media/libsoundtouch/src/InterpolateShannon.cpp

   1 ////////////////////////////////////////////////////////////////////////////////
   2 ///
   3 /// Sample interpolation routine using 8-tap band-limited Shannon interpolation
   4 /// with kaiser window.
   5 ///
   6 /// Notice. This algorithm is remarkably much heavier than linear or cubic
   7 /// interpolation, and not remarkably better than cubic algorithm. Thus mostly
   8 /// for experimental purposes
   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 #include <math.h>
  38 #include "InterpolateShannon.h"
  39 #include "STTypes.h"
  40
  41 using namespace soundtouch;
  42
  43
  44 /// Kaiser window with beta = 2.0
  45 /// Values scaled down by 5% to avoid overflows
  46 static const double _kaiser8[8] =
  47 {
  48    0.41778693317814,
  49    0.64888025049173,
  50    0.83508562409944,
  51    0.93887857733412,
  52    0.93887857733412,
  53    0.83508562409944,
  54    0.64888025049173,
  55    0.41778693317814
  56 };
  57
  58
  59 InterpolateShannon::InterpolateShannon()
  60 {
  61     fract = 0;
  62 }
  63
  64
  65 void InterpolateShannon::resetRegisters()
  66 {
  67     fract = 0;
  68 }
  69
  70
  71 #define PI 3.1415926536
  72 #define sinc(x) (sin(PI * (x)) / (PI * (x)))
  73
  74 /// Transpose mono audio. Returns number of produced output samples, and
  75 /// updates "srcSamples" to amount of consumed source samples
  76 int InterpolateShannon::transposeMono(SAMPLETYPE *pdest,
  77                     const SAMPLETYPE *psrc,
  78                     int &srcSamples)
  79 {
  80     int i;
  81     int srcSampleEnd = srcSamples - 8;
  82     int srcCount = 0;
  83
  84     i = 0;
  85     while (srcCount < srcSampleEnd)
  86     {
  87         double out;
  88         assert(fract < 1.0);
  89
  90         out  = psrc[0] * sinc(-3.0 - fract) * _kaiser8[0];
  91         out += psrc[1] * sinc(-2.0 - fract) * _kaiser8[1];
  92         out += psrc[2] * sinc(-1.0 - fract) * _kaiser8[2];
  93         if (fract < 1e-6)
  94         {
  95             out += psrc[3] * _kaiser8[3];     // sinc(0) = 1
  96         }
  97         else
  98         {
  99             out += psrc[3] * sinc(- fract) * _kaiser8[3];
 100         }
 101         out += psrc[4] * sinc( 1.0 - fract) * _kaiser8[4];
 102         out += psrc[5] * sinc( 2.0 - fract) * _kaiser8[5];
 103         out += psrc[6] * sinc( 3.0 - fract) * _kaiser8[6];
 104         out += psrc[7] * sinc( 4.0 - fract) * _kaiser8[7];
 105
 106         pdest[i] = (SAMPLETYPE)out;
 107         i ++;
 108
 109         // update position fraction
 110         fract += rate;
 111         // update whole positions
 112         int whole = (int)fract;
 113         fract -= whole;
 114         psrc += whole;
 115         srcCount += whole;
 116     }
 117     srcSamples = srcCount;
 118     return i;
 119 }
 120
 121
 122 /// Transpose stereo audio. Returns number of produced output samples, and
 123 /// updates "srcSamples" to amount of consumed source samples
 124 int InterpolateShannon::transposeStereo(SAMPLETYPE *pdest,
 125                     const SAMPLETYPE *psrc,
 126                     int &srcSamples)
 127 {
 128     int i;
 129     int srcSampleEnd = srcSamples - 8;
 130     int srcCount = 0;
 131
 132     i = 0;
 133     while (srcCount < srcSampleEnd)
 134     {
 135         double out0, out1, w;
 136         assert(fract < 1.0);
 137
 138         w = sinc(-3.0 - fract) * _kaiser8[0];
 139         out0 = psrc[0] * w; out1 = psrc[1] * w;
 140         w = sinc(-2.0 - fract) * _kaiser8[1];
 141         out0 += psrc[2] * w; out1 += psrc[3] * w;
 142         w = sinc(-1.0 - fract) * _kaiser8[2];
 143         out0 += psrc[4] * w; out1 += psrc[5] * w;
 144         w = _kaiser8[3] * ((fract < 1e-5) ? 1.0 : sinc(- fract));   // sinc(0) = 1
 145         out0 += psrc[6] * w; out1 += psrc[7] * w;
 146         w = sinc( 1.0 - fract) * _kaiser8[4];
 147         out0 += psrc[8] * w; out1 += psrc[9] * w;
 148         w = sinc( 2.0 - fract) * _kaiser8[5];
 149         out0 += psrc[10] * w; out1 += psrc[11] * w;
 150         w = sinc( 3.0 - fract) * _kaiser8[6];
 151         out0 += psrc[12] * w; out1 += psrc[13] * w;
 152         w = sinc( 4.0 - fract) * _kaiser8[7];
 153         out0 += psrc[14] * w; out1 += psrc[15] * w;
 154
 155         pdest[2*i]   = (SAMPLETYPE)out0;
 156         pdest[2*i+1] = (SAMPLETYPE)out1;
 157         i ++;
 158
 159         // update position fraction
 160         fract += rate;
 161         // update whole positions
 162         int whole = (int)fract;
 163         fract -= whole;
 164         psrc += 2*whole;
 165         srcCount += whole;
 166     }
 167     srcSamples = srcCount;
 168     return i;
 169 }
 170
 171
 172 /// Transpose stereo audio. Returns number of produced output samples, and
 173 /// updates "srcSamples" to amount of consumed source samples
 174 int InterpolateShannon::transposeMulti(SAMPLETYPE *pdest,
 175                     const SAMPLETYPE *psrc,
 176                     int &srcSamples)
 177 {
 178     // not implemented
 179     assert(false);
 180     return 0;
 181 }