The Tor Browser: media/libsoundtouch/src/AAFilter.h@b8a032363ba2

Incorporate requested changes from Mozilla in review:
https://bugzilla.mozilla.org/show_bug.cgi?id=1123480#c6

     1 ////////////////////////////////////////////////////////////////////////////////

     2 ///

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

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

     5 /// with several performance-increasing tweaks.

     6 ///

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

     8 /// transposing the sample rate with interpolation.

     9 ///

    10 /// Author        : Copyright (c) Olli Parviainen

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

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

    13 ///

    14 ////////////////////////////////////////////////////////////////////////////////

    15 //

    16 // Last changed  : $Date: 2014-01-07 13:41:23 -0600 (Tue, 07 Jan 2014) $

    17 // File revision : $Revision: 4 $

    18 //

    19 // $Id: AAFilter.h 187 2014-01-07 19:41:23Z oparviai $

    20 //

    21 ////////////////////////////////////////////////////////////////////////////////

    22 //

    23 // License :

    24 //

    25 //  SoundTouch audio processing library

    26 //  Copyright (c) Olli Parviainen

    27 //

    28 //  This library is free software; you can redistribute it and/or

    29 //  modify it under the terms of the GNU Lesser General Public

    30 //  License as published by the Free Software Foundation; either

    31 //  version 2.1 of the License, or (at your option) any later version.

    32 //

    33 //  This library is distributed in the hope that it will be useful,

    34 //  but WITHOUT ANY WARRANTY; without even the implied warranty of

    35 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

    36 //  Lesser General Public License for more details.

    37 //

    38 //  You should have received a copy of the GNU Lesser General Public

    39 //  License along with this library; if not, write to the Free Software

    40 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA

    41 //

    42 ////////////////////////////////////////////////////////////////////////////////

    44 #ifndef AAFilter_H

    45 #define AAFilter_H

    47 #include "STTypes.h"

    48 #include "FIFOSampleBuffer.h"

    50 namespace soundtouch

    51 {

    53 class AAFilter

    54 {

    55 protected:

    56     class FIRFilter *pFIR;

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

    59     double cutoffFreq;

    61     /// num of filter taps

    62     uint length;

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

    65     void calculateCoeffs();

    66 public:

    67     AAFilter(uint length);

    69     ~AAFilter();

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

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

    73     /// frequencies than that.

    74     void setCutoffFreq(double newCutoffFreq);

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

    77     void setLength(uint newLength);

    79     uint getLength() const;

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

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

    83     /// smaller than the amount of input samples.

    84     uint evaluate(SAMPLETYPE *dest,

    85                   const SAMPLETYPE *src,

    86                   uint numSamples,

    87                   uint numChannels) const;

    89     /// Applies the filter to the given src & dest pipes, so that processed amount of

    90     /// samples get removed from src, and produced amount added to dest

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

    92     /// smaller than the amount of input samples.

    93     uint evaluate(FIFOSampleBuffer &dest,

    94                   FIFOSampleBuffer &src) const;

    96 };

    98 }

   100 #endif

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