class:: Median
summary:: Median filter.
categories::  UGens>Filters>Nonlinear


Description::

Returns the median of the last length input points. This non-linear
filter is good at reducing impulse noise from a signal.


classmethods::

method::ar, kr

argument::length

Number of input points in which to find the median. Must be an
odd number from 1 to 31. If
code::length::  is 1
then Median has no effect.


argument::in

The input signal.


argument::mul

Output will be multiplied by this value.


argument::add

This value will be added to the output.


Examples::

code::

// 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)
});
)

::