/*
* _______ _____ _____ _____
* |__ __| | __ \ / ____| __ \
* | | __ _ _ __ ___ ___ ___| | | | (___ | |__) |
* | |/ _` | '__/ __|/ _ \/ __| | | |\___ \| ___/
* | | (_| | | \__ \ (_) \__ \ |__| |____) | |
* |_|\__,_|_| |___/\___/|___/_____/|_____/|_|
*
* -------------------------------------------------------------
*
* 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.
*
*/
package be.tarsos.dsp.pitch;
/**
* An implementation of the AUBIO_YIN pitch tracking algorithm. See <a href=
* "http://recherche.ircam.fr/equipes/pcm/cheveign/ps/2002_JASA_YIN_proof.pdf"
* >the YIN paper.</a> Implementation based on <a
* href="http://aubio.org">aubio</a>
*
* @author Joren Six
* @author Paul Brossier
*/
public final class Yin 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;
/**
* 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 Yin(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 Yin(final float audioSampleRate, final int bufferSize, final double yinThreshold) {
this.sampleRate = audioSampleRate;
this.threshold = yinThreshold;
yinBuffer = new float[bufferSize / 2];
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.
*/
private void difference(final float[] audioBuffer) {
int index, tau;
float delta;
for (tau = 0; tau < yinBuffer.length; tau++) {
yinBuffer[tau] = 0;
}
for (tau = 1; tau < yinBuffer.length; tau++) {
for (index = 0; index < yinBuffer.length; index++) {
delta = audioBuffer[index] - audioBuffer[index + tau];
yinBuffer[tau] += delta * delta;
}
}
}
/**
* 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) {
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;
}
}