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Diffstat (limited to 'media/libsoundtouch/src/InterpolateShannon.cpp')
| -rw-r--r-- | media/libsoundtouch/src/InterpolateShannon.cpp | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/media/libsoundtouch/src/InterpolateShannon.cpp b/media/libsoundtouch/src/InterpolateShannon.cpp new file mode 100644 index 0000000000..975d872ad6 --- /dev/null +++ b/media/libsoundtouch/src/InterpolateShannon.cpp @@ -0,0 +1,181 @@ +//////////////////////////////////////////////////////////////////////////////// +/// +/// Sample interpolation routine using 8-tap band-limited Shannon interpolation +/// with kaiser window. +/// +/// Notice. This algorithm is remarkably much heavier than linear or cubic +/// interpolation, and not remarkably better than cubic algorithm. Thus mostly +/// for experimental purposes +/// +/// Author : Copyright (c) Olli Parviainen +/// Author e-mail : oparviai 'at' iki.fi +/// SoundTouch WWW: http://www.surina.net/soundtouch +/// +//////////////////////////////////////////////////////////////////////////////// +// +// 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 +// +//////////////////////////////////////////////////////////////////////////////// + +#include <math.h> +#include "InterpolateShannon.h" +#include "STTypes.h" + +using namespace soundtouch; + + +/// Kaiser window with beta = 2.0 +/// Values scaled down by 5% to avoid overflows +static const double _kaiser8[8] = +{ + 0.41778693317814, + 0.64888025049173, + 0.83508562409944, + 0.93887857733412, + 0.93887857733412, + 0.83508562409944, + 0.64888025049173, + 0.41778693317814 +}; + + +InterpolateShannon::InterpolateShannon() +{ + fract = 0; +} + + +void InterpolateShannon::resetRegisters() +{ + fract = 0; +} + + +#define PI 3.1415926536 +#define sinc(x) (sin(PI * (x)) / (PI * (x))) + +/// Transpose mono audio. Returns number of produced output samples, and +/// updates "srcSamples" to amount of consumed source samples +int InterpolateShannon::transposeMono(SAMPLETYPE *pdest, + const SAMPLETYPE *psrc, + int &srcSamples) +{ + int i; + int srcSampleEnd = srcSamples - 8; + int srcCount = 0; + + i = 0; + while (srcCount < srcSampleEnd) + { + double out; + assert(fract < 1.0); + + out = psrc[0] * sinc(-3.0 - fract) * _kaiser8[0]; + out += psrc[1] * sinc(-2.0 - fract) * _kaiser8[1]; + out += psrc[2] * sinc(-1.0 - fract) * _kaiser8[2]; + if (fract < 1e-6) + { + out += psrc[3] * _kaiser8[3]; // sinc(0) = 1 + } + else + { + out += psrc[3] * sinc(- fract) * _kaiser8[3]; + } + out += psrc[4] * sinc( 1.0 - fract) * _kaiser8[4]; + out += psrc[5] * sinc( 2.0 - fract) * _kaiser8[5]; + out += psrc[6] * sinc( 3.0 - fract) * _kaiser8[6]; + out += psrc[7] * sinc( 4.0 - fract) * _kaiser8[7]; + + pdest[i] = (SAMPLETYPE)out; + i ++; + + // update position fraction + fract += rate; + // update whole positions + int whole = (int)fract; + fract -= whole; + psrc += whole; + srcCount += whole; + } + srcSamples = srcCount; + return i; +} + + +/// Transpose stereo audio. Returns number of produced output samples, and +/// updates "srcSamples" to amount of consumed source samples +int InterpolateShannon::transposeStereo(SAMPLETYPE *pdest, + const SAMPLETYPE *psrc, + int &srcSamples) +{ + int i; + int srcSampleEnd = srcSamples - 8; + int srcCount = 0; + + i = 0; + while (srcCount < srcSampleEnd) + { + double out0, out1, w; + assert(fract < 1.0); + + w = sinc(-3.0 - fract) * _kaiser8[0]; + out0 = psrc[0] * w; out1 = psrc[1] * w; + w = sinc(-2.0 - fract) * _kaiser8[1]; + out0 += psrc[2] * w; out1 += psrc[3] * w; + w = sinc(-1.0 - fract) * _kaiser8[2]; + out0 += psrc[4] * w; out1 += psrc[5] * w; + w = _kaiser8[3] * ((fract < 1e-5) ? 1.0 : sinc(- fract)); // sinc(0) = 1 + out0 += psrc[6] * w; out1 += psrc[7] * w; + w = sinc( 1.0 - fract) * _kaiser8[4]; + out0 += psrc[8] * w; out1 += psrc[9] * w; + w = sinc( 2.0 - fract) * _kaiser8[5]; + out0 += psrc[10] * w; out1 += psrc[11] * w; + w = sinc( 3.0 - fract) * _kaiser8[6]; + out0 += psrc[12] * w; out1 += psrc[13] * w; + w = sinc( 4.0 - fract) * _kaiser8[7]; + out0 += psrc[14] * w; out1 += psrc[15] * w; + + pdest[2*i] = (SAMPLETYPE)out0; + pdest[2*i+1] = (SAMPLETYPE)out1; + i ++; + + // update position fraction + fract += rate; + // update whole positions + int whole = (int)fract; + fract -= whole; + psrc += 2*whole; + srcCount += whole; + } + srcSamples = srcCount; + return i; +} + + +/// Transpose stereo audio. Returns number of produced output samples, and +/// updates "srcSamples" to amount of consumed source samples +int InterpolateShannon::transposeMulti(SAMPLETYPE *pdest, + const SAMPLETYPE *psrc, + int &srcSamples) +{ + // not implemented + assert(false); + return 0; +} |