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<section id="convolution-filters-py-circular-convolution">
<h1>05-convolution-filters.py - Circular convolution.<a class="headerlink" href="#convolution-filters-py-circular-convolution" title="Permalink to this heading">¶</a></h1>
<p>A circular convolution is defined as the integral of the
product of two functions after one is reversed and shifted.</p>
<p>Circular convolution allows to implement very complex FIR
filters, at a CPU cost that is related to the filter impulse
response (kernel) length.</p>
<p>Within pyo, there is a family of IR* filter objects using
circular convolution with predefined kernel:</p>
<ul class="simple">
<li><p>IRAverage : moving average filter</p></li>
<li><p>IRFM : FM-like filter</p></li>
<li><p>IRPulse : comb-like filter</p></li>
<li><p>RWinSinc : break wall filters (lp, hp, hp, br)</p></li>
</ul>
<p>For general circular convolution, use the Convolve object
with a PyoTableObject as the kernel, as in this example:</p>
<p>A white noise is filtered by four impulses taken from the input mic.</p>
<p>Call r1.play(), r2.play(), r3.play() or r4.play() in the Interpreter
field while making some noise in the mic to fill the impulse response
tables. The slider handles the morphing between the four kernels.</p>
<p>Call t1.view(), t2.view(), t3.view() or t4.view() to view impulse
response tables.</p>
<p>Because circular convolution is very expensive, TLEN (in samples)
should be keep small.</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="c1"># duplex=1 to tell the Server we need both input and output sounds.</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="n">duplex</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span><span class="o">.</span><span class="n">boot</span><span class="p">()</span>
<span class="c1"># Length of the impulse response in samples.</span>
<span class="n">TLEN</span> <span class="o">=</span> <span class="mi">512</span>
<span class="c1"># Conversion to seconds for NewTable objects.</span>
<span class="n">DUR</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/functions/conv.html#pyo.sampsToSec" title="pyo.sampsToSec"><span class="n">sampsToSec</span></a><span class="p">(</span><span class="n">TLEN</span><span class="p">)</span>
<span class="c1"># Excitation signal for the filters.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Noise" title="pyo.lib.generators.Noise"><span class="n">sf</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Noise" title="pyo.lib.generators.Noise"><span class="n">Noise</span></a><span class="p">(</span><span class="mf">0.5</span><span class="p">)</span>
<span class="c1"># Signal from the mic to record the kernels.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">inmic</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">Input</span></a><span class="p">()</span>
<span class="c1"># Four tables and recorders.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t1</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">NewTable</span></a><span class="p">(</span><span class="n">length</span><span class="o">=</span><span class="n">DUR</span><span class="p">,</span> <span class="n">chnls</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">r1</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">TableRec</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">inmic</span></a><span class="p">,</span> <span class="n">table</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t1</span></a><span class="p">,</span> <span class="n">fadetime</span><span class="o">=</span><span class="mf">0.001</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t2</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">NewTable</span></a><span class="p">(</span><span class="n">length</span><span class="o">=</span><span class="n">DUR</span><span class="p">,</span> <span class="n">chnls</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">r2</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">TableRec</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">inmic</span></a><span class="p">,</span> <span class="n">table</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t2</span></a><span class="p">,</span> <span class="n">fadetime</span><span class="o">=</span><span class="mf">0.001</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t3</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">NewTable</span></a><span class="p">(</span><span class="n">length</span><span class="o">=</span><span class="n">DUR</span><span class="p">,</span> <span class="n">chnls</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">r3</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">TableRec</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">inmic</span></a><span class="p">,</span> <span class="n">table</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t3</span></a><span class="p">,</span> <span class="n">fadetime</span><span class="o">=</span><span class="mf">0.001</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t4</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">NewTable</span></a><span class="p">(</span><span class="n">length</span><span class="o">=</span><span class="n">DUR</span><span class="p">,</span> <span class="n">chnls</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">r4</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableRec" title="pyo.lib.tableprocess.TableRec"><span class="n">TableRec</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Input" title="pyo.lib.generators.Input"><span class="n">inmic</span></a><span class="p">,</span> <span class="n">table</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t4</span></a><span class="p">,</span> <span class="n">fadetime</span><span class="o">=</span><span class="mf">0.001</span><span class="p">)</span>
<span class="c1"># Interpolation control between the tables.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">pha</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">Sig</span></a><span class="p">(</span><span class="mi">0</span><span class="p">)</span>
<span class="n">pha</span><span class="o">.</span><span class="n">ctrl</span><span class="p">(</span><span class="n">title</span><span class="o">=</span><span class="s2">"Impulse responses morphing"</span><span class="p">)</span>
<span class="c1"># Morphing between the four impulse responses.</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">res</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">NewTable</span></a><span class="p">(</span><span class="n">length</span><span class="o">=</span><span class="n">DUR</span><span class="p">,</span> <span class="n">chnls</span><span class="o">=</span><span class="mi">1</span><span class="p">)</span>
<a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableMorph" title="pyo.lib.tableprocess.TableMorph"><span class="n">morp</span></a> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tableprocess.html#pyo.TableMorph" title="pyo.lib.tableprocess.TableMorph"><span class="n">TableMorph</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/controls.html#pyo.Sig" title="pyo.lib._core.Sig"><span class="n">pha</span></a><span class="p">,</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">res</span></a><span class="p">,</span> <span class="p">[</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t1</span></a><span class="p">,</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t2</span></a><span class="p">,</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t3</span></a><span class="p">,</span> <a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">t4</span></a><span class="p">])</span>
<span class="c1"># Circular convolution between the excitation and the morphed kernel.</span>
<span class="n">a</span> <span class="o">=</span> <a class="sphinx-codeautolink-a" href="../../api/classes/effects.html#pyo.Convolve" title="pyo.lib.effects.Convolve"><span class="n">Convolve</span></a><span class="p">(</span><a class="sphinx-codeautolink-a" href="../../api/classes/generators.html#pyo.Noise" title="pyo.lib.generators.Noise"><span class="n">sf</span></a><span class="p">,</span> <span class="n">table</span><span class="o">=</span><a class="sphinx-codeautolink-a" href="../../api/classes/tables.html#pyo.NewTable" title="pyo.lib.tables.NewTable"><span class="n">res</span></a><span class="p">,</span> <span class="n">size</span><span class="o">=</span><span class="n">res</span><span class="o">.</span><span class="n">getSize</span><span class="p">(),</span> <span class="n">mul</span><span class="o">=</span><span class="mf">0.1</span><span class="p">)</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="o">.</span><span class="n">out</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>
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