Help/UGens/FFT/StereoConvolution2L.html

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  29 <p class="p1"><span class="s1"><b>StereoConvolution2L<span class="Apple-tab-span">      </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></b></span><b>stereo real-time convolver with linear interpolation</b></p>
  30 <p class="p1">add</p>
  31 <p class="p1"><b>StereoConvolution2L.ar(in, kernelL, kernelR, trigger, framesize, crossfade, mul, add)</b></p>
  32 <p class="p2"><br></p>
  33 <p class="p1">Strict convolution with fixed kernel which can be updated using a trigger signal. There is a linear crossfade between the buffers upon change.</p>
  34 <p class="p1">Like <a href="Convolution2L.html"><span class="s2">Convolution2L</span></a>, but convolves with two buffers and outputs a stereo signal. This saves one FFT transformation per period, as compared to using two copies of <b>Convolution2L</b>.</p>
  35 <p class="p1">Useful applications could include stereo reverberation or HRTF convolution.</p>
  36 <p class="p3"><br></p>
  37 <p class="p1">See Steven W Smith, The Scientist and Engineer's Guide to Digital Signal Processing:<span class="Apple-converted-space"> </span></p>
  38 <p class="p1">chapter 18:<span class="Apple-converted-space"> </span><span class="s3"> http:// www.dspguide.com/ch18.htm</span><span class="Apple-converted-space"> </span></p>
  39 <p class="p3"><br></p>
  40 <p class="p1"><b>in</b> - processing target</p>
  41 <p class="p1"><b>kernelL</b> - buffer index for the fixed kernel of the left channel, may be modulated in combination with the trigger</p>
  42 <p class="p1"><b>kernelR </b>- buffer index for the fixed kernel of the right channel, may be modulated in combination with the trigger</p>
  43 <p class="p1"><b>trigger</b> - update the kernel on a change from &lt;=0 to &gt;0</p>
  44 <p class="p1"><b>framesize </b>- size of FFT frame, must be a power of two. Convolution uses twice this number internally, maximum value you can give this argument is 2^16=65536. Note that it gets progressively more expensive to run for higher powers! 512, 1024, 2048, 4096 standard.</p>
  45 <p class="p1"><b>crossfade</b> - The number of periods over which a crossfade is made. The default is 1. This must be an integer.</p>
  46 <p class="p3"><br></p>
  47 <p class="p1">See also <a href="Convolution2.html"><span class="s4">Convolution2</span></a> and <a href="Convolution2L.html"><span class="s2">Convolution2L</span></a>.</p>
  48 <p class="p2"><br></p>
  49 <p class="p2"><br></p>
  50 <p class="p2"><br></p>
  51 <p class="p4"><span class="s5">(</span>//allocate three buffers</p>
  52 <p class="p5">b = <span class="s6">Buffer</span>.alloc(s,2048);</p>
  53 <p class="p5">c = <span class="s6">Buffer</span>.alloc(s,2048);</p>
  54 <p class="p5">d = <span class="s6">Buffer</span>.alloc(s,2048);</p>
  55 <p class="p2"><br></p>
  56 <p class="p5">b.zero;</p>
  57 <p class="p5">c.zero;</p>
  58 <p class="p5">d.zero;</p>
  59 <p class="p5">)</p>
  60 <p class="p2"><br></p>
  61 <p class="p5">(</p>
  62 <p class="p5">50.do({ <span class="s6">|it|</span> c.set(20*it+10, 1.0.rand); });</p>
  63 <p class="p5">3.do({ <span class="s6">|it|</span> b.set(400*it+100, 1); });</p>
  64 <p class="p5">20.do({ <span class="s6">|it|</span> d.set(40*it+20, 1); });</p>
  65 <p class="p5">)</p>
  66 <p class="p2"><br></p>
  67 <p class="p2"><br></p>
  68 <p class="p5">(</p>
  69 <p class="p5"><span class="s7">SynthDef</span>(<span class="s8">\conv_test</span>, { <span class="s7">arg</span> kernel1, kernel2, t_trig=0;</p>
  70 <p class="p5"><span class="Apple-tab-span">     </span><span class="s7">var</span> input;</p>
  71 <p class="p2"><span class="Apple-tab-span">     </span><span class="Apple-tab-span">    </span></p>
  72 <p class="p5"><span class="Apple-tab-span">     </span>input=<span class="s7">Impulse</span>.ar(1);</p>
  73 <p class="p2"><br></p>
  74 <p class="p6"><span class="s5"><span class="Apple-tab-span">    </span></span>//must have power of two framesize</p>
  75 <p class="p5"><span class="Apple-tab-span">     </span><span class="s7">Out</span>.ar(0,<span class="s7">StereoConvolution2L</span>.ar(input,kernel1, kernel2,t_trig,2048, 1, 0.5));</p>
  76 <p class="p5">}).add</p>
  77 <p class="p2"><br></p>
  78 <p class="p5">)</p>
  79 <p class="p2"><br></p>
  80 <p class="p2"><br></p>
  81 <p class="p5">x = <span class="s6">Synth</span>(<span class="s8">\conv_test</span>, [<span class="s9">\kernel1</span>,b,<span class="s9">\kernel2</span>,c]);</p>
  82 <p class="p2"><br></p>
  83 <p class="p4">// changing the buffer number:</p>
  84 <p class="p5">x.set(<span class="s9">\kernel1</span>,d);</p>
  85 <p class="p4"><span class="s5">x.set(</span><span class="s9">\t_trig</span><span class="s5">,1); </span>// after this trigger, the change will take effect.</p>
  86 <p class="p5">x.set(<span class="s9">\kernel2</span>,d);</p>
  87 <p class="p4"><span class="s5">x.set(</span><span class="s9">\t_trig</span><span class="s5">,1); </span>// after this trigger, the change will take effect.</p>
  88 <p class="p2"><br></p>
  89 <p class="p5">d.zero;</p>
  90 <p class="p4"><span class="s5">40.do({ </span><span class="s6">|it|</span><span class="s5"> d.set(20*it+10, 1); });</span>// changing the buffers' contents</p>
  91 <p class="p4"><span class="s5">x.set(</span><span class="s9">\t_trig</span><span class="s5">,1); </span>// after this trigger, the change will take effect.</p>
  92 <p class="p2"><br></p>
  93 <p class="p5">x.set(<span class="s9">\kernel1</span>,b);</p>
  94 <p class="p4"><span class="s5">x.set(</span><span class="s9">\t_trig</span><span class="s5">,1); </span>// after this trigger, the change will take effect.</p>
  95 <p class="p2"><br></p>
  96 <p class="p5">x.free;</p>
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