Help/UGens/FFT/pvcalc.html

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  26 <p class="p1"><b>pvcalc<span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span>Process the bins of an FFT chain</b></p>
  27 <p class="p2"><br></p>
  28 <p class="p3"><b><span class="Apple-tab-span">  </span>chain = chain.pvcalc(numframes, func, frombin, tobin, zeroothers)</b></p>
  29 <p class="p2"><br></p>
  30 <p class="p3">pvcalc applies function <b>func</b> to the frequency-domain data of an FFT chain. <b>func</b> should be a function that takes two arrays as inputs (magnitude, and phase) and returns a resulting pair of arrays [magnitude, phase].</p>
  31 <p class="p2"><br></p>
  32 <p class="p3"><b>frombin</b>, <b>tobin</b>, and <b>zeroothers</b> are optional arguments which limit the processing to a specified integer range of FFT bins. If <b>zeroothers</b> is set to 1 then bins outside of the range being processed are silenced.</p>
  33 <p class="p2"><br></p>
  34 <p class="p3">See <a href="pvcollect.html"><span class="s1">pvcollect</span></a> for discussion of efficiency considerations. See also <a href="pvcalc2.html"><span class="s1">pvcalc2</span></a>, <a href="UnpackFFT.html"><span class="s1">UnpackFFT</span></a>.</p>
  35 <p class="p2"><br></p>
  36 <p class="p2"><br></p>
  37 <p class="p3"><b>Examples</b></p>
  38 <p class="p2"><br></p>
  39 <p class="p4">(</p>
  40 <p class="p4">s.boot.doWhenBooted{</p>
  41 <p class="p5"><span class="s2"><span class="Apple-tab-span">    </span>c = </span><span class="s3">Buffer</span><span class="s2">.read(s,</span>"sounds/a11wlk01.wav"<span class="s2">);</span></p>
  42 <p class="p4">}</p>
  43 <p class="p4">)</p>
  44 <p class="p6"><br></p>
  45 <p class="p4">(</p>
  46 <p class="p4">x = {</p>
  47 <p class="p4"><span class="Apple-tab-span">     </span><span class="s4">var</span> in, chain, v;</p>
  48 <p class="p4"><span class="Apple-tab-span">     </span>in = <span class="s4">PlayBuf</span>.ar(1, c, <span class="s4">BufRateScale</span>.kr(c), loop: 1);</p>
  49 <p class="p4"><span class="Apple-tab-span">     </span>chain = <span class="s4">FFT</span>(<span class="s4">LocalBuf</span>(1024), in);</p>
  50 <p class="p6"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span></p>
  51 <p class="p4"><span class="Apple-tab-span">     </span>chain = chain.pvcalc(1024, {<span class="s4">|mags, phases|</span></p>
  52 <p class="p7">//////// Try uncommenting each of these lines in turn and re-running the synth:</p>
  53 <p class="p4"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span>[mags * {1.5.rand}.dup(mags.size), phases + {pi.rand}.dup(phases.size)]; <span class="s5">// Arbitrary filter, arbitrary phase shift</span></p>
  54 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>//[mags.reverse, phases.reverse]; // Upside-down!</p>
  55 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>//[mags.differentiate, phases.differentiate]; // Differentiate along frequency axis</p>
  56 <p class="p7"><span class="s2"><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></span>//[mags[30..] ++ mags[..30], phases[30..] ++ phases[..30]]; // ".rotate" doesn't work directly, but this is equivalent</p>
  57 <p class="p4"><span class="Apple-tab-span">     </span>}, frombin: 0, tobin: 250, zeroothers: 0);</p>
  58 <p class="p6"><span class="Apple-tab-span">     </span></p>
  59 <p class="p4"><span class="Apple-tab-span">     </span><span class="s4">Out</span>.ar(0, 0.5 * <span class="s4">IFFT</span>(chain).dup);</p>
  60 <p class="p4">}.play(s);</p>
  61 <p class="p4">)</p>
  62 <p class="p4">x.free;</p>
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