librubberband/src/finer/Guide.h

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Rubber Band Library
    An audio time-stretching and pitch-shifting library.
    Copyright 2007-2022 Particular Programs Ltd.

    This program is free software; you can redistribute it and/or
    modify it under the terms of the GNU General Public License as
    published by the Free Software Foundation; either version 2 of the
    License, or (at your option) any later version.  See the file
    COPYING included with this distribution for more information.

    Alternatively, if you have a valid commercial licence for the
    Rubber Band Library obtained by agreement with the copyright
    holders, you may redistribute and/or modify it under the terms
    described in that licence.

    If you wish to distribute code using the Rubber Band Library
    under terms other than those of the GNU General Public License,
    you must obtain a valid commercial licence before doing so.
*/

#ifndef RUBBERBAND_GUIDE_H
#define RUBBERBAND_GUIDE_H

namespace RubberBand
{

class Guide
{
public:
    struct FftBand {
        int fftSize;
        float f0;
        float f1;
        FftBand(int _s, float _f0, float _f1) :
            fftSize(_s), f0(_f0), f1(_f1) { }
    };

    struct PhaseLockBand {
        int p;
        float beta;
        float f0;
        float f1;
        PhaseLockBand(int _p, float _beta, float _f0, float _f1) :
            p(_p), beta(_beta), f0(_f0), f1(_f1) { }
    };

    struct Range {
        bool present;
        float f0;
        float f1;
        Range() : present(false), f0(0.f), f1(0.f) { }
    };
        
    struct Guidance {
        FftBand fftBands[3];
        PhaseLockBand phaseLockBands[5];
        Range kick;
        Range lowPercussive;
        Range highPercussive;
        Range phaseReset;
        Range channelLock;
    };

    struct Parameters {
        int fftSize;
        double sampleRate;
        Parameters(int _fftSize, double _sampleRate) :
            fftSize(_fftSize), sampleRate(_sampleRate) { }
    };

    Guide(Parameters parameters) :
        m_parameters(parameters) { }
    
    void calculate(double ratio,
                   const float *const magnitudes,
                   const int *const troughs,
                   const float *const prevMagnitudes,
                   const BinSegmenter::Segmentation &segmentation,
                   const BinSegmenter::Segmentation &prevSegmentation,
                   const BinSegmenter::Segmentation &nextSegmentation,
                   Guidance &guidance) const {

        bool potentialKick = checkPotentialKick(magnitudes, prevMagnitudes);

        guidance.kick.present = false;
        guidance.lowPercussive.present = false;
        guidance.highPercussive.present = false;
        guidance.phaseReset.present = false;

        guidance.channelLock.present = true;
        guidance.channelLock.f0 = 0.0;
        guidance.channelLock.f1 = 600.0;

        if (segmentation.percussiveBelow > 40.0) {
            guidance.lowPercussive.present = true;
            guidance.lowPercussive.f0 = 0.0;
            guidance.lowPercussive.f1 = segmentation.percussiveBelow;
        }

        if (potentialKick && prevSegmentation.percussiveBelow < 40.0) {
            guidance.kick = guidance.lowPercussive;
        }
        
        if (segmentation.residualAbove > segmentation.percussiveAbove) {
            guidance.highPercussive.present = true;
            guidance.highPercussive.f0 = segmentation.percussiveAbove;
            guidance.highPercussive.f1 = segmentation.residualAbove;
        }

        double bigGap = 4000.0;
        if (ratio > 1.0 &&
            segmentation.residualAbove >
            segmentation.percussiveAbove + bigGap &&
            prevSegmentation.residualAbove <
            prevSegmentation.percussiveAbove + bigGap) {
            guidance.phaseReset.present = true;
            guidance.phaseReset.f0 = std::min(segmentation.percussiveAbove,
                                              nextSegmentation.percussiveAbove);
            if (guidance.phaseReset.f0 < 200.0) {
                guidance.phaseReset.f0 = 0.0;
            }
            guidance.phaseReset.f1 = std::max(segmentation.residualAbove,
                                              nextSegmentation.residualAbove);
        }

        double higher = snapToTrough(4800.0, troughs);
        double lower = snapToTrough(700.0, troughs);
        double nyquist = m_parameters.sampleRate / 2.0;

        guidance.fftBands[0].fftSize = roundUp(int(ceil(nyquist/8.0)));
        guidance.fftBands[0].f0 = 0.0;
        guidance.fftBands[0].f1 = lower;
        
        guidance.fftBands[1].fftSize = roundUp(int(ceil(nyquist/16.0)));
        guidance.fftBands[1].f0 = lower;
        guidance.fftBands[1].f1 = higher;
        
        guidance.fftBands[2].fftSize = roundUp(int(ceil(nyquist/32.0)));
        guidance.fftBands[2].f0 = higher;
        guidance.fftBands[2].f1 = nyquist;
        
        double mid = std::max(lower, 1600.0);

        guidance.phaseLockBands[0].p = 1;
        guidance.phaseLockBands[0].beta = betaFor(300.0, ratio);
        guidance.phaseLockBands[0].f0 = 0.0;
        guidance.phaseLockBands[0].f1 = lower;
        
        guidance.phaseLockBands[1].p = 2;
        guidance.phaseLockBands[1].beta = betaFor(1600.0, ratio);
        guidance.phaseLockBands[1].f0 = lower;
        guidance.phaseLockBands[1].f1 = mid;
        
        guidance.phaseLockBands[2].p = 3;
        guidance.phaseLockBands[2].beta = betaFor(5000.0, ratio);
        guidance.phaseLockBands[2].f0 = mid;
        guidance.phaseLockBands[2].f1 = higher;
        
        guidance.phaseLockBands[3].p = 4;
        guidance.phaseLockBands[3].beta = betaFor(10000.0, ratio);
        guidance.phaseLockBands[3].f0 = higher;
        guidance.phaseLockBands[3].f1 = nyquist;
    }

protected:
    Parameters m_parameters;
    
    int binForFrequency(double f) const {
        return int(round(f * double(m_parameters.fftSize) /
                         m_parameters.sampleRate));
    }
    double frequencyForBin(int b) const {
        return (double(b) * m_parameters.sampleRate)
            / double(m_parameters.fftSize);
    }

    // near-dupe with R2 RubberBandStretcher::Impl
    int roundUp(int value) const {
        if (value < 1) return 1;
        if (!(value & (value - 1))) return value;
        int bits = 0;
        while (value) { ++bits; value >>= 1; }
        value = 1 << bits;
        return value;
    }
    
    bool checkPotentialKick(const float *const magnitudes,
                            const float *const prevMagnitudes) const {
        int b = binForFrequency(200.0);
        float here = 0.0, there = 0.0;
        for (int i = 1; i <= b; ++i) {
            here += magnitudes[i];
        }
        for (int i = 1; i <= b; ++i) {
            there += prevMagnitudes[i];
        }
        return (here > 10.e-3f && here > there * 1.4f);
    }

    double snapToTrough(double f, const int *const troughs) const {
        return frequencyForBin(troughs[binForFrequency(f)]);
    }

    double betaFor(double f, double ratio) const {
        double b = (2.0 + ratio) / 3.0;
        double limit = 10000.0;
        if (f > limit) {
            return b;
        } else {
            return 1.0 + f * (b - 1.0) / limit;
        }
    }
};

}

#endif