Signalsmith-Audio/signalsmith-stretch
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Randomise time-stretch slightly when it goes past 2x

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Geraint 2023-05-01 07:47:18 +01:00
parent 801b54da5b
commit 605091c29e
1 changed files with 13 additions and 4 deletions
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17
signalsmith-stretch.h
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@ -8,12 +8,15 @@ SIGNALSMITH_DSP_VERSION_CHECK(1, 3, 3); // Check version is compatible
#include <vector>
#include <algorithm>
#include <functional>
#include <random>
namespace signalsmith { namespace stretch {
template<typename Sample=float>
struct SignalsmithStretch {
SignalsmithStretch() : randomEngine(std::random_device{}()) {}
int blockSamples() const {
return stft.windowSize();
}
@ -230,6 +233,7 @@ struct SignalsmithStretch {
private:
using Complex = std::complex<Sample>;
static constexpr Sample noiseFloor{1e-15};
static constexpr Sample maxCleanStretch{2}; // time-stretch ratio before we start randomising phases
int silenceCounter = 0;
bool silenceFirst = true;
@ -328,11 +332,15 @@ private:
Prediction * predictionsForChannel(int c) {
return channelPredictions.data() + c*stft.bands();
}
std::default_random_engine randomEngine;
void processSpectrum(bool newSpectrum, Sample timeFactor) {
int bands = stft.bands();
timeFactor = std::min<Sample>(2, timeFactor); // For now, limit the intra-block time stretching to 2x
bool randomTimeFactor = (timeFactor > maxCleanStretch);
timeFactor = std::min<Sample>(maxCleanStretch*2, timeFactor);
std::uniform_real_distribution<Sample> timeFactorDist(maxCleanStretch*2 - timeFactor, timeFactor);
if (newSpectrum) {
for (int c = 0; c < channels; ++c) {
@ -372,10 +380,11 @@ private:
outputBin.output = phase/(std::max(prevEnergy, prediction.energy) + noiseFloor);
if (b > 0) {
Complex downInput = getFractional<&Band::input>(c, mapPoint.inputBin - timeFactor);
Sample binTimeFactor = randomTimeFactor ? timeFactorDist(randomEngine) : timeFactor;
Complex downInput = getFractional<&Band::input>(c, mapPoint.inputBin - binTimeFactor);
prediction.shortVerticalTwist = signalsmith::perf::mul<true>(prediction.input, downInput);
if (b >= longVerticalStep) {
Complex longDownInput = getFractional<&Band::input>(c, mapPoint.inputBin - longVerticalStep*timeFactor);
Complex longDownInput = getFractional<&Band::input>(c, mapPoint.inputBin - longVerticalStep*binTimeFactor);
prediction.longVerticalTwist = signalsmith::perf::mul<true>(prediction.input, longDownInput);
} else {
prediction.longVerticalTwist = 0;