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

///

/// Sampled sound tempo changer/time stretch algorithm. Changes the sound tempo 

/// while maintaining the original pitch by using a time domain WSOLA-like method 

/// with several performance-increasing tweaks.

///

/// Anti-alias filter is used to prevent folding of high frequencies when 

/// transposing the sample rate with interpolation.

///

/// Author        : Copyright (c) Olli Parviainen

/// Author e-mail : oparviai 'at' iki.fi

/// SoundTouch WWW: http://www.surina.net/soundtouch

///

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

//

// Last changed  : $Date: 2008-02-10 18:26:55 +0200 (Sun, 10 Feb 2008) $

// File revision : $Revision: 4 $

//

// $Id: AAFilter.h 11 2008-02-10 16:26:55Z 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 AAFilter_H

#define AAFilter_H



#include "STTypes.h"



namespace soundtouch

{



class AAFilter

{

protected:

    class FIRFilter *pFIR;



    /// Low-pass filter cut-off frequency, negative = invalid

    double cutoffFreq;



    /// num of filter taps

    uint length;



    /// Calculate the FIR coefficients realizing the given cutoff-frequency

    void calculateCoeffs();

public:

    AAFilter(uint length);



    ~AAFilter();



    /// Sets new anti-alias filter cut-off edge frequency, scaled to sampling 

    /// frequency (nyquist frequency = 0.5). The filter will cut off the 

    /// frequencies than that.

    void setCutoffFreq(double newCutoffFreq);



    /// Sets number of FIR filter taps, i.e. ~filter complexity

    void setLength(uint newLength);



    uint getLength() const;



    /// Applies the filter to the given sequence of samples. 

    /// Note : The amount of outputted samples is by value of 'filter length' 

    /// smaller than the amount of input samples.

    uint evaluate(SAMPLETYPE *dest, 

                  const SAMPLETYPE *src, 

                  uint numSamples, 

                  uint numChannels) const;

};



}



#endif