media/libsoundtouch/src/AAFilter.h

   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 // License :
  17 //
  18 //  SoundTouch audio processing library
  19 //  Copyright (c) Olli Parviainen
  20 //
  21 //  This library is free software; you can redistribute it and/or
  22 //  modify it under the terms of the GNU Lesser General Public
  23 //  License as published by the Free Software Foundation; either
  24 //  version 2.1 of the License, or (at your option) any later version.
  25 //
  26 //  This library is distributed in the hope that it will be useful,
  27 //  but WITHOUT ANY WARRANTY; without even the implied warranty of
  28 //  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  29 //  Lesser General Public License for more details.
  30 //
  31 //  You should have received a copy of the GNU Lesser General Public
  32 //  License along with this library; if not, write to the Free Software
  33 //  Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  34 //
  35 ////////////////////////////////////////////////////////////////////////////////
  36
  37 #ifndef AAFilter_H
  38 #define AAFilter_H
  39
  40 #include "STTypes.h"
  41 #include "FIFOSampleBuffer.h"
  42
  43 namespace soundtouch
  44 {
  45
  46 class AAFilter
  47 {
  48 protected:
  49     class FIRFilter *pFIR;
  50
  51     /// Low-pass filter cut-off frequency, negative = invalid
  52     double cutoffFreq;
  53
  54     /// num of filter taps
  55     uint length;
  56
  57     /// Calculate the FIR coefficients realizing the given cutoff-frequency
  58     void calculateCoeffs();
  59 public:
  60     AAFilter(uint length);
  61
  62     ~AAFilter();
  63
  64     /// Sets new anti-alias filter cut-off edge frequency, scaled to sampling
  65     /// frequency (nyquist frequency = 0.5). The filter will cut off the
  66     /// frequencies than that.
  67     void setCutoffFreq(double newCutoffFreq);
  68
  69     /// Sets number of FIR filter taps, i.e. ~filter complexity
  70     void setLength(uint newLength);
  71
  72     uint getLength() const;
  73
  74     /// Applies the filter to the given sequence of samples.
  75     /// Note : The amount of outputted samples is by value of 'filter length'
  76     /// smaller than the amount of input samples.
  77     uint evaluate(SAMPLETYPE *dest,
  78                   const SAMPLETYPE *src,
  79                   uint numSamples,
  80                   uint numChannels) const;
  81
  82     /// Applies the filter to the given src & dest pipes, so that processed amount of
  83     /// samples get removed from src, and produced amount added to dest
  84     /// Note : The amount of outputted samples is by value of 'filter length'
  85     /// smaller than the amount of input samples.
  86     uint evaluate(FIFOSampleBuffer &dest,
  87                   FIFOSampleBuffer &src) const;
  88
  89 };
  90
  91 }
  92
  93 #endif