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