caesar: tu quoque, Brute, fili mi'
</pre></div>
<p>And finally inserted in a filtergraph like:
</p><div class="example">
<pre class="example">drawtext=text=\'Caesar: tu quoque\, Brute\, fili mi\'
</pre></div>
<p>See the “Quoting and escaping” section in the ffmpeg-utils manual
for more information about the escaping and quoting rules adopted by
FFmpeg.
</p>
<a name="Audio-Filters"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Audio-Filters">5 Audio Filters</a></h1>
<p>When you configure your FFmpeg build, you can disable any of the
existing filters using <code>--disable-filters</code>.
The configure output will show the audio filters included in your
build.
</p>
<p>Below is a description of the currently available audio filters.
</p>
<a name="aconvert"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-aconvert">5.1 aconvert</a></h2>
<p>Convert the input audio format to the specified formats.
</p>
<p>The filter accepts a string of the form:
"<var>sample_format</var>:<var>channel_layout</var>".
</p>
<p><var>sample_format</var> specifies the sample format, and can be a string or the
corresponding numeric value defined in ‘<tt>libavutil/samplefmt.h</tt>’. Use ’p’
suffix for a planar sample format.
</p>
<p><var>channel_layout</var> specifies the channel layout, and can be a string
or the corresponding number value defined in ‘<tt>libavutil/channel_layout.h</tt>’.
</p>
<p>The special parameter "auto", signifies that the filter will
automatically select the output format depending on the output filter.
</p>
<p>Some examples follow.
</p>
<ul>
<li>
Convert input to float, planar, stereo:
<div class="example">
<pre class="example">aconvert=fltp:stereo
</pre></div>
</li><li>
Convert input to unsigned 8-bit, automatically select out channel layout:
<div class="example">
<pre class="example">aconvert=u8:auto
</pre></div>
</li></ul>
<a name="aformat"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-aformat">5.2 aformat</a></h2>
<p>Set output format constraints for the input audio. The framework will
negotiate the most appropriate format to minimize conversions.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>sample_fmts</samp>’</dt>
<dd><p>A comma-separated list of requested sample formats.
</p>
</dd>
<dt>‘<samp>sample_rates</samp>’</dt>
<dd><p>A comma-separated list of requested sample rates.
</p>
</dd>
<dt>‘<samp>channel_layouts</samp>’</dt>
<dd><p>A comma-separated list of requested channel layouts.
</p>
</dd>
</dl>
<p>If a parameter is omitted, all values are allowed.
</p>
<p>For example to force the output to either unsigned 8-bit or signed 16-bit stereo:
</p><div class="example">
<pre class="example">aformat='sample_fmts=u8,s16:channel_layouts=stereo'
</pre></div>
<a name="amerge"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-amerge">5.3 amerge</a></h2>
<p>Merge two or more audio streams into a single multi-channel stream.
</p>
<p>The filter accepts the following named options:
</p>
<dl compact="compact">
<dt>‘<samp>inputs</samp>’</dt>
<dd><p>Set the number of inputs. Default is 2.
</p>
</dd>
</dl>
<p>If the channel layouts of the inputs are disjoint, and therefore compatible,
the channel layout of the output will be set accordingly and the channels
will be reordered as necessary. If the channel layouts of the inputs are not
disjoint, the output will have all the channels of the first input then all
the channels of the second input, in that order, and the channel layout of
the output will be the default value corresponding to the total number of
channels.
</p>
<p>For example, if the first input is in 2.1 (FL+FR+LF) and the second input
is FC+BL+BR, then the output will be in 5.1, with the channels in the
following order: a1, a2, b1, a3, b2, b3 (a1 is the first channel of the
first input, b1 is the first channel of the second input).
</p>
<p>On the other hand, if both input are in stereo, the output channels will be
in the default order: a1, a2, b1, b2, and the channel layout will be
arbitrarily set to 4.0, which may or may not be the expected value.
</p>
<p>All inputs must have the same sample rate, and format.
</p>
<p>If inputs do not have the same duration, the output will stop with the
shortest.
</p>
<p>Example: merge two mono files into a stereo stream:
</p><div class="example">
<pre class="example">amovie=left.wav [l] ; amovie=right.mp3 [r] ; [l] [r] amerge
</pre></div>
<p>Example: multiple merges:
</p><div class="example">
<pre class="example">ffmpeg -f lavfi -i "
amovie=input.mkv:si=0 [a0];
amovie=input.mkv:si=1 [a1];
amovie=input.mkv:si=2 [a2];
amovie=input.mkv:si=3 [a3];
amovie=input.mkv:si=4 [a4];
amovie=input.mkv:si=5 [a5];
[a0][a1][a2][a3][a4][a5] amerge=inputs=6" -c:a pcm_s16le output.mkv
</pre></div>
<a name="amix"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-amix">5.4 amix</a></h2>
<p>Mixes multiple audio inputs into a single output.
</p>
<p>For example
</p><div class="example">
<pre class="example">ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex amix=inputs=3:duration=first:dropout_transition=3 OUTPUT
</pre></div>
<p>will mix 3 input audio streams to a single output with the same duration as the
first input and a dropout transition time of 3 seconds.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>inputs</samp>’</dt>
<dd><p>Number of inputs. If unspecified, it defaults to 2.
</p>
</dd>
<dt>‘<samp>duration</samp>’</dt>
<dd><p>How to determine the end-of-stream.
</p><dl compact="compact">
<dt>‘<samp>longest</samp>’</dt>
<dd><p>Duration of longest input. (default)
</p>
</dd>
<dt>‘<samp>shortest</samp>’</dt>
<dd><p>Duration of shortest input.
</p>
</dd>
<dt>‘<samp>first</samp>’</dt>
<dd><p>Duration of first input.
</p>
</dd>
</dl>
</dd>
<dt>‘<samp>dropout_transition</samp>’</dt>
<dd><p>Transition time, in seconds, for volume renormalization when an input
stream ends. The default value is 2 seconds.
</p>
</dd>
</dl>
<a name="anull"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-anull">5.5 anull</a></h2>
<p>Pass the audio source unchanged to the output.
</p>
<a name="apad"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-apad">5.6 apad</a></h2>
<p>Pad the end of a audio stream with silence, this can be used together with
-shortest to extend audio streams to the same length as the video stream.
</p>
<p><a name="aresample"></a>
</p><a name="aresample-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-aresample-1">5.7 aresample</a></h2>
<p>Resample the input audio to the specified parameters, using the
libswresample library. If none are specified then the filter will
automatically convert between its input and output.
</p>
<p>This filter is also able to stretch/squeeze the audio data to make it match
the timestamps or to inject silence / cut out audio to make it match the
timestamps, do a combination of both or do neither.
</p>
<p>The filter accepts the syntax
[<var>sample_rate</var>:]<var>resampler_options</var>, where <var>sample_rate</var>
expresses a sample rate and <var>resampler_options</var> is a list of
<var>key</var>=<var>value</var> pairs, separated by ":". See the
ffmpeg-resampler manual for the complete list of supported options.
</p>
<p>For example, to resample the input audio to 44100Hz:
</p><div class="example">
<pre class="example">aresample=44100
</pre></div>
<p>To stretch/squeeze samples to the given timestamps, with a maximum of 1000
samples per second compensation:
</p><div class="example">
<pre class="example">aresample=async=1000
</pre></div>
<a name="asetnsamples"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-asetnsamples">5.8 asetnsamples</a></h2>
<p>Set the number of samples per each output audio frame.
</p>
<p>The last output packet may contain a different number of samples, as
the filter will flush all the remaining samples when the input audio
signal its end.
</p>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<dl compact="compact">
<dt>‘<samp>nb_out_samples, n</samp>’</dt>
<dd><p>Set the number of frames per each output audio frame. The number is
intended as the number of samples <em>per each channel</em>.
Default value is 1024.
</p>
</dd>
<dt>‘<samp>pad, p</samp>’</dt>
<dd><p>If set to 1, the filter will pad the last audio frame with zeroes, so
that the last frame will contain the same number of samples as the
previous ones. Default value is 1.
</p></dd>
</dl>
<p>For example, to set the number of per-frame samples to 1234 and
disable padding for the last frame, use:
</p><div class="example">
<pre class="example">asetnsamples=n=1234:p=0
</pre></div>
<a name="ashowinfo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-ashowinfo">5.9 ashowinfo</a></h2>
<p>Show a line containing various information for each input audio frame.
The input audio is not modified.
</p>
<p>The shown line contains a sequence of key/value pairs of the form
<var>key</var>:<var>value</var>.
</p>
<p>A description of each shown parameter follows:
</p>
<dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>sequential number of the input frame, starting from 0
</p>
</dd>
<dt>‘<samp>pts</samp>’</dt>
<dd><p>Presentation timestamp of the input frame, in time base units; the time base
depends on the filter input pad, and is usually 1/<var>sample_rate</var>.
</p>
</dd>
<dt>‘<samp>pts_time</samp>’</dt>
<dd><p>presentation timestamp of the input frame in seconds
</p>
</dd>
<dt>‘<samp>pos</samp>’</dt>
<dd><p>position of the frame in the input stream, -1 if this information in
unavailable and/or meaningless (for example in case of synthetic audio)
</p>
</dd>
<dt>‘<samp>fmt</samp>’</dt>
<dd><p>sample format
</p>
</dd>
<dt>‘<samp>chlayout</samp>’</dt>
<dd><p>channel layout
</p>
</dd>
<dt>‘<samp>rate</samp>’</dt>
<dd><p>sample rate for the audio frame
</p>
</dd>
<dt>‘<samp>nb_samples</samp>’</dt>
<dd><p>number of samples (per channel) in the frame
</p>
</dd>
<dt>‘<samp>checksum</samp>’</dt>
<dd><p>Adler-32 checksum (printed in hexadecimal) of the audio data. For planar audio
the data is treated as if all the planes were concatenated.
</p>
</dd>
<dt>‘<samp>plane_checksums</samp>’</dt>
<dd><p>A list of Adler-32 checksums for each data plane.
</p></dd>
</dl>
<a name="asplit"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-asplit">5.10 asplit</a></h2>
<p>Split input audio into several identical outputs.
</p>
<p>The filter accepts a single parameter which specifies the number of outputs. If
unspecified, it defaults to 2.
</p>
<p>For example:
</p><div class="example">
<pre class="example">[in] asplit [out0][out1]
</pre></div>
<p>will create two separate outputs from the same input.
</p>
<p>To create 3 or more outputs, you need to specify the number of
outputs, like in:
</p><div class="example">
<pre class="example">[in] asplit=3 [out0][out1][out2]
</pre></div>
<div class="example">
<pre class="example">ffmpeg -i INPUT -filter_complex asplit=5 OUTPUT
</pre></div>
<p>will create 5 copies of the input audio.
</p>
<a name="astreamsync"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-astreamsync">5.11 astreamsync</a></h2>
<p>Forward two audio streams and control the order the buffers are forwarded.
</p>
<p>The argument to the filter is an expression deciding which stream should be
forwarded next: if the result is negative, the first stream is forwarded; if
the result is positive or zero, the second stream is forwarded. It can use
the following variables:
</p>
<dl compact="compact">
<dt><var>b1 b2</var></dt>
<dd><p>number of buffers forwarded so far on each stream
</p></dd>
<dt><var>s1 s2</var></dt>
<dd><p>number of samples forwarded so far on each stream
</p></dd>
<dt><var>t1 t2</var></dt>
<dd><p>current timestamp of each stream
</p></dd>
</dl>
<p>The default value is <code>t1-t2</code>, which means to always forward the stream
that has a smaller timestamp.
</p>
<p>Example: stress-test <code>amerge</code> by randomly sending buffers on the wrong
input, while avoiding too much of a desynchronization:
</p><div class="example">
<pre class="example">amovie=file.ogg [a] ; amovie=file.mp3 [b] ;
[a] [b] astreamsync=(2*random(1))-1+tanh(5*(t1-t2)) [a2] [b2] ;
[a2] [b2] amerge
</pre></div>
<a name="atempo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-atempo">5.12 atempo</a></h2>
<p>Adjust audio tempo.
</p>
<p>The filter accepts exactly one parameter, the audio tempo. If not
specified then the filter will assume nominal 1.0 tempo. Tempo must
be in the [0.5, 2.0] range.
</p>
<p>For example, to slow down audio to 80% tempo:
</p><div class="example">
<pre class="example">atempo=0.8
</pre></div>
<p>For example, to speed up audio to 125% tempo:
</p><div class="example">
<pre class="example">atempo=1.25
</pre></div>
<a name="earwax"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-earwax">5.13 earwax</a></h2>
<p>Make audio easier to listen to on headphones.
</p>
<p>This filter adds ‘cues’ to 44.1kHz stereo (i.e. audio CD format) audio
so that when listened to on headphones the stereo image is moved from
inside your head (standard for headphones) to outside and in front of
the listener (standard for speakers).
</p>
<p>Ported from SoX.
</p>
<a name="pan"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-pan">5.14 pan</a></h2>
<p>Mix channels with specific gain levels. The filter accepts the output
channel layout followed by a set of channels definitions.
</p>
<p>This filter is also designed to remap efficiently the channels of an audio
stream.
</p>
<p>The filter accepts parameters of the form:
"<var>l</var>:<var>outdef</var>:<var>outdef</var>:..."
</p>
<dl compact="compact">
<dt>‘<samp>l</samp>’</dt>
<dd><p>output channel layout or number of channels
</p>
</dd>
<dt>‘<samp>outdef</samp>’</dt>
<dd><p>output channel specification, of the form:
"<var>out_name</var>=[<var>gain</var>*]<var>in_name</var>[+[<var>gain</var>*]<var>in_name</var>...]"
</p>
</dd>
<dt>‘<samp>out_name</samp>’</dt>
<dd><p>output channel to define, either a channel name (FL, FR, etc.) or a channel
number (c0, c1, etc.)
</p>
</dd>
<dt>‘<samp>gain</samp>’</dt>
<dd><p>multiplicative coefficient for the channel, 1 leaving the volume unchanged
</p>
</dd>
<dt>‘<samp>in_name</samp>’</dt>
<dd><p>input channel to use, see out_name for details; it is not possible to mix
named and numbered input channels
</p></dd>
</dl>
<p>If the ‘=’ in a channel specification is replaced by ‘<’, then the gains for
that specification will be renormalized so that the total is 1, thus
avoiding clipping noise.
</p>
<a name="Mixing-examples"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Mixing-examples">5.14.1 Mixing examples</a></h3>
<p>For example, if you want to down-mix from stereo to mono, but with a bigger
factor for the left channel:
</p><div class="example">
<pre class="example">pan=1:c0=0.9*c0+0.1*c1
</pre></div>
<p>A customized down-mix to stereo that works automatically for 3-, 4-, 5- and
7-channels surround:
</p><div class="example">
<pre class="example">pan=stereo: FL < FL + 0.5*FC + 0.6*BL + 0.6*SL : FR < FR + 0.5*FC + 0.6*BR + 0.6*SR
</pre></div>
<p>Note that <code>ffmpeg</code> integrates a default down-mix (and up-mix) system
that should be preferred (see "-ac" option) unless you have very specific
needs.
</p>
<a name="Remapping-examples"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Remapping-examples">5.14.2 Remapping examples</a></h3>
<p>The channel remapping will be effective if, and only if:
</p>
<ul>
<li> gain coefficients are zeroes or ones,
</li><li> only one input per channel output,
</li></ul>
<p>If all these conditions are satisfied, the filter will notify the user ("Pure
channel mapping detected"), and use an optimized and lossless method to do the
remapping.
</p>
<p>For example, if you have a 5.1 source and want a stereo audio stream by
dropping the extra channels:
</p><div class="example">
<pre class="example">pan="stereo: c0=FL : c1=FR"
</pre></div>
<p>Given the same source, you can also switch front left and front right channels
and keep the input channel layout:
</p><div class="example">
<pre class="example">pan="5.1: c0=c1 : c1=c0 : c2=c2 : c3=c3 : c4=c4 : c5=c5"
</pre></div>
<p>If the input is a stereo audio stream, you can mute the front left channel (and
still keep the stereo channel layout) with:
</p><div class="example">
<pre class="example">pan="stereo:c1=c1"
</pre></div>
<p>Still with a stereo audio stream input, you can copy the right channel in both
front left and right:
</p><div class="example">
<pre class="example">pan="stereo: c0=FR : c1=FR"
</pre></div>
<a name="silencedetect"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-silencedetect">5.15 silencedetect</a></h2>
<p>Detect silence in an audio stream.
</p>
<p>This filter logs a message when it detects that the input audio volume is less
or equal to a noise tolerance value for a duration greater or equal to the
minimum detected noise duration.
</p>
<p>The printed times and duration are expressed in seconds.
</p>
<dl compact="compact">
<dt>‘<samp>duration, d</samp>’</dt>
<dd><p>Set silence duration until notification (default is 2 seconds).
</p>
</dd>
<dt>‘<samp>noise, n</samp>’</dt>
<dd><p>Set noise tolerance. Can be specified in dB (in case "dB" is appended to the
specified value) or amplitude ratio. Default is -60dB, or 0.001.
</p></dd>
</dl>
<p>Detect 5 seconds of silence with -50dB noise tolerance:
</p><div class="example">
<pre class="example">silencedetect=n=-50dB:d=5
</pre></div>
<p>Complete example with <code>ffmpeg</code> to detect silence with 0.0001 noise
tolerance in ‘<tt>silence.mp3</tt>’:
</p><div class="example">
<pre class="example">ffmpeg -f lavfi -i amovie=silence.mp3,silencedetect=noise=0.0001 -f null -
</pre></div>
<a name="asyncts"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-asyncts">5.16 asyncts</a></h2>
<p>Synchronize audio data with timestamps by squeezing/stretching it and/or
dropping samples/adding silence when needed.
</p>
<p>As an alternative, you can use <a href="#aresample">aresample</a> to do squeezing/stretching.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>compensate</samp>’</dt>
<dd><p>Enable stretching/squeezing the data to make it match the timestamps. Disabled
by default. When disabled, time gaps are covered with silence.
</p>
</dd>
<dt>‘<samp>min_delta</samp>’</dt>
<dd><p>Minimum difference between timestamps and audio data (in seconds) to trigger
adding/dropping samples. Default value is 0.1. If you get non-perfect sync with
this filter, try setting this parameter to 0.
</p>
</dd>
<dt>‘<samp>max_comp</samp>’</dt>
<dd><p>Maximum compensation in samples per second. Relevant only with compensate=1.
Default value 500.
</p>
</dd>
<dt>‘<samp>first_pts</samp>’</dt>
<dd><p>Assume the first pts should be this value. The time base is 1 / sample rate.
This allows for padding/trimming at the start of stream. By default, no
assumption is made about the first frame’s expected pts, so no padding or
trimming is done. For example, this could be set to 0 to pad the beginning with
silence if an audio stream starts after the video stream or to trim any samples
with a negative pts due to encoder delay.
</p>
</dd>
</dl>
<a name="channelsplit"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-channelsplit">5.17 channelsplit</a></h2>
<p>Split each channel in input audio stream into a separate output stream.
</p>
<p>This filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>channel_layout</samp>’</dt>
<dd><p>Channel layout of the input stream. Default is "stereo".
</p></dd>
</dl>
<p>For example, assuming a stereo input MP3 file
</p><div class="example">
<pre class="example">ffmpeg -i in.mp3 -filter_complex channelsplit out.mkv
</pre></div>
<p>will create an output Matroska file with two audio streams, one containing only
the left channel and the other the right channel.
</p>
<p>To split a 5.1 WAV file into per-channel files
</p><div class="example">
<pre class="example">ffmpeg -i in.wav -filter_complex
'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]'
-map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]'
front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]'
side_right.wav
</pre></div>
<a name="channelmap"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-channelmap">5.18 channelmap</a></h2>
<p>Remap input channels to new locations.
</p>
<p>This filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>channel_layout</samp>’</dt>
<dd><p>Channel layout of the output stream.
</p>
</dd>
<dt>‘<samp>map</samp>’</dt>
<dd><p>Map channels from input to output. The argument is a comma-separated list of
mappings, each in the <code><var>in_channel</var>-<var>out_channel</var></code> or
<var>in_channel</var> form. <var>in_channel</var> can be either the name of the input
channel (e.g. FL for front left) or its index in the input channel layout.
<var>out_channel</var> is the name of the output channel or its index in the output
channel layout. If <var>out_channel</var> is not given then it is implicitly an
index, starting with zero and increasing by one for each mapping.
</p></dd>
</dl>
<p>If no mapping is present, the filter will implicitly map input channels to
output channels preserving index.
</p>
<p>For example, assuming a 5.1+downmix input MOV file
</p><div class="example">
<pre class="example">ffmpeg -i in.mov -filter 'channelmap=map=DL-FL\,DR-FR' out.wav
</pre></div>
<p>will create an output WAV file tagged as stereo from the downmix channels of
the input.
</p>
<p>To fix a 5.1 WAV improperly encoded in AAC’s native channel order
</p><div class="example">
<pre class="example">ffmpeg -i in.wav -filter 'channelmap=1\,2\,0\,5\,3\,4:channel_layout=5.1' out.wav
</pre></div>
<a name="join"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-join">5.19 join</a></h2>
<p>Join multiple input streams into one multi-channel stream.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>inputs</samp>’</dt>
<dd><p>Number of input streams. Defaults to 2.
</p>
</dd>
<dt>‘<samp>channel_layout</samp>’</dt>
<dd><p>Desired output channel layout. Defaults to stereo.
</p>
</dd>
<dt>‘<samp>map</samp>’</dt>
<dd><p>Map channels from inputs to output. The argument is a comma-separated list of
mappings, each in the <code><var>input_idx</var>.<var>in_channel</var>-<var>out_channel</var></code>
form. <var>input_idx</var> is the 0-based index of the input stream. <var>in_channel</var>
can be either the name of the input channel (e.g. FL for front left) or its
index in the specified input stream. <var>out_channel</var> is the name of the output
channel.
</p></dd>
</dl>
<p>The filter will attempt to guess the mappings when those are not specified
explicitly. It does so by first trying to find an unused matching input channel
and if that fails it picks the first unused input channel.
</p>
<p>E.g. to join 3 inputs (with properly set channel layouts)
</p><div class="example">
<pre class="example">ffmpeg -i INPUT1 -i INPUT2 -i INPUT3 -filter_complex join=inputs=3 OUTPUT
</pre></div>
<p>To build a 5.1 output from 6 single-channel streams:
</p><div class="example">
<pre class="example">ffmpeg -i fl -i fr -i fc -i sl -i sr -i lfe -filter_complex
'join=inputs=6:channel_layout=5.1:map=0.0-FL\,1.0-FR\,2.0-FC\,3.0-SL\,4.0-SR\,5.0-LFE'
out
</pre></div>
<a name="resample"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-resample">5.20 resample</a></h2>
<p>Convert the audio sample format, sample rate and channel layout. This filter is
not meant to be used directly.
</p>
<a name="volume"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-volume">5.21 volume</a></h2>
<p>Adjust the input audio volume.
</p>
<p>The filter accepts the following named parameters. If the key of the
first options is omitted, the arguments are interpreted according to
the following syntax:
</p><div class="example">
<pre class="example">volume=<var>volume</var>:<var>precision</var>
</pre></div>
<dl compact="compact">
<dt>‘<samp>volume</samp>’</dt>
<dd><p>Expresses how the audio volume will be increased or decreased.
</p>
<p>Output values are clipped to the maximum value.
</p>
<p>The output audio volume is given by the relation:
</p><div class="example">
<pre class="example"><var>output_volume</var> = <var>volume</var> * <var>input_volume</var>
</pre></div>
<p>Default value for <var>volume</var> is 1.0.
</p>
</dd>
<dt>‘<samp>precision</samp>’</dt>
<dd><p>Set the mathematical precision.
</p>
<p>This determines which input sample formats will be allowed, which affects the
precision of the volume scaling.
</p>
<dl compact="compact">
<dt>‘<samp>fixed</samp>’</dt>
<dd><p>8-bit fixed-point; limits input sample format to U8, S16, and S32.
</p></dd>
<dt>‘<samp>float</samp>’</dt>
<dd><p>32-bit floating-point; limits input sample format to FLT. (default)
</p></dd>
<dt>‘<samp>double</samp>’</dt>
<dd><p>64-bit floating-point; limits input sample format to DBL.
</p></dd>
</dl>
</dd>
</dl>
<a name="Examples"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples">5.21.1 Examples</a></h3>
<ul>
<li>
Halve the input audio volume:
<div class="example">
<pre class="example">volume=volume=0.5
volume=volume=1/2
volume=volume=-6.0206dB
</pre></div>
<p>In all the above example the named key for ‘<samp>volume</samp>’ can be
omitted, for example like in:
</p><div class="example">
<pre class="example">volume=0.5
</pre></div>
</li><li>
Increase input audio power by 6 decibels using fixed-point precision:
<div class="example">
<pre class="example">volume=volume=6dB:precision=fixed
</pre></div>
</li></ul>
<a name="volumedetect"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-volumedetect">5.22 volumedetect</a></h2>
<p>Detect the volume of the input video.
</p>
<p>The filter has no parameters. The input is not modified. Statistics about
the volume will be printed in the log when the input stream end is reached.
</p>
<p>In particular it will show the mean volume (root mean square), maximum
volume (on a per-sample basis), and the beginning of an histogram of the
registered volume values (from the maximum value to a cumulated 1/1000 of
the samples).
</p>
<p>All volumes are in decibels relative to the maximum PCM value.
</p>
<p>Here is an excerpt of the output:
</p><div class="example">
<pre class="example">[Parsed_volumedetect_0 0xa23120] mean_volume: -27 dB
[Parsed_volumedetect_0 0xa23120] max_volume: -4 dB
[Parsed_volumedetect_0 0xa23120] histogram_4db: 6
[Parsed_volumedetect_0 0xa23120] histogram_5db: 62
[Parsed_volumedetect_0 0xa23120] histogram_6db: 286
[Parsed_volumedetect_0 0xa23120] histogram_7db: 1042
[Parsed_volumedetect_0 0xa23120] histogram_8db: 2551
[Parsed_volumedetect_0 0xa23120] histogram_9db: 4609
[Parsed_volumedetect_0 0xa23120] histogram_10db: 8409
</pre></div>
<p>It means that:
</p><ul>
<li>
The mean square energy is approximately -27 dB, or 10^-2.7.
</li><li>
The largest sample is at -4 dB, or more precisely between -4 dB and -5 dB.
</li><li>
There are 6 samples at -4 dB, 62 at -5 dB, 286 at -6 dB, etc.
</li></ul>
<p>In other words, raising the volume by +4 dB does not cause any clipping,
raising it by +5 dB causes clipping for 6 samples, etc.
</p>
<a name="Audio-Sources"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Audio-Sources">6 Audio Sources</a></h1>
<p>Below is a description of the currently available audio sources.
</p>
<a name="abuffer-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-abuffer-1">6.1 abuffer</a></h2>
<p>Buffer audio frames, and make them available to the filter chain.
</p>
<p>This source is mainly intended for a programmatic use, in particular
through the interface defined in ‘<tt>libavfilter/asrc_abuffer.h</tt>’.
</p>
<p>It accepts the following mandatory parameters:
<var>sample_rate</var>:<var>sample_fmt</var>:<var>channel_layout</var>
</p>
<dl compact="compact">
<dt>‘<samp>sample_rate</samp>’</dt>
<dd><p>The sample rate of the incoming audio buffers.
</p>
</dd>
<dt>‘<samp>sample_fmt</samp>’</dt>
<dd><p>The sample format of the incoming audio buffers.
Either a sample format name or its corresponging integer representation from
the enum AVSampleFormat in ‘<tt>libavutil/samplefmt.h</tt>’
</p>
</dd>
<dt>‘<samp>channel_layout</samp>’</dt>
<dd><p>The channel layout of the incoming audio buffers.
Either a channel layout name from channel_layout_map in
‘<tt>libavutil/channel_layout.c</tt>’ or its corresponding integer representation
from the AV_CH_LAYOUT_* macros in ‘<tt>libavutil/channel_layout.h</tt>’
</p>
</dd>
</dl>
<p>For example:
</p><div class="example">
<pre class="example">abuffer=44100:s16p:stereo
</pre></div>
<p>will instruct the source to accept planar 16bit signed stereo at 44100Hz.
Since the sample format with name "s16p" corresponds to the number
6 and the "stereo" channel layout corresponds to the value 0x3, this is
equivalent to:
</p><div class="example">
<pre class="example">abuffer=44100:6:0x3
</pre></div>
<a name="aevalsrc"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-aevalsrc">6.2 aevalsrc</a></h2>
<p>Generate an audio signal specified by an expression.
</p>
<p>This source accepts in input one or more expressions (one for each
channel), which are evaluated and used to generate a corresponding
audio signal.
</p>
<p>It accepts the syntax: <var>exprs</var>[::<var>options</var>].
<var>exprs</var> is a list of expressions separated by ":", one for each
separate channel. In case the <var>channel_layout</var> is not
specified, the selected channel layout depends on the number of
provided expressions.
</p>
<p><var>options</var> is an optional sequence of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<p>The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>channel_layout, c</samp>’</dt>
<dd><p>Set the channel layout. The number of channels in the specified layout
must be equal to the number of specified expressions.
</p>
</dd>
<dt>‘<samp>duration, d</samp>’</dt>
<dd><p>Set the minimum duration of the sourced audio. See the function
<code>av_parse_time()</code> for the accepted format.
Note that the resulting duration may be greater than the specified
duration, as the generated audio is always cut at the end of a
complete frame.
</p>
<p>If not specified, or the expressed duration is negative, the audio is
supposed to be generated forever.
</p>
</dd>
<dt>‘<samp>nb_samples, n</samp>’</dt>
<dd><p>Set the number of samples per channel per each output frame,
default to 1024.
</p>
</dd>
<dt>‘<samp>sample_rate, s</samp>’</dt>
<dd><p>Specify the sample rate, default to 44100.
</p></dd>
</dl>
<p>Each expression in <var>exprs</var> can contain the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>number of the evaluated sample, starting from 0
</p>
</dd>
<dt>‘<samp>t</samp>’</dt>
<dd><p>time of the evaluated sample expressed in seconds, starting from 0
</p>
</dd>
<dt>‘<samp>s</samp>’</dt>
<dd><p>sample rate
</p>
</dd>
</dl>
<a name="Examples-16"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-16">6.2.1 Examples</a></h3>
<ul>
<li>
Generate silence:
<div class="example">
<pre class="example">aevalsrc=0
</pre></div>
</li><li>
Generate a sin signal with frequency of 440 Hz, set sample rate to
8000 Hz:
<div class="example">
<pre class="example">aevalsrc="sin(440*2*PI*t)::s=8000"
</pre></div>
</li><li>
Generate a two channels signal, specify the channel layout (Front
Center + Back Center) explicitly:
<div class="example">
<pre class="example">aevalsrc="sin(420*2*PI*t):cos(430*2*PI*t)::c=FC|BC"
</pre></div>
</li><li>
Generate white noise:
<div class="example">
<pre class="example">aevalsrc="-2+random(0)"
</pre></div>
</li><li>
Generate an amplitude modulated signal:
<div class="example">
<pre class="example">aevalsrc="sin(10*2*PI*t)*sin(880*2*PI*t)"
</pre></div>
</li><li>
Generate 2.5 Hz binaural beats on a 360 Hz carrier:
<div class="example">
<pre class="example">aevalsrc="0.1*sin(2*PI*(360-2.5/2)*t) : 0.1*sin(2*PI*(360+2.5/2)*t)"
</pre></div>
</li></ul>
<a name="anullsrc"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-anullsrc">6.3 anullsrc</a></h2>
<p>Null audio source, return unprocessed audio frames. It is mainly useful
as a template and to be employed in analysis / debugging tools, or as
the source for filters which ignore the input data (for example the sox
synth filter).
</p>
<p>It accepts an optional sequence of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<p>The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>sample_rate, s</samp>’</dt>
<dd><p>Specify the sample rate, and defaults to 44100.
</p>
</dd>
<dt>‘<samp>channel_layout, cl</samp>’</dt>
<dd>
<p>Specify the channel layout, and can be either an integer or a string
representing a channel layout. The default value of <var>channel_layout</var>
is "stereo".
</p>
<p>Check the channel_layout_map definition in
‘<tt>libavutil/channel_layout.c</tt>’ for the mapping between strings and
channel layout values.
</p>
</dd>
<dt>‘<samp>nb_samples, n</samp>’</dt>
<dd><p>Set the number of samples per requested frames.
</p>
</dd>
</dl>
<p>Follow some examples:
</p><div class="example">
<pre class="example"># set the sample rate to 48000 Hz and the channel layout to AV_CH_LAYOUT_MONO.
anullsrc=r=48000:cl=4
# same as
anullsrc=r=48000:cl=mono
</pre></div>
<a name="abuffer"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-abuffer">6.4 abuffer</a></h2>
<p>Buffer audio frames, and make them available to the filter chain.
</p>
<p>This source is not intended to be part of user-supplied graph descriptions but
for insertion by calling programs through the interface defined in
‘<tt>libavfilter/buffersrc.h</tt>’.
</p>
<p>It accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>time_base</samp>’</dt>
<dd><p>Timebase which will be used for timestamps of submitted frames. It must be
either a floating-point number or in <var>numerator</var>/<var>denominator</var> form.
</p>
</dd>
<dt>‘<samp>sample_rate</samp>’</dt>
<dd><p>Audio sample rate.
</p>
</dd>
<dt>‘<samp>sample_fmt</samp>’</dt>
<dd><p>Name of the sample format, as returned by <code>av_get_sample_fmt_name()</code>.
</p>
</dd>
<dt>‘<samp>channel_layout</samp>’</dt>
<dd><p>Channel layout of the audio data, in the form that can be accepted by
<code>av_get_channel_layout()</code>.
</p></dd>
</dl>
<p>All the parameters need to be explicitly defined.
</p>
<a name="flite"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-flite">6.5 flite</a></h2>
<p>Synthesize a voice utterance using the libflite library.
</p>
<p>To enable compilation of this filter you need to configure FFmpeg with
<code>--enable-libflite</code>.
</p>
<p>Note that the flite library is not thread-safe.
</p>
<p>The source accepts parameters as a list of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>list_voices</samp>’</dt>
<dd><p>If set to 1, list the names of the available voices and exit
immediately. Default value is 0.
</p>
</dd>
<dt>‘<samp>nb_samples, n</samp>’</dt>
<dd><p>Set the maximum number of samples per frame. Default value is 512.
</p>
</dd>
<dt>‘<samp>textfile</samp>’</dt>
<dd><p>Set the filename containing the text to speak.
</p>
</dd>
<dt>‘<samp>text</samp>’</dt>
<dd><p>Set the text to speak.
</p>
</dd>
<dt>‘<samp>voice, v</samp>’</dt>
<dd><p>Set the voice to use for the speech synthesis. Default value is
<code>kal</code>. See also the <var>list_voices</var> option.
</p></dd>
</dl>
<a name="Examples-13"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-13">6.5.1 Examples</a></h3>
<ul>
<li>
Read from file ‘<tt>speech.txt</tt>’, and synthetize the text using the
standard flite voice:
<div class="example">
<pre class="example">flite=textfile=speech.txt
</pre></div>
</li><li>
Read the specified text selecting the <code>slt</code> voice:
<div class="example">
<pre class="example">flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
</pre></div>
</li><li>
Input text to ffmpeg:
<div class="example">
<pre class="example">ffmpeg -f lavfi -i flite=text='So fare thee well, poor devil of a Sub-Sub, whose commentator I am':voice=slt
</pre></div>
</li><li>
Make ‘<tt>ffplay</tt>’ speak the specified text, using <code>flite</code> and
the <code>lavfi</code> device:
<div class="example">
<pre class="example">ffplay -f lavfi flite=text='No more be grieved for which that thou hast done.'
</pre></div>
</li></ul>
<p>For more information about libflite, check:
<a href="http://www.speech.cs.cmu.edu/flite/">http://www.speech.cs.cmu.edu/flite/</a>
</p>
<a name="Audio-Sinks"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Audio-Sinks">7 Audio Sinks</a></h1>
<p>Below is a description of the currently available audio sinks.
</p>
<a name="abuffersink-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-abuffersink-1">7.1 abuffersink</a></h2>
<p>Buffer audio frames, and make them available to the end of filter chain.
</p>
<p>This sink is mainly intended for programmatic use, in particular
through the interface defined in ‘<tt>libavfilter/buffersink.h</tt>’.
</p>
<p>It requires a pointer to an AVABufferSinkContext structure, which
defines the incoming buffers’ formats, to be passed as the opaque
parameter to <code>avfilter_init_filter</code> for initialization.
</p>
<a name="anullsink"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-anullsink">7.2 anullsink</a></h2>
<p>Null audio sink, do absolutely nothing with the input audio. It is
mainly useful as a template and to be employed in analysis / debugging
tools.
</p>
<a name="abuffersink"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-abuffersink">7.3 abuffersink</a></h2>
<p>This sink is intended for programmatic use. Frames that arrive on this sink can
be retrieved by the calling program using the interface defined in
‘<tt>libavfilter/buffersink.h</tt>’.
</p>
<p>This filter accepts no parameters.
</p>
<a name="Video-Filters"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Video-Filters">8 Video Filters</a></h1>
<p>When you configure your FFmpeg build, you can disable any of the
existing filters using <code>--disable-filters</code>.
The configure output will show the video filters included in your
build.
</p>
<p>Below is a description of the currently available video filters.
</p>
<a name="alphaextract"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-alphaextract">8.1 alphaextract</a></h2>
<p>Extract the alpha component from the input as a grayscale video. This
is especially useful with the <var>alphamerge</var> filter.
</p>
<a name="alphamerge"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-alphamerge">8.2 alphamerge</a></h2>
<p>Add or replace the alpha component of the primary input with the
grayscale value of a second input. This is intended for use with
<var>alphaextract</var> to allow the transmission or storage of frame
sequences that have alpha in a format that doesn’t support an alpha
channel.
</p>
<p>For example, to reconstruct full frames from a normal YUV-encoded video
and a separate video created with <var>alphaextract</var>, you might use:
</p><div class="example">
<pre class="example">movie=in_alpha.mkv [alpha]; [in][alpha] alphamerge [out]
</pre></div>
<p>Since this filter is designed for reconstruction, it operates on frame
sequences without considering timestamps, and terminates when either
input reaches end of stream. This will cause problems if your encoding
pipeline drops frames. If you’re trying to apply an image as an
overlay to a video stream, consider the <var>overlay</var> filter instead.
</p>
<a name="ass"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-ass">8.3 ass</a></h2>
<p>Same as the <a href="#subtitles">subtitles</a> filter, except that it doesn’t require libavcodec
and libavformat to work. On the other hand, it is limited to ASS (Advanced
Substation Alpha) subtitles files.
</p>
<a name="bbox"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-bbox">8.4 bbox</a></h2>
<p>Compute the bounding box for the non-black pixels in the input frame
luminance plane.
</p>
<p>This filter computes the bounding box containing all the pixels with a
luminance value greater than the minimum allowed value.
The parameters describing the bounding box are printed on the filter
log.
</p>
<a name="blackdetect"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-blackdetect">8.5 blackdetect</a></h2>
<p>Detect video intervals that are (almost) completely black. Can be
useful to detect chapter transitions, commercials, or invalid
recordings. Output lines contains the time for the start, end and
duration of the detected black interval expressed in seconds.
</p>
<p>In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.
</p>
<p>This filter accepts a list of options in the form of
<var>key</var>=<var>value</var> pairs separated by ":". A description of the
accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>black_min_duration, d</samp>’</dt>
<dd><p>Set the minimum detected black duration expressed in seconds. It must
be a non-negative floating point number.
</p>
<p>Default value is 2.0.
</p>
</dd>
<dt>‘<samp>picture_black_ratio_th, pic_th</samp>’</dt>
<dd><p>Set the threshold for considering a picture "black".
Express the minimum value for the ratio:
</p><div class="example">
<pre class="example"><var>nb_black_pixels</var> / <var>nb_pixels</var>
</pre></div>
<p>for which a picture is considered black.
Default value is 0.98.
</p>
</dd>
<dt>‘<samp>pixel_black_th, pix_th</samp>’</dt>
<dd><p>Set the threshold for considering a pixel "black".
</p>
<p>The threshold expresses the maximum pixel luminance value for which a
pixel is considered "black". The provided value is scaled according to
the following equation:
</p><div class="example">
<pre class="example"><var>absolute_threshold</var> = <var>luminance_minimum_value</var> + <var>pixel_black_th</var> * <var>luminance_range_size</var>
</pre></div>
<p><var>luminance_range_size</var> and <var>luminance_minimum_value</var> depend on
the input video format, the range is [0-255] for YUV full-range
formats and [16-235] for YUV non full-range formats.
</p>
<p>Default value is 0.10.
</p></dd>
</dl>
<p>The following example sets the maximum pixel threshold to the minimum
value, and detects only black intervals of 2 or more seconds:
</p><div class="example">
<pre class="example">blackdetect=d=2:pix_th=0.00
</pre></div>
<a name="blackframe"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-blackframe">8.6 blackframe</a></h2>
<p>Detect frames that are (almost) completely black. Can be useful to
detect chapter transitions or commercials. Output lines consist of
the frame number of the detected frame, the percentage of blackness,
the position in the file if known or -1 and the timestamp in seconds.
</p>
<p>In order to display the output lines, you need to set the loglevel at
least to the AV_LOG_INFO value.
</p>
<p>The filter accepts the syntax:
</p><div class="example">
<pre class="example">blackframe[=<var>amount</var>:[<var>threshold</var>]]
</pre></div>
<p><var>amount</var> is the percentage of the pixels that have to be below the
threshold, and defaults to 98.
</p>
<p><var>threshold</var> is the threshold below which a pixel value is
considered black, and defaults to 32.
</p>
<a name="boxblur"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-boxblur">8.7 boxblur</a></h2>
<p>Apply boxblur algorithm to the input video.
</p>
<p>This filter accepts the parameters:
<var>luma_radius</var>:<var>luma_power</var>:<var>chroma_radius</var>:<var>chroma_power</var>:<var>alpha_radius</var>:<var>alpha_power</var>
</p>
<p>Chroma and alpha parameters are optional, if not specified they default
to the corresponding values set for <var>luma_radius</var> and
<var>luma_power</var>.
</p>
<p><var>luma_radius</var>, <var>chroma_radius</var>, and <var>alpha_radius</var> represent
the radius in pixels of the box used for blurring the corresponding
input plane. They are expressions, and can contain the following
constants:
</p><dl compact="compact">
<dt>‘<samp>w, h</samp>’</dt>
<dd><p>the input width and height in pixels
</p>
</dd>
<dt>‘<samp>cw, ch</samp>’</dt>
<dd><p>the input chroma image width and height in pixels
</p>
</dd>
<dt>‘<samp>hsub, vsub</samp>’</dt>
<dd><p>horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>The radius must be a non-negative number, and must not be greater than
the value of the expression <code>min(w,h)/2</code> for the luma and alpha planes,
and of <code>min(cw,ch)/2</code> for the chroma planes.
</p>
<p><var>luma_power</var>, <var>chroma_power</var>, and <var>alpha_power</var> represent
how many times the boxblur filter is applied to the corresponding
plane.
</p>
<p>Some examples follow:
</p>
<ul>
<li>
Apply a boxblur filter with luma, chroma, and alpha radius
set to 2:
<div class="example">
<pre class="example">boxblur=2:1
</pre></div>
</li><li>
Set luma radius to 2, alpha and chroma radius to 0
<div class="example">
<pre class="example">boxblur=2:1:0:0:0:0
</pre></div>
</li><li>
Set luma and chroma radius to a fraction of the video dimension
<div class="example">
<pre class="example">boxblur=min(h\,w)/10:1:min(cw\,ch)/10:1
</pre></div>
</li></ul>
<a name="colormatrix"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-colormatrix">8.8 colormatrix</a></h2>
<p>The colormatrix filter allows conversion between any of the following color
space: BT.709 (<var>bt709</var>), BT.601 (<var>bt601</var>), SMPTE-240M (<var>smpte240m</var>)
and FCC (<var>fcc</var>).
</p>
<p>The syntax of the parameters is <var>source</var>:<var>destination</var>:
</p>
<div class="example">
<pre class="example">colormatrix=bt601:smpte240m
</pre></div>
<a name="copy"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-copy">8.9 copy</a></h2>
<p>Copy the input source unchanged to the output. Mainly useful for
testing purposes.
</p>
<a name="crop"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-crop">8.10 crop</a></h2>
<p>Crop the input video.
</p>
<p>This filter accepts a list of <var>key</var>=<var>value</var> pairs as argument,
separated by ’:’. If the key of the first options is omitted, the
arguments are interpreted according to the syntax
<var>out_w</var>:<var>out_h</var>:<var>x</var>:<var>y</var>:<var>keep_aspect</var>.
</p>
<p>A description of the accepted options follows:
</p><dl compact="compact">
<dt>‘<samp>w, out_w</samp>’</dt>
<dd><p>Set the crop area width. It defaults to <code>iw</code>.
This expression is evaluated only once during the filter
configuration.
</p>
</dd>
<dt>‘<samp>h, out_h</samp>’</dt>
<dd><p>Set the crop area width. It defaults to <code>ih</code>.
This expression is evaluated only once during the filter
configuration.
</p>
</dd>
<dt>‘<samp>x</samp>’</dt>
<dd><p>Set the expression for the x top-left coordinate of the cropped area.
It defaults to <code>(in_w-out_w)/2</code>.
This expression is evaluated per-frame.
</p>
</dd>
<dt>‘<samp>y</samp>’</dt>
<dd><p>Set the expression for the y top-left coordinate of the cropped area.
It defaults to <code>(in_h-out_h)/2</code>.
This expression is evaluated per-frame.
</p>
</dd>
<dt>‘<samp>keep_aspect</samp>’</dt>
<dd><p>If set to 1 will force the output display aspect ratio
to be the same of the input, by changing the output sample aspect
ratio. It defaults to 0.
</p></dd>
</dl>
<p>The <var>out_w</var>, <var>out_h</var>, <var>x</var>, <var>y</var> parameters are
expressions containing the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>the computed values for <var>x</var> and <var>y</var>. They are evaluated for
each new frame.
</p>
</dd>
<dt>‘<samp>in_w, in_h</samp>’</dt>
<dd><p>the input width and height
</p>
</dd>
<dt>‘<samp>iw, ih</samp>’</dt>
<dd><p>same as <var>in_w</var> and <var>in_h</var>
</p>
</dd>
<dt>‘<samp>out_w, out_h</samp>’</dt>
<dd><p>the output (cropped) width and height
</p>
</dd>
<dt>‘<samp>ow, oh</samp>’</dt>
<dd><p>same as <var>out_w</var> and <var>out_h</var>
</p>
</dd>
<dt>‘<samp>a</samp>’</dt>
<dd><p>same as <var>iw</var> / <var>ih</var>
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>input sample aspect ratio
</p>
</dd>
<dt>‘<samp>dar</samp>’</dt>
<dd><p>input display aspect ratio, it is the same as (<var>iw</var> / <var>ih</var>) * <var>sar</var>
</p>
</dd>
<dt>‘<samp>hsub, vsub</samp>’</dt>
<dd><p>horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p>
</dd>
<dt>‘<samp>n</samp>’</dt>
<dd><p>the number of input frame, starting from 0
</p>
</dd>
<dt>‘<samp>pos</samp>’</dt>
<dd><p>the position in the file of the input frame, NAN if unknown
</p>
</dd>
<dt>‘<samp>t</samp>’</dt>
<dd><p>timestamp expressed in seconds, NAN if the input timestamp is unknown
</p>
</dd>
</dl>
<p>The expression for <var>out_w</var> may depend on the value of <var>out_h</var>,
and the expression for <var>out_h</var> may depend on <var>out_w</var>, but they
cannot depend on <var>x</var> and <var>y</var>, as <var>x</var> and <var>y</var> are
evaluated after <var>out_w</var> and <var>out_h</var>.
</p>
<p>The <var>x</var> and <var>y</var> parameters specify the expressions for the
position of the top-left corner of the output (non-cropped) area. They
are evaluated for each frame. If the evaluated value is not valid, it
is approximated to the nearest valid value.
</p>
<p>The expression for <var>x</var> may depend on <var>y</var>, and the expression
for <var>y</var> may depend on <var>x</var>.
</p>
<a name="Examples-11"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-11">8.10.1 Examples</a></h3>
<ul>
<li>
Crop area with size 100x100 at position (12,34).
<div class="example">
<pre class="example">crop=100:100:12:34
</pre></div>
<p>Using named options, the example above becomes:
</p><div class="example">
<pre class="example">crop=w=100:h=100:x=12:y=34
</pre></div>
</li><li>
Crop the central input area with size 100x100:
<div class="example">
<pre class="example">crop=100:100
</pre></div>
</li><li>
Crop the central input area with size 2/3 of the input video:
<div class="example">
<pre class="example">crop=2/3*in_w:2/3*in_h
</pre></div>
</li><li>
Crop the input video central square:
<div class="example">
<pre class="example">crop=in_h
</pre></div>
</li><li>
Delimit the rectangle with the top-left corner placed at position
100:100 and the right-bottom corner corresponding to the right-bottom
corner of the input image:
<div class="example">
<pre class="example">crop=in_w-100:in_h-100:100:100
</pre></div>
</li><li>
Crop 10 pixels from the left and right borders, and 20 pixels from
the top and bottom borders
<div class="example">
<pre class="example">crop=in_w-2*10:in_h-2*20
</pre></div>
</li><li>
Keep only the bottom right quarter of the input image:
<div class="example">
<pre class="example">crop=in_w/2:in_h/2:in_w/2:in_h/2
</pre></div>
</li><li>
Crop height for getting Greek harmony:
<div class="example">
<pre class="example">crop=in_w:1/PHI*in_w
</pre></div>
</li><li>
Appply trembling effect:
<div class="example">
<pre class="example">crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(n/10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(n/7)
</pre></div>
</li><li>
Apply erratic camera effect depending on timestamp:
<div class="example">
<pre class="example">crop=in_w/2:in_h/2:(in_w-out_w)/2+((in_w-out_w)/2)*sin(t*10):(in_h-out_h)/2 +((in_h-out_h)/2)*sin(t*13)"
</pre></div>
</li><li>
Set x depending on the value of y:
<div class="example">
<pre class="example">crop=in_w/2:in_h/2:y:10+10*sin(n/10)
</pre></div>
</li></ul>
<a name="cropdetect"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-cropdetect">8.11 cropdetect</a></h2>
<p>Auto-detect crop size.
</p>
<p>Calculate necessary cropping parameters and prints the recommended
parameters through the logging system. The detected dimensions
correspond to the non-black area of the input video.
</p>
<p>It accepts the syntax:
</p><div class="example">
<pre class="example">cropdetect[=<var>limit</var>[:<var>round</var>[:<var>reset</var>]]]
</pre></div>
<dl compact="compact">
<dt>‘<samp>limit</samp>’</dt>
<dd><p>Threshold, which can be optionally specified from nothing (0) to
everything (255), defaults to 24.
</p>
</dd>
<dt>‘<samp>round</samp>’</dt>
<dd><p>Value which the width/height should be divisible by, defaults to
16. The offset is automatically adjusted to center the video. Use 2 to
get only even dimensions (needed for 4:2:2 video). 16 is best when
encoding to most video codecs.
</p>
</dd>
<dt>‘<samp>reset</samp>’</dt>
<dd><p>Counter that determines after how many frames cropdetect will reset
the previously detected largest video area and start over to detect
the current optimal crop area. Defaults to 0.
</p>
<p>This can be useful when channel logos distort the video area. 0
indicates never reset and return the largest area encountered during
playback.
</p></dd>
</dl>
<a name="decimate"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-decimate">8.12 decimate</a></h2>
<p>This filter drops frames that do not differ greatly from the previous
frame in order to reduce framerate. The main use of this filter is
for very-low-bitrate encoding (e.g. streaming over dialup modem), but
it could in theory be used for fixing movies that were
inverse-telecined incorrectly.
</p>
<p>It accepts the following parameters:
<var>max</var>:<var>hi</var>:<var>lo</var>:<var>frac</var>.
</p>
<dl compact="compact">
<dt>‘<samp>max</samp>’</dt>
<dd><p>Set the maximum number of consecutive frames which can be dropped (if
positive), or the minimum interval between dropped frames (if
negative). If the value is 0, the frame is dropped unregarding the
number of previous sequentially dropped frames.
</p>
<p>Default value is 0.
</p>
</dd>
<dt>‘<samp>hi, lo, frac</samp>’</dt>
<dd><p>Set the dropping threshold values.
</p>
<p>Values for <var>hi</var> and <var>lo</var> are for 8x8 pixel blocks and
represent actual pixel value differences, so a threshold of 64
corresponds to 1 unit of difference for each pixel, or the same spread
out differently over the block.
</p>
<p>A frame is a candidate for dropping if no 8x8 blocks differ by more
than a threshold of <var>hi</var>, and if no more than <var>frac</var> blocks (1
meaning the whole image) differ by more than a threshold of <var>lo</var>.
</p>
<p>Default value for <var>hi</var> is 64*12, default value for <var>lo</var> is
64*5, and default value for <var>frac</var> is 0.33.
</p></dd>
</dl>
<a name="delogo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-delogo">8.13 delogo</a></h2>
<p>Suppress a TV station logo by a simple interpolation of the surrounding
pixels. Just set a rectangle covering the logo and watch it disappear
(and sometimes something even uglier appear - your mileage may vary).
</p>
<p>The filter accepts parameters as a string of the form
"<var>x</var>:<var>y</var>:<var>w</var>:<var>h</var>:<var>band</var>", or as a list of
<var>key</var>=<var>value</var> pairs, separated by ":".
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>Specify the top left corner coordinates of the logo. They must be
specified.
</p>
</dd>
<dt>‘<samp>w, h</samp>’</dt>
<dd><p>Specify the width and height of the logo to clear. They must be
specified.
</p>
</dd>
<dt>‘<samp>band, t</samp>’</dt>
<dd><p>Specify the thickness of the fuzzy edge of the rectangle (added to
<var>w</var> and <var>h</var>). The default value is 4.
</p>
</dd>
<dt>‘<samp>show</samp>’</dt>
<dd><p>When set to 1, a green rectangle is drawn on the screen to simplify
finding the right <var>x</var>, <var>y</var>, <var>w</var>, <var>h</var> parameters, and
<var>band</var> is set to 4. The default value is 0.
</p>
</dd>
</dl>
<p>Some examples follow.
</p>
<ul>
<li>
Set a rectangle covering the area with top left corner coordinates 0,0
and size 100x77, setting a band of size 10:
<div class="example">
<pre class="example">delogo=0:0:100:77:10
</pre></div>
</li><li>
As the previous example, but use named options:
<div class="example">
<pre class="example">delogo=x=0:y=0:w=100:h=77:band=10
</pre></div>
</li></ul>
<a name="deshake"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-deshake">8.14 deshake</a></h2>
<p>Attempt to fix small changes in horizontal and/or vertical shift. This
filter helps remove camera shake from hand-holding a camera, bumping a
tripod, moving on a vehicle, etc.
</p>
<p>The filter accepts parameters as a string of the form
"<var>x</var>:<var>y</var>:<var>w</var>:<var>h</var>:<var>rx</var>:<var>ry</var>:<var>edge</var>:<var>blocksize</var>:<var>contrast</var>:<var>search</var>:<var>filename</var>"
</p>
<p>A description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>x, y, w, h</samp>’</dt>
<dd><p>Specify a rectangular area where to limit the search for motion
vectors.
If desired the search for motion vectors can be limited to a
rectangular area of the frame defined by its top left corner, width
and height. These parameters have the same meaning as the drawbox
filter which can be used to visualise the position of the bounding
box.
</p>
<p>This is useful when simultaneous movement of subjects within the frame
might be confused for camera motion by the motion vector search.
</p>
<p>If any or all of <var>x</var>, <var>y</var>, <var>w</var> and <var>h</var> are set to -1
then the full frame is used. This allows later options to be set
without specifying the bounding box for the motion vector search.
</p>
<p>Default - search the whole frame.
</p>
</dd>
<dt>‘<samp>rx, ry</samp>’</dt>
<dd><p>Specify the maximum extent of movement in x and y directions in the
range 0-64 pixels. Default 16.
</p>
</dd>
<dt>‘<samp>edge</samp>’</dt>
<dd><p>Specify how to generate pixels to fill blanks at the edge of the
frame. An integer from 0 to 3 as follows:
</p><dl compact="compact">
<dt>‘<samp>0</samp>’</dt>
<dd><p>Fill zeroes at blank locations
</p></dd>
<dt>‘<samp>1</samp>’</dt>
<dd><p>Original image at blank locations
</p></dd>
<dt>‘<samp>2</samp>’</dt>
<dd><p>Extruded edge value at blank locations
</p></dd>
<dt>‘<samp>3</samp>’</dt>
<dd><p>Mirrored edge at blank locations
</p></dd>
</dl>
<p>The default setting is mirror edge at blank locations.
</p>
</dd>
<dt>‘<samp>blocksize</samp>’</dt>
<dd><p>Specify the blocksize to use for motion search. Range 4-128 pixels,
default 8.
</p>
</dd>
<dt>‘<samp>contrast</samp>’</dt>
<dd><p>Specify the contrast threshold for blocks. Only blocks with more than
the specified contrast (difference between darkest and lightest
pixels) will be considered. Range 1-255, default 125.
</p>
</dd>
<dt>‘<samp>search</samp>’</dt>
<dd><p>Specify the search strategy 0 = exhaustive search, 1 = less exhaustive
search. Default - exhaustive search.
</p>
</dd>
<dt>‘<samp>filename</samp>’</dt>
<dd><p>If set then a detailed log of the motion search is written to the
specified file.
</p>
</dd>
</dl>
<a name="drawbox"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-drawbox">8.15 drawbox</a></h2>
<p>Draw a colored box on the input image.
</p>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>Specify the top left corner coordinates of the box. Default to 0.
</p>
</dd>
<dt>‘<samp>width, w</samp>’</dt>
<dt>‘<samp>height, h</samp>’</dt>
<dd><p>Specify the width and height of the box, if 0 they are interpreted as
the input width and height. Default to 0.
</p>
</dd>
<dt>‘<samp>color, c</samp>’</dt>
<dd><p>Specify the color of the box to write, it can be the name of a color
(case insensitive match) or a 0xRRGGBB[AA] sequence. If the special
value <code>invert</code> is used, the box edge color is the same as the
video with inverted luma.
</p>
</dd>
<dt>‘<samp>thickness, t</samp>’</dt>
<dd><p>Set the thickness of the box edge. Default value is <code>4</code>.
</p></dd>
</dl>
<p>If the key of the first options is omitted, the arguments are
interpreted according to the following syntax:
</p><div class="example">
<pre class="example">drawbox=<var>x</var>:<var>y</var>:<var>width</var>:<var>height</var>:<var>color</var>:<var>thickness</var>
</pre></div>
<p>Some examples follow:
</p><ul>
<li>
Draw a black box around the edge of the input image:
<div class="example">
<pre class="example">drawbox
</pre></div>
</li><li>
Draw a box with color red and an opacity of 50%:
<div class="example">
<pre class="example">drawbox=10:20:200:60:red@0.5
</pre></div>
<p>The previous example can be specified as:
</p><div class="example">
<pre class="example">drawbox=x=10:y=20:w=200:h=60:color=red@0.5
</pre></div>
</li><li>
Fill the box with pink color:
<div class="example">
<pre class="example">drawbox=x=10:y=10:w=100:h=100:color=pink@0.5:t=max
</pre></div>
</li></ul>
<p><a name="drawtext"></a>
</p><a name="drawtext-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-drawtext-1">8.16 drawtext</a></h2>
<p>Draw text string or text from specified file on top of video using the
libfreetype library.
</p>
<p>To enable compilation of this filter you need to configure FFmpeg with
<code>--enable-libfreetype</code>.
</p>
<a name="Syntax"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Syntax">8.16.1 Syntax</a></h3>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>box</samp>’</dt>
<dd><p>Used to draw a box around text using background color.
Value should be either 1 (enable) or 0 (disable).
The default value of <var>box</var> is 0.
</p>
</dd>
<dt>‘<samp>boxcolor</samp>’</dt>
<dd><p>The color to be used for drawing box around text.
Either a string (e.g. "yellow") or in 0xRRGGBB[AA] format
(e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of <var>boxcolor</var> is "white".
</p>
</dd>
<dt>‘<samp>draw</samp>’</dt>
<dd><p>Set an expression which specifies if the text should be drawn. If the
expression evaluates to 0, the text is not drawn. This is useful for
specifying that the text should be drawn only when specific conditions
are met.
</p>
<p>Default value is "1".
</p>
<p>See below for the list of accepted constants and functions.
</p>
</dd>
<dt>‘<samp>expansion</samp>’</dt>
<dd><p>Select how the <var>text</var> is expanded. Can be either <code>none</code>,
<code>strftime</code> (default for compatibity reasons but deprecated) or
<code>normal</code>. See the <a href="#drawtext_005fexpansion">Text expansion</a> section
below for details.
</p>
</dd>
<dt>‘<samp>fix_bounds</samp>’</dt>
<dd><p>If true, check and fix text coords to avoid clipping.
</p>
</dd>
<dt>‘<samp>fontcolor</samp>’</dt>
<dd><p>The color to be used for drawing fonts.
Either a string (e.g. "red") or in 0xRRGGBB[AA] format
(e.g. "0xff000033"), possibly followed by an alpha specifier.
The default value of <var>fontcolor</var> is "black".
</p>
</dd>
<dt>‘<samp>fontfile</samp>’</dt>
<dd><p>The font file to be used for drawing text. Path must be included.
This parameter is mandatory.
</p>
</dd>
<dt>‘<samp>fontsize</samp>’</dt>
<dd><p>The font size to be used for drawing text.
The default value of <var>fontsize</var> is 16.
</p>
</dd>
<dt>‘<samp>ft_load_flags</samp>’</dt>
<dd><p>Flags to be used for loading the fonts.
</p>
<p>The flags map the corresponding flags supported by libfreetype, and are
a combination of the following values:
</p><dl compact="compact">
<dt><var>default</var></dt>
<dt><var>no_scale</var></dt>
<dt><var>no_hinting</var></dt>
<dt><var>render</var></dt>
<dt><var>no_bitmap</var></dt>
<dt><var>vertical_layout</var></dt>
<dt><var>force_autohint</var></dt>
<dt><var>crop_bitmap</var></dt>
<dt><var>pedantic</var></dt>
<dt><var>ignore_global_advance_width</var></dt>
<dt><var>no_recurse</var></dt>
<dt><var>ignore_transform</var></dt>
<dt><var>monochrome</var></dt>
<dt><var>linear_design</var></dt>
<dt><var>no_autohint</var></dt>
<dt><var>end table</var></dt>
</dl>
<p>Default value is "render".
</p>
<p>For more information consult the documentation for the FT_LOAD_*
libfreetype flags.
</p>
</dd>
<dt>‘<samp>shadowcolor</samp>’</dt>
<dd><p>The color to be used for drawing a shadow behind the drawn text. It
can be a color name (e.g. "yellow") or a string in the 0xRRGGBB[AA]
form (e.g. "0xff00ff"), possibly followed by an alpha specifier.
The default value of <var>shadowcolor</var> is "black".
</p>
</dd>
<dt>‘<samp>shadowx, shadowy</samp>’</dt>
<dd><p>The x and y offsets for the text shadow position with respect to the
position of the text. They can be either positive or negative
values. Default value for both is "0".
</p>
</dd>
<dt>‘<samp>tabsize</samp>’</dt>
<dd><p>The size in number of spaces to use for rendering the tab.
Default value is 4.
</p>
</dd>
<dt>‘<samp>timecode</samp>’</dt>
<dd><p>Set the initial timecode representation in "hh:mm:ss[:;.]ff"
format. It can be used with or without text parameter. <var>timecode_rate</var>
option must be specified.
</p>
</dd>
<dt>‘<samp>timecode_rate, rate, r</samp>’</dt>
<dd><p>Set the timecode frame rate (timecode only).
</p>
</dd>
<dt>‘<samp>text</samp>’</dt>
<dd><p>The text string to be drawn. The text must be a sequence of UTF-8
encoded characters.
This parameter is mandatory if no file is specified with the parameter
<var>textfile</var>.
</p>
</dd>
<dt>‘<samp>textfile</samp>’</dt>
<dd><p>A text file containing text to be drawn. The text must be a sequence
of UTF-8 encoded characters.
</p>
<p>This parameter is mandatory if no text string is specified with the
parameter <var>text</var>.
</p>
<p>If both <var>text</var> and <var>textfile</var> are specified, an error is thrown.
</p>
</dd>
<dt>‘<samp>reload</samp>’</dt>
<dd><p>If set to 1, the <var>textfile</var> will be reloaded before each frame.
Be sure to update it atomically, or it may be read partially, or even fail.
</p>
</dd>
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>The expressions which specify the offsets where text will be drawn
within the video frame. They are relative to the top/left border of the
output image.
</p>
<p>The default value of <var>x</var> and <var>y</var> is "0".
</p>
<p>See below for the list of accepted constants and functions.
</p></dd>
</dl>
<p>The parameters for <var>x</var> and <var>y</var> are expressions containing the
following constants and functions:
</p>
<dl compact="compact">
<dt>‘<samp>dar</samp>’</dt>
<dd><p>input display aspect ratio, it is the same as (<var>w</var> / <var>h</var>) * <var>sar</var>
</p>
</dd>
<dt>‘<samp>hsub, vsub</samp>’</dt>
<dd><p>horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p>
</dd>
<dt>‘<samp>line_h, lh</samp>’</dt>
<dd><p>the height of each text line
</p>
</dd>
<dt>‘<samp>main_h, h, H</samp>’</dt>
<dd><p>the input height
</p>
</dd>
<dt>‘<samp>main_w, w, W</samp>’</dt>
<dd><p>the input width
</p>
</dd>
<dt>‘<samp>max_glyph_a, ascent</samp>’</dt>
<dd><p>the maximum distance from the baseline to the highest/upper grid
coordinate used to place a glyph outline point, for all the rendered
glyphs.
It is a positive value, due to the grid’s orientation with the Y axis
upwards.
</p>
</dd>
<dt>‘<samp>max_glyph_d, descent</samp>’</dt>
<dd><p>the maximum distance from the baseline to the lowest grid coordinate
used to place a glyph outline point, for all the rendered glyphs.
This is a negative value, due to the grid’s orientation, with the Y axis
upwards.
</p>
</dd>
<dt>‘<samp>max_glyph_h</samp>’</dt>
<dd><p>maximum glyph height, that is the maximum height for all the glyphs
contained in the rendered text, it is equivalent to <var>ascent</var> -
<var>descent</var>.
</p>
</dd>
<dt>‘<samp>max_glyph_w</samp>’</dt>
<dd><p>maximum glyph width, that is the maximum width for all the glyphs
contained in the rendered text
</p>
</dd>
<dt>‘<samp>n</samp>’</dt>
<dd><p>the number of input frame, starting from 0
</p>
</dd>
<dt>‘<samp>rand(min, max)</samp>’</dt>
<dd><p>return a random number included between <var>min</var> and <var>max</var>
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>input sample aspect ratio
</p>
</dd>
<dt>‘<samp>t</samp>’</dt>
<dd><p>timestamp expressed in seconds, NAN if the input timestamp is unknown
</p>
</dd>
<dt>‘<samp>text_h, th</samp>’</dt>
<dd><p>the height of the rendered text
</p>
</dd>
<dt>‘<samp>text_w, tw</samp>’</dt>
<dd><p>the width of the rendered text
</p>
</dd>
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>the x and y offset coordinates where the text is drawn.
</p>
<p>These parameters allow the <var>x</var> and <var>y</var> expressions to refer
each other, so you can for example specify <code>y=x/dar</code>.
</p></dd>
</dl>
<p>If libavfilter was built with <code>--enable-fontconfig</code>, then
‘<samp>fontfile</samp>’ can be a fontconfig pattern or omitted.
</p>
<p><a name="drawtext_005fexpansion"></a>
</p><a name="Text-expansion"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Text-expansion">8.16.2 Text expansion</a></h3>
<p>If ‘<samp>expansion</samp>’ is set to <code>strftime</code> (which is the default for
now), the filter recognizes strftime() sequences in the provided text and
expands them accordingly. Check the documentation of strftime(). This
feature is deprecated.
</p>
<p>If ‘<samp>expansion</samp>’ is set to <code>none</code>, the text is printed verbatim.
</p>
<p>If ‘<samp>expansion</samp>’ is set to <code>normal</code> (which will be the default),
the following expansion mechanism is used.
</p>
<p>The backslash character ’\’, followed by any character, always expands to
the second character.
</p>
<p>Sequence of the form <code>%{...}</code> are expanded. The text between the
braces is a function name, possibly followed by arguments separated by ’:’.
If the arguments contain special characters or delimiters (’:’ or ’}’),
they should be escaped.
</p>
<p>Note that they probably must also be escaped as the value for the
‘<samp>text</samp>’ option in the filter argument string and as the filter
argument in the filter graph description, and possibly also for the shell,
that makes up to four levels of escaping; using a text file avoids these
problems.
</p>
<p>The following functions are available:
</p>
<dl compact="compact">
<dt><code>expr, e</code></dt>
<dd><p>The expression evaluation result.
</p>
<p>It must take one argument specifying the expression to be evaluated,
which accepts the same constants and functions as the <var>x</var> and
<var>y</var> values. Note that not all constants should be used, for
example the text size is not known when evaluating the expression, so
the constants <var>text_w</var> and <var>text_h</var> will have an undefined
value.
</p>
</dd>
<dt><code>gmtime</code></dt>
<dd><p>The time at which the filter is running, expressed in UTC.
It can accept an argument: a strftime() format string.
</p>
</dd>
<dt><code>localtime</code></dt>
<dd><p>The time at which the filter is running, expressed in the local time zone.
It can accept an argument: a strftime() format string.
</p>
</dd>
<dt><code>n, frame_num</code></dt>
<dd><p>The frame number, starting from 0.
</p>
</dd>
<dt><code>pts</code></dt>
<dd><p>The timestamp of the current frame, in seconds, with microsecond accuracy.
</p>
</dd>
</dl>
<a name="Examples-1"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-1">8.16.3 Examples</a></h3>
<p>Some examples follow.
</p>
<ul>
<li>
Draw "Test Text" with font FreeSerif, using the default values for the
optional parameters.
<div class="example">
<pre class="example">drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text'"
</pre></div>
</li><li>
Draw ’Test Text’ with font FreeSerif of size 24 at position x=100
and y=50 (counting from the top-left corner of the screen), text is
yellow with a red box around it. Both the text and the box have an
opacity of 20%.
<div class="example">
<pre class="example">drawtext="fontfile=/usr/share/fonts/truetype/freefont/FreeSerif.ttf: text='Test Text':\
x=100: y=50: fontsize=24: fontcolor=yellow@0.2: box=1: boxcolor=red@0.2"
</pre></div>
<p>Note that the double quotes are not necessary if spaces are not used
within the parameter list.
</p>
</li><li>
Show the text at the center of the video frame:
<div class="example">
<pre class="example">drawtext="fontsize=30:fontfile=FreeSerif.ttf:text='hello world':x=(w-text_w)/2:y=(h-text_h-line_h)/2"
</pre></div>
</li><li>
Show a text line sliding from right to left in the last row of the video
frame. The file ‘<tt>LONG_LINE</tt>’ is assumed to contain a single line
with no newlines.
<div class="example">
<pre class="example">drawtext="fontsize=15:fontfile=FreeSerif.ttf:text=LONG_LINE:y=h-line_h:x=-50*t"
</pre></div>
</li><li>
Show the content of file ‘<tt>CREDITS</tt>’ off the bottom of the frame and scroll up.
<div class="example">
<pre class="example">drawtext="fontsize=20:fontfile=FreeSerif.ttf:textfile=CREDITS:y=h-20*t"
</pre></div>
</li><li>
Draw a single green letter "g", at the center of the input video.
The glyph baseline is placed at half screen height.
<div class="example">
<pre class="example">drawtext="fontsize=60:fontfile=FreeSerif.ttf:fontcolor=green:text=g:x=(w-max_glyph_w)/2:y=h/2-ascent"
</pre></div>
</li><li>
Show text for 1 second every 3 seconds:
<div class="example">
<pre class="example">drawtext="fontfile=FreeSerif.ttf:fontcolor=white:x=100:y=x/dar:draw=lt(mod(t\,3)\,1):text='blink'"
</pre></div>
</li><li>
Use fontconfig to set the font. Note that the colons need to be escaped.
<div class="example">
<pre class="example">drawtext='fontfile=Linux Libertine O-40\:style=Semibold:text=FFmpeg'
</pre></div>
</li><li>
Print the date of a real-time encoding (see strftime(3)):
<div class="example">
<pre class="example">drawtext='fontfile=FreeSans.ttf:expansion=normal:text=%{localtime:%a %b %d %Y}'
</pre></div>
</li></ul>
<p>For more information about libfreetype, check:
<a href="http://www.freetype.org/">http://www.freetype.org/</a>.
</p>
<p>For more information about fontconfig, check:
<a href="http://freedesktop.org/software/fontconfig/fontconfig-user.html">http://freedesktop.org/software/fontconfig/fontconfig-user.html</a>.
</p>
<a name="edgedetect"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-edgedetect">8.17 edgedetect</a></h2>
<p>Detect and draw edges. The filter uses the Canny Edge Detection algorithm.
</p>
<p>This filter accepts the following optional named parameters:
</p>
<dl compact="compact">
<dt>‘<samp>low, high</samp>’</dt>
<dd><p>Set low and high threshold values used by the Canny thresholding
algorithm.
</p>
<p>The high threshold selects the "strong" edge pixels, which are then
connected through 8-connectivity with the "weak" edge pixels selected
by the low threshold.
</p>
<p><var>low</var> and <var>high</var> threshold values must be choosen in the range
[0,1], and <var>low</var> should be lesser or equal to <var>high</var>.
</p>
<p>Default value for <var>low</var> is <code>20/255</code>, and default value for <var>high</var>
is <code>50/255</code>.
</p></dd>
</dl>
<p>Example:
</p><div class="example">
<pre class="example">edgedetect=low=0.1:high=0.4
</pre></div>
<a name="fade"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-fade">8.18 fade</a></h2>
<p>Apply fade-in/out effect to input video.
</p>
<p>It accepts the parameters:
<var>type</var>:<var>start_frame</var>:<var>nb_frames</var>[:<var>options</var>]
</p>
<p><var>type</var> specifies if the effect type, can be either "in" for
fade-in, or "out" for a fade-out effect.
</p>
<p><var>start_frame</var> specifies the number of the start frame for starting
to apply the fade effect.
</p>
<p><var>nb_frames</var> specifies the number of frames for which the fade
effect has to last. At the end of the fade-in effect the output video
will have the same intensity as the input video, at the end of the
fade-out transition the output video will be completely black.
</p>
<p><var>options</var> is an optional sequence of <var>key</var>=<var>value</var> pairs,
separated by ":". The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>type, t</samp>’</dt>
<dd><p>See <var>type</var>.
</p>
</dd>
<dt>‘<samp>start_frame, s</samp>’</dt>
<dd><p>See <var>start_frame</var>.
</p>
</dd>
<dt>‘<samp>nb_frames, n</samp>’</dt>
<dd><p>See <var>nb_frames</var>.
</p>
</dd>
<dt>‘<samp>alpha</samp>’</dt>
<dd><p>If set to 1, fade only alpha channel, if one exists on the input.
Default value is 0.
</p></dd>
</dl>
<p>A few usage examples follow, usable too as test scenarios.
</p><div class="example">
<pre class="example"># fade in first 30 frames of video
fade=in:0:30
# fade out last 45 frames of a 200-frame video
fade=out:155:45
# fade in first 25 frames and fade out last 25 frames of a 1000-frame video
fade=in:0:25, fade=out:975:25
# make first 5 frames black, then fade in from frame 5-24
fade=in:5:20
# fade in alpha over first 25 frames of video
fade=in:0:25:alpha=1
</pre></div>
<a name="field"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-field">8.19 field</a></h2>
<p>Extract a single field from an interlaced image using stride
arithmetic to avoid wasting CPU time. The output frames are marked as
non-interlaced.
</p>
<p>This filter accepts the following named options:
</p><dl compact="compact">
<dt>‘<samp>type</samp>’</dt>
<dd><p>Specify whether to extract the top (if the value is <code>0</code> or
<code>top</code>) or the bottom field (if the value is <code>1</code> or
<code>bottom</code>).
</p></dd>
</dl>
<p>If the option key is not specified, the first value sets the <var>type</var>
option. For example:
</p><div class="example">
<pre class="example">field=bottom
</pre></div>
<p>is equivalent to:
</p><div class="example">
<pre class="example">field=type=bottom
</pre></div>
<a name="fieldorder"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-fieldorder">8.20 fieldorder</a></h2>
<p>Transform the field order of the input video.
</p>
<p>It accepts one parameter which specifies the required field order that
the input interlaced video will be transformed to. The parameter can
assume one of the following values:
</p>
<dl compact="compact">
<dt>‘<samp>0 or bff</samp>’</dt>
<dd><p>output bottom field first
</p></dd>
<dt>‘<samp>1 or tff</samp>’</dt>
<dd><p>output top field first
</p></dd>
</dl>
<p>Default value is "tff".
</p>
<p>Transformation is achieved by shifting the picture content up or down
by one line, and filling the remaining line with appropriate picture content.
This method is consistent with most broadcast field order converters.
</p>
<p>If the input video is not flagged as being interlaced, or it is already
flagged as being of the required output field order then this filter does
not alter the incoming video.
</p>
<p>This filter is very useful when converting to or from PAL DV material,
which is bottom field first.
</p>
<p>For example:
</p><div class="example">
<pre class="example">ffmpeg -i in.vob -vf "fieldorder=bff" out.dv
</pre></div>
<a name="fifo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-fifo">8.21 fifo</a></h2>
<p>Buffer input images and send them when they are requested.
</p>
<p>This filter is mainly useful when auto-inserted by the libavfilter
framework.
</p>
<p>The filter does not take parameters.
</p>
<a name="format"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-format">8.22 format</a></h2>
<p>Convert the input video to one of the specified pixel formats.
Libavfilter will try to pick one that is supported for the input to
the next filter.
</p>
<p>The filter accepts a list of pixel format names, separated by ":",
for example "yuv420p:monow:rgb24".
</p>
<p>Some examples follow:
</p><div class="example">
<pre class="example"># convert the input video to the format "yuv420p"
format=yuv420p
# convert the input video to any of the formats in the list
format=yuv420p:yuv444p:yuv410p
</pre></div>
<a name="fps"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-fps">8.23 fps</a></h2>
<p>Convert the video to specified constant framerate by duplicating or dropping
frames as necessary.
</p>
<p>This filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>fps</samp>’</dt>
<dd><p>Desired output framerate. The default is <code>25</code>.
</p>
</dd>
<dt>‘<samp>round</samp>’</dt>
<dd><p>Rounding method.
</p>
<p>Possible values are:
</p><dl compact="compact">
<dt>‘<samp>zero</samp>’</dt>
<dd><p>zero round towards 0
</p></dd>
<dt>‘<samp>inf</samp>’</dt>
<dd><p>round away from 0
</p></dd>
<dt>‘<samp>down</samp>’</dt>
<dd><p>round towards -infinity
</p></dd>
<dt>‘<samp>up</samp>’</dt>
<dd><p>round towards +infinity
</p></dd>
<dt>‘<samp>near</samp>’</dt>
<dd><p>round to nearest
</p></dd>
</dl>
<p>The default is <code>near</code>.
</p>
</dd>
</dl>
<p>Alternatively, the options can be specified as a flat string:
<var>fps</var>[:<var>round</var>].
</p>
<p>See also the <a href="#setpts">setpts</a> filter.
</p>
<a name="framestep"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-framestep">8.24 framestep</a></h2>
<p>Select one frame every N.
</p>
<p>This filter accepts in input a string representing a positive
integer. Default argument is <code>1</code>.
</p>
<p><a name="frei0r"></a>
</p><a name="frei0r-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-frei0r-1">8.25 frei0r</a></h2>
<p>Apply a frei0r effect to the input video.
</p>
<p>To enable compilation of this filter you need to install the frei0r
header and configure FFmpeg with <code>--enable-frei0r</code>.
</p>
<p>The filter supports the syntax:
</p><div class="example">
<pre class="example"><var>filter_name</var>[{:|=}<var>param1</var>:<var>param2</var>:...:<var>paramN</var>]
</pre></div>
<p><var>filter_name</var> is the name of the frei0r effect to load. If the
environment variable <code>FREI0R_PATH</code> is defined, the frei0r effect
is searched in each one of the directories specified by the colon (or
semicolon on Windows platforms) separated list in <code>FREIOR_PATH</code>,
otherwise in the standard frei0r paths, which are in this order:
‘<tt>HOME/.frei0r-1/lib/</tt>’, ‘<tt>/usr/local/lib/frei0r-1/</tt>’,
‘<tt>/usr/lib/frei0r-1/</tt>’.
</p>
<p><var>param1</var>, <var>param2</var>, ... , <var>paramN</var> specify the parameters
for the frei0r effect.
</p>
<p>A frei0r effect parameter can be a boolean (whose values are specified
with "y" and "n"), a double, a color (specified by the syntax
<var>R</var>/<var>G</var>/<var>B</var>, <var>R</var>, <var>G</var>, and <var>B</var> being float
numbers from 0.0 to 1.0) or by an <code>av_parse_color()</code> color
description), a position (specified by the syntax <var>X</var>/<var>Y</var>,
<var>X</var> and <var>Y</var> being float numbers) and a string.
</p>
<p>The number and kind of parameters depend on the loaded effect. If an
effect parameter is not specified the default value is set.
</p>
<p>Some examples follow:
</p>
<ul>
<li>
Apply the distort0r effect, set the first two double parameters:
<div class="example">
<pre class="example">frei0r=distort0r:0.5:0.01
</pre></div>
</li><li>
Apply the colordistance effect, take a color as first parameter:
<div class="example">
<pre class="example">frei0r=colordistance:0.2/0.3/0.4
frei0r=colordistance:violet
frei0r=colordistance:0x112233
</pre></div>
</li><li>
Apply the perspective effect, specify the top left and top right image
positions:
<div class="example">
<pre class="example">frei0r=perspective:0.2/0.2:0.8/0.2
</pre></div>
</li></ul>
<p>For more information see:
<a href="http://frei0r.dyne.org">http://frei0r.dyne.org</a>
</p>
<a name="geq"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-geq">8.26 geq</a></h2>
<p>The filter takes one, two or three equations as parameter, separated by ’:’.
The first equation is mandatory and applies to the luma plane. The two
following are respectively for chroma blue and chroma red planes.
</p>
<p>The filter syntax allows named parameters:
</p>
<dl compact="compact">
<dt>‘<samp>lum_expr</samp>’</dt>
<dd><p>the luminance expression
</p></dd>
<dt>‘<samp>cb_expr</samp>’</dt>
<dd><p>the chrominance blue expression
</p></dd>
<dt>‘<samp>cr_expr</samp>’</dt>
<dd><p>the chrominance red expression
</p></dd>
</dl>
<p>If one of the chrominance expression is not defined, it falls back on the other
one. If none of them are specified, they will evaluate the luminance
expression.
</p>
<p>The expressions can use the following variables and functions:
</p>
<dl compact="compact">
<dt>‘<samp>N</samp>’</dt>
<dd><p>The sequential number of the filtered frame, starting from <code>0</code>.
</p>
</dd>
<dt>‘<samp>X, Y</samp>’</dt>
<dd><p>The coordinates of the current sample.
</p>
</dd>
<dt>‘<samp>W, H</samp>’</dt>
<dd><p>The width and height of the image.
</p>
</dd>
<dt>‘<samp>SW, SH</samp>’</dt>
<dd><p>Width and height scale depending on the currently filtered plane. It is the
ratio between the corresponding luma plane number of pixels and the current
plane ones. E.g. for YUV4:2:0 the values are <code>1,1</code> for the luma plane, and
<code>0.5,0.5</code> for chroma planes.
</p>
</dd>
<dt>‘<samp>T</samp>’</dt>
<dd><p>Time of the current frame, expressed in seconds.
</p>
</dd>
<dt>‘<samp>p(x, y)</samp>’</dt>
<dd><p>Return the value of the pixel at location (<var>x</var>,<var>y</var>) of the current
plane.
</p>
</dd>
<dt>‘<samp>lum(x, y)</samp>’</dt>
<dd><p>Return the value of the pixel at location (<var>x</var>,<var>y</var>) of the luminance
plane.
</p>
</dd>
<dt>‘<samp>cb(x, y)</samp>’</dt>
<dd><p>Return the value of the pixel at location (<var>x</var>,<var>y</var>) of the
blue-difference chroma plane.
</p>
</dd>
<dt>‘<samp>cr(x, y)</samp>’</dt>
<dd><p>Return the value of the pixel at location (<var>x</var>,<var>y</var>) of the
red-difference chroma plane.
</p></dd>
</dl>
<p>For functions, if <var>x</var> and <var>y</var> are outside the area, the value will be
automatically clipped to the closer edge.
</p>
<p>Some examples follow:
</p>
<ul>
<li>
Flip the image horizontally:
<div class="example">
<pre class="example">geq=p(W-X\,Y)
</pre></div>
</li><li>
Generate a bidimensional sine wave, with angle <code>PI/3</code> and a
wavelength of 100 pixels:
<div class="example">
<pre class="example">geq=128 + 100*sin(2*(PI/100)*(cos(PI/3)*(X-50*T) + sin(PI/3)*Y)):128:128
</pre></div>
</li><li>
Generate a fancy enigmatic moving light:
<div class="example">
<pre class="example">nullsrc=s=256x256,geq=random(1)/hypot(X-cos(N*0.07)*W/2-W/2\,Y-sin(N*0.09)*H/2-H/2)^2*1000000*sin(N*0.02):128:128
</pre></div>
</li></ul>
<a name="gradfun"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-gradfun">8.27 gradfun</a></h2>
<p>Fix the banding artifacts that are sometimes introduced into nearly flat
regions by truncation to 8bit color depth.
Interpolate the gradients that should go where the bands are, and
dither them.
</p>
<p>This filter is designed for playback only. Do not use it prior to
lossy compression, because compression tends to lose the dither and
bring back the bands.
</p>
<p>The filter accepts a list of options in the form of <var>key</var>=<var>value</var> pairs
separated by ":". A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>strength</samp>’</dt>
<dd><p>The maximum amount by which the filter will change
any one pixel. Also the threshold for detecting nearly flat
regions. Acceptable values range from <code>0.51</code> to <code>64</code>, default value
is <code>1.2</code>.
</p>
</dd>
<dt>‘<samp>radius</samp>’</dt>
<dd><p>The neighborhood to fit the gradient to. A larger
radius makes for smoother gradients, but also prevents the filter from
modifying the pixels near detailed regions. Acceptable values are
<code>8-32</code>, default value is <code>16</code>.
</p>
</dd>
</dl>
<p>Alternatively, the options can be specified as a flat string:
<var>strength</var>[:<var>radius</var>]
</p>
<a name="Examples-9"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-9">8.27.1 Examples</a></h3>
<ul>
<li>
Apply the filter with a <code>3.5</code> strength and radius of <code>8</code>:
<div class="example">
<pre class="example">gradfun=3.5:8
</pre></div>
</li><li>
Specify radius, omitting the strength (which will fall-back to the default
value):
<div class="example">
<pre class="example">gradfun=radius=8
</pre></div>
</li></ul>
<a name="hflip"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-hflip">8.28 hflip</a></h2>
<p>Flip the input video horizontally.
</p>
<p>For example to horizontally flip the input video with <code>ffmpeg</code>:
</p><div class="example">
<pre class="example">ffmpeg -i in.avi -vf "hflip" out.avi
</pre></div>
<a name="histeq"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-histeq">8.29 histeq</a></h2>
<p>This filter applies a global color histogram equalization on a
per-frame basis.
</p>
<p>It can be used to correct video that has a compressed range of pixel
intensities. The filter redistributes the pixel intensities to
equalize their distribution across the intensity range. It may be
viewed as an "automatically adjusting contrast filter". This filter is
useful only for correcting degraded or poorly captured source
video.
</p>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var>
pairs, separated by ":". If the key of the first options is omitted,
the arguments are interpreted according to syntax
<var>strength</var>:<var>intensity</var>:<var>antibanding</var>.
</p>
<p>This filter accepts the following named options:
</p>
<dl compact="compact">
<dt>‘<samp>strength</samp>’</dt>
<dd><p>Determine the amount of equalization to be applied. As the strength
is reduced, the distribution of pixel intensities more-and-more
approaches that of the input frame. The value must be a float number
in the range [0,1] and defaults to 0.200.
</p>
</dd>
<dt>‘<samp>intensity</samp>’</dt>
<dd><p>Set the maximum intensity that can generated and scale the output
values appropriately. The strength should be set as desired and then
the intensity can be limited if needed to avoid washing-out. The value
must be a float number in the range [0,1] and defaults to 0.210.
</p>
</dd>
<dt>‘<samp>antibanding</samp>’</dt>
<dd><p>Set the antibanding level. If enabled the filter will randomly vary
the luminance of output pixels by a small amount to avoid banding of
the histogram. Possible values are <code>none</code>, <code>weak</code> or
<code>strong</code>. It defaults to <code>none</code>.
</p></dd>
</dl>
<a name="hqdn3d"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-hqdn3d">8.30 hqdn3d</a></h2>
<p>High precision/quality 3d denoise filter. This filter aims to reduce
image noise producing smooth images and making still images really
still. It should enhance compressibility.
</p>
<p>It accepts the following optional parameters:
<var>luma_spatial</var>:<var>chroma_spatial</var>:<var>luma_tmp</var>:<var>chroma_tmp</var>
</p>
<dl compact="compact">
<dt>‘<samp>luma_spatial</samp>’</dt>
<dd><p>a non-negative float number which specifies spatial luma strength,
defaults to 4.0
</p>
</dd>
<dt>‘<samp>chroma_spatial</samp>’</dt>
<dd><p>a non-negative float number which specifies spatial chroma strength,
defaults to 3.0*<var>luma_spatial</var>/4.0
</p>
</dd>
<dt>‘<samp>luma_tmp</samp>’</dt>
<dd><p>a float number which specifies luma temporal strength, defaults to
6.0*<var>luma_spatial</var>/4.0
</p>
</dd>
<dt>‘<samp>chroma_tmp</samp>’</dt>
<dd><p>a float number which specifies chroma temporal strength, defaults to
<var>luma_tmp</var>*<var>chroma_spatial</var>/<var>luma_spatial</var>
</p></dd>
</dl>
<a name="hue"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-hue">8.31 hue</a></h2>
<p>Modify the hue and/or the saturation of the input.
</p>
<p>This filter accepts the following optional named options:
</p>
<dl compact="compact">
<dt>‘<samp>h</samp>’</dt>
<dd><p>Specify the hue angle as a number of degrees. It accepts a float
number or an expression, and defaults to 0.0.
</p>
</dd>
<dt>‘<samp>H</samp>’</dt>
<dd><p>Specify the hue angle as a number of degrees. It accepts a float
number or an expression, and defaults to 0.0.
</p>
</dd>
<dt>‘<samp>s</samp>’</dt>
<dd><p>Specify the saturation in the [-10,10] range. It accepts a float number and
defaults to 1.0.
</p></dd>
</dl>
<p>The <var>h</var>, <var>H</var> and <var>s</var> parameters are expressions containing the
following constants:
</p>
<dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>frame count of the input frame starting from 0
</p>
</dd>
<dt>‘<samp>pts</samp>’</dt>
<dd><p>presentation timestamp of the input frame expressed in time base units
</p>
</dd>
<dt>‘<samp>r</samp>’</dt>
<dd><p>frame rate of the input video, NAN if the input frame rate is unknown
</p>
</dd>
<dt>‘<samp>t</samp>’</dt>
<dd><p>timestamp expressed in seconds, NAN if the input timestamp is unknown
</p>
</dd>
<dt>‘<samp>tb</samp>’</dt>
<dd><p>time base of the input video
</p></dd>
</dl>
<p>The options can also be set using the syntax: <var>hue</var>:<var>saturation</var>
</p>
<p>In this case <var>hue</var> is expressed in degrees.
</p>
<p>Some examples follow:
</p><ul>
<li>
Set the hue to 90 degrees and the saturation to 1.0:
<div class="example">
<pre class="example">hue=h=90:s=1
</pre></div>
</li><li>
Same command but expressing the hue in radians:
<div class="example">
<pre class="example">hue=H=PI/2:s=1
</pre></div>
</li><li>
Same command without named options, hue must be expressed in degrees:
<div class="example">
<pre class="example">hue=90:1
</pre></div>
</li><li>
Note that "h:s" syntax does not support expressions for the values of
h and s, so the following example will issue an error:
<div class="example">
<pre class="example">hue=PI/2:1
</pre></div>
</li><li>
Rotate hue and make the saturation swing between 0
and 2 over a period of 1 second:
<div class="example">
<pre class="example">hue="H=2*PI*t: s=sin(2*PI*t)+1"
</pre></div>
</li><li>
Apply a 3 seconds saturation fade-in effect starting at 0:
<div class="example">
<pre class="example">hue="s=min(t/3\,1)"
</pre></div>
<p>The general fade-in expression can be written as:
</p><div class="example">
<pre class="example">hue="s=min(0\, max((t-START)/DURATION\, 1))"
</pre></div>
</li><li>
Apply a 3 seconds saturation fade-out effect starting at 5 seconds:
<div class="example">
<pre class="example">hue="s=max(0\, min(1\, (8-t)/3))"
</pre></div>
<p>The general fade-out expression can be written as:
</p><div class="example">
<pre class="example">hue="s=max(0\, min(1\, (START+DURATION-t)/DURATION))"
</pre></div>
</li></ul>
<a name="Commands"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Commands">8.31.1 Commands</a></h3>
<p>This filter supports the following command:
</p><dl compact="compact">
<dt>‘<samp>reinit</samp>’</dt>
<dd><p>Modify the hue and/or the saturation of the input video.
The command accepts the same named options and syntax than when calling the
filter from the command-line.
</p>
<p>If a parameter is omitted, it is kept at its current value.
</p></dd>
</dl>
<a name="idet"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-idet">8.32 idet</a></h2>
<p>Interlaceing detect filter. This filter tries to detect if the input is
interlaced or progressive. Top or bottom field first.
</p>
<a name="kerndeint"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-kerndeint">8.33 kerndeint</a></h2>
<p>Deinterlace input video by applying Donald Graft’s adaptive kernel
deinterling. Work on interlaced parts of a video to produce
progressive frames.
</p>
<p>This filter accepts parameters as a list of <var>key</var>=<var>value</var>
pairs, separated by ":". If the key of the first options is omitted,
the arguments are interpreted according to the following syntax:
<var>thresh</var>:<var>map</var>:<var>order</var>:<var>sharp</var>:<var>twoway</var>.
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>thresh</samp>’</dt>
<dd><p>Set the threshold which affects the filter’s tolerance when
determining if a pixel line must be processed. It must be an integer
in the range [0,255] and defaults to 10. A value of 0 will result in
applying the process on every pixels.
</p>
</dd>
<dt>‘<samp>map</samp>’</dt>
<dd><p>Paint pixels exceeding the threshold value to white if set to 1.
Default is 0.
</p>
</dd>
<dt>‘<samp>order</samp>’</dt>
<dd><p>Set the fields order. Swap fields if set to 1, leave fields alone if
0. Default is 0.
</p>
</dd>
<dt>‘<samp>sharp</samp>’</dt>
<dd><p>Enable additional sharpening if set to 1. Default is 0.
</p>
</dd>
<dt>‘<samp>twoway</samp>’</dt>
<dd><p>Enable twoway sharpening if set to 1. Default is 0.
</p></dd>
</dl>
<a name="Examples-15"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-15">8.33.1 Examples</a></h3>
<ul>
<li>
Apply default values:
<div class="example">
<pre class="example">kerndeint=thresh=10:map=0:order=0:sharp=0:twoway=0
</pre></div>
</li><li>
Enable additional sharpening:
<div class="example">
<pre class="example">kerndeint=sharp=1
</pre></div>
</li><li>
Paint processed pixels in white:
<div class="example">
<pre class="example">kerndeint=map=1
</pre></div>
</li></ul>
<a name="lut_002c-lutrgb_002c-lutyuv"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-lut_002c-lutrgb_002c-lutyuv">8.34 lut, lutrgb, lutyuv</a></h2>
<p>Compute a look-up table for binding each pixel component input value
to an output value, and apply it to input video.
</p>
<p><var>lutyuv</var> applies a lookup table to a YUV input video, <var>lutrgb</var>
to an RGB input video.
</p>
<p>These filters accept in input a ":"-separated list of options, which
specify the expressions used for computing the lookup table for the
corresponding pixel component values.
</p>
<p>The <var>lut</var> filter requires either YUV or RGB pixel formats in
input, and accepts the options:
</p><dl compact="compact">
<dt>‘<samp><var>c0</var> (first pixel component)</samp>’</dt>
<dt>‘<samp><var>c1</var> (second pixel component)</samp>’</dt>
<dt>‘<samp><var>c2</var> (third pixel component)</samp>’</dt>
<dt>‘<samp><var>c3</var> (fourth pixel component, corresponds to the alpha component)</samp>’</dt>
</dl>
<p>The exact component associated to each option depends on the format in
input.
</p>
<p>The <var>lutrgb</var> filter requires RGB pixel formats in input, and
accepts the options:
</p><dl compact="compact">
<dt>‘<samp><var>r</var> (red component)</samp>’</dt>
<dt>‘<samp><var>g</var> (green component)</samp>’</dt>
<dt>‘<samp><var>b</var> (blue component)</samp>’</dt>
<dt>‘<samp><var>a</var> (alpha component)</samp>’</dt>
</dl>
<p>The <var>lutyuv</var> filter requires YUV pixel formats in input, and
accepts the options:
</p><dl compact="compact">
<dt>‘<samp><var>y</var> (Y/luminance component)</samp>’</dt>
<dt>‘<samp><var>u</var> (U/Cb component)</samp>’</dt>
<dt>‘<samp><var>v</var> (V/Cr component)</samp>’</dt>
<dt>‘<samp><var>a</var> (alpha component)</samp>’</dt>
</dl>
<p>The expressions can contain the following constants and functions:
</p>
<dl compact="compact">
<dt>‘<samp>w, h</samp>’</dt>
<dd><p>the input width and height
</p>
</dd>
<dt>‘<samp>val</samp>’</dt>
<dd><p>input value for the pixel component
</p>
</dd>
<dt>‘<samp>clipval</samp>’</dt>
<dd><p>the input value clipped in the <var>minval</var>-<var>maxval</var> range
</p>
</dd>
<dt>‘<samp>maxval</samp>’</dt>
<dd><p>maximum value for the pixel component
</p>
</dd>
<dt>‘<samp>minval</samp>’</dt>
<dd><p>minimum value for the pixel component
</p>
</dd>
<dt>‘<samp>negval</samp>’</dt>
<dd><p>the negated value for the pixel component value clipped in the
<var>minval</var>-<var>maxval</var> range , it corresponds to the expression
"maxval-clipval+minval"
</p>
</dd>
<dt>‘<samp>clip(val)</samp>’</dt>
<dd><p>the computed value in <var>val</var> clipped in the
<var>minval</var>-<var>maxval</var> range
</p>
</dd>
<dt>‘<samp>gammaval(gamma)</samp>’</dt>
<dd><p>the computed gamma correction value of the pixel component value
clipped in the <var>minval</var>-<var>maxval</var> range, corresponds to the
expression
"pow((clipval-minval)/(maxval-minval)\,<var>gamma</var>)*(maxval-minval)+minval"
</p>
</dd>
</dl>
<p>All expressions default to "val".
</p>
<p>Some examples follow:
</p><div class="example">
<pre class="example"># negate input video
lutrgb="r=maxval+minval-val:g=maxval+minval-val:b=maxval+minval-val"
lutyuv="y=maxval+minval-val:u=maxval+minval-val:v=maxval+minval-val"
# the above is the same as
lutrgb="r=negval:g=negval:b=negval"
lutyuv="y=negval:u=negval:v=negval"
# negate luminance
lutyuv=y=negval
# remove chroma components, turns the video into a graytone image
lutyuv="u=128:v=128"
# apply a luma burning effect
lutyuv="y=2*val"
# remove green and blue components
lutrgb="g=0:b=0"
# set a constant alpha channel value on input
format=rgba,lutrgb=a="maxval-minval/2"
# correct luminance gamma by a 0.5 factor
lutyuv=y=gammaval(0.5)
</pre></div>
<a name="mp"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-mp">8.35 mp</a></h2>
<p>Apply an MPlayer filter to the input video.
</p>
<p>This filter provides a wrapper around most of the filters of
MPlayer/MEncoder.
</p>
<p>This wrapper is considered experimental. Some of the wrapped filters
may not work properly and we may drop support for them, as they will
be implemented natively into FFmpeg. Thus you should avoid
depending on them when writing portable scripts.
</p>
<p>The filters accepts the parameters:
<var>filter_name</var>[:=]<var>filter_params</var>
</p>
<p><var>filter_name</var> is the name of a supported MPlayer filter,
<var>filter_params</var> is a string containing the parameters accepted by
the named filter.
</p>
<p>The list of the currently supported filters follows:
</p><dl compact="compact">
<dt><var>detc</var></dt>
<dt><var>dint</var></dt>
<dt><var>divtc</var></dt>
<dt><var>down3dright</var></dt>
<dt><var>dsize</var></dt>
<dt><var>eq2</var></dt>
<dt><var>eq</var></dt>
<dt><var>fil</var></dt>
<dt><var>fspp</var></dt>
<dt><var>harddup</var></dt>
<dt><var>il</var></dt>
<dt><var>ilpack</var></dt>
<dt><var>ivtc</var></dt>
<dt><var>kerndeint</var></dt>
<dt><var>mcdeint</var></dt>
<dt><var>noise</var></dt>
<dt><var>ow</var></dt>
<dt><var>perspective</var></dt>
<dt><var>phase</var></dt>
<dt><var>pp7</var></dt>
<dt><var>pullup</var></dt>
<dt><var>qp</var></dt>
<dt><var>sab</var></dt>
<dt><var>softpulldown</var></dt>
<dt><var>softskip</var></dt>
<dt><var>spp</var></dt>
<dt><var>telecine</var></dt>
<dt><var>tinterlace</var></dt>
<dt><var>unsharp</var></dt>
<dt><var>uspp</var></dt>
</dl>
<p>The parameter syntax and behavior for the listed filters are the same
of the corresponding MPlayer filters. For detailed instructions check
the "VIDEO FILTERS" section in the MPlayer manual.
</p>
<p>Some examples follow:
</p><ul>
<li>
Adjust gamma, brightness, contrast:
<div class="example">
<pre class="example">mp=eq2=1.0:2:0.5
</pre></div>
</li><li>
Add temporal noise to input video:
<div class="example">
<pre class="example">mp=noise=20t
</pre></div>
</li></ul>
<p>See also mplayer(1), <a href="http://www.mplayerhq.hu/">http://www.mplayerhq.hu/</a>.
</p>
<a name="negate"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-negate">8.36 negate</a></h2>
<p>Negate input video.
</p>
<p>This filter accepts an integer in input, if non-zero it negates the
alpha component (if available). The default value in input is 0.
</p>
<a name="noformat"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-noformat">8.37 noformat</a></h2>
<p>Force libavfilter not to use any of the specified pixel formats for the
input to the next filter.
</p>
<p>The filter accepts a list of pixel format names, separated by ":",
for example "yuv420p:monow:rgb24".
</p>
<p>Some examples follow:
</p><div class="example">
<pre class="example"># force libavfilter to use a format different from "yuv420p" for the
# input to the vflip filter
noformat=yuv420p,vflip
# convert the input video to any of the formats not contained in the list
noformat=yuv420p:yuv444p:yuv410p
</pre></div>
<a name="null"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-null">8.38 null</a></h2>
<p>Pass the video source unchanged to the output.
</p>
<a name="ocv"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-ocv">8.39 ocv</a></h2>
<p>Apply video transform using libopencv.
</p>
<p>To enable this filter install libopencv library and headers and
configure FFmpeg with <code>--enable-libopencv</code>.
</p>
<p>The filter takes the parameters: <var>filter_name</var>{:=}<var>filter_params</var>.
</p>
<p><var>filter_name</var> is the name of the libopencv filter to apply.
</p>
<p><var>filter_params</var> specifies the parameters to pass to the libopencv
filter. If not specified the default values are assumed.
</p>
<p>Refer to the official libopencv documentation for more precise
information:
<a href="http://opencv.willowgarage.com/documentation/c/image_filtering.html">http://opencv.willowgarage.com/documentation/c/image_filtering.html</a>
</p>
<p>Follows the list of supported libopencv filters.
</p>
<p><a name="dilate"></a>
</p><a name="dilate-1"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-dilate-1">8.39.1 dilate</a></h3>
<p>Dilate an image by using a specific structuring element.
This filter corresponds to the libopencv function <code>cvDilate</code>.
</p>
<p>It accepts the parameters: <var>struct_el</var>:<var>nb_iterations</var>.
</p>
<p><var>struct_el</var> represents a structuring element, and has the syntax:
<var>cols</var>x<var>rows</var>+<var>anchor_x</var>x<var>anchor_y</var>/<var>shape</var>
</p>
<p><var>cols</var> and <var>rows</var> represent the number of columns and rows of
the structuring element, <var>anchor_x</var> and <var>anchor_y</var> the anchor
point, and <var>shape</var> the shape for the structuring element, and
can be one of the values "rect", "cross", "ellipse", "custom".
</p>
<p>If the value for <var>shape</var> is "custom", it must be followed by a
string of the form "=<var>filename</var>". The file with name
<var>filename</var> is assumed to represent a binary image, with each
printable character corresponding to a bright pixel. When a custom
<var>shape</var> is used, <var>cols</var> and <var>rows</var> are ignored, the number
or columns and rows of the read file are assumed instead.
</p>
<p>The default value for <var>struct_el</var> is "3x3+0x0/rect".
</p>
<p><var>nb_iterations</var> specifies the number of times the transform is
applied to the image, and defaults to 1.
</p>
<p>Follow some example:
</p><div class="example">
<pre class="example"># use the default values
ocv=dilate
# dilate using a structuring element with a 5x5 cross, iterate two times
ocv=dilate=5x5+2x2/cross:2
# read the shape from the file diamond.shape, iterate two times
# the file diamond.shape may contain a pattern of characters like this:
# *
# ***
# *****
# ***
# *
# the specified cols and rows are ignored (but not the anchor point coordinates)
ocv=0x0+2x2/custom=diamond.shape:2
</pre></div>
<a name="erode"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-erode">8.39.2 erode</a></h3>
<p>Erode an image by using a specific structuring element.
This filter corresponds to the libopencv function <code>cvErode</code>.
</p>
<p>The filter accepts the parameters: <var>struct_el</var>:<var>nb_iterations</var>,
with the same syntax and semantics as the <a href="#dilate">dilate</a> filter.
</p>
<a name="smooth"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-smooth">8.39.3 smooth</a></h3>
<p>Smooth the input video.
</p>
<p>The filter takes the following parameters:
<var>type</var>:<var>param1</var>:<var>param2</var>:<var>param3</var>:<var>param4</var>.
</p>
<p><var>type</var> is the type of smooth filter to apply, and can be one of
the following values: "blur", "blur_no_scale", "median", "gaussian",
"bilateral". The default value is "gaussian".
</p>
<p><var>param1</var>, <var>param2</var>, <var>param3</var>, and <var>param4</var> are
parameters whose meanings depend on smooth type. <var>param1</var> and
<var>param2</var> accept integer positive values or 0, <var>param3</var> and
<var>param4</var> accept float values.
</p>
<p>The default value for <var>param1</var> is 3, the default value for the
other parameters is 0.
</p>
<p>These parameters correspond to the parameters assigned to the
libopencv function <code>cvSmooth</code>.
</p>
<p><a name="overlay"></a>
</p><a name="overlay-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-overlay-1">8.40 overlay</a></h2>
<p>Overlay one video on top of another.
</p>
<p>It takes two inputs and one output, the first input is the "main"
video on which the second input is overlayed.
</p>
<p>This filter accepts a list of <var>key</var>=<var>value</var> pairs as argument,
separated by ":". If the key of the first options is omitted, the
arguments are interpreted according to the syntax <var>x</var>:<var>y</var>.
</p>
<p>A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>Set the expression for the x and y coordinates of the overlayed video
on the main video. Default value is 0.
</p>
<p>The <var>x</var> and <var>y</var> expressions can contain the following
parameters:
</p><dl compact="compact">
<dt>‘<samp>main_w, main_h</samp>’</dt>
<dd><p>main input width and height
</p>
</dd>
<dt>‘<samp>W, H</samp>’</dt>
<dd><p>same as <var>main_w</var> and <var>main_h</var>
</p>
</dd>
<dt>‘<samp>overlay_w, overlay_h</samp>’</dt>
<dd><p>overlay input width and height
</p>
</dd>
<dt>‘<samp>w, h</samp>’</dt>
<dd><p>same as <var>overlay_w</var> and <var>overlay_h</var>
</p></dd>
</dl>
</dd>
<dt>‘<samp>rgb</samp>’</dt>
<dd><p>If set to 1, force the filter to accept inputs in the RGB
color space. Default value is 0.
</p></dd>
</dl>
<p>Be aware that frames are taken from each input video in timestamp
order, hence, if their initial timestamps differ, it is a a good idea
to pass the two inputs through a <var>setpts=PTS-STARTPTS</var> filter to
have them begin in the same zero timestamp, as it does the example for
the <var>movie</var> filter.
</p>
<p>You can chain together more overlays but you should test the
efficiency of such approach.
</p>
<a name="Examples-7"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-7">8.40.1 Examples</a></h3>
<ul>
<li>
Draw the overlay at 10 pixels from the bottom right corner of the main
video:
<div class="example">
<pre class="example">overlay=main_w-overlay_w-10:main_h-overlay_h-10
</pre></div>
<p>Using named options the example above becomes:
</p><div class="example">
<pre class="example">overlay=x=main_w-overlay_w-10:y=main_h-overlay_h-10
</pre></div>
</li><li>
Insert a transparent PNG logo in the bottom left corner of the input,
using the <code>ffmpeg</code> tool with the <code>-filter_complex</code> option:
<div class="example">
<pre class="example">ffmpeg -i input -i logo -filter_complex 'overlay=10:main_h-overlay_h-10' output
</pre></div>
</li><li>
Insert 2 different transparent PNG logos (second logo on bottom
right corner) using the <code>ffmpeg</code> tool:
<div class="example">
<pre class="example">ffmpeg -i input -i logo1 -i logo2 -filter_complex 'overlay=10:H-h-10,overlay=W-w-10:H-h-10' output
</pre></div>
</li><li>
Add a transparent color layer on top of the main video, WxH specifies
the size of the main input to the overlay filter:
<div class="example">
<pre class="example">color=red@.3:WxH [over]; [in][over] overlay [out]
</pre></div>
</li><li>
Play an original video and a filtered version (here with the deshake
filter) side by side using the <code>ffplay</code> tool:
<div class="example">
<pre class="example">ffplay input.avi -vf 'split[a][b]; [a]pad=iw*2:ih[src]; [b]deshake[filt]; [src][filt]overlay=w'
</pre></div>
<p>The above command is the same as:
</p><div class="example">
<pre class="example">ffplay input.avi -vf 'split[b], pad=iw*2[src], [b]deshake, [src]overlay=w'
</pre></div>
</li><li>
Chain several overlays in cascade:
<div class="example">
<pre class="example">nullsrc=s=200x200 [bg];
testsrc=s=100x100, split=4 [in0][in1][in2][in3];
[in0] lutrgb=r=0, [bg] overlay=0:0 [mid0];
[in1] lutrgb=g=0, [mid0] overlay=100:0 [mid1];
[in2] lutrgb=b=0, [mid1] overlay=0:100 [mid2];
[in3] null, [mid2] overlay=100:100 [out0]
</pre></div>
</li></ul>
<a name="pad"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-pad">8.41 pad</a></h2>
<p>Add paddings to the input image, and places the original input at the
given coordinates <var>x</var>, <var>y</var>.
</p>
<p>It accepts the following parameters:
<var>width</var>:<var>height</var>:<var>x</var>:<var>y</var>:<var>color</var>.
</p>
<p>The parameters <var>width</var>, <var>height</var>, <var>x</var>, and <var>y</var> are
expressions containing the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>in_w, in_h</samp>’</dt>
<dd><p>the input video width and height
</p>
</dd>
<dt>‘<samp>iw, ih</samp>’</dt>
<dd><p>same as <var>in_w</var> and <var>in_h</var>
</p>
</dd>
<dt>‘<samp>out_w, out_h</samp>’</dt>
<dd><p>the output width and height, that is the size of the padded area as
specified by the <var>width</var> and <var>height</var> expressions
</p>
</dd>
<dt>‘<samp>ow, oh</samp>’</dt>
<dd><p>same as <var>out_w</var> and <var>out_h</var>
</p>
</dd>
<dt>‘<samp>x, y</samp>’</dt>
<dd><p>x and y offsets as specified by the <var>x</var> and <var>y</var>
expressions, or NAN if not yet specified
</p>
</dd>
<dt>‘<samp>a</samp>’</dt>
<dd><p>same as <var>iw</var> / <var>ih</var>
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>input sample aspect ratio
</p>
</dd>
<dt>‘<samp>dar</samp>’</dt>
<dd><p>input display aspect ratio, it is the same as (<var>iw</var> / <var>ih</var>) * <var>sar</var>
</p>
</dd>
<dt>‘<samp>hsub, vsub</samp>’</dt>
<dd><p>horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>Follows the description of the accepted parameters.
</p>
<dl compact="compact">
<dt>‘<samp>width, height</samp>’</dt>
<dd>
<p>Specify the size of the output image with the paddings added. If the
value for <var>width</var> or <var>height</var> is 0, the corresponding input size
is used for the output.
</p>
<p>The <var>width</var> expression can reference the value set by the
<var>height</var> expression, and vice versa.
</p>
<p>The default value of <var>width</var> and <var>height</var> is 0.
</p>
</dd>
<dt>‘<samp>x, y</samp>’</dt>
<dd>
<p>Specify the offsets where to place the input image in the padded area
with respect to the top/left border of the output image.
</p>
<p>The <var>x</var> expression can reference the value set by the <var>y</var>
expression, and vice versa.
</p>
<p>The default value of <var>x</var> and <var>y</var> is 0.
</p>
</dd>
<dt>‘<samp>color</samp>’</dt>
<dd>
<p>Specify the color of the padded area, it can be the name of a color
(case insensitive match) or a 0xRRGGBB[AA] sequence.
</p>
<p>The default value of <var>color</var> is "black".
</p>
</dd>
</dl>
<a name="Examples-8"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-8">8.41.1 Examples</a></h3>
<ul>
<li>
Add paddings with color "violet" to the input video. Output video
size is 640x480, the top-left corner of the input video is placed at
column 0, row 40:
<div class="example">
<pre class="example">pad=640:480:0:40:violet
</pre></div>
</li><li>
Pad the input to get an output with dimensions increased by 3/2,
and put the input video at the center of the padded area:
<div class="example">
<pre class="example">pad="3/2*iw:3/2*ih:(ow-iw)/2:(oh-ih)/2"
</pre></div>
</li><li>
Pad the input to get a squared output with size equal to the maximum
value between the input width and height, and put the input video at
the center of the padded area:
<div class="example">
<pre class="example">pad="max(iw\,ih):ow:(ow-iw)/2:(oh-ih)/2"
</pre></div>
</li><li>
Pad the input to get a final w/h ratio of 16:9:
<div class="example">
<pre class="example">pad="ih*16/9:ih:(ow-iw)/2:(oh-ih)/2"
</pre></div>
</li><li>
In case of anamorphic video, in order to set the output display aspect
correctly, it is necessary to use <var>sar</var> in the expression,
according to the relation:
<div class="example">
<pre class="example">(ih * X / ih) * sar = output_dar
X = output_dar / sar
</pre></div>
<p>Thus the previous example needs to be modified to:
</p><div class="example">
<pre class="example">pad="ih*16/9/sar:ih:(ow-iw)/2:(oh-ih)/2"
</pre></div>
</li><li>
Double output size and put the input video in the bottom-right
corner of the output padded area:
<div class="example">
<pre class="example">pad="2*iw:2*ih:ow-iw:oh-ih"
</pre></div>
</li></ul>
<a name="pixdesctest"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-pixdesctest">8.42 pixdesctest</a></h2>
<p>Pixel format descriptor test filter, mainly useful for internal
testing. The output video should be equal to the input video.
</p>
<p>For example:
</p><div class="example">
<pre class="example">format=monow, pixdesctest
</pre></div>
<p>can be used to test the monowhite pixel format descriptor definition.
</p>
<a name="pp"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-pp">8.43 pp</a></h2>
<p>Enable the specified chain of postprocessing subfilters using libpostproc. This
library should be automatically selected with a GPL build (<code>--enable-gpl</code>).
Subfilters must be separated by ’/’ and can be disabled by prepending a ’-’.
Each subfilter and some options have a short and a long name that can be used
interchangeably, i.e. dr/dering are the same.
</p>
<p>All subfilters share common options to determine their scope:
</p>
<dl compact="compact">
<dt>‘<samp>a/autoq</samp>’</dt>
<dd><p>Honor the quality commands for this subfilter.
</p>
</dd>
<dt>‘<samp>c/chrom</samp>’</dt>
<dd><p>Do chrominance filtering, too (default).
</p>
</dd>
<dt>‘<samp>y/nochrom</samp>’</dt>
<dd><p>Do luminance filtering only (no chrominance).
</p>
</dd>
<dt>‘<samp>n/noluma</samp>’</dt>
<dd><p>Do chrominance filtering only (no luminance).
</p></dd>
</dl>
<p>These options can be appended after the subfilter name, separated by a ’:’.
</p>
<p>Available subfilters are:
</p>
<dl compact="compact">
<dt>‘<samp>hb/hdeblock[:difference[:flatness]]</samp>’</dt>
<dd><p>Horizontal deblocking filter
</p><dl compact="compact">
<dt>‘<samp>difference</samp>’</dt>
<dd><p>Difference factor where higher values mean more deblocking (default: <code>32</code>).
</p></dd>
<dt>‘<samp>flatness</samp>’</dt>
<dd><p>Flatness threshold where lower values mean more deblocking (default: <code>39</code>).
</p></dd>
</dl>
</dd>
<dt>‘<samp>vb/vdeblock[:difference[:flatness]]</samp>’</dt>
<dd><p>Vertical deblocking filter
</p><dl compact="compact">
<dt>‘<samp>difference</samp>’</dt>
<dd><p>Difference factor where higher values mean more deblocking (default: <code>32</code>).
</p></dd>
<dt>‘<samp>flatness</samp>’</dt>
<dd><p>Flatness threshold where lower values mean more deblocking (default: <code>39</code>).
</p></dd>
</dl>
</dd>
<dt>‘<samp>ha/hadeblock[:difference[:flatness]]</samp>’</dt>
<dd><p>Accurate horizontal deblocking filter
</p><dl compact="compact">
<dt>‘<samp>difference</samp>’</dt>
<dd><p>Difference factor where higher values mean more deblocking (default: <code>32</code>).
</p></dd>
<dt>‘<samp>flatness</samp>’</dt>
<dd><p>Flatness threshold where lower values mean more deblocking (default: <code>39</code>).
</p></dd>
</dl>
</dd>
<dt>‘<samp>va/vadeblock[:difference[:flatness]]</samp>’</dt>
<dd><p>Accurate vertical deblocking filter
</p><dl compact="compact">
<dt>‘<samp>difference</samp>’</dt>
<dd><p>Difference factor where higher values mean more deblocking (default: <code>32</code>).
</p></dd>
<dt>‘<samp>flatness</samp>’</dt>
<dd><p>Flatness threshold where lower values mean more deblocking (default: <code>39</code>).
</p></dd>
</dl>
</dd>
</dl>
<p>The horizontal and vertical deblocking filters share the difference and
flatness values so you cannot set different horizontal and vertical
thresholds.
</p>
<dl compact="compact">
<dt>‘<samp>h1/x1hdeblock</samp>’</dt>
<dd><p>Experimental horizontal deblocking filter
</p>
</dd>
<dt>‘<samp>v1/x1vdeblock</samp>’</dt>
<dd><p>Experimental vertical deblocking filter
</p>
</dd>
<dt>‘<samp>dr/dering</samp>’</dt>
<dd><p>Deringing filter
</p>
</dd>
<dt>‘<samp>tn/tmpnoise[:threshold1[:threshold2[:threshold3]]], temporal noise reducer</samp>’</dt>
<dd><dl compact="compact">
<dt>‘<samp>threshold1</samp>’</dt>
<dd><p>larger -> stronger filtering
</p></dd>
<dt>‘<samp>threshold2</samp>’</dt>
<dd><p>larger -> stronger filtering
</p></dd>
<dt>‘<samp>threshold3</samp>’</dt>
<dd><p>larger -> stronger filtering
</p></dd>
</dl>
</dd>
<dt>‘<samp>al/autolevels[:f/fullyrange], automatic brightness / contrast correction</samp>’</dt>
<dd><dl compact="compact">
<dt>‘<samp>f/fullyrange</samp>’</dt>
<dd><p>Stretch luminance to <code>0-255</code>.
</p></dd>
</dl>
</dd>
<dt>‘<samp>lb/linblenddeint</samp>’</dt>
<dd><p>Linear blend deinterlacing filter that deinterlaces the given block by
filtering all lines with a <code>(1 2 1)</code> filter.
</p>
</dd>
<dt>‘<samp>li/linipoldeint</samp>’</dt>
<dd><p>Linear interpolating deinterlacing filter that deinterlaces the given block by
linearly interpolating every second line.
</p>
</dd>
<dt>‘<samp>ci/cubicipoldeint</samp>’</dt>
<dd><p>Cubic interpolating deinterlacing filter deinterlaces the given block by
cubically interpolating every second line.
</p>
</dd>
<dt>‘<samp>md/mediandeint</samp>’</dt>
<dd><p>Median deinterlacing filter that deinterlaces the given block by applying a
median filter to every second line.
</p>
</dd>
<dt>‘<samp>fd/ffmpegdeint</samp>’</dt>
<dd><p>FFmpeg deinterlacing filter that deinterlaces the given block by filtering every
second line with a <code>(-1 4 2 4 -1)</code> filter.
</p>
</dd>
<dt>‘<samp>l5/lowpass5</samp>’</dt>
<dd><p>Vertically applied FIR lowpass deinterlacing filter that deinterlaces the given
block by filtering all lines with a <code>(-1 2 6 2 -1)</code> filter.
</p>
</dd>
<dt>‘<samp>fq/forceQuant[:quantizer]</samp>’</dt>
<dd><p>Overrides the quantizer table from the input with the constant quantizer you
specify.
</p><dl compact="compact">
<dt>‘<samp>quantizer</samp>’</dt>
<dd><p>Quantizer to use
</p></dd>
</dl>
</dd>
<dt>‘<samp>de/default</samp>’</dt>
<dd><p>Default pp filter combination (<code>hb:a,vb:a,dr:a</code>)
</p>
</dd>
<dt>‘<samp>fa/fast</samp>’</dt>
<dd><p>Fast pp filter combination (<code>h1:a,v1:a,dr:a</code>)
</p>
</dd>
<dt>‘<samp>ac</samp>’</dt>
<dd><p>High quality pp filter combination (<code>ha:a:128:7,va:a,dr:a</code>)
</p></dd>
</dl>
<a name="Examples-3"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-3">8.43.1 Examples</a></h3>
<ul>
<li>
Apply horizontal and vertical deblocking, deringing and automatic
brightness/contrast:
<div class="example">
<pre class="example">pp=hb/vb/dr/al
</pre></div>
</li><li>
Apply default filters without brightness/contrast correction:
<div class="example">
<pre class="example">pp=de/-al
</pre></div>
</li><li>
Apply default filters and temporal denoiser:
<div class="example">
<pre class="example">pp=default/tmpnoise:1:2:3
</pre></div>
</li><li>
Apply deblocking on luminance only, and switch vertical deblocking on or off
automatically depending on available CPU time:
<div class="example">
<pre class="example">pp=hb:y/vb:a
</pre></div>
</li></ul>
<a name="removelogo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-removelogo">8.44 removelogo</a></h2>
<p>Suppress a TV station logo, using an image file to determine which
pixels comprise the logo. It works by filling in the pixels that
comprise the logo with neighboring pixels.
</p>
<p>This filter requires one argument which specifies the filter bitmap
file, which can be any image format supported by libavformat. The
width and height of the image file must match those of the video
stream being processed.
</p>
<p>Pixels in the provided bitmap image with a value of zero are not
considered part of the logo, non-zero pixels are considered part of
the logo. If you use white (255) for the logo and black (0) for the
rest, you will be safe. For making the filter bitmap, it is
recommended to take a screen capture of a black frame with the logo
visible, and then using a threshold filter followed by the erode
filter once or twice.
</p>
<p>If needed, little splotches can be fixed manually. Remember that if
logo pixels are not covered, the filter quality will be much
reduced. Marking too many pixels as part of the logo does not hurt as
much, but it will increase the amount of blurring needed to cover over
the image and will destroy more information than necessary, and extra
pixels will slow things down on a large logo.
</p>
<a name="scale"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-scale">8.45 scale</a></h2>
<p>Scale (resize) the input video, using the libswscale library.
</p>
<p>The scale filter forces the output display aspect ratio to be the same
of the input, by changing the output sample aspect ratio.
</p>
<p>This filter accepts a list of named options in the form of
<var>key</var>=<var>value</var> pairs separated by ":". If the key for the first
two options is not specified, the assumed keys for the first two
values are <code>w</code> and <code>h</code>. If the first option has no key and
can be interpreted like a video size specification, it will be used
to set the video size.
</p>
<p>A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>width, w</samp>’</dt>
<dd><p>Set the video width expression, default value is <code>iw</code>. See below
for the list of accepted constants.
</p>
</dd>
<dt>‘<samp>height, h</samp>’</dt>
<dd><p>Set the video heiht expression, default value is <code>ih</code>.
See below for the list of accepted constants.
</p>
</dd>
<dt>‘<samp>interl</samp>’</dt>
<dd><p>Set the interlacing. It accepts the following values:
</p>
<dl compact="compact">
<dt>‘<samp>1</samp>’</dt>
<dd><p>force interlaced aware scaling
</p>
</dd>
<dt>‘<samp>0</samp>’</dt>
<dd><p>do not apply interlaced scaling
</p>
</dd>
<dt>‘<samp>-1</samp>’</dt>
<dd><p>select interlaced aware scaling depending on whether the source frames
are flagged as interlaced or not
</p></dd>
</dl>
<p>Default value is <code>0</code>.
</p>
</dd>
<dt>‘<samp>flags</samp>’</dt>
<dd><p>Set libswscale scaling flags. If not explictly specified the filter
applies a bilinear scaling algorithm.
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Set the video size, the value must be a valid abbreviation or in the
form <var>width</var>x<var>height</var>.
</p></dd>
</dl>
<p>The values of the <var>w</var> and <var>h</var> options are expressions
containing the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>in_w, in_h</samp>’</dt>
<dd><p>the input width and height
</p>
</dd>
<dt>‘<samp>iw, ih</samp>’</dt>
<dd><p>same as <var>in_w</var> and <var>in_h</var>
</p>
</dd>
<dt>‘<samp>out_w, out_h</samp>’</dt>
<dd><p>the output (cropped) width and height
</p>
</dd>
<dt>‘<samp>ow, oh</samp>’</dt>
<dd><p>same as <var>out_w</var> and <var>out_h</var>
</p>
</dd>
<dt>‘<samp>a</samp>’</dt>
<dd><p>same as <var>iw</var> / <var>ih</var>
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>input sample aspect ratio
</p>
</dd>
<dt>‘<samp>dar</samp>’</dt>
<dd><p>input display aspect ratio, it is the same as (<var>iw</var> / <var>ih</var>) * <var>sar</var>
</p>
</dd>
<dt>‘<samp>hsub, vsub</samp>’</dt>
<dd><p>horizontal and vertical chroma subsample values. For example for the
pixel format "yuv422p" <var>hsub</var> is 2 and <var>vsub</var> is 1.
</p></dd>
</dl>
<p>If the input image format is different from the format requested by
the next filter, the scale filter will convert the input to the
requested format.
</p>
<p>If the value for <var>width</var> or <var>height</var> is 0, the respective input
size is used for the output.
</p>
<p>If the value for <var>width</var> or <var>height</var> is -1, the scale filter will
use, for the respective output size, a value that maintains the aspect
ratio of the input image.
</p>
<a name="Examples-6"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-6">8.45.1 Examples</a></h3>
<ul>
<li>
Scale the input video to a size of 200x100:
<div class="example">
<pre class="example">scale=200:100
</pre></div>
<p>This is equivalent to:
</p><div class="example">
<pre class="example">scale=w=200:h=100
</pre></div>
<p>or:
</p><div class="example">
<pre class="example">scale=200x100
</pre></div>
</li><li>
Specify a size abbreviation for the output size:
<div class="example">
<pre class="example">scale=qcif
</pre></div>
<p>which can also be written as:
</p><div class="example">
<pre class="example">scale=size=qcif
</pre></div>
</li><li>
Scale the input to 2x:
<div class="example">
<pre class="example">scale=2*iw:2*ih
</pre></div>
</li><li>
The above is the same as:
<div class="example">
<pre class="example">scale=2*in_w:2*in_h
</pre></div>
</li><li>
Scale the input to 2x with forced interlaced scaling:
<div class="example">
<pre class="example">scale=2*iw:2*ih:interl=1
</pre></div>
</li><li>
Scale the input to half size:
<div class="example">
<pre class="example">scale=iw/2:ih/2
</pre></div>
</li><li>
Increase the width, and set the height to the same size:
<div class="example">
<pre class="example">scale=3/2*iw:ow
</pre></div>
</li><li>
Seek for Greek harmony:
<div class="example">
<pre class="example">scale=iw:1/PHI*iw
scale=ih*PHI:ih
</pre></div>
</li><li>
Increase the height, and set the width to 3/2 of the height:
<div class="example">
<pre class="example">scale=3/2*oh:3/5*ih
</pre></div>
</li><li>
Increase the size, but make the size a multiple of the chroma:
<div class="example">
<pre class="example">scale="trunc(3/2*iw/hsub)*hsub:trunc(3/2*ih/vsub)*vsub"
</pre></div>
</li><li>
Increase the width to a maximum of 500 pixels, keep the same input
aspect ratio:
<div class="example">
<pre class="example">scale='min(500\, iw*3/2):-1'
</pre></div>
</li></ul>
<a name="setdar_002c-setsar"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-setdar_002c-setsar">8.46 setdar, setsar</a></h2>
<p>The <code>setdar</code> filter sets the Display Aspect Ratio for the filter
output video.
</p>
<p>This is done by changing the specified Sample (aka Pixel) Aspect
Ratio, according to the following equation:
</p><div class="example">
<pre class="example"><var>DAR</var> = <var>HORIZONTAL_RESOLUTION</var> / <var>VERTICAL_RESOLUTION</var> * <var>SAR</var>
</pre></div>
<p>Keep in mind that the <code>setdar</code> filter does not modify the pixel
dimensions of the video frame. Also the display aspect ratio set by
this filter may be changed by later filters in the filterchain,
e.g. in case of scaling or if another "setdar" or a "setsar" filter is
applied.
</p>
<p>The <code>setsar</code> filter sets the Sample (aka Pixel) Aspect Ratio for
the filter output video.
</p>
<p>Note that as a consequence of the application of this filter, the
output display aspect ratio will change according to the equation
above.
</p>
<p>Keep in mind that the sample aspect ratio set by the <code>setsar</code>
filter may be changed by later filters in the filterchain, e.g. if
another "setsar" or a "setdar" filter is applied.
</p>
<p>The <code>setdar</code> and <code>setsar</code> filters accept a string in the
form <var>num</var>:<var>den</var> expressing an aspect ratio, or the following
named options, expressed as a sequence of <var>key</var>=<var>value</var> pairs,
separated by ":".
</p>
<dl compact="compact">
<dt>‘<samp>max</samp>’</dt>
<dd><p>Set the maximum integer value to use for expressing numerator and
denominator when reducing the expressed aspect ratio to a rational.
Default value is <code>100</code>.
</p>
</dd>
<dt>‘<samp>r, ratio:</samp>’</dt>
<dd><p>Set the aspect ratio used by the filter.
</p>
<p>The parameter can be a floating point number string, an expression, or
a string of the form <var>num</var>:<var>den</var>, where <var>num</var> and
<var>den</var> are the numerator and denominator of the aspect ratio. If
the parameter is not specified, it is assumed the value "0".
In case the form "<var>num</var>:<var>den</var>" the <code>:</code> character should
be escaped.
</p></dd>
</dl>
<p>If the keys are omitted in the named options list, the specifed values
are assumed to be <var>ratio</var> and <var>max</var> in that order.
</p>
<p>For example to change the display aspect ratio to 16:9, specify:
</p><div class="example">
<pre class="example">setdar='16:9'
</pre></div>
<p>The example above is equivalent to:
</p><div class="example">
<pre class="example">setdar=1.77777
</pre></div>
<p>To change the sample aspect ratio to 10:11, specify:
</p><div class="example">
<pre class="example">setsar='10:11'
</pre></div>
<p>To set a display aspect ratio of 16:9, and specify a maximum integer value of
1000 in the aspect ratio reduction, use the command:
</p><div class="example">
<pre class="example">setdar=ratio='16:9':max=1000
</pre></div>
<a name="setfield"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-setfield">8.47 setfield</a></h2>
<p>Force field for the output video frame.
</p>
<p>The <code>setfield</code> filter marks the interlace type field for the
output frames. It does not change the input frame, but only sets the
corresponding property, which affects how the frame is treated by
following filters (e.g. <code>fieldorder</code> or <code>yadif</code>).
</p>
<p>This filter accepts a single option ‘<samp>mode</samp>’, which can be
specified either by setting <code>mode=VALUE</code> or setting the value
alone. Available values are:
</p>
<dl compact="compact">
<dt>‘<samp>auto</samp>’</dt>
<dd><p>Keep the same field property.
</p>
</dd>
<dt>‘<samp>bff</samp>’</dt>
<dd><p>Mark the frame as bottom-field-first.
</p>
</dd>
<dt>‘<samp>tff</samp>’</dt>
<dd><p>Mark the frame as top-field-first.
</p>
</dd>
<dt>‘<samp>prog</samp>’</dt>
<dd><p>Mark the frame as progressive.
</p></dd>
</dl>
<a name="showinfo"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-showinfo">8.48 showinfo</a></h2>
<p>Show a line containing various information for each input video frame.
The input video is not modified.
</p>
<p>The shown line contains a sequence of key/value pairs of the form
<var>key</var>:<var>value</var>.
</p>
<p>A description of each shown parameter follows:
</p>
<dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>sequential number of the input frame, starting from 0
</p>
</dd>
<dt>‘<samp>pts</samp>’</dt>
<dd><p>Presentation TimeStamp of the input frame, expressed as a number of
time base units. The time base unit depends on the filter input pad.
</p>
</dd>
<dt>‘<samp>pts_time</samp>’</dt>
<dd><p>Presentation TimeStamp of the input frame, expressed as a number of
seconds
</p>
</dd>
<dt>‘<samp>pos</samp>’</dt>
<dd><p>position of the frame in the input stream, -1 if this information in
unavailable and/or meaningless (for example in case of synthetic video)
</p>
</dd>
<dt>‘<samp>fmt</samp>’</dt>
<dd><p>pixel format name
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>sample aspect ratio of the input frame, expressed in the form
<var>num</var>/<var>den</var>
</p>
</dd>
<dt>‘<samp>s</samp>’</dt>
<dd><p>size of the input frame, expressed in the form
<var>width</var>x<var>height</var>
</p>
</dd>
<dt>‘<samp>i</samp>’</dt>
<dd><p>interlaced mode ("P" for "progressive", "T" for top field first, "B"
for bottom field first)
</p>
</dd>
<dt>‘<samp>iskey</samp>’</dt>
<dd><p>1 if the frame is a key frame, 0 otherwise
</p>
</dd>
<dt>‘<samp>type</samp>’</dt>
<dd><p>picture type of the input frame ("I" for an I-frame, "P" for a
P-frame, "B" for a B-frame, "?" for unknown type).
Check also the documentation of the <code>AVPictureType</code> enum and of
the <code>av_get_picture_type_char</code> function defined in
‘<tt>libavutil/avutil.h</tt>’.
</p>
</dd>
<dt>‘<samp>checksum</samp>’</dt>
<dd><p>Adler-32 checksum (printed in hexadecimal) of all the planes of the input frame
</p>
</dd>
<dt>‘<samp>plane_checksum</samp>’</dt>
<dd><p>Adler-32 checksum (printed in hexadecimal) of each plane of the input frame,
expressed in the form "[<var>c0</var> <var>c1</var> <var>c2</var> <var>c3</var>]"
</p></dd>
</dl>
<a name="smartblur"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-smartblur">8.49 smartblur</a></h2>
<p>Blur the input video without impacting the outlines.
</p>
<p>The filter accepts the following parameters:
<var>luma_radius</var>:<var>luma_strength</var>:<var>luma_threshold</var>[:<var>chroma_radius</var>:<var>chroma_strength</var>:<var>chroma_threshold</var>]
</p>
<p>Parameters prefixed by <var>luma</var> indicate that they work on the
luminance of the pixels whereas parameters prefixed by <var>chroma</var>
refer to the chrominance of the pixels.
</p>
<p>If the chroma parameters are not set, the luma parameters are used for
either the luminance and the chrominance of the pixels.
</p>
<p><var>luma_radius</var> or <var>chroma_radius</var> must be a float number in the
range [0.1,5.0] that specifies the variance of the gaussian filter
used to blur the image (slower if larger).
</p>
<p><var>luma_strength</var> or <var>chroma_strength</var> must be a float number in
the range [-1.0,1.0] that configures the blurring. A value included in
[0.0,1.0] will blur the image whereas a value included in [-1.0,0.0]
will sharpen the image.
</p>
<p><var>luma_threshold</var> or <var>chroma_threshold</var> must be an integer in
the range [-30,30] that is used as a coefficient to determine whether
a pixel should be blurred or not. A value of 0 will filter all the
image, a value included in [0,30] will filter flat areas and a value
included in [-30,0] will filter edges.
</p>
<p><a name="subtitles"></a>
</p><a name="subtitles-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-subtitles-1">8.50 subtitles</a></h2>
<p>Draw subtitles on top of input video using the libass library.
</p>
<p>To enable compilation of this filter you need to configure FFmpeg with
<code>--enable-libass</code>. This filter also requires a build with libavcodec and
libavformat to convert the passed subtitles file to ASS (Advanced Substation
Alpha) subtitles format.
</p>
<p>This filter accepts the following named options, expressed as a
sequence of <var>key</var>=<var>value</var> pairs, separated by ":".
</p>
<dl compact="compact">
<dt>‘<samp>filename, f</samp>’</dt>
<dd><p>Set the filename of the subtitle file to read. It must be specified.
</p>
</dd>
<dt>‘<samp>original_size</samp>’</dt>
<dd><p>Specify the size of the original video, the video for which the ASS file
was composed. Due to a misdesign in ASS aspect ratio arithmetic, this is
necessary to correctly scale the fonts if the aspect ratio has been changed.
</p></dd>
</dl>
<p>If the first key is not specified, it is assumed that the first value
specifies the ‘<samp>filename</samp>’.
</p>
<p>For example, to render the file ‘<tt>sub.srt</tt>’ on top of the input
video, use the command:
</p><div class="example">
<pre class="example">subtitles=sub.srt
</pre></div>
<p>which is equivalent to:
</p><div class="example">
<pre class="example">subtitles=filename=sub.srt
</pre></div>
<a name="split"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-split">8.51 split</a></h2>
<p>Split input video into several identical outputs.
</p>
<p>The filter accepts a single parameter which specifies the number of outputs. If
unspecified, it defaults to 2.
</p>
<p>For example
</p><div class="example">
<pre class="example">ffmpeg -i INPUT -filter_complex split=5 OUTPUT
</pre></div>
<p>will create 5 copies of the input video.
</p>
<p>For example:
</p><div class="example">
<pre class="example">[in] split [splitout1][splitout2];
[splitout1] crop=100:100:0:0 [cropout];
[splitout2] pad=200:200:100:100 [padout];
</pre></div>
<p>will create two separate outputs from the same input, one cropped and
one padded.
</p>
<a name="super2xsai"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-super2xsai">8.52 super2xsai</a></h2>
<p>Scale the input by 2x and smooth using the Super2xSaI (Scale and
Interpolate) pixel art scaling algorithm.
</p>
<p>Useful for enlarging pixel art images without reducing sharpness.
</p>
<a name="swapuv"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-swapuv">8.53 swapuv</a></h2>
<p>Swap U & V plane.
</p>
<a name="thumbnail"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-thumbnail">8.54 thumbnail</a></h2>
<p>Select the most representative frame in a given sequence of consecutive frames.
</p>
<p>It accepts as argument the frames batch size to analyze (default <var>N</var>=100);
in a set of <var>N</var> frames, the filter will pick one of them, and then handle
the next batch of <var>N</var> frames until the end.
</p>
<p>Since the filter keeps track of the whole frames sequence, a bigger <var>N</var>
value will result in a higher memory usage, so a high value is not recommended.
</p>
<p>The following example extract one picture each 50 frames:
</p><div class="example">
<pre class="example">thumbnail=50
</pre></div>
<p>Complete example of a thumbnail creation with <code>ffmpeg</code>:
</p><div class="example">
<pre class="example">ffmpeg -i in.avi -vf thumbnail,scale=300:200 -frames:v 1 out.png
</pre></div>
<a name="tile"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-tile">8.55 tile</a></h2>
<p>Tile several successive frames together.
</p>
<p>It accepts a list of options in the form of <var>key</var>=<var>value</var> pairs
separated by ":". A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>layout</samp>’</dt>
<dd><p>Set the grid size (i.e. the number of lines and columns) in the form
"<var>w</var>x<var>h</var>".
</p>
</dd>
<dt>‘<samp>margin</samp>’</dt>
<dd><p>Set the outer border margin in pixels.
</p>
</dd>
<dt>‘<samp>padding</samp>’</dt>
<dd><p>Set the inner border thickness (i.e. the number of pixels between frames). For
more advanced padding options (such as having different values for the edges),
refer to the pad video filter.
</p>
</dd>
<dt>‘<samp>nb_frames</samp>’</dt>
<dd><p>Set the maximum number of frames to render in the given area. It must be less
than or equal to <var>w</var>x<var>h</var>. The default value is <code>0</code>, meaning all
the area will be used.
</p>
</dd>
</dl>
<p>Alternatively, the options can be specified as a flat string:
</p>
<p><var>layout</var>[:<var>nb_frames</var>[:<var>margin</var>[:<var>padding</var>]]]
</p>
<p>For example, produce 8x8 PNG tiles of all keyframes (‘<samp>-skip_frame
nokey</samp>’) in a movie:
</p><div class="example">
<pre class="example">ffmpeg -skip_frame nokey -i file.avi -vf 'scale=128:72,tile=8x8' -an -vsync 0 keyframes%03d.png
</pre></div>
<p>The ‘<samp>-vsync 0</samp>’ is necessary to prevent <code>ffmpeg</code> from
duplicating each output frame to accomodate the originally detected frame
rate.
</p>
<p>Another example to display <code>5</code> pictures in an area of <code>3x2</code> frames,
with <code>7</code> pixels between them, and <code>2</code> pixels of initial margin, using
mixed flat and named options:
</p><div class="example">
<pre class="example">tile=3x2:nb_frames=5:padding=7:margin=2
</pre></div>
<a name="tinterlace"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-tinterlace">8.56 tinterlace</a></h2>
<p>Perform various types of temporal field interlacing.
</p>
<p>Frames are counted starting from 1, so the first input frame is
considered odd.
</p>
<p>This filter accepts options in the form of <var>key</var>=<var>value</var> pairs
separated by ":".
Alternatively, the <var>mode</var> option can be specified as a value alone,
optionally followed by a ":" and further ":" separated <var>key</var>=<var>value</var>
pairs.
</p>
<p>A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>mode</samp>’</dt>
<dd><p>Specify the mode of the interlacing. This option can also be specified
as a value alone. See below for a list of values for this option.
</p>
<p>Available values are:
</p>
<dl compact="compact">
<dt>‘<samp>merge, 0</samp>’</dt>
<dd><p>Move odd frames into the upper field, even into the lower field,
generating a double height frame at half framerate.
</p>
</dd>
<dt>‘<samp>drop_odd, 1</samp>’</dt>
<dd><p>Only output even frames, odd frames are dropped, generating a frame with
unchanged height at half framerate.
</p>
</dd>
<dt>‘<samp>drop_even, 2</samp>’</dt>
<dd><p>Only output odd frames, even frames are dropped, generating a frame with
unchanged height at half framerate.
</p>
</dd>
<dt>‘<samp>pad, 3</samp>’</dt>
<dd><p>Expand each frame to full height, but pad alternate lines with black,
generating a frame with double height at the same input framerate.
</p>
</dd>
<dt>‘<samp>interleave_top, 4</samp>’</dt>
<dd><p>Interleave the upper field from odd frames with the lower field from
even frames, generating a frame with unchanged height at half framerate.
</p>
</dd>
<dt>‘<samp>interleave_bottom, 5</samp>’</dt>
<dd><p>Interleave the lower field from odd frames with the upper field from
even frames, generating a frame with unchanged height at half framerate.
</p>
</dd>
<dt>‘<samp>interlacex2, 6</samp>’</dt>
<dd><p>Double frame rate with unchanged height. Frames are inserted each
containing the second temporal field from the previous input frame and
the first temporal field from the next input frame. This mode relies on
the top_field_first flag. Useful for interlaced video displays with no
field synchronisation.
</p></dd>
</dl>
<p>Numeric values are deprecated but are accepted for backward
compatibility reasons.
</p>
<p>Default mode is <code>merge</code>.
</p>
</dd>
<dt>‘<samp>flags</samp>’</dt>
<dd><p>Specify flags influencing the filter process.
</p>
<p>Available value for <var>flags</var> is:
</p>
<dl compact="compact">
<dt>‘<samp>low_pass_filter, vlfp</samp>’</dt>
<dd><p>Enable vertical low-pass filtering in the filter.
Vertical low-pass filtering is required when creating an interlaced
destination from a progressive source which contains high-frequency
vertical detail. Filtering will reduce interlace ’twitter’ and Moire
patterning.
</p>
<p>Vertical low-pass filtering can only be enabled for ‘<samp>mode</samp>’
<var>interleave_top</var> and <var>interleave_bottom</var>.
</p>
</dd>
</dl>
</dd>
</dl>
<a name="transpose"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-transpose">8.57 transpose</a></h2>
<p>Transpose rows with columns in the input video and optionally flip it.
</p>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var>
pairs, separated by ’:’. If the key of the first options is omitted,
the arguments are interpreted according to the syntax
<var>dir</var>:<var>passthrough</var>.
</p>
<dl compact="compact">
<dt>‘<samp>dir</samp>’</dt>
<dd><p>Specify the transposition direction. Can assume the following values:
</p>
<dl compact="compact">
<dt>‘<samp>0, 4</samp>’</dt>
<dd><p>Rotate by 90 degrees counterclockwise and vertically flip (default), that is:
</p><div class="example">
<pre class="example">L.R L.l
. . -> . .
l.r R.r
</pre></div>
</dd>
<dt>‘<samp>1, 5</samp>’</dt>
<dd><p>Rotate by 90 degrees clockwise, that is:
</p><div class="example">
<pre class="example">L.R l.L
. . -> . .
l.r r.R
</pre></div>
</dd>
<dt>‘<samp>2, 6</samp>’</dt>
<dd><p>Rotate by 90 degrees counterclockwise, that is:
</p><div class="example">
<pre class="example">L.R R.r
. . -> . .
l.r L.l
</pre></div>
</dd>
<dt>‘<samp>3, 7</samp>’</dt>
<dd><p>Rotate by 90 degrees clockwise and vertically flip, that is:
</p><div class="example">
<pre class="example">L.R r.R
. . -> . .
l.r l.L
</pre></div>
</dd>
</dl>
<p>For values between 4-7, the transposition is only done if the input
video geometry is portrait and not landscape. These values are
deprecated, the <code>passthrough</code> option should be used instead.
</p>
</dd>
<dt>‘<samp>passthrough</samp>’</dt>
<dd><p>Do not apply the transposition if the input geometry matches the one
specified by the specified value. It accepts the following values:
</p><dl compact="compact">
<dt>‘<samp>none</samp>’</dt>
<dd><p>Always apply transposition.
</p></dd>
<dt>‘<samp>portrait</samp>’</dt>
<dd><p>Preserve portrait geometry (when <var>height</var> >= <var>width</var>).
</p></dd>
<dt>‘<samp>landscape</samp>’</dt>
<dd><p>Preserve landscape geometry (when <var>width</var> >= <var>height</var>).
</p></dd>
</dl>
<p>Default value is <code>none</code>.
</p></dd>
</dl>
<p>For example to rotate by 90 degrees clockwise and preserve portrait
layout:
</p><div class="example">
<pre class="example">transpose=dir=1:passthrough=portrait
</pre></div>
<p>The command above can also be specified as:
</p><div class="example">
<pre class="example">transpose=1:portrait
</pre></div>
<a name="unsharp"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-unsharp">8.58 unsharp</a></h2>
<p>Sharpen or blur the input video.
</p>
<p>It accepts the following parameters:
<var>luma_msize_x</var>:<var>luma_msize_y</var>:<var>luma_amount</var>:<var>chroma_msize_x</var>:<var>chroma_msize_y</var>:<var>chroma_amount</var>
</p>
<p>Negative values for the amount will blur the input video, while positive
values will sharpen. All parameters are optional and default to the
equivalent of the string ’5:5:1.0:5:5:0.0’.
</p>
<dl compact="compact">
<dt>‘<samp>luma_msize_x</samp>’</dt>
<dd><p>Set the luma matrix horizontal size. It can be an integer between 3
and 13, default value is 5.
</p>
</dd>
<dt>‘<samp>luma_msize_y</samp>’</dt>
<dd><p>Set the luma matrix vertical size. It can be an integer between 3
and 13, default value is 5.
</p>
</dd>
<dt>‘<samp>luma_amount</samp>’</dt>
<dd><p>Set the luma effect strength. It can be a float number between -2.0
and 5.0, default value is 1.0.
</p>
</dd>
<dt>‘<samp>chroma_msize_x</samp>’</dt>
<dd><p>Set the chroma matrix horizontal size. It can be an integer between 3
and 13, default value is 5.
</p>
</dd>
<dt>‘<samp>chroma_msize_y</samp>’</dt>
<dd><p>Set the chroma matrix vertical size. It can be an integer between 3
and 13, default value is 5.
</p>
</dd>
<dt>‘<samp>chroma_amount</samp>’</dt>
<dd><p>Set the chroma effect strength. It can be a float number between -2.0
and 5.0, default value is 0.0.
</p>
</dd>
</dl>
<div class="example">
<pre class="example"># Strong luma sharpen effect parameters
unsharp=7:7:2.5
# Strong blur of both luma and chroma parameters
unsharp=7:7:-2:7:7:-2
# Use the default values with <code>ffmpeg</code>
ffmpeg -i in.avi -vf "unsharp" out.mp4
</pre></div>
<a name="vflip"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-vflip">8.59 vflip</a></h2>
<p>Flip the input video vertically.
</p>
<div class="example">
<pre class="example">ffmpeg -i in.avi -vf "vflip" out.avi
</pre></div>
<a name="yadif"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-yadif">8.60 yadif</a></h2>
<p>Deinterlace the input video ("yadif" means "yet another deinterlacing
filter").
</p>
<p>The filter accepts parameters as a list of <var>key</var>=<var>value</var>
pairs, separated by ":". If the key of the first options is omitted,
the arguments are interpreted according to syntax
<var>mode</var>:<var>parity</var>:<var>deint</var>.
</p>
<p>The description of the accepted parameters follows.
</p>
<dl compact="compact">
<dt>‘<samp>mode</samp>’</dt>
<dd><p>Specify the interlacing mode to adopt. Accept one of the following
values:
</p>
<dl compact="compact">
<dt>‘<samp>0, send_frame</samp>’</dt>
<dd><p>output 1 frame for each frame
</p></dd>
<dt>‘<samp>1, send_field</samp>’</dt>
<dd><p>output 1 frame for each field
</p></dd>
<dt>‘<samp>2, send_frame_nospatial</samp>’</dt>
<dd><p>like <code>send_frame</code> but skip spatial interlacing check
</p></dd>
<dt>‘<samp>3, send_field_nospatial</samp>’</dt>
<dd><p>like <code>send_field</code> but skip spatial interlacing check
</p></dd>
</dl>
<p>Default value is <code>send_frame</code>.
</p>
</dd>
<dt>‘<samp>parity</samp>’</dt>
<dd><p>Specify the picture field parity assumed for the input interlaced
video. Accept one of the following values:
</p>
<dl compact="compact">
<dt>‘<samp>0, tff</samp>’</dt>
<dd><p>assume top field first
</p></dd>
<dt>‘<samp>1, bff</samp>’</dt>
<dd><p>assume bottom field first
</p></dd>
<dt>‘<samp>-1, auto</samp>’</dt>
<dd><p>enable automatic detection
</p></dd>
</dl>
<p>Default value is <code>auto</code>.
If interlacing is unknown or decoder does not export this information,
top field first will be assumed.
</p>
</dd>
<dt>‘<samp>deint</samp>’</dt>
<dd><p>Specify which frames to deinterlace. Accept one of the following
values:
</p>
<dl compact="compact">
<dt>‘<samp>0, all</samp>’</dt>
<dd><p>deinterlace all frames
</p></dd>
<dt>‘<samp>1, interlaced</samp>’</dt>
<dd><p>only deinterlace frames marked as interlaced
</p></dd>
</dl>
<p>Default value is <code>all</code>.
</p></dd>
</dl>
<a name="Video-Sources"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Video-Sources">9 Video Sources</a></h1>
<p>Below is a description of the currently available video sources.
</p>
<a name="buffer"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-buffer">9.1 buffer</a></h2>
<p>Buffer video frames, and make them available to the filter chain.
</p>
<p>This source is mainly intended for a programmatic use, in particular
through the interface defined in ‘<tt>libavfilter/vsrc_buffer.h</tt>’.
</p>
<p>It accepts a list of options in the form of <var>key</var>=<var>value</var> pairs
separated by ":". A description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>video_size</samp>’</dt>
<dd><p>Specify the size (width and height) of the buffered video frames.
</p>
</dd>
<dt>‘<samp>pix_fmt</samp>’</dt>
<dd><p>A string representing the pixel format of the buffered video frames.
It may be a number corresponding to a pixel format, or a pixel format
name.
</p>
</dd>
<dt>‘<samp>time_base</samp>’</dt>
<dd><p>Specify the timebase assumed by the timestamps of the buffered frames.
</p>
</dd>
<dt>‘<samp>time_base</samp>’</dt>
<dd><p>Specify the frame rate expected for the video stream.
</p>
</dd>
<dt>‘<samp>pixel_aspect</samp>’</dt>
<dd><p>Specify the sample aspect ratio assumed by the video frames.
</p>
</dd>
<dt>‘<samp>sws_param</samp>’</dt>
<dd><p>Specify the optional parameters to be used for the scale filter which
is automatically inserted when an input change is detected in the
input size or format.
</p></dd>
</dl>
<p>For example:
</p><div class="example">
<pre class="example">buffer=size=320x240:pix_fmt=yuv410p:time_base=1/24:pixel_aspect=1/1
</pre></div>
<p>will instruct the source to accept video frames with size 320x240 and
with format "yuv410p", assuming 1/24 as the timestamps timebase and
square pixels (1:1 sample aspect ratio).
Since the pixel format with name "yuv410p" corresponds to the number 6
(check the enum AVPixelFormat definition in ‘<tt>libavutil/pixfmt.h</tt>’),
this example corresponds to:
</p><div class="example">
<pre class="example">buffer=size=320x240:pixfmt=6:time_base=1/24:pixel_aspect=1/1
</pre></div>
<p>Alternatively, the options can be specified as a flat string, but this
syntax is deprecated:
</p>
<p><var>width</var>:<var>height</var>:<var>pix_fmt</var>:<var>time_base.num</var>:<var>time_base.den</var>:<var>pixel_aspect.num</var>:<var>pixel_aspect.den</var>[:<var>sws_param</var>]
</p>
<a name="cellauto"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-cellauto">9.2 cellauto</a></h2>
<p>Create a pattern generated by an elementary cellular automaton.
</p>
<p>The initial state of the cellular automaton can be defined through the
‘<samp>filename</samp>’, and ‘<samp>pattern</samp>’ options. If such options are
not specified an initial state is created randomly.
</p>
<p>At each new frame a new row in the video is filled with the result of
the cellular automaton next generation. The behavior when the whole
frame is filled is defined by the ‘<samp>scroll</samp>’ option.
</p>
<p>This source accepts a list of options in the form of
<var>key</var>=<var>value</var> pairs separated by ":". A description of the
accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>filename, f</samp>’</dt>
<dd><p>Read the initial cellular automaton state, i.e. the starting row, from
the specified file.
In the file, each non-whitespace character is considered an alive
cell, a newline will terminate the row, and further characters in the
file will be ignored.
</p>
</dd>
<dt>‘<samp>pattern, p</samp>’</dt>
<dd><p>Read the initial cellular automaton state, i.e. the starting row, from
the specified string.
</p>
<p>Each non-whitespace character in the string is considered an alive
cell, a newline will terminate the row, and further characters in the
string will be ignored.
</p>
</dd>
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Set the video rate, that is the number of frames generated per second.
Default is 25.
</p>
</dd>
<dt>‘<samp>random_fill_ratio, ratio</samp>’</dt>
<dd><p>Set the random fill ratio for the initial cellular automaton row. It
is a floating point number value ranging from 0 to 1, defaults to
1/PHI.
</p>
<p>This option is ignored when a file or a pattern is specified.
</p>
</dd>
<dt>‘<samp>random_seed, seed</samp>’</dt>
<dd><p>Set the seed for filling randomly the initial row, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.
</p>
</dd>
<dt>‘<samp>rule</samp>’</dt>
<dd><p>Set the cellular automaton rule, it is a number ranging from 0 to 255.
Default value is 110.
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Set the size of the output video.
</p>
<p>If ‘<samp>filename</samp>’ or ‘<samp>pattern</samp>’ is specified, the size is set
by default to the width of the specified initial state row, and the
height is set to <var>width</var> * PHI.
</p>
<p>If ‘<samp>size</samp>’ is set, it must contain the width of the specified
pattern string, and the specified pattern will be centered in the
larger row.
</p>
<p>If a filename or a pattern string is not specified, the size value
defaults to "320x518" (used for a randomly generated initial state).
</p>
</dd>
<dt>‘<samp>scroll</samp>’</dt>
<dd><p>If set to 1, scroll the output upward when all the rows in the output
have been already filled. If set to 0, the new generated row will be
written over the top row just after the bottom row is filled.
Defaults to 1.
</p>
</dd>
<dt>‘<samp>start_full, full</samp>’</dt>
<dd><p>If set to 1, completely fill the output with generated rows before
outputting the first frame.
This is the default behavior, for disabling set the value to 0.
</p>
</dd>
<dt>‘<samp>stitch</samp>’</dt>
<dd><p>If set to 1, stitch the left and right row edges together.
This is the default behavior, for disabling set the value to 0.
</p></dd>
</dl>
<a name="Examples-10"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-10">9.2.1 Examples</a></h3>
<ul>
<li>
Read the initial state from ‘<tt>pattern</tt>’, and specify an output of
size 200x400.
<div class="example">
<pre class="example">cellauto=f=pattern:s=200x400
</pre></div>
</li><li>
Generate a random initial row with a width of 200 cells, with a fill
ratio of 2/3:
<div class="example">
<pre class="example">cellauto=ratio=2/3:s=200x200
</pre></div>
</li><li>
Create a pattern generated by rule 18 starting by a single alive cell
centered on an initial row with width 100:
<div class="example">
<pre class="example">cellauto=p=@:s=100x400:full=0:rule=18
</pre></div>
</li><li>
Specify a more elaborated initial pattern:
<div class="example">
<pre class="example">cellauto=p='@@ @ @@':s=100x400:full=0:rule=18
</pre></div>
</li></ul>
<a name="mandelbrot"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-mandelbrot">9.3 mandelbrot</a></h2>
<p>Generate a Mandelbrot set fractal, and progressively zoom towards the
point specified with <var>start_x</var> and <var>start_y</var>.
</p>
<p>This source accepts a list of options in the form of
<var>key</var>=<var>value</var> pairs separated by ":". A description of the
accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>end_pts</samp>’</dt>
<dd><p>Set the terminal pts value. Default value is 400.
</p>
</dd>
<dt>‘<samp>end_scale</samp>’</dt>
<dd><p>Set the terminal scale value.
Must be a floating point value. Default value is 0.3.
</p>
</dd>
<dt>‘<samp>inner</samp>’</dt>
<dd><p>Set the inner coloring mode, that is the algorithm used to draw the
Mandelbrot fractal internal region.
</p>
<p>It shall assume one of the following values:
</p><dl compact="compact">
<dt>‘<samp>black</samp>’</dt>
<dd><p>Set black mode.
</p></dd>
<dt>‘<samp>convergence</samp>’</dt>
<dd><p>Show time until convergence.
</p></dd>
<dt>‘<samp>mincol</samp>’</dt>
<dd><p>Set color based on point closest to the origin of the iterations.
</p></dd>
<dt>‘<samp>period</samp>’</dt>
<dd><p>Set period mode.
</p></dd>
</dl>
<p>Default value is <var>mincol</var>.
</p>
</dd>
<dt>‘<samp>bailout</samp>’</dt>
<dd><p>Set the bailout value. Default value is 10.0.
</p>
</dd>
<dt>‘<samp>maxiter</samp>’</dt>
<dd><p>Set the maximum of iterations performed by the rendering
algorithm. Default value is 7189.
</p>
</dd>
<dt>‘<samp>outer</samp>’</dt>
<dd><p>Set outer coloring mode.
It shall assume one of following values:
</p><dl compact="compact">
<dt>‘<samp>iteration_count</samp>’</dt>
<dd><p>Set iteration cound mode.
</p></dd>
<dt>‘<samp>normalized_iteration_count</samp>’</dt>
<dd><p>set normalized iteration count mode.
</p></dd>
</dl>
<p>Default value is <var>normalized_iteration_count</var>.
</p>
</dd>
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Set frame rate, expressed as number of frames per second. Default
value is "25".
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Set frame size. Default value is "640x480".
</p>
</dd>
<dt>‘<samp>start_scale</samp>’</dt>
<dd><p>Set the initial scale value. Default value is 3.0.
</p>
</dd>
<dt>‘<samp>start_x</samp>’</dt>
<dd><p>Set the initial x position. Must be a floating point value between
-100 and 100. Default value is -0.743643887037158704752191506114774.
</p>
</dd>
<dt>‘<samp>start_y</samp>’</dt>
<dd><p>Set the initial y position. Must be a floating point value between
-100 and 100. Default value is -0.131825904205311970493132056385139.
</p></dd>
</dl>
<a name="mptestsrc"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-mptestsrc">9.4 mptestsrc</a></h2>
<p>Generate various test patterns, as generated by the MPlayer test filter.
</p>
<p>The size of the generated video is fixed, and is 256x256.
This source is useful in particular for testing encoding features.
</p>
<p>This source accepts an optional sequence of <var>key</var>=<var>value</var> pairs,
separated by ":". The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
<var>frame_rate_num</var>/<var>frame_rate_den</var>, an integer number, a float
number or a valid video frame rate abbreviation. The default value is
"25".
</p>
</dd>
<dt>‘<samp>duration, d</samp>’</dt>
<dd><p>Set the video duration of the sourced video. The accepted syntax is:
</p><div class="example">
<pre class="example">[-]HH:MM:SS[.m...]
[-]S+[.m...]
</pre></div>
<p>See also the function <code>av_parse_time()</code>.
</p>
<p>If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.
</p>
</dd>
<dt>‘<samp>test, t</samp>’</dt>
<dd>
<p>Set the number or the name of the test to perform. Supported tests are:
</p><dl compact="compact">
<dt>‘<samp>dc_luma</samp>’</dt>
<dt>‘<samp>dc_chroma</samp>’</dt>
<dt>‘<samp>freq_luma</samp>’</dt>
<dt>‘<samp>freq_chroma</samp>’</dt>
<dt>‘<samp>amp_luma</samp>’</dt>
<dt>‘<samp>amp_chroma</samp>’</dt>
<dt>‘<samp>cbp</samp>’</dt>
<dt>‘<samp>mv</samp>’</dt>
<dt>‘<samp>ring1</samp>’</dt>
<dt>‘<samp>ring2</samp>’</dt>
<dt>‘<samp>all</samp>’</dt>
</dl>
<p>Default value is "all", which will cycle through the list of all tests.
</p></dd>
</dl>
<p>For example the following:
</p><div class="example">
<pre class="example">testsrc=t=dc_luma
</pre></div>
<p>will generate a "dc_luma" test pattern.
</p>
<a name="frei0r_005fsrc"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-frei0r_005fsrc">9.5 frei0r_src</a></h2>
<p>Provide a frei0r source.
</p>
<p>To enable compilation of this filter you need to install the frei0r
header and configure FFmpeg with <code>--enable-frei0r</code>.
</p>
<p>The source supports the syntax:
</p><div class="example">
<pre class="example"><var>size</var>:<var>rate</var>:<var>src_name</var>[{=|:}<var>param1</var>:<var>param2</var>:...:<var>paramN</var>]
</pre></div>
<p><var>size</var> is the size of the video to generate, may be a string of the
form <var>width</var>x<var>height</var> or a frame size abbreviation.
<var>rate</var> is the rate of the video to generate, may be a string of
the form <var>num</var>/<var>den</var> or a frame rate abbreviation.
<var>src_name</var> is the name to the frei0r source to load. For more
information regarding frei0r and how to set the parameters read the
section <a href="#frei0r">frei0r</a> in the description of the video filters.
</p>
<p>For example, to generate a frei0r partik0l source with size 200x200
and frame rate 10 which is overlayed on the overlay filter main input:
</p><div class="example">
<pre class="example">frei0r_src=200x200:10:partik0l=1234 [overlay]; [in][overlay] overlay
</pre></div>
<a name="life"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-life">9.6 life</a></h2>
<p>Generate a life pattern.
</p>
<p>This source is based on a generalization of John Conway’s life game.
</p>
<p>The sourced input represents a life grid, each pixel represents a cell
which can be in one of two possible states, alive or dead. Every cell
interacts with its eight neighbours, which are the cells that are
horizontally, vertically, or diagonally adjacent.
</p>
<p>At each interaction the grid evolves according to the adopted rule,
which specifies the number of neighbor alive cells which will make a
cell stay alive or born. The ‘<samp>rule</samp>’ option allows to specify
the rule to adopt.
</p>
<p>This source accepts a list of options in the form of
<var>key</var>=<var>value</var> pairs separated by ":". A description of the
accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>filename, f</samp>’</dt>
<dd><p>Set the file from which to read the initial grid state. In the file,
each non-whitespace character is considered an alive cell, and newline
is used to delimit the end of each row.
</p>
<p>If this option is not specified, the initial grid is generated
randomly.
</p>
</dd>
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Set the video rate, that is the number of frames generated per second.
Default is 25.
</p>
</dd>
<dt>‘<samp>random_fill_ratio, ratio</samp>’</dt>
<dd><p>Set the random fill ratio for the initial random grid. It is a
floating point number value ranging from 0 to 1, defaults to 1/PHI.
It is ignored when a file is specified.
</p>
</dd>
<dt>‘<samp>random_seed, seed</samp>’</dt>
<dd><p>Set the seed for filling the initial random grid, must be an integer
included between 0 and UINT32_MAX. If not specified, or if explicitly
set to -1, the filter will try to use a good random seed on a best
effort basis.
</p>
</dd>
<dt>‘<samp>rule</samp>’</dt>
<dd><p>Set the life rule.
</p>
<p>A rule can be specified with a code of the kind "S<var>NS</var>/B<var>NB</var>",
where <var>NS</var> and <var>NB</var> are sequences of numbers in the range 0-8,
<var>NS</var> specifies the number of alive neighbor cells which make a
live cell stay alive, and <var>NB</var> the number of alive neighbor cells
which make a dead cell to become alive (i.e. to "born").
"s" and "b" can be used in place of "S" and "B", respectively.
</p>
<p>Alternatively a rule can be specified by an 18-bits integer. The 9
high order bits are used to encode the next cell state if it is alive
for each number of neighbor alive cells, the low order bits specify
the rule for "borning" new cells. Higher order bits encode for an
higher number of neighbor cells.
For example the number 6153 = <code>(12<<9)+9</code> specifies a stay alive
rule of 12 and a born rule of 9, which corresponds to "S23/B03".
</p>
<p>Default value is "S23/B3", which is the original Conway’s game of life
rule, and will keep a cell alive if it has 2 or 3 neighbor alive
cells, and will born a new cell if there are three alive cells around
a dead cell.
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Set the size of the output video.
</p>
<p>If ‘<samp>filename</samp>’ is specified, the size is set by default to the
same size of the input file. If ‘<samp>size</samp>’ is set, it must contain
the size specified in the input file, and the initial grid defined in
that file is centered in the larger resulting area.
</p>
<p>If a filename is not specified, the size value defaults to "320x240"
(used for a randomly generated initial grid).
</p>
</dd>
<dt>‘<samp>stitch</samp>’</dt>
<dd><p>If set to 1, stitch the left and right grid edges together, and the
top and bottom edges also. Defaults to 1.
</p>
</dd>
<dt>‘<samp>mold</samp>’</dt>
<dd><p>Set cell mold speed. If set, a dead cell will go from ‘<samp>death_color</samp>’ to
‘<samp>mold_color</samp>’ with a step of ‘<samp>mold</samp>’. ‘<samp>mold</samp>’ can have a
value from 0 to 255.
</p>
</dd>
<dt>‘<samp>life_color</samp>’</dt>
<dd><p>Set the color of living (or new born) cells.
</p>
</dd>
<dt>‘<samp>death_color</samp>’</dt>
<dd><p>Set the color of dead cells. If ‘<samp>mold</samp>’ is set, this is the first color
used to represent a dead cell.
</p>
</dd>
<dt>‘<samp>mold_color</samp>’</dt>
<dd><p>Set mold color, for definitely dead and moldy cells.
</p></dd>
</dl>
<a name="Examples-12"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-12">9.6.1 Examples</a></h3>
<ul>
<li>
Read a grid from ‘<tt>pattern</tt>’, and center it on a grid of size
300x300 pixels:
<div class="example">
<pre class="example">life=f=pattern:s=300x300
</pre></div>
</li><li>
Generate a random grid of size 200x200, with a fill ratio of 2/3:
<div class="example">
<pre class="example">life=ratio=2/3:s=200x200
</pre></div>
</li><li>
Specify a custom rule for evolving a randomly generated grid:
<div class="example">
<pre class="example">life=rule=S14/B34
</pre></div>
</li><li>
Full example with slow death effect (mold) using <code>ffplay</code>:
<div class="example">
<pre class="example">ffplay -f lavfi life=s=300x200:mold=10:r=60:ratio=0.1:death_color=#C83232:life_color=#00ff00,scale=1200:800:flags=16
</pre></div>
</li></ul>
<a name="color_002c-nullsrc_002c-rgbtestsrc_002c-smptebars_002c-testsrc"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-color_002c-nullsrc_002c-rgbtestsrc_002c-smptebars_002c-testsrc">9.7 color, nullsrc, rgbtestsrc, smptebars, testsrc</a></h2>
<p>The <code>color</code> source provides an uniformly colored input.
</p>
<p>The <code>nullsrc</code> source returns unprocessed video frames. It is
mainly useful to be employed in analysis / debugging tools, or as the
source for filters which ignore the input data.
</p>
<p>The <code>rgbtestsrc</code> source generates an RGB test pattern useful for
detecting RGB vs BGR issues. You should see a red, green and blue
stripe from top to bottom.
</p>
<p>The <code>smptebars</code> source generates a color bars pattern, based on
the SMPTE Engineering Guideline EG 1-1990.
</p>
<p>The <code>testsrc</code> source generates a test video pattern, showing a
color pattern, a scrolling gradient and a timestamp. This is mainly
intended for testing purposes.
</p>
<p>These sources accept an optional sequence of <var>key</var>=<var>value</var> pairs,
separated by ":". The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>color, c</samp>’</dt>
<dd><p>Specify the color of the source, only used in the <code>color</code>
source. It can be the name of a color (case insensitive match) or a
0xRRGGBB[AA] sequence, possibly followed by an alpha specifier. The
default value is "black".
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Specify the size of the sourced video, it may be a string of the form
<var>width</var>x<var>height</var>, or the name of a size abbreviation. The
default value is "320x240".
</p>
</dd>
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Specify the frame rate of the sourced video, as the number of frames
generated per second. It has to be a string in the format
<var>frame_rate_num</var>/<var>frame_rate_den</var>, an integer number, a float
number or a valid video frame rate abbreviation. The default value is
"25".
</p>
</dd>
<dt>‘<samp>sar</samp>’</dt>
<dd><p>Set the sample aspect ratio of the sourced video.
</p>
</dd>
<dt>‘<samp>duration, d</samp>’</dt>
<dd><p>Set the video duration of the sourced video. The accepted syntax is:
</p><div class="example">
<pre class="example">[-]HH[:MM[:SS[.m...]]]
[-]S+[.m...]
</pre></div>
<p>See also the function <code>av_parse_time()</code>.
</p>
<p>If not specified, or the expressed duration is negative, the video is
supposed to be generated forever.
</p>
</dd>
<dt>‘<samp>decimals, n</samp>’</dt>
<dd><p>Set the number of decimals to show in the timestamp, only used in the
<code>testsrc</code> source.
</p>
<p>The displayed timestamp value will correspond to the original
timestamp value multiplied by the power of 10 of the specified
value. Default value is 0.
</p></dd>
</dl>
<p>For example the following:
</p><div class="example">
<pre class="example">testsrc=duration=5.3:size=qcif:rate=10
</pre></div>
<p>will generate a video with a duration of 5.3 seconds, with size
176x144 and a frame rate of 10 frames per second.
</p>
<p>The following graph description will generate a red source
with an opacity of 0.2, with size "qcif" and a frame rate of 10
frames per second.
</p><div class="example">
<pre class="example">color=c=red@0.2:s=qcif:r=10
</pre></div>
<p>If the input content is to be ignored, <code>nullsrc</code> can be used. The
following command generates noise in the luminance plane by employing
the <code>geq</code> filter:
</p><div class="example">
<pre class="example">nullsrc=s=256x256, geq=random(1)*255:128:128
</pre></div>
<a name="Video-Sinks"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Video-Sinks">10 Video Sinks</a></h1>
<p>Below is a description of the currently available video sinks.
</p>
<a name="buffersink"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-buffersink">10.1 buffersink</a></h2>
<p>Buffer video frames, and make them available to the end of the filter
graph.
</p>
<p>This sink is mainly intended for a programmatic use, in particular
through the interface defined in ‘<tt>libavfilter/buffersink.h</tt>’.
</p>
<p>It does not require a string parameter in input, but you need to
specify a pointer to a list of supported pixel formats terminated by
-1 in the opaque parameter provided to <code>avfilter_init_filter</code>
when initializing this sink.
</p>
<a name="nullsink"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-nullsink">10.2 nullsink</a></h2>
<p>Null video sink, do absolutely nothing with the input video. It is
mainly useful as a template and to be employed in analysis / debugging
tools.
</p>
<a name="Multimedia-Filters"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Multimedia-Filters">11 Multimedia Filters</a></h1>
<p>Below is a description of the currently available multimedia filters.
</p>
<a name="aselect_002c-select"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-aselect_002c-select">11.1 aselect, select</a></h2>
<p>Select frames to pass in output.
</p>
<p>These filters accept a single option ‘<samp>expr</samp>’ or ‘<samp>e</samp>’
specifying the select expression, which can be specified either by
specyfing <code>expr=VALUE</code> or specifying the expression
alone.
</p>
<p>The select expression is evaluated for each input frame. If the
evaluation result is a non-zero value, the frame is selected and
passed to the output, otherwise it is discarded.
</p>
<p>The expression can contain the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>the sequential number of the filtered frame, starting from 0
</p>
</dd>
<dt>‘<samp>selected_n</samp>’</dt>
<dd><p>the sequential number of the selected frame, starting from 0
</p>
</dd>
<dt>‘<samp>prev_selected_n</samp>’</dt>
<dd><p>the sequential number of the last selected frame, NAN if undefined
</p>
</dd>
<dt>‘<samp>TB</samp>’</dt>
<dd><p>timebase of the input timestamps
</p>
</dd>
<dt>‘<samp>pts</samp>’</dt>
<dd><p>the PTS (Presentation TimeStamp) of the filtered video frame,
expressed in <var>TB</var> units, NAN if undefined
</p>
</dd>
<dt>‘<samp>t</samp>’</dt>
<dd><p>the PTS (Presentation TimeStamp) of the filtered video frame,
expressed in seconds, NAN if undefined
</p>
</dd>
<dt>‘<samp>prev_pts</samp>’</dt>
<dd><p>the PTS of the previously filtered video frame, NAN if undefined
</p>
</dd>
<dt>‘<samp>prev_selected_pts</samp>’</dt>
<dd><p>the PTS of the last previously filtered video frame, NAN if undefined
</p>
</dd>
<dt>‘<samp>prev_selected_t</samp>’</dt>
<dd><p>the PTS of the last previously selected video frame, NAN if undefined
</p>
</dd>
<dt>‘<samp>start_pts</samp>’</dt>
<dd><p>the PTS of the first video frame in the video, NAN if undefined
</p>
</dd>
<dt>‘<samp>start_t</samp>’</dt>
<dd><p>the time of the first video frame in the video, NAN if undefined
</p>
</dd>
<dt>‘<samp>pict_type <em>(video only)</em></samp>’</dt>
<dd><p>the type of the filtered frame, can assume one of the following
values:
</p><dl compact="compact">
<dt>‘<samp>I</samp>’</dt>
<dt>‘<samp>P</samp>’</dt>
<dt>‘<samp>B</samp>’</dt>
<dt>‘<samp>S</samp>’</dt>
<dt>‘<samp>SI</samp>’</dt>
<dt>‘<samp>SP</samp>’</dt>
<dt>‘<samp>BI</samp>’</dt>
</dl>
</dd>
<dt>‘<samp>interlace_type <em>(video only)</em></samp>’</dt>
<dd><p>the frame interlace type, can assume one of the following values:
</p><dl compact="compact">
<dt>‘<samp>PROGRESSIVE</samp>’</dt>
<dd><p>the frame is progressive (not interlaced)
</p></dd>
<dt>‘<samp>TOPFIRST</samp>’</dt>
<dd><p>the frame is top-field-first
</p></dd>
<dt>‘<samp>BOTTOMFIRST</samp>’</dt>
<dd><p>the frame is bottom-field-first
</p></dd>
</dl>
</dd>
<dt>‘<samp>consumed_sample_n <em>(audio only)</em></samp>’</dt>
<dd><p>the number of selected samples before the current frame
</p>
</dd>
<dt>‘<samp>samples_n <em>(audio only)</em></samp>’</dt>
<dd><p>the number of samples in the current frame
</p>
</dd>
<dt>‘<samp>sample_rate <em>(audio only)</em></samp>’</dt>
<dd><p>the input sample rate
</p>
</dd>
<dt>‘<samp>key</samp>’</dt>
<dd><p>1 if the filtered frame is a key-frame, 0 otherwise
</p>
</dd>
<dt>‘<samp>pos</samp>’</dt>
<dd><p>the position in the file of the filtered frame, -1 if the information
is not available (e.g. for synthetic video)
</p>
</dd>
<dt>‘<samp>scene <em>(video only)</em></samp>’</dt>
<dd><p>value between 0 and 1 to indicate a new scene; a low value reflects a low
probability for the current frame to introduce a new scene, while a higher
value means the current frame is more likely to be one (see the example below)
</p>
</dd>
</dl>
<p>The default value of the select expression is "1".
</p>
<a name="Examples-4"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-4">11.1.1 Examples</a></h3>
<ul>
<li>
Select all frames in input:
<div class="example">
<pre class="example">select
</pre></div>
<p>The example above is the same as:
</p><div class="example">
<pre class="example">select=1
</pre></div>
</li><li>
Skip all frames:
<div class="example">
<pre class="example">select=0
</pre></div>
</li><li>
Select only I-frames:
<div class="example">
<pre class="example">select='eq(pict_type\,I)'
</pre></div>
</li><li>
Select one frame every 100:
<div class="example">
<pre class="example">select='not(mod(n\,100))'
</pre></div>
</li><li>
Select only frames contained in the 10-20 time interval:
<div class="example">
<pre class="example">select='gte(t\,10)*lte(t\,20)'
</pre></div>
</li><li>
Select only I frames contained in the 10-20 time interval:
<div class="example">
<pre class="example">select='gte(t\,10)*lte(t\,20)*eq(pict_type\,I)'
</pre></div>
</li><li>
Select frames with a minimum distance of 10 seconds:
<div class="example">
<pre class="example">select='isnan(prev_selected_t)+gte(t-prev_selected_t\,10)'
</pre></div>
</li><li>
Use aselect to select only audio frames with samples number > 100:
<div class="example">
<pre class="example">aselect='gt(samples_n\,100)'
</pre></div>
</li><li>
Create a mosaic of the first scenes:
<div class="example">
<pre class="example">ffmpeg -i video.avi -vf select='gt(scene\,0.4)',scale=160:120,tile -frames:v 1 preview.png
</pre></div>
<p>Comparing <var>scene</var> against a value between 0.3 and 0.5 is generally a sane
choice.
</p></li></ul>
<a name="asendcmd_002c-sendcmd"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-asendcmd_002c-sendcmd">11.2 asendcmd, sendcmd</a></h2>
<p>Send commands to filters in the filtergraph.
</p>
<p>These filters read commands to be sent to other filters in the
filtergraph.
</p>
<p><code>asendcmd</code> must be inserted between two audio filters,
<code>sendcmd</code> must be inserted between two video filters, but apart
from that they act the same way.
</p>
<p>The specification of commands can be provided in the filter arguments
with the <var>commands</var> option, or in a file specified by the
<var>filename</var> option.
</p>
<p>These filters accept the following options:
</p><dl compact="compact">
<dt>‘<samp>commands, c</samp>’</dt>
<dd><p>Set the commands to be read and sent to the other filters.
</p></dd>
<dt>‘<samp>filename, f</samp>’</dt>
<dd><p>Set the filename of the commands to be read and sent to the other
filters.
</p></dd>
</dl>
<a name="Commands-syntax"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Commands-syntax">11.2.1 Commands syntax</a></h3>
<p>A commands description consists of a sequence of interval
specifications, comprising a list of commands to be executed when a
particular event related to that interval occurs. The occurring event
is typically the current frame time entering or leaving a given time
interval.
</p>
<p>An interval is specified by the following syntax:
</p><div class="example">
<pre class="example"><var>START</var>[-<var>END</var>] <var>COMMANDS</var>;
</pre></div>
<p>The time interval is specified by the <var>START</var> and <var>END</var> times.
<var>END</var> is optional and defaults to the maximum time.
</p>
<p>The current frame time is considered within the specified interval if
it is included in the interval [<var>START</var>, <var>END</var>), that is when
the time is greater or equal to <var>START</var> and is lesser than
<var>END</var>.
</p>
<p><var>COMMANDS</var> consists of a sequence of one or more command
specifications, separated by ",", relating to that interval. The
syntax of a command specification is given by:
</p><div class="example">
<pre class="example">[<var>FLAGS</var>] <var>TARGET</var> <var>COMMAND</var> <var>ARG</var>
</pre></div>
<p><var>FLAGS</var> is optional and specifies the type of events relating to
the time interval which enable sending the specified command, and must
be a non-null sequence of identifier flags separated by "+" or "|" and
enclosed between "[" and "]".
</p>
<p>The following flags are recognized:
</p><dl compact="compact">
<dt>‘<samp>enter</samp>’</dt>
<dd><p>The command is sent when the current frame timestamp enters the
specified interval. In other words, the command is sent when the
previous frame timestamp was not in the given interval, and the
current is.
</p>
</dd>
<dt>‘<samp>leave</samp>’</dt>
<dd><p>The command is sent when the current frame timestamp leaves the
specified interval. In other words, the command is sent when the
previous frame timestamp was in the given interval, and the
current is not.
</p></dd>
</dl>
<p>If <var>FLAGS</var> is not specified, a default value of <code>[enter]</code> is
assumed.
</p>
<p><var>TARGET</var> specifies the target of the command, usually the name of
the filter class or a specific filter instance name.
</p>
<p><var>COMMAND</var> specifies the name of the command for the target filter.
</p>
<p><var>ARG</var> is optional and specifies the optional list of argument for
the given <var>COMMAND</var>.
</p>
<p>Between one interval specification and another, whitespaces, or
sequences of characters starting with <code>#</code> until the end of line,
are ignored and can be used to annotate comments.
</p>
<p>A simplified BNF description of the commands specification syntax
follows:
</p><div class="example">
<pre class="example"><var>COMMAND_FLAG</var> ::= "enter" | "leave"
<var>COMMAND_FLAGS</var> ::= <var>COMMAND_FLAG</var> [(+|"|")<var>COMMAND_FLAG</var>]
<var>COMMAND</var> ::= ["[" <var>COMMAND_FLAGS</var> "]"] <var>TARGET</var> <var>COMMAND</var> [<var>ARG</var>]
<var>COMMANDS</var> ::= <var>COMMAND</var> [,<var>COMMANDS</var>]
<var>INTERVAL</var> ::= <var>START</var>[-<var>END</var>] <var>COMMANDS</var>
<var>INTERVALS</var> ::= <var>INTERVAL</var>[;<var>INTERVALS</var>]
</pre></div>
<a name="Examples-2"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-2">11.2.2 Examples</a></h3>
<ul>
<li>
Specify audio tempo change at second 4:
<div class="example">
<pre class="example">asendcmd=c='4.0 atempo tempo 1.5',atempo
</pre></div>
</li><li>
Specify a list of drawtext and hue commands in a file.
<div class="example">
<pre class="example"># show text in the interval 5-10
5.0-10.0 [enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=hello world',
[leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=';
# desaturate the image in the interval 15-20
15.0-20.0 [enter] hue reinit s=0,
[enter] drawtext reinit 'fontfile=FreeSerif.ttf:text=nocolor',
[leave] hue reinit s=1,
[leave] drawtext reinit 'fontfile=FreeSerif.ttf:text=color';
# apply an exponential saturation fade-out effect, starting from time 25
25 [enter] hue s=exp(t-25)
</pre></div>
<p>A filtergraph allowing to read and process the above command list
stored in a file ‘<tt>test.cmd</tt>’, can be specified with:
</p><div class="example">
<pre class="example">sendcmd=f=test.cmd,drawtext=fontfile=FreeSerif.ttf:text='',hue
</pre></div>
</li></ul>
<p><a name="setpts"></a>
</p><a name="asetpts_002c-setpts"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-asetpts_002c-setpts">11.3 asetpts, setpts</a></h2>
<p>Change the PTS (presentation timestamp) of the input frames.
</p>
<p><code>asetpts</code> works on audio frames, <code>setpts</code> on video frames.
</p>
<p>Accept in input an expression evaluated through the eval API, which
can contain the following constants:
</p>
<dl compact="compact">
<dt>‘<samp>FRAME_RATE</samp>’</dt>
<dd><p>frame rate, only defined for constant frame-rate video
</p>
</dd>
<dt>‘<samp>PTS</samp>’</dt>
<dd><p>the presentation timestamp in input
</p>
</dd>
<dt>‘<samp>N</samp>’</dt>
<dd><p>the count of the input frame, starting from 0.
</p>
</dd>
<dt>‘<samp>NB_CONSUMED_SAMPLES</samp>’</dt>
<dd><p>the number of consumed samples, not including the current frame (only
audio)
</p>
</dd>
<dt>‘<samp>NB_SAMPLES</samp>’</dt>
<dd><p>the number of samples in the current frame (only audio)
</p>
</dd>
<dt>‘<samp>SAMPLE_RATE</samp>’</dt>
<dd><p>audio sample rate
</p>
</dd>
<dt>‘<samp>STARTPTS</samp>’</dt>
<dd><p>the PTS of the first frame
</p>
</dd>
<dt>‘<samp>STARTT</samp>’</dt>
<dd><p>the time in seconds of the first frame
</p>
</dd>
<dt>‘<samp>INTERLACED</samp>’</dt>
<dd><p>tell if the current frame is interlaced
</p>
</dd>
<dt>‘<samp>T</samp>’</dt>
<dd><p>the time in seconds of the current frame
</p>
</dd>
<dt>‘<samp>TB</samp>’</dt>
<dd><p>the time base
</p>
</dd>
<dt>‘<samp>POS</samp>’</dt>
<dd><p>original position in the file of the frame, or undefined if undefined
for the current frame
</p>
</dd>
<dt>‘<samp>PREV_INPTS</samp>’</dt>
<dd><p>previous input PTS
</p>
</dd>
<dt>‘<samp>PREV_INT</samp>’</dt>
<dd><p>previous input time in seconds
</p>
</dd>
<dt>‘<samp>PREV_OUTPTS</samp>’</dt>
<dd><p>previous output PTS
</p>
</dd>
<dt>‘<samp>PREV_OUTT</samp>’</dt>
<dd><p>previous output time in seconds
</p></dd>
</dl>
<a name="Examples-5"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-5">11.3.1 Examples</a></h3>
<ul>
<li>
Start counting PTS from zero
<div class="example">
<pre class="example">setpts=PTS-STARTPTS
</pre></div>
</li><li>
Apply fast motion effect:
<div class="example">
<pre class="example">setpts=0.5*PTS
</pre></div>
</li><li>
Apply slow motion effect:
<div class="example">
<pre class="example">setpts=2.0*PTS
</pre></div>
</li><li>
Set fixed rate of 25 frames per second:
<div class="example">
<pre class="example">setpts=N/(25*TB)
</pre></div>
</li><li>
Set fixed rate 25 fps with some jitter:
<div class="example">
<pre class="example">setpts='1/(25*TB) * (N + 0.05 * sin(N*2*PI/25))'
</pre></div>
</li><li>
Apply an offset of 10 seconds to the input PTS:
<div class="example">
<pre class="example">setpts=PTS+10/TB
</pre></div>
</li></ul>
<a name="ebur128"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-ebur128">11.4 ebur128</a></h2>
<p>EBU R128 scanner filter. This filter takes an audio stream as input and outputs
it unchanged. By default, it logs a message at a frequency of 10Hz with the
Momentary loudness (identified by <code>M</code>), Short-term loudness (<code>S</code>),
Integrated loudness (<code>I</code>) and Loudness Range (<code>LRA</code>).
</p>
<p>The filter also has a video output (see the <var>video</var> option) with a real
time graph to observe the loudness evolution. The graphic contains the logged
message mentioned above, so it is not printed anymore when this option is set,
unless the verbose logging is set. The main graphing area contains the
short-term loudness (3 seconds of analysis), and the gauge on the right is for
the momentary loudness (400 milliseconds).
</p>
<p>More information about the Loudness Recommendation EBU R128 on
<a href="http://tech.ebu.ch/loudness">http://tech.ebu.ch/loudness</a>.
</p>
<p>The filter accepts the following named parameters:
</p>
<dl compact="compact">
<dt>‘<samp>video</samp>’</dt>
<dd><p>Activate the video output. The audio stream is passed unchanged whether this
option is set or no. The video stream will be the first output stream if
activated. Default is <code>0</code>.
</p>
</dd>
<dt>‘<samp>size</samp>’</dt>
<dd><p>Set the video size. This option is for video only. Default and minimum
resolution is <code>640x480</code>.
</p>
</dd>
<dt>‘<samp>meter</samp>’</dt>
<dd><p>Set the EBU scale meter. Default is <code>9</code>. Common values are <code>9</code> and
<code>18</code>, respectively for EBU scale meter +9 and EBU scale meter +18. Any
other integer value between this range is allowed.
</p>
</dd>
</dl>
<p>Example of real-time graph using <code>ffplay</code>, with a EBU scale meter +18:
</p><div class="example">
<pre class="example">ffplay -f lavfi -i "amovie=input.mp3,ebur128=video=1:meter=18 [out0][out1]"
</pre></div>
<p>Run an analysis with <code>ffmpeg</code>:
</p><div class="example">
<pre class="example">ffmpeg -nostats -i input.mp3 -filter_complex ebur128 -f null -
</pre></div>
<a name="settb_002c-asettb"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-settb_002c-asettb">11.5 settb, asettb</a></h2>
<p>Set the timebase to use for the output frames timestamps.
It is mainly useful for testing timebase configuration.
</p>
<p>It accepts in input an arithmetic expression representing a rational.
The expression can contain the constants "AVTB" (the
default timebase), "intb" (the input timebase) and "sr" (the sample rate,
audio only).
</p>
<p>The default value for the input is "intb".
</p>
<a name="Examples-14"></a>
<h3 class="subsection"><a href="ffmpeg-filters.html#toc-Examples-14">11.5.1 Examples</a></h3>
<ul>
<li>
Set the timebase to 1/25:
<div class="example">
<pre class="example">settb=1/25
</pre></div>
</li><li>
Set the timebase to 1/10:
<div class="example">
<pre class="example">settb=0.1
</pre></div>
</li><li>
Set the timebase to 1001/1000:
<div class="example">
<pre class="example">settb=1+0.001
</pre></div>
</li><li>
Set the timebase to 2*intb:
<div class="example">
<pre class="example">settb=2*intb
</pre></div>
</li><li>
Set the default timebase value:
<div class="example">
<pre class="example">settb=AVTB
</pre></div>
</li></ul>
<a name="concat"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-concat">11.6 concat</a></h2>
<p>Concatenate audio and video streams, joining them together one after the
other.
</p>
<p>The filter works on segments of synchronized video and audio streams. All
segments must have the same number of streams of each type, and that will
also be the number of streams at output.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>Set the number of segments. Default is 2.
</p>
</dd>
<dt>‘<samp>v</samp>’</dt>
<dd><p>Set the number of output video streams, that is also the number of video
streams in each segment. Default is 1.
</p>
</dd>
<dt>‘<samp>a</samp>’</dt>
<dd><p>Set the number of output audio streams, that is also the number of video
streams in each segment. Default is 0.
</p>
</dd>
<dt>‘<samp>unsafe</samp>’</dt>
<dd><p>Activate unsafe mode: do not fail if segments have a different format.
</p>
</dd>
</dl>
<p>The filter has <var>v</var>+<var>a</var> outputs: first <var>v</var> video outputs, then
<var>a</var> audio outputs.
</p>
<p>There are <var>n</var>x(<var>v</var>+<var>a</var>) inputs: first the inputs for the first
segment, in the same order as the outputs, then the inputs for the second
segment, etc.
</p>
<p>Related streams do not always have exactly the same duration, for various
reasons including codec frame size or sloppy authoring. For that reason,
related synchronized streams (e.g. a video and its audio track) should be
concatenated at once. The concat filter will use the duration of the longest
stream in each segment (except the last one), and if necessary pad shorter
audio streams with silence.
</p>
<p>For this filter to work correctly, all segments must start at timestamp 0.
</p>
<p>All corresponding streams must have the same parameters in all segments; the
filtering system will automatically select a common pixel format for video
streams, and a common sample format, sample rate and channel layout for
audio streams, but other settings, such as resolution, must be converted
explicitly by the user.
</p>
<p>Different frame rates are acceptable but will result in variable frame rate
at output; be sure to configure the output file to handle it.
</p>
<p>Examples:
</p><ul>
<li>
Concatenate an opening, an episode and an ending, all in bilingual version
(video in stream 0, audio in streams 1 and 2):
<div class="example">
<pre class="example">ffmpeg -i opening.mkv -i episode.mkv -i ending.mkv -filter_complex \
'[0:0] [0:1] [0:2] [1:0] [1:1] [1:2] [2:0] [2:1] [2:2]
concat=n=3:v=1:a=2 [v] [a1] [a2]' \
-map '[v]' -map '[a1]' -map '[a2]' output.mkv
</pre></div>
</li><li>
Concatenate two parts, handling audio and video separately, using the
(a)movie sources, and adjusting the resolution:
<div class="example">
<pre class="example">movie=part1.mp4, scale=512:288 [v1] ; amovie=part1.mp4 [a1] ;
movie=part2.mp4, scale=512:288 [v2] ; amovie=part2.mp4 [a2] ;
[v1] [v2] concat [outv] ; [a1] [a2] concat=v=0:a=1 [outa]
</pre></div>
<p>Note that a desync will happen at the stitch if the audio and video streams
do not have exactly the same duration in the first file.
</p>
</li></ul>
<a name="showspectrum"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-showspectrum">11.7 showspectrum</a></h2>
<p>Convert input audio to a video output, representing the audio frequency
spectrum.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Specify the video size for the output. Default value is <code>640x480</code>.
</p></dd>
<dt>‘<samp>slide</samp>’</dt>
<dd><p>Specify if the spectrum should slide along the window. Default value is
<code>0</code>.
</p></dd>
</dl>
<p>The usage is very similar to the showwaves filter; see the examples in that
section.
</p>
<a name="showwaves"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-showwaves">11.8 showwaves</a></h2>
<p>Convert input audio to a video output, representing the samples waves.
</p>
<p>The filter accepts the following named parameters:
</p><dl compact="compact">
<dt>‘<samp>n</samp>’</dt>
<dd><p>Set the number of samples which are printed on the same column. A
larger value will decrease the frame rate. Must be a positive
integer. This option can be set only if the value for <var>rate</var>
is not explicitly specified.
</p>
</dd>
<dt>‘<samp>rate, r</samp>’</dt>
<dd><p>Set the (approximate) output frame rate. This is done by setting the
option <var>n</var>. Default value is "25".
</p>
</dd>
<dt>‘<samp>size, s</samp>’</dt>
<dd><p>Specify the video size for the output. Default value is "600x240".
</p></dd>
</dl>
<p>Some examples follow.
</p><ul>
<li>
Output the input file audio and the corresponding video representation
at the same time:
<div class="example">
<pre class="example">amovie=a.mp3,asplit[out0],showwaves[out1]
</pre></div>
</li><li>
Create a synthetic signal and show it with showwaves, forcing a
framerate of 30 frames per second:
<div class="example">
<pre class="example">aevalsrc=sin(1*2*PI*t)*sin(880*2*PI*t):cos(2*PI*200*t),asplit[out0],showwaves=r=30[out1]
</pre></div>
</li></ul>
<a name="Multimedia-Sources"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Multimedia-Sources">12 Multimedia Sources</a></h1>
<p>Below is a description of the currently available multimedia sources.
</p>
<a name="amovie"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-amovie">12.1 amovie</a></h2>
<p>This is the same as <a href="#movie">movie</a> source, except it selects an audio
stream by default.
</p>
<p><a name="movie"></a>
</p><a name="movie-1"></a>
<h2 class="section"><a href="ffmpeg-filters.html#toc-movie-1">12.2 movie</a></h2>
<p>Read audio and/or video stream(s) from a movie container.
</p>
<p>It accepts the syntax: <var>movie_name</var>[:<var>options</var>] where
<var>movie_name</var> is the name of the resource to read (not necessarily
a file but also a device or a stream accessed through some protocol),
and <var>options</var> is an optional sequence of <var>key</var>=<var>value</var>
pairs, separated by ":".
</p>
<p>The description of the accepted options follows.
</p>
<dl compact="compact">
<dt>‘<samp>format_name, f</samp>’</dt>
<dd><p>Specifies the format assumed for the movie to read, and can be either
the name of a container or an input device. If not specified the
format is guessed from <var>movie_name</var> or by probing.
</p>
</dd>
<dt>‘<samp>seek_point, sp</samp>’</dt>
<dd><p>Specifies the seek point in seconds, the frames will be output
starting from this seek point, the parameter is evaluated with
<code>av_strtod</code> so the numerical value may be suffixed by an IS
postfix. Default value is "0".
</p>
</dd>
<dt>‘<samp>streams, s</samp>’</dt>
<dd><p>Specifies the streams to read. Several streams can be specified,
separated by "+". The source will then have as many outputs, in the
same order. The syntax is explained in the “Stream specifiers”
section in the ffmpeg manual. Two special names, "dv" and "da" specify
respectively the default (best suited) video and audio stream. Default
is "dv", or "da" if the filter is called as "amovie".
</p>
</dd>
<dt>‘<samp>stream_index, si</samp>’</dt>
<dd><p>Specifies the index of the video stream to read. If the value is -1,
the best suited video stream will be automatically selected. Default
value is "-1". Deprecated. If the filter is called "amovie", it will select
audio instead of video.
</p>
</dd>
<dt>‘<samp>loop</samp>’</dt>
<dd><p>Specifies how many times to read the stream in sequence.
If the value is less than 1, the stream will be read again and again.
Default value is "1".
</p>
<p>Note that when the movie is looped the source timestamps are not
changed, so it will generate non monotonically increasing timestamps.
</p></dd>
</dl>
<p>This filter allows to overlay a second video on top of main input of
a filtergraph as shown in this graph:
</p><div class="example">
<pre class="example">input -----------> deltapts0 --> overlay --> output
^
|
movie --> scale--> deltapts1 -------+
</pre></div>
<p>Some examples follow.
</p>
<ul>
<li>
Skip 3.2 seconds from the start of the avi file in.avi, and overlay it
on top of the input labelled as "in":
<div class="example">
<pre class="example">movie=in.avi:seek_point=3.2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
</pre></div>
</li><li>
Read from a video4linux2 device, and overlay it on top of the input
labelled as "in":
<div class="example">
<pre class="example">movie=/dev/video0:f=video4linux2, scale=180:-1, setpts=PTS-STARTPTS [movie];
[in] setpts=PTS-STARTPTS, [movie] overlay=16:16 [out]
</pre></div>
</li><li>
Read the first video stream and the audio stream with id 0x81 from
dvd.vob; the video is connected to the pad named "video" and the audio is
connected to the pad named "audio":
<div class="example">
<pre class="example">movie=dvd.vob:s=v:0+#0x81 [video] [audio]
</pre></div>
</li></ul>
<a name="See-Also"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-See-Also">13 See Also</a></h1>
<p><a href="ffmpeg.html">ffmpeg</a>, <a href="ffplay.html">ffplay</a>, <a href="ffprobe.html">ffprobe</a>, <a href="ffserver.html">ffserver</a>,
<a href="libavfilter.html">libavfilter</a>
</p>
<a name="Authors"></a>
<h1 class="chapter"><a href="ffmpeg-filters.html#toc-Authors">14 Authors</a></h1>
<p>The FFmpeg developers.
</p>
<p>For details about the authorship, see the Git history of the project
(git://source.ffmpeg.org/ffmpeg), e.g. by typing the command
<code>git log</code> in the FFmpeg source directory, or browsing the
online repository at <a href="http://source.ffmpeg.org">http://source.ffmpeg.org</a>.
</p>
<p>Maintainers for the specific components are listed in the file
‘<tt>MAINTAINERS</tt>’ in the source code tree.
</p>
<footer class="footer pagination-right">
<span class="label label-info">This document was generated on <i>June 12, 2013</i> using <a href="http://www.nongnu.org/texi2html/"><i>texi2html 5.0</i></a>.</span></footer></div>
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