Help/UGens/Filters/Median.html

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  26 <p class="p1"><span class="s1"><b>Median<span class="Apple-tab-span">   </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span><span class="Apple-tab-span">    </span></b></span><b>median filter</b></p>
  27 <p class="p2"><br></p>
  28 <p class="p3"><span class="s2"><b>Inherits from: </b><a href="../../Core/Object.html"><span class="s3"><b>Object</b></span></a></span><span class="s3"><b> : </b><a href="../../Core/Kernel/AbstractFunction.html"><span class="s4"><b>AbstractFunction</b></span></a><b> : </b><a href="../UGen.html"><span class="s4"><b>UGen</b></span></a><b> : </b><a href="../Filter.html"><span class="s4"><b>Filter</b></span></a><b><span class="Apple-converted-space"> </span></b></span></p>
  29 <p class="p2"><br></p>
  30 <p class="p1"><b>Median.ar(length, in, mul, add)</b></p>
  31 <p class="p1"><b>Median.kr(length, in, mul, add)</b></p>
  32 <p class="p2"><br></p>
  33 <p class="p2"><br></p>
  34 <p class="p1">Returns the median of the last <b>length</b> input points.<span class="Apple-converted-space"> </span></p>
  35 <p class="p1">This non linear filter is good at reducing impulse noise<span class="Apple-converted-space">  </span>from a signal.</p>
  36 <p class="p1"><b>length</b> - number of input points in which to find the median. Must be an odd number from 1 to 31.</p>
  37 <p class="p1">If length is 1 then Median has no effect.</p>
  38 <p class="p1"><b>in</b> - input signal to be processed</p>
  39 <p class="p4"><br></p>
  40 <p class="p5">// a signal with impulse noise.</p>
  41 <p class="p6">{ <span class="s3">Saw</span>.ar(500, 0.1) + <span class="s3">Dust2</span>.ar(100, 0.9) }.play;</p>
  42 <p class="p7"><br></p>
  43 <p class="p5">// after applying median filter</p>
  44 <p class="p6">{ <span class="s3">Median</span>.ar(3, <span class="s3">Saw</span>.ar(500, 0.1) + <span class="s3">Dust2</span>.ar(100, 0.9)) }.play;</p>
  45 <p class="p7"><br></p>
  46 <p class="p5">// The median length can be increased for longer duration noise.</p>
  47 <p class="p8"><br></p>
  48 <p class="p5">// a signal with longer impulse noise.</p>
  49 <p class="p6">{ <span class="s3">Saw</span>.ar(500, 0.1) + <span class="s3">LPZ1</span>.ar(<span class="s3">Dust2</span>.ar(100, 0.9)) }.play;</p>
  50 <p class="p7"><br></p>
  51 <p class="p5">// length 3 doesn't help here because the impulses are 2 samples long.</p>
  52 <p class="p6">{ <span class="s3">Median</span>.ar(3, <span class="s3">Saw</span>.ar(500, 0.1) + <span class="s3">LPZ1</span>.ar(<span class="s3">Dust2</span>.ar(100, 0.9))) }.play;</p>
  53 <p class="p7"><br></p>
  54 <p class="p5">// length 5 does better</p>
  55 <p class="p6">{ <span class="s3">Median</span>.ar(5, <span class="s3">Saw</span>.ar(500, 0.1) + <span class="s3">LPZ1</span>.ar(<span class="s3">Dust2</span>.ar(100, 0.9))) }.play;</p>
  56 <p class="p7"><br></p>
  57 <p class="p5">// long Median filters begin chopping off the peaks of the waveform</p>
  58 <p class="p6">(</p>
  59 <p class="p6">{<span class="Apple-converted-space"> </span></p>
  60 <p class="p6"><span class="Apple-tab-span">     </span>x = <span class="s3">SinOsc</span>.ar(1000, 0, 0.2);</p>
  61 <p class="p6"><span class="Apple-tab-span">     </span>[x, <span class="s3">Median</span>.ar(31, x)]</p>
  62 <p class="p6">}.play;</p>
  63 <p class="p6">)</p>
  64 <p class="p7"><br></p>
  65 <p class="p5">// another noise reduction application:</p>
  66 <p class="p8"><br></p>
  67 <p class="p6"><span class="s3">Synth</span>.play({ <span class="s3">WhiteNoise</span>.ar(0.1) + <span class="s3">SinOsc</span>.ar(800,0,0.1) });</p>
  68 <p class="p7"><br></p>
  69 <p class="p5">// use Median filter for high frequency noise</p>
  70 <p class="p6"><span class="s3">Synth</span>.play({ <span class="s3">Median</span>.ar(31, <span class="s3">WhiteNoise</span>.ar(0.1) + <span class="s3">SinOsc</span>.ar(800,0,0.1)) });</p>
  71 <p class="p7"><br></p>
  72 <p class="p6">(</p>
  73 <p class="p5">// use LeakDC for low frequency noise</p>
  74 <p class="p6"><span class="s3">Synth</span>.play({<span class="Apple-converted-space"> </span></p>
  75 <p class="p6"><span class="Apple-tab-span">     </span><span class="s3">LeakDC</span>.ar(<span class="s3">Median</span>.ar(31, <span class="s3">WhiteNoise</span>.ar(0.1) + <span class="s3">SinOsc</span>.ar(800,0,0.1)), 0.9)</p>
  76 <p class="p6">});</p>
  77 <p class="p6">)</p>
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