libavcodec/atrac.c

   1 /*
   2  * Atrac common functions
   3  * Copyright (c) 2006-2008 Maxim Poliakovski
   4  * Copyright (c) 2006-2008 Benjamin Larsson
   5  *
   6  * This file is part of FFmpeg.
   7  *
   8  * FFmpeg is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License as published by the Free Software Foundation; either
  11  * version 2.1 of the License, or (at your option) any later version.
  12  *
  13  * FFmpeg is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  16  * Lesser General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU Lesser General Public
  19  * License along with FFmpeg; if not, write to the Free Software
  20  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  21  */
  22
  23 /**
  24  * @file libavcodec/atrac.c
  25  */
  26
  27 #include <math.h>
  28 #include <stddef.h>
  29 #include <stdio.h>
  30
  31 #include "avcodec.h"
  32 #include "dsputil.h"
  33
  34 float sf_table[64];
  35 float qmf_window[48];
  36
  37 static const float qmf_48tap_half[24] = {
  38    -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
  39     0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
  40     0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
  41    -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
  42    -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
  43    -0.043596379,   -0.099384367,   0.13207909,    0.46424159
  44 };
  45
  46 /**
  47  * Generate common tables
  48  */
  49
  50 void atrac_generate_tables(void)
  51 {
  52     int i;
  53     float s;
  54
  55     /* Generate scale factors */
  56     if (!sf_table[63])
  57         for (i=0 ; i<64 ; i++)
  58             sf_table[i] = pow(2.0, (i - 15) / 3.0);
  59
  60     /* Generate the QMF window. */
  61     if (!qmf_window[47])
  62         for (i=0 ; i<24; i++) {
  63             s = qmf_48tap_half[i] * 2.0;
  64             qmf_window[i] = qmf_window[47 - i] = s;
  65         }
  66 }
  67
  68
  69 /**
  70  * Quadrature mirror synthesis filter.
  71  *
  72  * @param inlo      lower part of spectrum
  73  * @param inhi      higher part of spectrum
  74  * @param nIn       size of spectrum buffer
  75  * @param pOut      out buffer
  76  * @param delayBuf  delayBuf buffer
  77  * @param temp      temp buffer
  78  */
  79
  80
  81 void atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
  82 {
  83     int   i, j;
  84     float   *p1, *p3;
  85
  86     memcpy(temp, delayBuf, 46*sizeof(float));
  87
  88     p3 = temp + 46;
  89
  90     /* loop1 */
  91     for(i=0; i<nIn; i+=2){
  92         p3[2*i+0] = inlo[i  ] + inhi[i  ];
  93         p3[2*i+1] = inlo[i  ] - inhi[i  ];
  94         p3[2*i+2] = inlo[i+1] + inhi[i+1];
  95         p3[2*i+3] = inlo[i+1] - inhi[i+1];
  96     }
  97
  98     /* loop2 */
  99     p1 = temp;
 100     for (j = nIn; j != 0; j--) {
 101         float s1 = 0.0;
 102         float s2 = 0.0;
 103
 104         for (i = 0; i < 48; i += 2) {
 105             s1 += p1[i] * qmf_window[i];
 106             s2 += p1[i+1] * qmf_window[i+1];
 107         }
 108
 109         pOut[0] = s2;
 110         pOut[1] = s1;
 111
 112         p1 += 2;
 113         pOut += 2;
 114     }
 115
 116     /* Update the delay buffer. */
 117     memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
 118 }
 119