libs/soundtouch/BPMDetect.h

   1 ////////////////////////////////////////////////////////////////////////////////
   2 ///
   3 /// Beats-per-minute (BPM) detection routine.
   4 ///
   5 /// The beat detection algorithm works as follows:
   6 /// - Use function 'inputSamples' to input a chunks of samples to the class for
   7 ///   analysis. It's a good idea to enter a large sound file or stream in smallish
   8 ///   chunks of around few kilosamples in order not to extinguish too much RAM memory.
   9 /// - Input sound data is decimated to approx 500 Hz to reduce calculation burden,
  10 ///   which is basically ok as low (bass) frequencies mostly determine the beat rate.
  11 ///   Simple averaging is used for anti-alias filtering because the resulting signal
  12 ///   quality isn't of that high importance.
  13 /// - Decimated sound data is enveloped, i.e. the amplitude shape is detected by
  14 ///   taking absolute value that's smoothed by sliding average. Signal levels that
  15 ///   are below a couple of times the general RMS amplitude level are cut away to
  16 ///   leave only notable peaks there.
  17 /// - Repeating sound patterns (e.g. beats) are detected by calculating short-term
  18 ///   autocorrelation function of the enveloped signal.
  19 /// - After whole sound data file has been analyzed as above, the bpm level is
  20 ///   detected by function 'getBpm' that finds the highest peak of the autocorrelation
  21 ///   function, calculates it's precise location and converts this reading to bpm's.
  22 ///
  23 /// Author        : Copyright (c) Olli Parviainen
  24 /// Author e-mail : oparviai @ iki.fi
  25 /// SoundTouch WWW: http://www.iki.fi/oparviai/soundtouch
  26 ///
  27 ////////////////////////////////////////////////////////////////////////////////
  28 //
  29 // Last changed  : $Date$
  30 // File revision : $Revision$
  31 //
  32 // $Id$
  33 //
  34 ////////////////////////////////////////////////////////////////////////////////
  35 //
  36 // License :
  37 //
  38 //  SoundTouch audio processing library
  39 //  Copyright (c) Olli Parviainen
  40 //
  41 //  This library is free software; you can redistribute it and/or
  42 //  modify it under the terms of the GNU Lesser General Public
  43 //  License as published by the Free Software Foundation; either
  44 //  version 2.1 of the License, or (at your option) any later version.
  45 //
  46 //  This library is distributed in the hope that it will be useful,
  47 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  48 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  49 //  Lesser General Public License for more details.
  50 //
  51 //  You should have received a copy of the GNU Lesser General Public
  52 //  License along with this library; if not, write to the Free Software
  53 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  54 //
  55 ////////////////////////////////////////////////////////////////////////////////
  56
  57 #ifndef _BPMDetect_H_
  58 #define _BPMDetect_H_
  59
  60 #include "STTypes.h"
  61 #include "FIFOSampleBuffer.h"
  62
  63 /// Minimum allowed BPM rate. Used to restrict accepted result above a reasonable limit.
  64 #define MIN_BPM 45
  65
  66 /// Maximum allowed BPM rate. Used to restrict accepted result below a reasonable limit.
  67 #define MAX_BPM 230
  68
  69
  70 /// Class for calculating BPM rate for audio data.
  71 class BPMDetect
  72 {
  73 protected:
  74     /// Auto-correlation accumulator bins.
  75     float *xcorr;
  76
  77     /// Amplitude envelope sliding average approximation level accumulator
  78     float envelopeAccu;
  79
  80     /// RMS volume sliding average approximation level accumulator
  81     float RMSVolumeAccu;
  82
  83     /// Sample average counter.
  84     int decimateCount;
  85
  86     /// Sample average accumulator for FIFO-like decimation.
  87     soundtouch::LONG_SAMPLETYPE decimateSum;
  88
  89     /// Decimate sound by this coefficient to reach approx. 500 Hz.
  90     int decimateBy;
  91
  92     /// Auto-correlation window length
  93     int windowLen;
  94
  95     /// Number of channels (1 = mono, 2 = stereo)
  96     int channels;
  97
  98     /// sample rate
  99     int sampleRate;
 100
 101     /// Beginning of auto-correlation window: Autocorrelation isn't being updated for
 102     /// the first these many correlation bins.
 103     int windowStart;
 104
 105     /// FIFO-buffer for decimated processing samples.
 106     soundtouch::FIFOSampleBuffer *buffer;
 107
 108     /// Initialize the class for processing.
 109     void init(int numChannels, int sampleRate);
 110
 111     /// Updates auto-correlation function for given number of decimated samples that
 112     /// are read from the internal 'buffer' pipe (samples aren't removed from the pipe
 113     /// though).
 114     void updateXCorr(int process_samples      /// How many samples are processed.
 115                      );
 116
 117     /// Decimates samples to approx. 500 Hz.
 118     ///
 119     /// \return Number of output samples.
 120     int decimate(soundtouch::SAMPLETYPE *dest,      ///< Destination buffer
 121                  const soundtouch::SAMPLETYPE *src, ///< Source sample buffer
 122                  int numsamples                     ///< Number of source samples.
 123                  );
 124
 125     /// Calculates amplitude envelope for the buffer of samples.
 126     /// Result is output to 'samples'.
 127     void calcEnvelope(soundtouch::SAMPLETYPE *samples,  ///< Pointer to input/output data buffer
 128                       int numsamples                    ///< Number of samples in buffer
 129                       );
 130
 131 public:
 132     /// Constructor.
 133     BPMDetect(int numChannels,  ///< Number of channels in sample data.
 134               int sampleRate    ///< Sample rate in Hz.
 135               );
 136
 137     /// Destructor.
 138     virtual ~BPMDetect();
 139
 140     /// Inputs a block of samples for analyzing: Envelopes the samples and then
 141     /// updates the autocorrelation estimation. When whole song data has been input
 142     /// in smaller blocks using this function, read the resulting bpm with 'getBpm'
 143     /// function.
 144     ///
 145     /// Notice that data in 'samples' array can be disrupted in processing.
 146     void inputSamples(soundtouch::SAMPLETYPE *samples,  ///< Pointer to input/working data buffer
 147                       int numSamples                    ///< Number of samples in buffer
 148                       );
 149
 150
 151     /// Analyzes the results and returns the BPM rate. Use this function to read result
 152     /// after whole song data has been input to the class by consecutive calls of
 153     /// 'inputSamples' function.
 154     ///
 155     /// \return Beats-per-minute rate, or zero if detection failed.
 156     float getBpm();
 157 };
 158
 159 #endif // _BPMDetect_H_