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comparison: media/libsoundtouch/src/InterpolateShannon.cpp
media/libsoundtouch/src/InterpolateShannon.cpp
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| 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 // $Id: InterpolateShannon.cpp 195 2014-04-06 15:57:21Z oparviai $ | |
| 17 // | |
| 18 //////////////////////////////////////////////////////////////////////////////// | |
| 19 // | |
| 20 // License : | |
| 21 // | |
| 22 // SoundTouch audio processing library | |
| 23 // Copyright (c) Olli Parviainen | |
| 24 // | |
| 25 // This library is free software; you can redistribute it and/or | |
| 26 // modify it under the terms of the GNU Lesser General Public | |
| 27 // License as published by the Free Software Foundation; either | |
| 28 // version 2.1 of the License, or (at your option) any later version. | |
| 29 // | |
| 30 // This library is distributed in the hope that it will be useful, | |
| 31 // but WITHOUT ANY WARRANTY; without even the implied warranty of | |
| 32 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
| 33 // Lesser General Public License for more details. | |
| 34 // | |
| 35 // You should have received a copy of the GNU Lesser General Public | |
| 36 // License along with this library; if not, write to the Free Software | |
| 37 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA | |
| 38 // | |
| 39 //////////////////////////////////////////////////////////////////////////////// | |
| 40 | |
| 41 #include <math.h> | |
| 42 #include "InterpolateShannon.h" | |
| 43 #include "STTypes.h" | |
| 44 | |
| 45 using namespace soundtouch; | |
| 46 | |
| 47 | |
| 48 /// Kaiser window with beta = 2.0 | |
| 49 /// Values scaled down by 5% to avoid overflows | |
| 50 static const double _kaiser8[8] = | |
| 51 { | |
| 52 0.41778693317814, | |
| 53 0.64888025049173, | |
| 54 0.83508562409944, | |
| 55 0.93887857733412, | |
| 56 0.93887857733412, | |
| 57 0.83508562409944, | |
| 58 0.64888025049173, | |
| 59 0.41778693317814 | |
| 60 }; | |
| 61 | |
| 62 | |
| 63 InterpolateShannon::InterpolateShannon() | |
| 64 { | |
| 65 fract = 0; | |
| 66 } | |
| 67 | |
| 68 | |
| 69 void InterpolateShannon::resetRegisters() | |
| 70 { | |
| 71 fract = 0; | |
| 72 } | |
| 73 | |
| 74 | |
| 75 #define PI 3.1415926536 | |
| 76 #define sinc(x) (sin(PI * (x)) / (PI * (x))) | |
| 77 | |
| 78 /// Transpose mono audio. Returns number of produced output samples, and | |
| 79 /// updates "srcSamples" to amount of consumed source samples | |
| 80 int InterpolateShannon::transposeMono(SAMPLETYPE *pdest, | |
| 81 const SAMPLETYPE *psrc, | |
| 82 int &srcSamples) | |
| 83 { | |
| 84 int i; | |
| 85 int srcSampleEnd = srcSamples - 8; | |
| 86 int srcCount = 0; | |
| 87 | |
| 88 i = 0; | |
| 89 while (srcCount < srcSampleEnd) | |
| 90 { | |
| 91 double out; | |
| 92 assert(fract < 1.0); | |
| 93 | |
| 94 out = psrc[0] * sinc(-3.0 - fract) * _kaiser8[0]; | |
| 95 out += psrc[1] * sinc(-2.0 - fract) * _kaiser8[1]; | |
| 96 out += psrc[2] * sinc(-1.0 - fract) * _kaiser8[2]; | |
| 97 if (fract < 1e-6) | |
| 98 { | |
| 99 out += psrc[3] * _kaiser8[3]; // sinc(0) = 1 | |
| 100 } | |
| 101 else | |
| 102 { | |
| 103 out += psrc[3] * sinc(- fract) * _kaiser8[3]; | |
| 104 } | |
| 105 out += psrc[4] * sinc( 1.0 - fract) * _kaiser8[4]; | |
| 106 out += psrc[5] * sinc( 2.0 - fract) * _kaiser8[5]; | |
| 107 out += psrc[6] * sinc( 3.0 - fract) * _kaiser8[6]; | |
| 108 out += psrc[7] * sinc( 4.0 - fract) * _kaiser8[7]; | |
| 109 | |
| 110 pdest[i] = (SAMPLETYPE)out; | |
| 111 i ++; | |
| 112 | |
| 113 // update position fraction | |
| 114 fract += rate; | |
| 115 // update whole positions | |
| 116 int whole = (int)fract; | |
| 117 fract -= whole; | |
| 118 psrc += whole; | |
| 119 srcCount += whole; | |
| 120 } | |
| 121 srcSamples = srcCount; | |
| 122 return i; | |
| 123 } | |
| 124 | |
| 125 | |
| 126 /// Transpose stereo audio. Returns number of produced output samples, and | |
| 127 /// updates "srcSamples" to amount of consumed source samples | |
| 128 int InterpolateShannon::transposeStereo(SAMPLETYPE *pdest, | |
| 129 const SAMPLETYPE *psrc, | |
| 130 int &srcSamples) | |
| 131 { | |
| 132 int i; | |
| 133 int srcSampleEnd = srcSamples - 8; | |
| 134 int srcCount = 0; | |
| 135 | |
| 136 i = 0; | |
| 137 while (srcCount < srcSampleEnd) | |
| 138 { | |
| 139 double out0, out1, w; | |
| 140 assert(fract < 1.0); | |
| 141 | |
| 142 w = sinc(-3.0 - fract) * _kaiser8[0]; | |
| 143 out0 = psrc[0] * w; out1 = psrc[1] * w; | |
| 144 w = sinc(-2.0 - fract) * _kaiser8[1]; | |
| 145 out0 += psrc[2] * w; out1 += psrc[3] * w; | |
| 146 w = sinc(-1.0 - fract) * _kaiser8[2]; | |
| 147 out0 += psrc[4] * w; out1 += psrc[5] * w; | |
| 148 w = _kaiser8[3] * ((fract < 1e-5) ? 1.0 : sinc(- fract)); // sinc(0) = 1 | |
| 149 out0 += psrc[6] * w; out1 += psrc[7] * w; | |
| 150 w = sinc( 1.0 - fract) * _kaiser8[4]; | |
| 151 out0 += psrc[8] * w; out1 += psrc[9] * w; | |
| 152 w = sinc( 2.0 - fract) * _kaiser8[5]; | |
| 153 out0 += psrc[10] * w; out1 += psrc[11] * w; | |
| 154 w = sinc( 3.0 - fract) * _kaiser8[6]; | |
| 155 out0 += psrc[12] * w; out1 += psrc[13] * w; | |
| 156 w = sinc( 4.0 - fract) * _kaiser8[7]; | |
| 157 out0 += psrc[14] * w; out1 += psrc[15] * w; | |
| 158 | |
| 159 pdest[2*i] = (SAMPLETYPE)out0; | |
| 160 pdest[2*i+1] = (SAMPLETYPE)out1; | |
| 161 i ++; | |
| 162 | |
| 163 // update position fraction | |
| 164 fract += rate; | |
| 165 // update whole positions | |
| 166 int whole = (int)fract; | |
| 167 fract -= whole; | |
| 168 psrc += 2*whole; | |
| 169 srcCount += whole; | |
| 170 } | |
| 171 srcSamples = srcCount; | |
| 172 return i; | |
| 173 } | |
| 174 | |
| 175 | |
| 176 /// Transpose stereo audio. Returns number of produced output samples, and | |
| 177 /// updates "srcSamples" to amount of consumed source samples | |
| 178 int InterpolateShannon::transposeMulti(SAMPLETYPE *pdest, | |
| 179 const SAMPLETYPE *psrc, | |
| 180 int &srcSamples) | |
| 181 { | |
| 182 // not implemented | |
| 183 assert(false); | |
| 184 return 0; | |
| 185 } |
