Help/UGens/FFT/PackFFT.html

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  23 <p class="p1"><span class="s1"><b>PackFFT<span class="Apple-tab-span">  </span></b></span><b>Pack separate demand-rate FFT bin streams into an FFT chain buffer</b></p>
  24 <p class="p2"><br></p>
  25 <p class="p1"><b>PackFFT(chain, bufsize, magsphases)</b></p>
  26 <p class="p2"><br></p>
  27 <p class="p1">Takes an array of magnitudes and phases, and packs them into an <a href="FFT.html"><span class="s2">FFT</span></a> buffer ready for transforming back into time-domain audio using <a href="IFFT.html"><span class="s2">IFFT</span></a>.</p>
  28 <p class="p2"><br></p>
  29 <p class="p1">Most people won't need to use this directly - instead, use <a href="pvcollect.html"><span class="s2">pvcollect</span></a>, <a href="pvcalc.html"><span class="s2">pvcalc</span></a>, or <a href="pvcalc2.html"><span class="s2">pvcalc2</span></a>.</p>
  30 <p class="p2"><br></p>
  31 <p class="p1">The input data is <b>magsphases</b>, which should be a flat array containing magnitude and phase of all bins in ascending order.<span class="Apple-converted-space"> </span></p>
  32 <p class="p1"><span class="Apple-tab-span">     </span>e.g. [mag0, phase0, mag1, phase1, mag2, phase2, ... magN, phaseN]</p>
  33 <p class="p1">This input is typically demand-rate.</p>
  34 <p class="p2"><br></p>
  35 <p class="p1">This is technically similar to <a href="../Synth control/Demand Rate/Demand.html"><span class="s2">Demand</span></a> or <a href="../Synth control/Demand Rate/Duty.html"><span class="s2">Duty</span></a> in that it calls demand-rate UGens further up the graph to process the values, eventually calling <a href="UnpackFFT.html"><span class="s2">UnpackFFT</span></a>. These two ends of the process must in most cases see the same chain...! Otherwise behaviour is undefined and, who knows, possibly unpleasant.</p>
  36 <p class="p2"><br></p>
  37 <p class="p1">Optional parameters: <b>frombin</b> and <b>tobin</b> allow you to fill the supplied data only into a subset of the FFT bins (i.e. a single delimited frequency band), and if you do this, you can also optionally set <b>zeroothers</b> to 1 to zero all the magnitudes outside this band (otherwise they stay intact).</p>
  38 <p class="p2"><br></p>
  39 <p class="p1">For usage examples, see <a href="UnpackFFT.html"><span class="s2">UnpackFFT</span></a>, but also <a href="pvcollect.html"><span class="s2">pvcollect</span></a>, <a href="pvcalc.html"><span class="s2">pvcalc</span></a>, <a href="pvcalc2.html"><span class="s2">pvcalc2</span></a>.</p>
  40 <p class="p2"><br></p>
  41 <p class="p2"><br></p>
  42 <p class="p2"><br></p>
  43 <p class="p1">Here's an unusual example which uses PackFFT <i>without</i> using UnpackFFT first - essentially creating our FFT data from scratch.</p>
  44 <p class="p2"><br></p>
  45 <p class="p3"><br></p>
  46 <p class="p4">// Reminder: This isn't the intended typical usage! It's OK to do this though.</p>
  47 <p class="p5">(</p>
  48 <p class="p5">x = {</p>
  49 <p class="p5"><span class="Apple-tab-span">     </span><span class="s3">var</span> mags, phases, chain, sig;</p>
  50 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// Create simple undulating magnitudes</p>
  51 <p class="p5"><span class="Apple-tab-span">     </span>mags = {<span class="s3">FSinOsc</span>.kr(<span class="s3">ExpRand</span>(0.1, 1)).range(0, 1)}.dup(100);</p>
  52 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// Then give them a "rolloff" to make the sound less unpleasant</p>
  53 <p class="p5"><span class="Apple-tab-span">     </span>mags = mags<span class="Apple-converted-space">  </span>* ((1, 0.99 .. 0.01).squared);</p>
  54 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// Let's turn the bins on and off at different rates, I'm *sure* that'll sound interesting</p>
  55 <p class="p5"><span class="Apple-tab-span">     </span>mags = mags * {<span class="s3">LFPulse</span>.kr(2 ** <span class="s3">IRand</span>(-3, 5)).range(0, 1)}.dup(100);</p>
  56 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// Let's ignore phase for now</p>
  57 <p class="p5"><span class="Apple-tab-span">     </span>phases = 0.dup(100);</p>
  58 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// We need to create an FFT chain to feed our data in to.</p>
  59 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// The easiest way is to do an FFT on some signal which we then ignore!</p>
  60 <p class="p5"><span class="Apple-tab-span">     </span>chain = <span class="s3">FFT</span>(<span class="s3">LocalBuf</span>(512), <span class="s3">FSinOsc</span>.ar);</p>
  61 <p class="p4"><span class="s4"><span class="Apple-tab-span">    </span></span>// Now we can do the packing</p>
  62 <p class="p5"><span class="Apple-tab-span">     </span>chain = <span class="s3">PackFFT</span>(chain, 512, [mags, phases].flop.flatten, 0, 99, 1);</p>
  63 <p class="p5"><span class="Apple-tab-span">     </span>sig = <span class="s3">IFFT</span>(chain);</p>
  64 <p class="p5"><span class="Apple-tab-span">     </span><span class="s3">Out</span>.ar(0, sig.dup);</p>
  65 <p class="p5">}.play(s);</p>
  66 <p class="p5">)</p>
  67 <p class="p5">x.free;</p>
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