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><H1
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><A
NAME="section-basics-types"
>2.4. Mimetypes and Properties</A
></H1
><P
> <SPAN
CLASS="application"
>GStreamer</SPAN
> uses a type system to ensure that the data passed between
elements is in a recognized format. The type system is also important
for ensuring that the parameters required to fully specify a format match
up correctly when linking pads between elements. Each link that is
made between elements has a specified type and optionally a set of
properties.
</P
><DIV
CLASS="sect2"
><H2
CLASS="sect2"
><A
NAME="sect2-types-basictypes"
>2.4.1. The Basic Types</A
></H2
><P
> <SPAN
CLASS="application"
>GStreamer</SPAN
> already supports many basic media types. Following is a
table of a few of the basic types used for buffers in
<SPAN
CLASS="application"
>GStreamer</SPAN
>. The table contains the name ("mime type") and a
description of the type, the properties associated with the type, and
the meaning of each property. A full list of supported types is
included in <A
HREF="section-types-definitions.html"
>List of Defined Types</A
>.
</P
><DIV
CLASS="table"
><A
NAME="table-basictypes"
></A
><P
><B
>Table 2-1. Table of Example Types</B
></P
><TABLE
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><COL><COL><COL><COL><COL><COL><THEAD
><TR
><TH
>Mime Type</TH
><TH
>Description</TH
><TH
>Property</TH
><TH
>Property Type</TH
><TH
>Property Values</TH
><TH
>Property Description</TH
></TR
></THEAD
><TBODY
VALIGN="top"
><TR
><TD
ROWSPAN="2"
>audio/*</TD
><TD
ROWSPAN="2"
> <SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>All audio types</I
></SPAN
>
</TD
><TD
>rate</TD
><TD
>integer</TD
><TD
>greater than 0</TD
><TD
> The sample rate of the data, in samples (per channel) per second.
</TD
></TR
><TR
><TD
>channels</TD
><TD
>integer</TD
><TD
>greater than 0</TD
><TD
> The number of channels of audio data.
</TD
></TR
><TR
><TD
ROWSPAN="4"
>audio/x-raw-int</TD
><TD
ROWSPAN="4"
> Unstructured and uncompressed raw integer audio data.
</TD
><TD
>endianness</TD
><TD
>integer</TD
><TD
>G_BIG_ENDIAN (4321) or G_LITTLE_ENDIAN (1234)</TD
><TD
> The order of bytes in a sample. The value G_LITTLE_ENDIAN (1234)
means <SPAN
CLASS="QUOTE"
>"little-endian"</SPAN
> (byte-order is <SPAN
CLASS="QUOTE"
>"least
significant byte first"</SPAN
>). The value G_BIG_ENDIAN (4321)
means <SPAN
CLASS="QUOTE"
>"big-endian"</SPAN
> (byte order is <SPAN
CLASS="QUOTE"
>"most
significant byte first"</SPAN
>).
</TD
></TR
><TR
><TD
>signed</TD
><TD
>boolean</TD
><TD
>TRUE or FALSE</TD
><TD
> Whether the values of the integer samples are signed or not.
Signed samples use one bit to indicate sign (negative or
positive) of the value. Unsigned samples are always positive.
</TD
></TR
><TR
><TD
>width</TD
><TD
>integer</TD
><TD
>greater than 0</TD
><TD
> Number of bits allocated per sample.
</TD
></TR
><TR
><TD
>depth</TD
><TD
>integer</TD
><TD
>greater than 0</TD
><TD
> The number of bits used per sample. This must be less than or
equal to the width: If the depth is less than the width, the
low bits are assumed to be the ones used. For example, a width
of 32 and a depth of 24 means that each sample is stored in a
32 bit word, but only the low 24 bits are actually used.
</TD
></TR
><TR
><TD
ROWSPAN="4"
>audio/mpeg</TD
><TD
ROWSPAN="4"
> Audio data compressed using the MPEG audio encoding scheme.
</TD
><TD
>mpegversion</TD
><TD
>integer</TD
><TD
>1, 2 or 4</TD
><TD
> The MPEG-version used for encoding the data. The value 1 refers
to MPEG-1, -2 and -2.5 layer 1, 2 or 3. The values 2 and 4 refer
to the MPEG-AAC audio encoding schemes.
</TD
></TR
><TR
><TD
>framed</TD
><TD
>boolean</TD
><TD
>0 or 1</TD
><TD
> A true value indicates that each buffer contains exactly one
frame. A false value indicates that frames and buffers do not
necessarily match up.
</TD
></TR
><TR
><TD
>layer</TD
><TD
>integer</TD
><TD
>1, 2, or 3</TD
><TD
> The compression scheme layer used to compress the data
<SPAN
CLASS="emphasis"
><I
CLASS="emphasis"
>(only if mpegversion=1)</I
></SPAN
>.
</TD
></TR
><TR
><TD
>bitrate</TD
><TD
>integer</TD
><TD
>greater than 0</TD
><TD
> The bitrate, in bits per second. For VBR (variable bitrate)
MPEG data, this is the average bitrate.
</TD
></TR
><TR
><TD
>audio/x-vorbis</TD
><TD
>Vorbis audio data</TD
><TD
> </TD
><TD
> </TD
><TD
> </TD
><TD
> There are currently no specific properties defined for this type.
</TD
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