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<section id="handling-channels-py-managing-object-s-internal-audio-streams">
<h1>08-handling-channels.py - Managing object’s internal audio streams.<a class="headerlink" href="#handling-channels-py-managing-object-s-internal-audio-streams" title="Permalink to this heading">¶</a></h1>
<p>Because audio objects expand their number of streams according to lists
given to their arguments and the fact that an audio object is considered
as a list, if a multi-streams object is given as an argument to another
audio object, the later will also be expanded in order to process all
given streams. This is really powerful to create polyphonic processes
without copying long chunks of code but it can be very CPU expensive.</p>
<p>In this example, we create a square from a sum of sine waves. After that,
a chorus is applied to the resulting waveform. If we don’t mix down the
square wave, we got tens of Chorus objects in the processing chain (one
per sine). This can easily overrun the CPU. The exact same result can
be obtained with only one Chorus applied to the sum of the sine waves.
The <cite>mix(voices)</cite> method of the PyoObject helps the handling of channels
in order to save CPU cycles. Here, we down mix all streams to only two
streams (to maintain the stereo) before processing the Chorus arguments.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <a class="sphinx-codeautolink-a" href="../../api/alphabetical.html#module-pyo" title="pyo"><span class="nn">pyo</span></a> <span class="kn">import</span> <span class="o">*</span>
<span class="n">s</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/server.html#pyo.Server" title="pyo.lib.server.Server"><span class="n">Server</span></a><span class="p">()</span><span class="o">.</span><span class="n">boot</span><span class="p">()</span>
<span class="c1"># Sets fundamental frequency and highest harmonic.</span>
<span class="n">freq</span> <span class="o">=</span> <span class="mi">100</span>
<span class="n">high</span> <span class="o">=</span> <span class="mi">20</span>
<span class="c1"># Generates lists for frequencies and amplitudes</span>
<span class="n">harms</span> <span class="o">=</span> <span class="p">[</span><span class="n">freq</span> <span class="o">*</span> <span class="n">i</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">high</span><span class="p">)</span> <span class="k">if</span> <span class="n">i</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">1</span><span class="p">]</span>
<span class="n">amps</span> <span class="o">=</span> <span class="p">[</span><span class="mf">0.33</span> <span class="o">/</span> <span class="n">i</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span> <span class="n">high</span><span class="p">)</span> <span class="k">if</span> <span class="n">i</span> <span class="o">%</span> <span class="mi">2</span> <span class="o">==</span> <span class="mi">1</span><span class="p">]</span>
<span class="c1"># Creates a square wave by additive synthesis.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Sine" title="pyo.lib.generators.Sine"><span class="n">a</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Sine" title="pyo.lib.generators.Sine"><span class="n">Sine</span></a><span class="p">(</span><span class="n">freq</span><span class="o">=</span><span class="n">harms</span><span class="p">,</span> <span class="n">mul</span><span class="o">=</span><span class="n">amps</span><span class="p">)</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Number of Sine streams: </span><span class="si">%d</span><span class="s2">"</span> <span class="o">%</span> <span class="nb">len</span><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Sine" title="pyo.lib.generators.Sine"><span class="n">a</span></a><span class="p">))</span>
<span class="c1"># Mix down the number of streams of "a" before computing the Chorus.</span>
<span class="n">b</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/effects.html#pyo.Chorus" title="pyo.lib.effects.Chorus"><span class="n">Chorus</span></a><span class="p">(</span><span class="n">a</span><span class="o">.</span><span class="n">mix</span><span class="p">(</span><span class="mi">2</span><span class="p">),</span> <span class="n">feedback</span><span class="o">=</span><span class="mf">0.5</span><span class="p">)</span><span class="o">.</span><span class="n">out</span><span class="p">()</span>
<span class="nb">print</span><span class="p">(</span><span class="s2">"Number of Chorus streams: </span><span class="si">%d</span><span class="s2">"</span> <span class="o">%</span> <span class="nb">len</span><span class="p">(</span><span class="n">b</span><span class="p">))</span>
<span class="n">s</span><span class="o">.</span><span class="n">gui</span><span class="p">(</span><span class="nb">locals</span><span class="p">())</span>
</pre></div>
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