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<h2>
<span class="refentrytitle">pvsbufread</span>
</h2>
<p>pvsbufread —
This opcode reads a circular buffer of f-signals (streaming PV signals).
</p>
</div>
<div class="refsect1">
<a id="idm281472899857720"></a>
<h2>Description</h2>
<p>
This opcode reads from a circular buffer of length ilen (secs),
taking a handle for the buffer and a time pointer, which holds the
current read position (also in seconds). It is used in conjunction with a
<span class="emphasis"><em>pvsbuffer</em></span> opocde.
Reading is circular, wrapping around at the end of the buffer.
</p>
</div>
<div class="refsect1">
<a id="idm281472899796776"></a>
<h2>Syntax</h2>
<pre class="synopsis">fsig <span class="command"><strong>pvsbufread</strong></span> ktime, khandle[, ilo, ihi, iclear] </pre>
</div>
<div class="refsect1">
<a id="idm281472899794552"></a>
<h2>Initialisation</h2>
<p>
<span class="emphasis"><em>ilo, ihi</em></span> -- set the lowest and highest freqs to be read from the buffer (defaults to 0, Nyquist).
</p>
<p>
<span class="emphasis"><em>iclear</em></span> -- set to 1 to clear output fsig before every write (default 1), 0 tells the opcode not to clear
the output fsig. This is relevant when writing to subsets of an fsig frame using <span class="emphasis"><em>ilo</em></span>, <span class="emphasis"><em>ihi</em></span>.
</p>
</div>
<div class="refsect1">
<a id="idm281472899791032"></a>
<h2>Performance</h2>
<p>
<span class="emphasis"><em>fsig</em></span> -- output pv stream
</p>
<p>
<span class="emphasis"><em>ktime</em></span> -- time position of reading pointer (in secs).
</p>
<p>
<span class="emphasis"><em>khandle</em></span> -- handle identifying the buffer to be read. When using k-rate
handles, it is important to initialise the k-rate variable to a given existing handle. When changing
buffers, fsig buffers need to be compatible (same fsig format).
</p>
<p>
With this opcode and <a class="link" href="pvsbuffer.html" title="pvsbuffer"><em class="citetitle">pvsbuffer</em></a>, it is possible to, among other things:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">time-stretch/compress a fsig stream, by reading it at
different rates</li>
<li class="listitem">delay a fsig or portions of it.</li>
<li class="listitem">'brassage' two or more fsigs by switching buffers, since
the reading handles are k-rate. Note that, when using k-rate
handles, it is important to initialise the k-rate variable to a
given handle (so that the fsig initialisation can take place)
and it is only possible to switch handles between compatible
fsig buffers (with the same fftsize and overlap).</li>
</ul>
</div>
<p>
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<table border="0" summary="Note">
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<td rowspan="2" align="center" valign="top" width="25">
<img alt="[Note]" src="images/note.png" />
</td>
<th align="left">Note</th>
</tr>
<tr>
<td align="left" valign="top">
<p>It is important that the handle value passed to <span class="emphasis"><em>pvsbufread</em></span> is valid and was created by <a class="link" href="pvsbuffer.html" title="pvsbuffer"><em class="citetitle">pvsbuffer</em></a>. Csound will crash with invalid handles.
</p>
</td>
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<div class="refsect1">
<a id="idm281472899781272"></a>
<h2>Examples</h2>
<p>
Here is an example of the pvsbufread opcode. It does 'brassage' by switching between two buffers.
</p>
<div class="example">
<a id="idm281472899780216"></a>
<p class="title">
<strong>Example 745. Example of the pvsbufread opcode</strong>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<pre class="programlisting">
fsig1 <span class="opc">pvsanal</span> asig1, 1024, 256, 1024, 1
fsig2 <span class="opc">pvsanal</span> asig2, 1024, 256, 1024, 1
ibuf1, kt1 <span class="opc">pvsbuffer</span> fsig1, 10 <span class="comment">; 10-sec buf with fsig1</span>
ibuf2, kt2 <span class="opc">pvsbuffer</span> fsig2, 7 <span class="comment">; 7-sec buf with fsig2</span>
khan <span class="opc">init</span> ibuf1 <span class="comment">; initialise handle to buf1</span>
<span class="opc">if</span> ktrig <span class="op">></span> 0 <span class="opc">then</span> <span class="comment">; switch buffers according to trigger</span>
khan <span class="op">=</span> ibuf2
<span class="opc">else</span>
khan <span class="op">=</span> ibuf1
<span class="opc">endif</span>
fsb <span class="opc">pvsbufread</span> kt1, khan <span class="comment">; read buffer</span></pre>
</div>
</div>
<p><br class="example-break" />
</p>
<p>
Here is an example of the pvsbufread opcode. It uses the file <a class="ulink" href="examples/pvsbufread.csd" target="_top"><em class="citetitle">pvsbufread.csd</em></a>.
</p>
<div class="example">
<a id="idm281472899762728"></a>
<p class="title">
<strong>Example 746. Example of the pvsbufread opcode.</strong>
</p>
<div class="example-contents">
<p>See the sections <a class="link" href="UsingRealTime.html" title="Real-Time Audio"><em class="citetitle">Real-time Audio</em></a> and <a class="link" href="CommandFlags.html" title="Csound command line"><em class="citetitle">Command Line Flags</em></a> for more information on using command line flags.</p>
<div class="refsect1">
<a id="idm281472720926760"></a>
<pre class="programlisting">
<span class="nt"><CsoundSynthesizer></span>
<span class="nt"><CsOptions></span>
<span class="c1">; Select audio/midi flags here according to platform</span>
<span class="c1">; Audio out Audio in</span>
-odac <span class="c1">;;;RT audio I/O</span>
<span class="c1">; For Non-realtime ouput leave only the line below:</span>
<span class="c1">; -o pvsbufread.wav -W ;;; for file output any platform</span>
<span class="nt"></CsOptions></span>
<span class="nt"><CsInstruments></span>
<span class="vg">sr</span> <span class="o">=</span> <span class="mi">44100</span>
<span class="vg">ksmps</span> <span class="o">=</span> <span class="mi">16</span>
<span class="vg">nchnls</span> <span class="o">=</span> <span class="mi">1</span>
<span class="vg">0dbfs</span> <span class="o">=</span> <span class="mi">1</span>
<span class="c1">;; example written by joachim heintz 2009</span>
<span class="kd">opcode</span> <span class="nf">FileToPvsBuf</span><span class="p">,</span> <span class="kt">iik</span><span class="p">,</span> <span class="kt">Siiii</span>
<span class="c1">;;writes an audio file at the first k-cycle to a fft-buffer (via pvsbuffer)</span>
S<span class="n">file</span><span class="p">,</span> i<span class="n">fftsize</span><span class="p">,</span> i<span class="n">overlap</span><span class="p">,</span> i<span class="n">winsize</span><span class="p">,</span> i<span class="n">winshape</span> <span class="nb">xin</span>
k<span class="n">timek</span> <span class="nb">timeinstk</span>
<span class="k">if</span> k<span class="n">timek</span> <span class="o">==</span> <span class="mi">1</span> <span class="k">then</span>
i<span class="n">len</span> <span class="nb">filelen</span> S<span class="n">file</span>
k<span class="n">cycles</span> <span class="o">=</span> i<span class="n">len</span> <span class="o">*</span> <span class="vg">kr</span><span class="c1">; number of k-cycles to write the fft-buffer</span>
k<span class="n">count</span> <span class="nb">init</span> <span class="mi">0</span>
<span class="nl">loop</span><span class="p">:</span>
a<span class="n">in</span> <span class="nb">soundin</span> S<span class="n">file</span>
<span class="n">fftin</span> <span class="nb">pvsanal</span> a<span class="n">in</span><span class="p">,</span> i<span class="n">fftsize</span><span class="p">,</span> i<span class="n">overlap</span><span class="p">,</span> i<span class="n">winsize</span><span class="p">,</span> i<span class="n">winshape</span>
i<span class="n">buf</span><span class="p">,</span> k<span class="n">tim</span> <span class="nb">pvsbuffer</span> <span class="n">fftin</span><span class="p">,</span> i<span class="n">len</span> <span class="o">+</span> <span class="p">(</span>i<span class="n">fftsize</span> <span class="o">/</span> <span class="vg">sr</span><span class="p">)</span>
<span class="k">loop_lt</span> k<span class="n">count</span><span class="p">,</span> <span class="mi">1</span><span class="p">,</span> k<span class="n">cycles</span><span class="p">,</span> <span class="nl">loop</span>
<span class="nb">xout</span> i<span class="n">buf</span><span class="p">,</span> i<span class="n">len</span><span class="p">,</span> k<span class="n">tim</span>
<span class="k">endif</span>
<span class="kd">endop</span>
<span class="kd">instr</span> <span class="nf">1</span>
i<span class="n">fftsize</span> <span class="o">=</span> <span class="mi">1024</span>
i<span class="n">overlap</span> <span class="o">=</span> i<span class="n">fftsize</span> <span class="o">/</span> <span class="mi">4</span>
i<span class="n">winsize</span> <span class="o">=</span> i<span class="n">fftsize</span>
i<span class="n">winshape</span> <span class="o">=</span> <span class="mi">1</span><span class="c1">; von-Hann window</span>
i<span class="n">buffer</span><span class="p">,</span> i<span class="n">len</span><span class="p">,</span> k<span class="n">0</span> <span class="nf">FileToPvsBuf</span> <span class="s">"fox.wav"</span><span class="p">,</span> i<span class="n">fftsize</span><span class="p">,</span> i<span class="n">overlap</span><span class="p">,</span> i<span class="n">winsize</span><span class="p">,</span> i<span class="n">winshape</span>
k<span class="n">tmpnt</span> <span class="nb">linseg</span> i<span class="n">len</span><span class="p">,</span> <span class="nb">p3</span><span class="p">,</span> <span class="mi">0</span><span class="c1">; reads the buffer backwards in p3 seconds</span>
<span class="n">fread</span> <span class="nb">pvsbufread</span> k<span class="n">tmpnt</span><span class="p">,</span> i<span class="n">buffer</span>
a<span class="n">out</span> <span class="nb">pvsynth</span> <span class="n">fread</span>
<span class="nb">out</span> a<span class="n">out</span>
<span class="kd">endin</span>
<span class="nt"></CsInstruments></span>
<span class="nt"><CsScore></span>
<span class="nb">i</span> <span class="mi">1</span> <span class="mi">0</span> <span class="mi">5</span>
<span class="nb">e</span>
<span class="nt"></CsScore></span>
<span class="nt"></CsoundSynthesizer></span>
</pre>
</div>
</div>
</div>
<p><br class="example-break" />
</p>
</div>
<div class="refsect1">
<a id="idm281472899758440"></a>
<h2>See Also</h2>
<p>
<a class="link" href="pvsanal.html" title="pvsanal"><em class="citetitle">pvsanal</em></a>,
<a class="link" href="pvsynth.html" title="pvsynth"><em class="citetitle">pvsynth</em></a>,
<a class="link" href="pvsbuffer.html" title="pvsbuffer"><em class="citetitle">pvsbuffer</em></a>,
<a class="link" href="pvsadsyn.html" title="pvsadsyn"><em class="citetitle">pvsadsyn</em></a>
</p>
</div>
<div class="refsect1">
<a id="idm281472899753512"></a>
<h2>Credits</h2>
<p>
</p>
<table border="0" summary="Simple list" class="simplelist">
<tr>
<td>Author: Victor Lazzarini</td>
</tr>
<tr>
<td>July 2007</td>
</tr>
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