155 lines
3.6 KiB
Racket
155 lines
3.6 KiB
Racket
#lang scribble/manual
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@(require (for-label racket))
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@title{Compander}
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Compressor, expander, limiter, gate, ducker@section{categories}
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UGens>Dynamics
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@section{description}
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General purpose (hard-knee) dynamics processor.
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@section{classmethods}
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@section{method}
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ar
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@section{argument}
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in
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The signal to be compressed / expanded / gated.
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@section{argument}
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control
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The signal whose amplitude determines the gain applied to the input signal. Often the same as in (for standard gating or compression) but should be different for ducking.
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@section{argument}
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thresh
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Control signal amplitude threshold, which determines the break point between slopeBelow and slopeAbove. Usually 0..1. The control signal amplitude is calculated using RMS.
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@section{argument}
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slopeBelow
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Slope of the amplitude curve below the threshold. If this slope > 1.0, the amplitude will drop off more quickly the softer the control signal gets; when the control signal is close to 0 amplitude, the output should be exactly zero -- hence, noise gating. Values < 1.0 are possible, but it means that a very low-level control signal will cause the input signal to be amplified, which would raise the noise floor.
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@section{argument}
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slopeAbove
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Same thing, but above the threshold. Values < 1.0 achieve compression (louder signals are attenuated); > 1.0, you get expansion (louder signals are made even louder). For 3:1 compression, you would use a value of 1/3 here.
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@section{argument}
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clampTime
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The amount of time it takes for the amplitude adjustment to kick in fully. This is usually pretty small, not much more than 10 milliseconds (the default value). I often set it as low as 2 milliseconds (0.002).
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@section{argument}
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relaxTime
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The amount of time for the amplitude adjustment to be released. Usually a bit longer than clampTime; if both times are too short, you can get some (possibly unwanted) artifacts.
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@section{argument}
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mul
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@section{argument}
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add
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@section{discussion}
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If any of this is confusing, see http://en.wikipedia.org/wiki/Audio_level_compression
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@section{examples}
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@racketblock[
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(
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// example signal to process
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play({
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var z;
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z = Decay2.ar(
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Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)),
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0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)))
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})
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)
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::
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]
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@racketblock[
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(
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// noise gate
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play({
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var z;
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z = Decay2.ar(
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Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)),
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0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));
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Compander.ar(z, z,
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thresh: MouseX.kr(0.1, 1),
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slopeBelow: 10,
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slopeAbove: 1,
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clampTime: 0.01,
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relaxTime: 0.01
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);
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})
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)
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::
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]
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@racketblock[
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(
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// compressor
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play({
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var z;
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z = Decay2.ar(
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Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)),
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0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));
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Compander.ar(z, z,
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thresh: MouseX.kr(0.1, 1),
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slopeBelow: 1,
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slopeAbove: 0.5,
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clampTime: 0.01,
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relaxTime: 0.01
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);
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})
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)
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::
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]
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@racketblock[
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(
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// limiter
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play({
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var z;
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z = Decay2.ar(
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Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)),
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0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));
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Compander.ar(z, z,
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thresh: MouseX.kr(0.1, 1),
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slopeBelow: 1,
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slopeAbove: 0.1,
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clampTime: 0.01,
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relaxTime: 0.01
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);
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})
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)
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::
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]
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@racketblock[
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(
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// sustainer
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play({
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var z;
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z = Decay2.ar(
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Impulse.ar(8, 0,LFSaw.kr(0.3, 0, -0.3, 0.3)),
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0.001, 0.3, Mix.ar(Pulse.ar([80,81], 0.3)));
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Compander.ar(z, z,
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thresh: MouseX.kr(0.1, 1),
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slopeBelow: 0.1,
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slopeAbove: 1,
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clampTime: 0.01,
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relaxTime: 0.01
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)*0.1;
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})
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)
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::
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]
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