mirror of
https://github.com/RetroDECK/Duckstation.git
synced 2024-11-24 22:55:41 +00:00
206 lines
7.5 KiB
C++
206 lines
7.5 KiB
C++
////////////////////////////////////////////////////////////////////////////////
|
|
///
|
|
/// Beats-per-minute (BPM) detection routine.
|
|
///
|
|
/// The beat detection algorithm works as follows:
|
|
/// - Use function 'inputSamples' to input a chunks of samples to the class for
|
|
/// analysis. It's a good idea to enter a large sound file or stream in smallish
|
|
/// chunks of around few kilosamples in order not to extinguish too much RAM memory.
|
|
/// - Input sound data is decimated to approx 500 Hz to reduce calculation burden,
|
|
/// which is basically ok as low (bass) frequencies mostly determine the beat rate.
|
|
/// Simple averaging is used for anti-alias filtering because the resulting signal
|
|
/// quality isn't of that high importance.
|
|
/// - Decimated sound data is enveloped, i.e. the amplitude shape is detected by
|
|
/// taking absolute value that's smoothed by sliding average. Signal levels that
|
|
/// are below a couple of times the general RMS amplitude level are cut away to
|
|
/// leave only notable peaks there.
|
|
/// - Repeating sound patterns (e.g. beats) are detected by calculating short-term
|
|
/// autocorrelation function of the enveloped signal.
|
|
/// - After whole sound data file has been analyzed as above, the bpm level is
|
|
/// detected by function 'getBpm' that finds the highest peak of the autocorrelation
|
|
/// function, calculates it's precise location and converts this reading to bpm's.
|
|
///
|
|
/// Author : Copyright (c) Olli Parviainen
|
|
/// Author e-mail : oparviai 'at' iki.fi
|
|
/// SoundTouch WWW: http://www.surina.net/soundtouch
|
|
///
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
//
|
|
// License :
|
|
//
|
|
// SoundTouch audio processing library
|
|
// Copyright (c) Olli Parviainen
|
|
//
|
|
// This library is free software; you can redistribute it and/or
|
|
// modify it under the terms of the GNU Lesser General Public
|
|
// License as published by the Free Software Foundation; either
|
|
// version 2.1 of the License, or (at your option) any later version.
|
|
//
|
|
// This library is distributed in the hope that it will be useful,
|
|
// but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
// Lesser General Public License for more details.
|
|
//
|
|
// You should have received a copy of the GNU Lesser General Public
|
|
// License along with this library; if not, write to the Free Software
|
|
// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
|
|
//
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
#ifndef _BPMDetect_H_
|
|
#define _BPMDetect_H_
|
|
|
|
#include <vector>
|
|
#include "STTypes.h"
|
|
#include "FIFOSampleBuffer.h"
|
|
|
|
namespace soundtouch
|
|
{
|
|
|
|
/// Minimum allowed BPM rate. Used to restrict accepted result above a reasonable limit.
|
|
#define MIN_BPM 45
|
|
|
|
/// Maximum allowed BPM rate range. Used for calculating algorithm parametrs
|
|
#define MAX_BPM_RANGE 200
|
|
|
|
/// Maximum allowed BPM rate range. Used to restrict accepted result below a reasonable limit.
|
|
#define MAX_BPM_VALID 190
|
|
|
|
////////////////////////////////////////////////////////////////////////////////
|
|
|
|
typedef struct
|
|
{
|
|
float pos;
|
|
float strength;
|
|
} BEAT;
|
|
|
|
|
|
class IIR2_filter
|
|
{
|
|
double coeffs[5];
|
|
double prev[5];
|
|
|
|
public:
|
|
IIR2_filter(const double *lpf_coeffs);
|
|
float update(float x);
|
|
};
|
|
|
|
|
|
/// Class for calculating BPM rate for audio data.
|
|
class BPMDetect
|
|
{
|
|
protected:
|
|
/// Auto-correlation accumulator bins.
|
|
float *xcorr;
|
|
|
|
/// Sample average counter.
|
|
int decimateCount;
|
|
|
|
/// Sample average accumulator for FIFO-like decimation.
|
|
soundtouch::LONG_SAMPLETYPE decimateSum;
|
|
|
|
/// Decimate sound by this coefficient to reach approx. 500 Hz.
|
|
int decimateBy;
|
|
|
|
/// Auto-correlation window length
|
|
int windowLen;
|
|
|
|
/// Number of channels (1 = mono, 2 = stereo)
|
|
int channels;
|
|
|
|
/// sample rate
|
|
int sampleRate;
|
|
|
|
/// Beginning of auto-correlation window: Autocorrelation isn't being updated for
|
|
/// the first these many correlation bins.
|
|
int windowStart;
|
|
|
|
/// window functions for data preconditioning
|
|
float *hamw;
|
|
float *hamw2;
|
|
|
|
// beat detection variables
|
|
int pos;
|
|
int peakPos;
|
|
int beatcorr_ringbuffpos;
|
|
int init_scaler;
|
|
float peakVal;
|
|
float *beatcorr_ringbuff;
|
|
|
|
/// FIFO-buffer for decimated processing samples.
|
|
soundtouch::FIFOSampleBuffer *buffer;
|
|
|
|
/// Collection of detected beat positions
|
|
//BeatCollection beats;
|
|
std::vector<BEAT> beats;
|
|
|
|
// 2nd order low-pass-filter
|
|
IIR2_filter beat_lpf;
|
|
|
|
/// Updates auto-correlation function for given number of decimated samples that
|
|
/// are read from the internal 'buffer' pipe (samples aren't removed from the pipe
|
|
/// though).
|
|
void updateXCorr(int process_samples /// How many samples are processed.
|
|
);
|
|
|
|
/// Decimates samples to approx. 500 Hz.
|
|
///
|
|
/// \return Number of output samples.
|
|
int decimate(soundtouch::SAMPLETYPE *dest, ///< Destination buffer
|
|
const soundtouch::SAMPLETYPE *src, ///< Source sample buffer
|
|
int numsamples ///< Number of source samples.
|
|
);
|
|
|
|
/// Calculates amplitude envelope for the buffer of samples.
|
|
/// Result is output to 'samples'.
|
|
void calcEnvelope(soundtouch::SAMPLETYPE *samples, ///< Pointer to input/output data buffer
|
|
int numsamples ///< Number of samples in buffer
|
|
);
|
|
|
|
/// remove constant bias from xcorr data
|
|
void removeBias();
|
|
|
|
// Detect individual beat positions
|
|
void updateBeatPos(int process_samples);
|
|
|
|
|
|
public:
|
|
/// Constructor.
|
|
BPMDetect(int numChannels, ///< Number of channels in sample data.
|
|
int sampleRate ///< Sample rate in Hz.
|
|
);
|
|
|
|
/// Destructor.
|
|
virtual ~BPMDetect();
|
|
|
|
/// Inputs a block of samples for analyzing: Envelopes the samples and then
|
|
/// updates the autocorrelation estimation. When whole song data has been input
|
|
/// in smaller blocks using this function, read the resulting bpm with 'getBpm'
|
|
/// function.
|
|
///
|
|
/// Notice that data in 'samples' array can be disrupted in processing.
|
|
void inputSamples(const soundtouch::SAMPLETYPE *samples, ///< Pointer to input/working data buffer
|
|
int numSamples ///< Number of samples in buffer
|
|
);
|
|
|
|
/// Analyzes the results and returns the BPM rate. Use this function to read result
|
|
/// after whole song data has been input to the class by consecutive calls of
|
|
/// 'inputSamples' function.
|
|
///
|
|
/// \return Beats-per-minute rate, or zero if detection failed.
|
|
float getBpm();
|
|
|
|
/// Get beat position arrays. Note: The array includes also really low beat detection values
|
|
/// in absence of clear strong beats. Consumer may wish to filter low values away.
|
|
/// - "pos" receive array of beat positions
|
|
/// - "values" receive array of beat detection strengths
|
|
/// - max_num indicates max.size of "pos" and "values" array.
|
|
///
|
|
/// You can query a suitable array sized by calling this with NULL in "pos" & "values".
|
|
///
|
|
/// \return number of beats in the arrays.
|
|
int getBeats(float *pos, float *strength, int max_num);
|
|
};
|
|
}
|
|
#endif // _BPMDetect_H_
|