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https://github.com/FFmpeg/FFmpeg.git
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120 lines
3.0 KiB
C
120 lines
3.0 KiB
C
/*
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* Atrac common functions
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* Copyright (c) 2006-2008 Maxim Poliakovski
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* Copyright (c) 2006-2008 Benjamin Larsson
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file libavcodec/atrac.c
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*/
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#include <math.h>
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#include <stddef.h>
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#include <stdio.h>
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#include "avcodec.h"
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#include "dsputil.h"
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float sf_table[64];
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float qmf_window[48];
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static const float qmf_48tap_half[24] = {
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-0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
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0.0002422519, -0.00085293897,-0.0005205574, 0.0020340169,
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0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
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-0.000061169922,-0.01344162, 0.0024626821, 0.021736089,
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-0.007801671, -0.034090221, 0.01880949, 0.054326009,
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-0.043596379, -0.099384367, 0.13207909, 0.46424159
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};
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/**
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* Generate common tables
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*/
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void atrac_generate_tables(void)
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{
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int i;
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float s;
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/* Generate scale factors */
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if (!sf_table[63])
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for (i=0 ; i<64 ; i++)
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sf_table[i] = pow(2.0, (i - 15) / 3.0);
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/* Generate the QMF window. */
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if (!qmf_window[47])
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for (i=0 ; i<24; i++) {
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s = qmf_48tap_half[i] * 2.0;
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qmf_window[i] = qmf_window[47 - i] = s;
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}
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}
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/**
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* Quadrature mirror synthesis filter.
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*
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* @param inlo lower part of spectrum
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* @param inhi higher part of spectrum
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* @param nIn size of spectrum buffer
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* @param pOut out buffer
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* @param delayBuf delayBuf buffer
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* @param temp temp buffer
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*/
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void atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
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{
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int i, j;
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float *p1, *p3;
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memcpy(temp, delayBuf, 46*sizeof(float));
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p3 = temp + 46;
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/* loop1 */
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for(i=0; i<nIn; i+=2){
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p3[2*i+0] = inlo[i ] + inhi[i ];
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p3[2*i+1] = inlo[i ] - inhi[i ];
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p3[2*i+2] = inlo[i+1] + inhi[i+1];
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p3[2*i+3] = inlo[i+1] - inhi[i+1];
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}
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/* loop2 */
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p1 = temp;
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for (j = nIn; j != 0; j--) {
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float s1 = 0.0;
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float s2 = 0.0;
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for (i = 0; i < 48; i += 2) {
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s1 += p1[i] * qmf_window[i];
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s2 += p1[i+1] * qmf_window[i+1];
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}
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pOut[0] = s2;
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pOut[1] = s1;
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p1 += 2;
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pOut += 2;
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}
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/* Update the delay buffer. */
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memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
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}
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