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libavcodec/atrac.c

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00001 /*
00002  * Atrac common functions
00003  * Copyright (c) 2006-2008 Maxim Poliakovski
00004  * Copyright (c) 2006-2008 Benjamin Larsson
00005  *
00006  * This file is part of FFmpeg.
00007  *
00008  * FFmpeg is free software; you can redistribute it and/or
00009  * modify it under the terms of the GNU Lesser General Public
00010  * License as published by the Free Software Foundation; either
00011  * version 2.1 of the License, or (at your option) any later version.
00012  *
00013  * FFmpeg is distributed in the hope that it will be useful,
00014  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00015  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
00016  * Lesser General Public License for more details.
00017  *
00018  * You should have received a copy of the GNU Lesser General Public
00019  * License along with FFmpeg; if not, write to the Free Software
00020  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
00021  */
00022 
00027 #include <math.h>
00028 #include <stddef.h>
00029 #include <stdio.h>
00030 
00031 #include "avcodec.h"
00032 #include "dsputil.h"
00033 #include "atrac.h"
00034 
00035 float sf_table[64];
00036 float qmf_window[48];
00037 
00038 static const float qmf_48tap_half[24] = {
00039    -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
00040     0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
00041     0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
00042    -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
00043    -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
00044    -0.043596379,   -0.099384367,   0.13207909,    0.46424159
00045 };
00046 
00051 void atrac_generate_tables(void)
00052 {
00053     int i;
00054     float s;
00055 
00056     /* Generate scale factors */
00057     if (!sf_table[63])
00058         for (i=0 ; i<64 ; i++)
00059             sf_table[i] = pow(2.0, (i - 15) / 3.0);
00060 
00061     /* Generate the QMF window. */
00062     if (!qmf_window[47])
00063         for (i=0 ; i<24; i++) {
00064             s = qmf_48tap_half[i] * 2.0;
00065             qmf_window[i] = qmf_window[47 - i] = s;
00066         }
00067 }
00068 
00069 
00082 void atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
00083 {
00084     int   i, j;
00085     float   *p1, *p3;
00086 
00087     memcpy(temp, delayBuf, 46*sizeof(float));
00088 
00089     p3 = temp + 46;
00090 
00091     /* loop1 */
00092     for(i=0; i<nIn; i+=2){
00093         p3[2*i+0] = inlo[i  ] + inhi[i  ];
00094         p3[2*i+1] = inlo[i  ] - inhi[i  ];
00095         p3[2*i+2] = inlo[i+1] + inhi[i+1];
00096         p3[2*i+3] = inlo[i+1] - inhi[i+1];
00097     }
00098 
00099     /* loop2 */
00100     p1 = temp;
00101     for (j = nIn; j != 0; j--) {
00102         float s1 = 0.0;
00103         float s2 = 0.0;
00104 
00105         for (i = 0; i < 48; i += 2) {
00106             s1 += p1[i] * qmf_window[i];
00107             s2 += p1[i+1] * qmf_window[i+1];
00108         }
00109 
00110         pOut[0] = s2;
00111         pOut[1] = s1;
00112 
00113         p1 += 2;
00114         pOut += 2;
00115     }
00116 
00117     /* Update the delay buffer. */
00118     memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
00119 }
00120 

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