annotate audioio/PhaseVocoderTimeStretcher.h @ 23:a2ad974b0c8c

...

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

/*
    Sonic Visualiser
    An audio file viewer and annotation editor.
    Centre for Digital Music, Queen Mary, University of London.
    This file copyright 2006 Chris Cannam.
    
    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.
*/

#ifndef _PHASE_VOCODER_TIME_STRETCHER_H_
#define _PHASE_VOCODER_TIME_STRETCHER_H_

#include "base/Window.h"
#include "base/RingBuffer.h"

#include <fftw3.h>

/**
 * A time stretcher that alters the performance speed of audio,
 * preserving pitch.
 *
 * This is based on the straightforward phase vocoder with phase
 * unwrapping (as in e.g. the DAFX book pp275-), with optional
 * percussive transient detection to avoid smearing percussive notes
 * and resynchronise phases, and adding a stream API for real-time
 * use.  Principles and methods from Chris Duxbury, AES 2002 and 2004
 * thesis; Emmanuel Ravelli, DAFX 2005; Dan Barry, ISSC 2005 on
 * percussion detection; code by Chris Cannam.
 */

class PhaseVocoderTimeStretcher
{
public:
    PhaseVocoderTimeStretcher(size_t sampleRate,
                              size_t channels,
                              float ratio,
                              bool sharpen,
                              size_t maxProcessInputBlockSize);
    virtual ~PhaseVocoderTimeStretcher();

    /**
     * Process a block.  The input array contains the given number of
     * samples (on each channel); the output must have space for
     * lrintf(samples * m_ratio).
     * 
     * This function isn't really recommended, and I may yet remove it.
     * It should work correctly for some ratios, e.g. small powers of
     * two, if transient sharpening is off.  For other ratios it may
     * drop samples -- use putInput in a loop followed by getOutput
     * (when getAvailableOutputSamples reports enough) instead.
     *
     * Do not mix process calls with putInput/getOutput calls.
     */
    void process(float **input, float **output, size_t samples);

    /**
     * Return the number of samples that would need to be added via
     * putInput in order to provoke the time stretcher into doing some
     * time stretching and making more output samples available.
     * This will be an estimate, if transient sharpening is on.
     */
    size_t getRequiredInputSamples() const;

    /**
     * Put (and possibly process) a given number of input samples.
     * Number must not exceed the maxProcessInputBlockSize passed to
     * constructor.
     */
    void putInput(float **input, size_t samples);

    /**
     * Get the number of processed samples ready for reading.
     */
    size_t getAvailableOutputSamples() const;

    /**
     * Get some processed samples.
     */
    void getOutput(float **output, size_t samples);

    //!!! and reset?

    /**
     * Get the hop size for input.
     */
    size_t getInputIncrement() const { return m_n1; }

    /**
     * Get the hop size for output.
     */
    size_t getOutputIncrement() const { return m_n2; }

    /**
     * Get the window size for FFT processing.
     */
    size_t getWindowSize() const { return m_wlen; }

    /**
     * Get the stretch ratio.
     */
    float getRatio() const { return float(m_n2) / float(m_n1); }

    /**
     * Return whether this time stretcher will attempt to sharpen transients.
     */
    bool getSharpening() const { return m_sharpen; }

    /**
     * Get the latency added by the time stretcher, in sample frames.
     * This will be exact if transient sharpening is off, or approximate
     * if it is on.
     */
    size_t getProcessingLatency() const;

protected:
    /**
     * Process a single phase vocoder frame from "in" into
     * m_freq[channel].
     */
    void analyseBlock(size_t channel, float *in); // into m_freq[channel]

    /**
     * Examine m_freq[0..m_channels-1] and return whether a percussive
     * transient is found.
     */
    bool isTransient(); 

    /**
     * Resynthesise from m_freq[channel] adding in to "out",
     * adjusting phases on the basis of a prior step size of lastStep.
     * Also add the window shape in to the modulation array (if
     * present) -- for use in ensuring the output has the correct
     * magnitude afterwards.
     */
    void synthesiseBlock(size_t channel, float *out, float *modulation,
                         size_t lastStep);

    size_t m_sampleRate;
    size_t m_channels;
    float m_ratio;
    bool m_sharpen;
    size_t m_n1;
    size_t m_n2;
    size_t m_wlen;
    Window<float> *m_analysisWindow;
    Window<float> *m_synthesisWindow;

    int m_totalCount;
    int m_transientCount;
    int m_n2sum;

    float **m_prevPhase;
    float **m_prevAdjustedPhase;

    float *m_prevTransientMag;
    int  m_prevTransientScore;
    int  m_transientThreshold;
    bool m_prevTransient;

    float *m_tempbuf;
    float **m_time;
    fftwf_complex **m_freq;
    fftwf_plan *m_plan;
    fftwf_plan *m_iplan;
    
    RingBuffer<float> **m_inbuf;
    RingBuffer<float> **m_outbuf;
    float **m_mashbuf;
    float *m_modulationbuf;
};

#endif