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 Libav.
   7  *
   8  * Libav 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  * Libav 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 Libav; 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
  25  */
  26
  27 #include <math.h>
  28 #include <stddef.h>
  29 #include <stdio.h>
  30 #include <string.h>
  31
  32 #include "avcodec.h"
  33 #include "dsputil.h"
  34 #include "atrac.h"
  35
  36 float ff_atrac_sf_table[64];
  37 static float qmf_window[48];
  38
  39 static const float qmf_48tap_half[24] = {
  40    -0.00001461907, -0.00009205479,-0.000056157569,0.00030117269,
  41     0.0002422519,  -0.00085293897,-0.0005205574,  0.0020340169,
  42     0.00078333891, -0.0042153862, -0.00075614988, 0.0078402944,
  43    -0.000061169922,-0.01344162,    0.0024626821,  0.021736089,
  44    -0.007801671,   -0.034090221,   0.01880949,    0.054326009,
  45    -0.043596379,   -0.099384367,   0.13207909,    0.46424159
  46 };
  47
  48 /**
  49  * Generate common tables
  50  */
  51
  52 void ff_atrac_generate_tables(void)
  53 {
  54     int i;
  55     float s;
  56
  57     /* Generate scale factors */
  58     if (!ff_atrac_sf_table[63])
  59         for (i=0 ; i<64 ; i++)
  60             ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
  61
  62     /* Generate the QMF window. */
  63     if (!qmf_window[47])
  64         for (i=0 ; i<24; i++) {
  65             s = qmf_48tap_half[i] * 2.0;
  66             qmf_window[i] = qmf_window[47 - i] = s;
  67         }
  68 }
  69
  70
  71 /**
  72  * Quadrature mirror synthesis filter.
  73  *
  74  * @param inlo      lower part of spectrum
  75  * @param inhi      higher part of spectrum
  76  * @param nIn       size of spectrum buffer
  77  * @param pOut      out buffer
  78  * @param delayBuf  delayBuf buffer
  79  * @param temp      temp buffer
  80  */
  81
  82
  83 void ff_atrac_iqmf (float *inlo, float *inhi, unsigned int nIn, float *pOut, float *delayBuf, float *temp)
  84 {
  85     int   i, j;
  86     float   *p1, *p3;
  87
  88     memcpy(temp, delayBuf, 46*sizeof(float));
  89
  90     p3 = temp + 46;
  91
  92     /* loop1 */
  93     for(i=0; i<nIn; i+=2){
  94         p3[2*i+0] = inlo[i  ] + inhi[i  ];
  95         p3[2*i+1] = inlo[i  ] - inhi[i  ];
  96         p3[2*i+2] = inlo[i+1] + inhi[i+1];
  97         p3[2*i+3] = inlo[i+1] - inhi[i+1];
  98     }
  99
 100     /* loop2 */
 101     p1 = temp;
 102     for (j = nIn; j != 0; j--) {
 103         float s1 = 0.0;
 104         float s2 = 0.0;
 105
 106         for (i = 0; i < 48; i += 2) {
 107             s1 += p1[i] * qmf_window[i];
 108             s2 += p1[i+1] * qmf_window[i+1];
 109         }
 110
 111         pOut[0] = s2;
 112         pOut[1] = s1;
 113
 114         p1 += 2;
 115         pOut += 2;
 116     }
 117
 118     /* Update the delay buffer. */
 119     memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
 120 }