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<p class="p1"><b>PV_MagSmooth<span class="Apple-tab-span"> </span><span class="Apple-tab-span"> </span>Smooth spectral magnitudes over time</b></p>
<p class="p2"><br></p>
<p class="p3"><span class="Apple-tab-span"> </span><b>chain = PV_MagSmooth(chain, factor)</b></p>
<p class="p2"><br></p>
<p class="p4">Smooths out the magnitude of FFT bins over time using <i>recursive averaging</i>, according to <b>factor</b> which varies from 0 (no smoothing occurs) to 1 ("infinite" smoothing, magnitudes never change).</p>
<p class="p5"><br></p>
<p class="p4">For each bin, the calculation looks like:</p>
<p class="p4"><span class="Apple-tab-span"> </span>mag = (prevmag * factor) + (mag * (1-factor))</p>
<p class="p5"><br></p>
<p class="p4"><b>Example</b></p>
<p class="p2"><br></p>
<p class="p6">s.boot;</p>
<p class="p6">b = <span class="s1">Buffer</span>.alloc(s, 1024);</p>
<p class="p7"><span class="s2">c = </span><span class="s1">Buffer</span><span class="s2">.read(s, </span>"sounds/a11wlk01.wav"<span class="s2">);</span></p>
<p class="p8"><br></p>
<p class="p6">(</p>
<p class="p6">x = {</p>
<p class="p6"><span class="s1">var</span> son, chain, out;</p>
<p class="p8"><br></p>
<p class="p6">son = <span class="s1">PlayBuf</span>.ar(1, c, loop: 1);</p>
<p class="p8"><br></p>
<p class="p6">chain = <span class="s1">FFT</span>(b, son);</p>
<p class="p6">chain = <span class="s1">PV_MagSmooth</span>(chain, 1 - <span class="s1">MouseX</span>.kr(1, 0.00001, 1));</p>
<p class="p8"><br></p>
<p class="p6">out = <span class="s1">IFFT</span>(chain);</p>
<p class="p8"><br></p>
<p class="p6">(out * 0.3).dup</p>
<p class="p8"><br></p>
<p class="p6">}.play;</p>
<p class="p6">)</p>
<p class="p6">x.free;</p>
<p class="p8"><br></p>
<p class="p9">// This one subtracts the smoothed version away, to leave just the spiky bits!</p>
<p class="p9">// This is a fairly well-known basis of noise-removal by spectral subtraction,</p>
<p class="p9">// which works well if the noise is static or slow-changing while the signal<span class="Apple-converted-space"> </span></p>
<p class="p9">// is fast-changing.</p>
<p class="p9">// In this demo, mouse left/right controls the amount of smoothing,</p>
<p class="p9">//<span class="Apple-converted-space"> </span>and when the mousebutton is down you hear the "original"<span class="Apple-converted-space"> </span></p>
<p class="p9">//<span class="Apple-converted-space"> </span>(otherwise you hear the "cleaned" version).</p>
<p class="p6">d = <span class="s1">Buffer</span>.alloc(s, 1024);</p>
<p class="p6">(</p>
<p class="p6">x = {</p>
<p class="p6"><span class="s1">var</span> son, chain, chainorig, chainsmooth, out;</p>
<p class="p8"><br></p>
<p class="p6">son = <span class="s1">PlayBuf</span>.ar(1, c, loop: 1);</p>
<p class="p8"><br></p>
<p class="p6">chain = <span class="s1">FFT</span>(b, son);</p>
<p class="p6">chainorig = <span class="s1">PV_Copy</span>(chain, d);</p>
<p class="p6">chainsmooth = <span class="s1">PV_MagSmooth</span>(chain, 1 - <span class="s1">MouseX</span>.kr(1, 0.00001, 1));</p>
<p class="p6">chain = <span class="s1">PV_MagSubtract</span>(chainorig, chainsmooth, 1);</p>
<p class="p8"><br></p>
<p class="p6">out = <span class="s1">XFade2</span>.ar(<span class="s1">IFFT</span>(chain), son, <span class="s1">MouseButton</span>.kr(-1,1));</p>
<p class="p8"><br></p>
<p class="p6">(out * 0.3).dup</p>
<p class="p8"><br></p>
<p class="p6">}.play;</p>
<p class="p6">)</p>
<p class="p6">x.free;</p>
<p class="p8"><br></p>
<p class="p8"><br></p>
<p class="p8"><br></p>
<p class="p6">b.free; c.free;</p>
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