Median median filter

Median.ar(length, in, mul, add)

Returns the median of the last length input points.

This non linear filter is good at reducing impulse noise from a signal.

length - number of input points in which to find the median. Must be an odd number from 1 to 31.

If length is 1 then Median has no effect.

in - input signal to be processed

// a signal with impulse noise.

{ Saw.ar(500, 0.1) + Dust2.ar(100, 0.9) }.play;

// after applying median filter

{ Median.ar(3, Saw.ar(500, 0.1) + Dust2.ar(100, 0.9)) }.play;

// The median length can be increased for longer duration noise.

// a signal with longer impulse noise.

{ Saw.ar(500, 0.1) + LPZ1.ar(Dust2.ar(100, 0.9)) }.play;

// length 3 doesn't help here because the impulses are 2 samples long.

{ Median.ar(3, Saw.ar(500, 0.1) + LPZ1.ar(Dust2.ar(100, 0.9))) }.play;

// length 5 does better

{ Median.ar(5, Saw.ar(500, 0.1) + LPZ1.ar(Dust2.ar(100, 0.9))) }.play;

// long Median filters begin chopping off the peaks of the waveform

(

{

x = SinOsc.ar(1000, 0, 0.2);

[x, Median.ar(31, x)]

}.play;

)

// another noise reduction application:

Synth.play({ WhiteNoise.ar(0.1) + SinOsc.ar(800,0,0.1) });

// use Median filter for high frequency noise

Synth.play({ Median.ar(31, WhiteNoise.ar(0.1) + SinOsc.ar(800,0,0.1)) });

(

// use LeakDC for low frequency noise

Synth.play({

LeakDC.ar(Median.ar(31, WhiteNoise.ar(0.1) + SinOsc.ar(800,0,0.1)), 0.9)

});

)