110 lines
2.8 KiB
Text
110 lines
2.8 KiB
Text
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#lang scribble/manual
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@(require (for-label racket))
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@title{SubsampleOffset}
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Offset from synth start within one sample.@section{related}
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Classes/ControlRate, Classes/RadiansPerSample, Classes/SampleDur, Classes/SampleRate, Classes/OffsetOut
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@section{categories}
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UGens>Info
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@section{description}
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When a synth is created from a time stamped osc-bundle, it starts
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calculation at the next possible block (normally 64 samples). Using an
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OffsetOut UGen, one can delay the audio so that it matches sample
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accurately.
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For some synthesis methods, one needs subsample accuracy. SubsampleOffset
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provides the information where, within the current sample, the synth was
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scheduled. It can be used to offset envelopes or resample the audio
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output.
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@section{classmethods}
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@section{method}
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ir
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@section{Examples}
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@racketblock[
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// example: demonstrate cubic subsample interpolation
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// impulse train that can be moved between samples
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(
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SynthDef(\Help_SubsampleOffset, { |out, addOffset|
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var in, dt, sampDur, extraSamples, sampleOffset, resampledSignal;
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in = Impulse.ar(2000, 0, 0.3); // some input.
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sampDur = SampleDur.ir; // duration of one sample
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extraSamples = 4; // DelayC needs at least 4 samples buffer
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sampleOffset = 1 - SubsampleOffset.ir; // balance out subsample offset
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sampleOffset = sampleOffset + MouseX.kr(0, addOffset); // add a mouse dependent offset
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// cubic resampling:
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resampledSignal = DelayC.ar(in,
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maxdelaytime: sampDur * (1 + extraSamples),
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delaytime: sampDur * (sampleOffset + extraSamples)
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);
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OffsetOut.ar(out, resampledSignal)
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}).add;
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)
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// create 2 pulse trains 1 sample apart, move one relatively to the other.
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// when cursor is at the left, the impulses are adjacent, on the right, they are
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// exactly 1 sample apart.
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(
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var dt = s.sampleRate.reciprocal; // 1 sample delay
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s.sendBundle(0.2, [9, \Help_SubsampleOffset, s.nextNodeID, 1, 1, \out, 40, \addOffset, 3]);
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s.sendBundle(0.2 + dt, [9, \Help_SubsampleOffset, s.nextNodeID, 1, 1, \out, 40, \addOffset, 0]);
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)
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s.scope(1, 40, zoom: 0.2);
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// example of a subsample accurate sine grain:
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// (I don't hear a difference to normal sample accurate grains, but maybe
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// someone could add an example that shows the effect)
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(
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SynthDef("Help_Subsample_Grain",
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{ arg out=0, freq=440, sustain=0.005, attack=0.001;
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var env, offset, sig, sd;
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sd = SampleDur.ir;
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offset = (1 - SubsampleOffset.ir) * sd;
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// free synth after delay:
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Line.ar(1,0, attack + sustain + offset, doneAction: Done.freeSelf);
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env = EnvGen.kr(Env.perc(attack, sustain, 0.2));
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sig = SinOsc.ar(freq, 0, env);
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sig = DelayC.ar(sig, sd * 4, offset);
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OffsetOut.ar(out, sig);
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}, [\ir, \ir, \ir, \ir]).add;
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)
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(
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Routine {
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loop {
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s.sendBundle(0.2, [9, \Help_Subsample_Grain, -1, 1, 1, \freq, 1000]);
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rrand(0.001, 0.002).wait;
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}
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}.play;
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)
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::
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]
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