«Paulstretch for SuperCollider» by jpdrecourt
on 07 Apr'20 03:46 inThis is a port of the basic Paulstretch algorithm to SuperCollider (no onset detection). Mono version, for stereo, use 2 instances hard panned. The sound buffer needs to be mono too, so use Buffer.readChannel to extract separate channels. The stretch parameter is modulatable. That allows for phasing effects if using more than one instance.
Thanks to Paul for his feedback! Check his work at http://www.paulnasca.com/
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( SynthDef(\paulstretchMono, { |out = 0, bufnum, envBufnum, pan = 0, stretch = 50, window = 0.25, amp = 1| // Paulstretch for SuperCollider // Based on the Paul's Extreme Sound Stretch algorithm by Nasca Octavian PAUL // https://github.com/paulnasca/paulstretch_python/blob/master/paulstretch_steps.png // // By Jean-Philippe Drecourt // http://drecourt.com // April 2020 // // Arguments: // out: output bus (stereo output) // bufnum: the sound buffer. Must be Mono. (Use 2 instances with Buffer.readChannel for stereo) // envBufnum: The grain envelope buffer created as follows: //// envBuf = Buffer.alloc(s, s.sampleRate, 1); //// envSignal = Signal.newClear(s.sampleRate).waveFill({|x| (1 - x.pow(2)).pow(1.25)}, -1.0, 1.0); //// envBuf.loadCollection(envSignal); // pan: Equal power panning, useful for stereo use. // stretch: stretch factor (modulatable) // window: the suggested grain size, will be resized to closest fft window size // amp: amplification var trigPeriod, sig, chain, trig, pos, fftSize; // Calculating fft buffer size according to suggested window size fftSize = 2**floor(log2(window*SampleRate.ir)); // Grain parameters // The grain is the exact length of the FFT window trigPeriod = fftSize/SampleRate.ir; trig = Impulse.ar(1/trigPeriod); pos = Demand.ar(trig, 0, demandUGens: Dseries(0, trigPeriod/stretch)); // Extraction of 2 consecutive grains // Both grains need to be treated together for superposition afterwards sig = [GrainBuf.ar(1, trig, trigPeriod, bufnum, 1, pos, envbufnum: envBufnum), GrainBuf.ar(1, trig, trigPeriod, bufnum, 1, pos + (trigPeriod/(2*stretch)), envbufnum: envBufnum)]*amp; // FFT magic sig = sig.collect({ |item, i| chain = FFT(LocalBuf(fftSize), item, hop: 1.0, wintype: -1); // PV_Diffuser is only active if its trigger is 1 // And it needs to be reset for each grain to get the smooth envelope chain = PV_Diffuser(chain, 1 - trig); item = IFFT(chain, wintype: -1); }); // Reapply the grain envelope because the FFT phase randomization removes it sig = sig*PlayBuf.ar(1, envBufnum, 1/(trigPeriod), loop:1); // Delay second grain by half a grain length for superposition sig[1] = DelayC.ar(sig[1], trigPeriod/2, trigPeriod/2); // Panned output Out.ar(out, Pan2.ar(Mix.new(sig), pan)); }).add; ) // Example ({ var envBuf, envSignal, buffer; buffer = Buffer.read(s, Platform.resourceDir +/+ "sounds/a11wlk01.wav"); // The grain envelope envBuf = Buffer.alloc(s, s.sampleRate, 1); envSignal = Signal.newClear(s.sampleRate).waveFill({|x| (1 - x.pow(2)).pow(1.25)}, -1.0, 1.0); envBuf.loadCollection(envSignal); s.sync(); // Runs indefinitely Synth(\paulstretchMono, [\bufnum, buffer.bufnum, \envBufnum, envBuf.bufnum]); }.fork; )
reception
oh, I love this sound. Paulstretch is great, now we need to make thonk, remember that one? Altiverb people, I believe.
thonk+ yes! I used to massively over-use that back in the day…