////////////////////////////////////////////////////////////////////////////////

///

/// 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

///

////////////////////////////////////////////////////////////////////////////////

//

// Last changed  : $Date: 2008-12-25 14:20:01 +0200 (Thu, 25 Dec 2008) $

// File revision : $Revision: 4 $

//

// $Id: BPMDetect.h 33 2008-12-25 12:20:01Z oparviai $

//

////////////////////////////////////////////////////////////////////////////////

//

// 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 "STTypes.h"

#include "FIFOSampleBuffer.h"



//namespace soundtouch

//{



/// Minimum allowed BPM rate. Used to restrict accepted result above a reasonable limit.

#define MIN_BPM 29



/// Maximum allowed BPM rate. Used to restrict accepted result below a reasonable limit.

#define MAX_BPM 230





/// Class for calculating BPM rate for audio data.

class BPMDetect

{

protected:

    /// Auto-correlation accumulator bins.

    float *xcorr;

    

    /// Amplitude envelope sliding average approximation level accumulator

    float envelopeAccu;



    /// RMS volume sliding average approximation level accumulator

    float RMSVolumeAccu;



    /// 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;

 

    /// FIFO-buffer for decimated processing samples.

    soundtouch::FIFOSampleBuffer *buffer;



    /// Initialize the class for processing.

    void init(int numChannels, int sampleRate);



    /// 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

                      );



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(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();

};



//}



#endif // _BPMDetect_H_