diff dsp/tempotracking/DownBeat.cpp @ 54:5bec06ecc88a

* First cut at Matthew's downbeat estimator -- untested so far

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dsp/tempotracking/DownBeat.cpp	Tue Feb 10 12:52:43 2009 +0000
@@ -0,0 +1,241 @@
+/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
+
+/*
+    QM DSP Library
+
+    Centre for Digital Music, Queen Mary, University of London.
+    This file copyright 2008-2009 Matthew Davies and QMUL.
+    All rights reserved.
+*/
+
+#include "DownBeat.h"
+
+#include "maths/MathAliases.h"
+#include "maths/MathUtilities.h"
+#include "dsp/transforms/FFT.h"
+
+#include <iostream>
+#include <cstdlib>
+
+DownBeat::DownBeat(float originalSampleRate,
+                   size_t decimationFactor,
+                   size_t dfIncrement) :
+    m_rate(originalSampleRate),
+    m_factor(decimationFactor),
+    m_increment(dfIncrement),
+    m_decimator1(0),
+    m_decimator2(0),
+    m_buffer(0),
+    m_bufsiz(0),
+    m_buffill(0),
+    m_beatframesize(0),
+    m_beatframe(0)
+{
+    // beat frame size is next power of two up from 1.3 seconds at the
+    // downsampled rate (happens to produce 4096 for 44100 or 48000 at
+    // 16x decimation, which is our expected normal situation)
+    int bfs = int((m_rate / decimationFactor) * 1.3);
+    m_beatframesize = 1;
+    while (bfs) { bfs >>= 1; m_beatframesize <<= 1; }
+    std::cerr << "rate = " << m_rate << ", bfs = " << m_beatframesize << std::endl;
+    m_beatframe = new double[m_beatframesize];
+    m_fftRealOut = new double[m_beatframesize];
+    m_fftImagOut = new double[m_beatframesize];
+}
+
+DownBeat::~DownBeat()
+{
+    delete m_decimator1;
+    delete m_decimator2;
+    if (m_buffer) free(m_buffer);
+    delete[] m_decbuf;
+    delete[] m_beatframe;
+    delete[] m_fftRealOut;
+    delete[] m_fftImagOut;
+}
+
+void
+DownBeat::makeDecimators()
+{
+    if (m_factor < 2) return;
+    int highest = Decimator::getHighestSupportedFactor();
+    if (m_factor <= highest) {
+        m_decimator1 = new Decimator(m_increment, m_factor);
+        return;
+    }
+    m_decimator1 = new Decimator(m_increment, highest);
+    m_decimator2 = new Decimator(m_increment / highest, m_factor / highest);
+    m_decbuf = new double[m_factor / highest];
+}
+
+void
+DownBeat::pushAudioBlock(const double *audio)
+{
+    if (m_buffill + (m_increment / m_factor) > m_bufsiz) {
+        if (m_bufsiz == 0) m_bufsiz = m_increment * 16;
+        else m_bufsiz = m_bufsiz * 2;
+        if (!m_buffer) {
+            m_buffer = (double *)malloc(m_bufsiz * sizeof(double));
+        } else {
+            std::cerr << "DownBeat::pushAudioBlock: realloc m_buffer to " << m_bufsiz << std::endl;
+            m_buffer = (double *)realloc(m_buffer, m_bufsiz * sizeof(double));
+        }
+    }
+    if (!m_decimator1) makeDecimators();
+    if (m_decimator2) {
+        m_decimator1->process(audio, m_decbuf);
+        m_decimator2->process(m_decbuf, m_buffer + m_buffill);
+    } else {
+        m_decimator1->process(audio, m_buffer + m_buffill);
+    }
+    m_buffill += m_increment / m_factor;
+}
+    
+const double *
+DownBeat::getBufferedAudio(size_t &length) const
+{
+    length = m_buffill;
+    return m_buffer;
+}
+
+void
+DownBeat::findDownBeats(const double *audio,
+                        size_t audioLength,
+                        const d_vec_t &beats,
+                        i_vec_t &downbeats)
+{
+    // FIND DOWNBEATS BY PARTITIONING THE INPUT AUDIO FILE INTO BEAT SEGMENTS
+    // WHERE THE AUDIO FRAMES ARE DOWNSAMPLED  BY A FACTOR OF 16 (fs ~= 2700Hz)
+    // THEN TAKING THE JENSEN-SHANNON DIVERGENCE BETWEEN BEAT SYNCHRONOUS SPECTRAL FRAMES
+
+    // IMPLEMENTATION (MOSTLY) FOLLOWS:
+    //  DAVIES AND PLUMBLEY "A SPECTRAL DIFFERENCE APPROACH TO EXTRACTING DOWNBEATS IN MUSICAL AUDIO"
+    //  EUSIPCO 2006, FLORENCE, ITALY
+
+    d_vec_t newspec(m_beatframesize / 2); // magnitude spectrum of current beat
+    d_vec_t oldspec(m_beatframesize / 2); // magnitude spectrum of previous beat
+    d_vec_t specdiff;
+
+    if (audioLength == 0) return;
+
+    for (size_t i = 0; i + 1 < beats.size(); ++i) {
+
+        // Copy the extents of the current beat from downsampled array
+        // into beat frame buffer
+
+        size_t beatstart = (beats[i] * m_increment) / m_factor;
+        size_t beatend = (beats[i] * m_increment) / m_factor;
+        if (beatend >= audioLength) beatend = audioLength - 1;
+        if (beatend < beatstart) beatend = beatstart;
+        size_t beatlen = beatend - beatstart;
+
+        // Also apply a Hanning window to the beat frame buffer, sized
+        // to the beat extents rather than the frame size.  (Because
+        // the size varies, it's easier to do this by hand than use
+        // our Window abstraction.)
+
+        for (size_t j = 0; j < beatlen; ++j) {
+            double mul = 0.5 * (1.0 - cos(TWO_PI * (double(j) / double(beatlen))));
+            m_beatframe[j] = audio[beatstart + j] * mul;
+        }
+
+        for (size_t j = beatlen; j < m_beatframesize; ++j) {
+            m_beatframe[j] = 0.0;
+        }
+
+        // Now FFT beat frame
+        
+        FFT::process(m_beatframesize, false,
+                     m_beatframe, 0, m_fftRealOut, m_fftImagOut);
+        
+        // Calculate magnitudes
+
+        for (size_t j = 0; j < m_beatframesize/2; ++j) {
+            newspec[j] = sqrt(m_fftRealOut[j] * m_fftRealOut[j] +
+                              m_fftImagOut[j] * m_fftImagOut[j]);
+        }
+
+        // Preserve peaks by applying adaptive threshold
+
+        MathUtilities::adaptiveThreshold(newspec);
+
+        // Calculate JS divergence between new and old spectral frames
+
+        specdiff.push_back(measureSpecDiff(oldspec, newspec));
+
+        // Copy newspec across to old
+
+        for (size_t j = 0; j < m_beatframesize/2; ++j) {
+            oldspec[j] = newspec[j];
+        }
+    }
+
+    // We now have all spectral difference measures in specdiff
+
+    uint timesig = 4;   // SHOULD REPLACE THIS WITH A FIND_METER FUNCTION - OR USER PARAMETER
+    d_vec_t dbcand(timesig); // downbeat candidates
+
+    // look for beat transition which leads to greatest spectral change
+    for (int beat = 0; beat < timesig; ++beat) {
+        for (int example = beat; example < specdiff.size(); ++example) {
+            dbcand[beat] += (specdiff[example]) / timesig;
+        }
+    }
+
+    // first downbeat is beat at index of maximum value of dbcand
+    int dbind = MathUtilities::getMax(dbcand);
+
+    // remaining downbeats are at timesig intervals from the first
+    for (int i = dbind; i < beats.size(); i += timesig) {
+        downbeats.push_back(i);
+    }
+}
+
+double
+DownBeat::measureSpecDiff(d_vec_t oldspec, d_vec_t newspec)
+{
+    // JENSEN-SHANNON DIVERGENCE BETWEEN SPECTRAL FRAMES
+
+    uint SPECSIZE = 512;   // ONLY LOOK AT FIRST 512 SAMPLES OF SPECTRUM. 
+    if (SPECSIZE > oldspec.size()/4) {
+        SPECSIZE = oldspec.size()/4;
+    }
+    double SD = 0.;
+    double sd1 = 0.;
+
+    double sumnew = 0.;
+    double sumold = 0.;
+  
+    for (uint i = 0;i < SPECSIZE;i++)
+    {
+        newspec[i] +=EPS;
+        oldspec[i] +=EPS;
+        
+        sumnew+=newspec[i];
+        sumold+=oldspec[i];
+    } 
+    
+    for (uint i = 0;i < SPECSIZE;i++)
+    {
+        newspec[i] /= (sumnew);
+        oldspec[i] /= (sumold);
+        
+        // IF ANY SPECTRAL VALUES ARE 0 (SHOULDN'T BE ANY!) SET THEM TO 1
+        if (newspec[i] == 0)
+        {
+            newspec[i] = 1.;
+        }
+        
+        if (oldspec[i] == 0)
+        {
+            oldspec[i] = 1.;
+        }
+        
+        // JENSEN-SHANNON CALCULATION
+        sd1 = 0.5*oldspec[i] + 0.5*newspec[i];	
+        SD = SD + (-sd1*log(sd1)) + (0.5*(oldspec[i]*log(oldspec[i]))) + (0.5*(newspec[i]*log(newspec[i])));
+    }
+    
+    return SD;
+}
+