Help/UGens/FFT/SpecCentroid.html

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  24 <p class="p1"><b>SpecCentroid<span class="Apple-tab-span">      </span><span class="Apple-tab-span">    </span>Spectral centroid</b></p>
  25 <p class="p2"><br></p>
  26 <p class="p3"><b><span class="Apple-tab-span">  </span>SpecCentroid.kr(chain)</b></p>
  27 <p class="p2"><br></p>
  28 <p class="p3">Given an <a href="FFT.html"><span class="s1">FFT</span></a> <b>chain</b>, this measures the <i>spectral centroid</i>, which is the weighted mean frequency, or the "centre of mass" of the spectrum. (DC is ignored.)</p>
  29 <p class="p2"><br></p>
  30 <p class="p3">This can be a useful indicator of the perceptual <i>brightness</i> of a signal.</p>
  31 <p class="p2"><br></p>
  32 <p class="p2"><br></p>
  33 <p class="p3"><b>Example</b></p>
  34 <p class="p2"><br></p>
  35 <p class="p3">A <a href="../Oscillators/Blip.html"><span class="s2">Blip</span></a> oscillator is ideal for demonstrating this because the number of harmonics is directly manipulated: as the number of harmonics increases, the centroid is pushed higher. In the example, left-to-right changes the number of harmonics, but up-to-down changes the fundamental pitch; note the different effects of these two on the centroid.</p>
  36 <p class="p2"><br></p>
  37 <p class="p4">s.boot;</p>
  38 <p class="p4">b = <span class="s3">Buffer</span>.alloc(s,2048,1);</p>
  39 <p class="p4">(</p>
  40 <p class="p4">x = {</p>
  41 <p class="p4"><span class="s4">var</span> in, chain, freq, rq, centroid;</p>
  42 <p class="p5"><br></p>
  43 <p class="p6">//freq = LFPar.kr(0.3).exprange(100, 1000);</p>
  44 <p class="p4">freq = <span class="s4">MouseY</span>.kr(1000, 100, 1);</p>
  45 <p class="p5"><br></p>
  46 <p class="p4">in = <span class="s4">Blip</span>.ar(freq, <span class="s4">MouseX</span>.kr(1, 100, 1));</p>
  47 <p class="p5"><br></p>
  48 <p class="p4">chain = <span class="s4">FFT</span>(b, in);</p>
  49 <p class="p5"><br></p>
  50 <p class="p4">centroid = <span class="s4">SpecCentroid</span>.kr(chain);</p>
  51 <p class="p5"><br></p>
  52 <p class="p4"><span class="s4">Out</span>.ar(0, in.dup * 0.1);</p>
  53 <p class="p4">centroid.poll(10);</p>
  54 <p class="p4">}.play(s);</p>
  55 <p class="p4">)</p>
  56 <p class="p5"><br></p>
  57 <p class="p4">x.free;</p>
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