Cepstral Pitch Tracker

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

/* Copyright Chris Cannam - All Rights Reserved */

#include "NoteHypothesis.h"

#include <cmath>

#include "system/sysutils.h"

namespace Turbot {

NoteHypothesis::NoteHypothesis()

{

    m_state = New;

}

NoteHypothesis::~NoteHypothesis()

{

}

bool

NoteHypothesis::isWithinTolerance(Estimate s) const

{

    if (m_pending.empty()) {

        return true;

    }

    // check we are within a relatively close tolerance of the last

    // candidate

    Estimate last = m_pending[m_pending.size()-1];

    double r = s.freq / last.freq;

    int cents = lrint(1200.0 * (log(r) / log(2.0)));

    if (cents < -60 || cents > 60) return false;

    // and within a slightly bigger tolerance of the current mean

    double meanFreq = getMeanFrequency();

    r = s.freq / meanFreq;

    cents = lrint(1200.0 * (log(r) / log(2.0)));

    if (cents < -80 || cents > 80) return false;

    return true;

}

bool

NoteHypothesis::isOutOfDateFor(Estimate s) const

{

    if (m_pending.empty()) return false;

    return ((s.time - m_pending[m_pending.size()-1].time) > 

            RealTime::fromMilliseconds(40));

}

bool 

NoteHypothesis::isSatisfied() const

{

    if (m_pending.empty()) return false;

    double meanConfidence = 0.0;

    for (int i = 0; i < (int)m_pending.size(); ++i) {

        meanConfidence += m_pending[i].confidence;

    }

    meanConfidence /= m_pending.size();

    int lengthRequired = 10000;

    if (meanConfidence > 0.0) {

        lengthRequired = int(2.0 / meanConfidence + 0.5);

    }

    return ((int)m_pending.size() > lengthRequired);

}

bool

NoteHypothesis::accept(Estimate s)

{

    bool accept = false;

    switch (m_state) {

    case New:

        m_state = Provisional;

        accept = true;

        break;

    case Provisional:

        if (isOutOfDateFor(s)) {

            m_state = Rejected;

        } else if (isWithinTolerance(s)) {

            accept = true;

        }

        break;

    case Satisfied:

        if (isOutOfDateFor(s)) {

            m_state = Expired;

        } else if (isWithinTolerance(s)) {

            accept = true;

        }

        break;

    case Rejected:

        break;

    case Expired:

        break;

    }

    if (accept) {

        m_pending.push_back(s);

        if (m_state == Provisional && isSatisfied()) {

            m_state = Satisfied;

        }

    }

    return accept;

}        

NoteHypothesis::State

NoteHypothesis::getState() const

{

    return m_state;

}

NoteHypothesis::Estimates

NoteHypothesis::getAcceptedEstimates() const

{

    if (m_state == Satisfied || m_state == Expired) {

        return m_pending;

    } else {

        return Estimates();

    }

}

double

NoteHypothesis::getMeanFrequency() const

{

    double acc = 0.0;

    for (int i = 0; i < (int)m_pending.size(); ++i) {

        acc += m_pending[i].freq;

    }

    acc /= m_pending.size();

    return acc;

}

NoteHypothesis::Note

NoteHypothesis::getAveragedNote() const

{

    Note n;

    if (!(m_state == Satisfied || m_state == Expired)) {

        n.freq = 0.0;

        n.time = RealTime::zeroTime;

        n.duration = RealTime::zeroTime;

        return n;

    }

    n.time = m_pending.begin()->time;

    Estimates::const_iterator i = m_pending.end();

    --i;

    n.duration = i->time - n.time;

    // just mean frequency for now, but this isn't at all right perceptually

    n.freq = getMeanFrequency();

    return n;

}

}

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

/* Copyright Chris Cannam - All Rights Reserved */

#ifndef _NOTE_HYPOTHESIS_H_

#define _NOTE_HYPOTHESIS_H_

#include "base/RealTime.h"

#include <vector>

namespace Turbot {

/**

 * An agent used to test an incoming series of instantaneous pitch

 * estimates to see whether they fit a consistent single-note

 * relationship. Contains rules specific to testing note pitch and

 * timing.

 */

class NoteHypothesis

{

public:

    enum State {

	/// Just constructed, will provisionally accept any estimate

	New,

	/// Accepted at least one estimate, but not enough evidence to satisfy

	Provisional,

	/// Could not find enough consistency in offered estimates

	Rejected,

	/// Have accepted enough consistent estimates to satisfy hypothesis

	Satisfied,

	/// Have been satisfied, but evidence has now changed: we're done

	Expired

    };

    /**

     * Construct an empty hypothesis. This will be in New state and

     * will provisionally accept any estimate.

     */

    NoteHypothesis();

    /**

     * Destroy the hypothesis

     */

    ~NoteHypothesis();

    struct Estimate {

	double freq;

	RealTime time;

	double confidence;

    };

    typedef std::vector<Estimate> Estimates;

    /**

     * Test the given estimate to see whether it is consistent with

     * this hypothesis, and adjust the hypothesis' internal state

     * accordingly. If the estimate is not inconsistent with the

     * hypothesis, return true.

     */

    bool accept(Estimate);

    /**

     * Return the current state of this hypothesis.

     */

    State getState() const;

    /**

     * If the hypothesis has been satisfied (i.e. is in Satisfied or

     * Expired state), return the series of estimates that it

     * accepted. Otherwise return an empty list

     */

    Estimates getAcceptedEstimates() const;

    struct Note {

	double freq;

	RealTime time;

	RealTime duration;

    };

    /**

     * Return a single note roughly matching this hypothesis

     */

    Note getAveragedNote() const;

private:

    bool isWithinTolerance(Estimate) const;

    bool isOutOfDateFor(Estimate) const;

    bool isSatisfied() const;

    double getMeanFrequency() const;

    State m_state;

    Estimates m_pending;

};

}

#endif