/*
* _______ _____ _____ _____
* |__ __| | __ \ / ____| __ \
* | | __ _ _ __ ___ ___ ___| | | | (___ | |__) |
* | |/ _` | '__/ __|/ _ \/ __| | | |\___ \| ___/
* | | (_| | | \__ \ (_) \__ \ |__| |____) | |
* |_|\__,_|_| |___/\___/|___/_____/|_____/|_|
*
* -------------------------------------------------------------
*
* TarsosDSP is developed by Joren Six at IPEM, University Ghent
*
* -------------------------------------------------------------
*
* Info: http://0110.be/tag/TarsosDSP
* Github: https://github.com/JorenSix/TarsosDSP
* Releases: http://0110.be/releases/TarsosDSP/
*
* TarsosDSP includes modified source code by various authors,
* for credits and info, see README.
*
*/
/*
*
* I took Joren's Code and changed it so that
* it uses the FFT to calculate the difference function.
* TarsosDSP is developed by Joren Six at
* The Royal Academy of Fine Arts & Royal Conservatory,
* University College Ghent,
* Hoogpoort 64, 9000 Ghent - Belgium
*
* http://tarsos.0110.be/tag/TarsosDSP
*
*/
package be.tarsos.dsp.pitch;
import be.tarsos.dsp.util.fft.FloatFFT;
/**
* An implementation of the YIN pitch tracking algorithm which uses an FFT to
* calculate the difference function. This makes calculating the difference
* function more performant. See <a href=
* "http://recherche.ircam.fr/equipes/pcm/cheveign/ps/2002_JASA_YIN_proof.pdf"
* >the YIN paper.</a> This implementation is done by <a href="mailto:matthias.mauch@elec.qmul.ac.uk">Matthias Mauch</a> and is
* based on {@link Yin} which is based on the implementation found in <a
* href="http://aubio.org">aubio</a> by Paul Brossier.
*
* @author Matthias Mauch
* @author Joren Six
* @author Paul Brossier
*/
public final class FastYin implements PitchDetector {
/**
* The default YIN threshold value. Should be around 0.10~0.15. See YIN
* paper for more information.
*/
private static final double DEFAULT_THRESHOLD = 0.20;
/**
* The default size of an audio buffer (in samples).
*/
public static final int DEFAULT_BUFFER_SIZE = 2048;
/**
* The default overlap of two consecutive audio buffers (in samples).
*/
public static final int DEFAULT_OVERLAP = 1536;
/**
* The actual YIN threshold.
*/
private final double threshold;
/**
* The audio sample rate. Most audio has a sample rate of 44.1kHz.
*/
private final float sampleRate;
/**
* The buffer that stores the calculated values. It is exactly half the size
* of the input buffer.
*/
private final float[] yinBuffer;
/**
* The result of the pitch detection iteration.
*/
private final PitchDetectionResult result;
//------------------------ FFT instance members
/**
* Holds the FFT data, twice the length of the audio buffer.
*/
private final float[] audioBufferFFT;
/**
* Half of the data, disguised as a convolution kernel.
*/
private final float[] kernel;
/**
* Buffer to allow convolution via complex multiplication. It calculates the auto correlation function (ACF).
*/
private final float[] yinStyleACF;
/**
* An FFT object to quickly calculate the difference function.
*/
private final FloatFFT fft;
/**
* Create a new pitch detector for a stream with the defined sample rate.
* Processes the audio in blocks of the defined size.
*
* @param audioSampleRate
* The sample rate of the audio stream. E.g. 44.1 kHz.
* @param bufferSize
* The size of a buffer. E.g. 1024.
*/
public FastYin(final float audioSampleRate, final int bufferSize) {
this(audioSampleRate, bufferSize, DEFAULT_THRESHOLD);
}
/**
* Create a new pitch detector for a stream with the defined sample rate.
* Processes the audio in blocks of the defined size.
*
* @param audioSampleRate
* The sample rate of the audio stream. E.g. 44.1 kHz.
* @param bufferSize
* The size of a buffer. E.g. 1024.
* @param yinThreshold
* The parameter that defines which peaks are kept as possible
* pitch candidates. See the YIN paper for more details.
*/
public FastYin(final float audioSampleRate, final int bufferSize, final double yinThreshold) {
this.sampleRate = audioSampleRate;
this.threshold = yinThreshold;
yinBuffer = new float[bufferSize / 2];
//Initializations for FFT difference step
audioBufferFFT = new float[2*bufferSize];
kernel = new float[2*bufferSize];
yinStyleACF = new float[2*bufferSize];
fft = new FloatFFT(bufferSize);
result = new PitchDetectionResult();
}
/**
* The main flow of the YIN algorithm. Returns a pitch value in Hz or -1 if
* no pitch is detected.
*
* @return a pitch value in Hz or -1 if no pitch is detected.
*/
public PitchDetectionResult getPitch(final float[] audioBuffer) {
final int tauEstimate;
final float pitchInHertz;
// step 2
difference(audioBuffer);
// step 3
cumulativeMeanNormalizedDifference();
// step 4
tauEstimate = absoluteThreshold();
// step 5
if (tauEstimate != -1) {
final float betterTau = parabolicInterpolation(tauEstimate);
// step 6
// TODO Implement optimization for the AUBIO_YIN algorithm.
// 0.77% => 0.5% error rate,
// using the data of the YIN paper
// bestLocalEstimate()
// conversion to Hz
pitchInHertz = sampleRate / betterTau;
} else{
// no pitch found
pitchInHertz = -1;
}
result.setPitch(pitchInHertz);
return result;
}
/**
* Implements the difference function as described in step 2 of the YIN
* paper with an FFT to reduce the number of operations.
*/
private void difference(final float[] audioBuffer) {
// POWER TERM CALCULATION
// ... for the power terms in equation (7) in the Yin paper
float[] powerTerms = new float[yinBuffer.length];
for (int j = 0; j < yinBuffer.length; ++j) {
powerTerms[0] += audioBuffer[j] * audioBuffer[j];
}
// now iteratively calculate all others (saves a few multiplications)
for (int tau = 1; tau < yinBuffer.length; ++tau) {
powerTerms[tau] = powerTerms[tau-1] - audioBuffer[tau-1] * audioBuffer[tau-1] + audioBuffer[tau+yinBuffer.length] * audioBuffer[tau+yinBuffer.length];
}
// YIN-STYLE AUTOCORRELATION via FFT
// 1. data
for (int j = 0; j < audioBuffer.length; ++j) {
audioBufferFFT[2*j] = audioBuffer[j];
audioBufferFFT[2*j+1] = 0;
}
fft.complexForward(audioBufferFFT);
// 2. half of the data, disguised as a convolution kernel
for (int j = 0; j < yinBuffer.length; ++j) {
kernel[2*j] = audioBuffer[(yinBuffer.length-1)-j];
kernel[2*j+1] = 0;
kernel[2*j+audioBuffer.length] = 0;
kernel[2*j+audioBuffer.length+1] = 0;
}
fft.complexForward(kernel);
// 3. convolution via complex multiplication
for (int j = 0; j < audioBuffer.length; ++j) {
yinStyleACF[2*j] = audioBufferFFT[2*j]*kernel[2*j] - audioBufferFFT[2*j+1]*kernel[2*j+1]; // real
yinStyleACF[2*j+1] = audioBufferFFT[2*j+1]*kernel[2*j] + audioBufferFFT[2*j]*kernel[2*j+1]; // imaginary
}
fft.complexInverse(yinStyleACF, true);
// CALCULATION OF difference function
// ... according to (7) in the Yin paper.
for (int j = 0; j < yinBuffer.length; ++j) {
// taking only the real part
yinBuffer[j] = powerTerms[0] + powerTerms[j] - 2 * yinStyleACF[2 * (yinBuffer.length - 1 + j)];
}
}
/**
* The cumulative mean normalized difference function as described in step 3
* of the YIN paper. <br>
* <code>
* yinBuffer[0] == yinBuffer[1] = 1
* </code>
*/
private void cumulativeMeanNormalizedDifference() {
int tau;
yinBuffer[0] = 1;
float runningSum = 0;
for (tau = 1; tau < yinBuffer.length; tau++) {
runningSum += yinBuffer[tau];
yinBuffer[tau] *= tau / runningSum;
}
}
/**
* Implements step 4 of the AUBIO_YIN paper.
*/
private int absoluteThreshold() {
// Uses another loop construct
// than the AUBIO implementation
int tau;
// first two positions in yinBuffer are always 1
// So start at the third (index 2)
for (tau = 2; tau < yinBuffer.length; tau++) {
if (yinBuffer[tau] < threshold) {
while (tau + 1 < yinBuffer.length && yinBuffer[tau + 1] < yinBuffer[tau]) {
tau++;
}
// found tau, exit loop and return
// store the probability
// From the YIN paper: The threshold determines the list of
// candidates admitted to the set, and can be interpreted as the
// proportion of aperiodic power tolerated
// within a periodic signal.
//
// Since we want the periodicity and and not aperiodicity:
// periodicity = 1 - aperiodicity
result.setProbability(1 - yinBuffer[tau]);
break;
}
}
// if no pitch found, tau => -1
if (tau == yinBuffer.length || yinBuffer[tau] >= threshold || result.getProbability() > 1.0) {
tau = -1;
result.setProbability(0);
result.setPitched(false);
} else {
result.setPitched(true);
}
return tau;
}
/**
* Implements step 5 of the AUBIO_YIN paper. It refines the estimated tau
* value using parabolic interpolation. This is needed to detect higher
* frequencies more precisely. See http://fizyka.umk.pl/nrbook/c10-2.pdf and
* for more background
* http://fedc.wiwi.hu-berlin.de/xplore/tutorials/xegbohtmlnode62.html
*
* @param tauEstimate
* The estimated tau value.
* @return A better, more precise tau value.
*/
private float parabolicInterpolation(final int tauEstimate) {
final float betterTau;
final int x0;
final int x2;
if (tauEstimate < 1) {
x0 = tauEstimate;
} else {
x0 = tauEstimate - 1;
}
if (tauEstimate + 1 < yinBuffer.length) {
x2 = tauEstimate + 1;
} else {
x2 = tauEstimate;
}
if (x0 == tauEstimate) {
if (yinBuffer[tauEstimate] <= yinBuffer[x2]) {
betterTau = tauEstimate;
} else {
betterTau = x2;
}
} else if (x2 == tauEstimate) {
if (yinBuffer[tauEstimate] <= yinBuffer[x0]) {
betterTau = tauEstimate;
} else {
betterTau = x0;
}
} else {
float s0, s1, s2;
s0 = yinBuffer[x0];
s1 = yinBuffer[tauEstimate];
s2 = yinBuffer[x2];
// fixed AUBIO implementation, thanks to Karl Helgason:
// (2.0f * s1 - s2 - s0) was incorrectly multiplied with -1
betterTau = tauEstimate + (s2 - s0) / (2 * (2 * s1 - s2 - s0));
}
return betterTau;
}
}