libavcodec/atrac.c

   1 /*
   2  * common functions for the ATRAC family of decoders
   3  *
   4  * Copyright (c) 2006-2013 Maxim Poliakovski
   5  * Copyright (c) 2006-2008 Benjamin Larsson
   6  *
   7  * This file is part of FFmpeg.
   8  *
   9  * FFmpeg is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU Lesser General Public
  11  * License as published by the Free Software Foundation; either
  12  * version 2.1 of the License, or (at your option) any later version.
  13  *
  14  * FFmpeg is distributed in the hope that it will be useful,
  15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  17  * Lesser General Public License for more details.
  18  *
  19  * You should have received a copy of the GNU Lesser General Public
  20  * License along with FFmpeg; if not, write to the Free Software
  21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  22  */
  23
  24 /**
  25  * @file
  26  */
  27
  28 #include <math.h>
  29 #include <string.h>
  30
  31 #include "libavutil/attributes.h"
  32 #include "libavutil/thread.h"
  33
  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 static av_cold void atrac_generate_tables(void)
  49 {
  50     /* Generate scale factors */
  51     for (int i = 0; i < 64; i++)
  52         ff_atrac_sf_table[i] = pow(2.0, (i - 15) / 3.0);
  53
  54     /* Generate the QMF window. */
  55     for (int i = 0; i < 24; i++) {
  56         float s = qmf_48tap_half[i] * 2.0;
  57         qmf_window[i] = qmf_window[47 - i] = s;
  58     }
  59 }
  60
  61 av_cold void ff_atrac_generate_tables(void)
  62 {
  63     static AVOnce init_static_once = AV_ONCE_INIT;
  64     ff_thread_once(&init_static_once, atrac_generate_tables);
  65 }
  66
  67 av_cold void ff_atrac_init_gain_compensation(AtracGCContext *gctx, int id2exp_offset,
  68                                              int loc_scale)
  69 {
  70     int i;
  71
  72     gctx->loc_scale     = loc_scale;
  73     gctx->loc_size      = 1 << loc_scale;
  74     gctx->id2exp_offset = id2exp_offset;
  75
  76     /* Generate gain level table. */
  77     for (i = 0; i < 16; i++)
  78         gctx->gain_tab1[i] = powf(2.0, id2exp_offset - i);
  79
  80     /* Generate gain interpolation table. */
  81     for (i = -15; i < 16; i++)
  82         gctx->gain_tab2[i + 15] = powf(2.0, -1.0f / gctx->loc_size * i);
  83 }
  84
  85 void ff_atrac_gain_compensation(AtracGCContext *gctx, float *in, float *prev,
  86                                 AtracGainInfo *gc_now, AtracGainInfo *gc_next,
  87                                 int num_samples, float *out)
  88 {
  89     float lev, gc_scale, gain_inc;
  90     int i, pos, lastpos;
  91
  92     gc_scale = gc_next->num_points ? gctx->gain_tab1[gc_next->lev_code[0]]
  93                                    : 1.0f;
  94
  95     if (!gc_now->num_points) {
  96         for (pos = 0; pos < num_samples; pos++)
  97             out[pos] = in[pos] * gc_scale + prev[pos];
  98     } else {
  99         pos = 0;
 100
 101         for (i = 0; i < gc_now->num_points; i++) {
 102             lastpos = gc_now->loc_code[i] << gctx->loc_scale;
 103
 104             lev = gctx->gain_tab1[gc_now->lev_code[i]];
 105             gain_inc = gctx->gain_tab2[(i + 1 < gc_now->num_points ? gc_now->lev_code[i + 1]
 106                                                                    : gctx->id2exp_offset) -
 107                                        gc_now->lev_code[i] + 15];
 108
 109             /* apply constant gain level and overlap */
 110             for (; pos < lastpos; pos++)
 111                 out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
 112
 113             /* interpolate between two different gain levels */
 114             for (; pos < lastpos + gctx->loc_size; pos++) {
 115                 out[pos] = (in[pos] * gc_scale + prev[pos]) * lev;
 116                 lev *= gain_inc;
 117             }
 118         }
 119
 120         for (; pos < num_samples; pos++)
 121             out[pos] = in[pos] * gc_scale + prev[pos];
 122     }
 123
 124     /* copy the overlapping part into the delay buffer */
 125     memcpy(prev, &in[num_samples], num_samples * sizeof(float));
 126 }
 127
 128 void ff_atrac_iqmf(float *inlo, float *inhi, unsigned int nIn, float *pOut,
 129                    float *delayBuf, float *temp)
 130 {
 131     int   i, j;
 132     float   *p1, *p3;
 133
 134     memcpy(temp, delayBuf, 46*sizeof(float));
 135
 136     p3 = temp + 46;
 137
 138     /* loop1 */
 139     for(i=0; i<nIn; i+=2){
 140         p3[2*i+0] = inlo[i  ] + inhi[i  ];
 141         p3[2*i+1] = inlo[i  ] - inhi[i  ];
 142         p3[2*i+2] = inlo[i+1] + inhi[i+1];
 143         p3[2*i+3] = inlo[i+1] - inhi[i+1];
 144     }
 145
 146     /* loop2 */
 147     p1 = temp;
 148     for (j = nIn; j != 0; j--) {
 149         float s1 = 0.0;
 150         float s2 = 0.0;
 151
 152         for (i = 0; i < 48; i += 2) {
 153             s1 += p1[i] * qmf_window[i];
 154             s2 += p1[i+1] * qmf_window[i+1];
 155         }
 156
 157         pOut[0] = s2;
 158         pOut[1] = s1;
 159
 160         p1 += 2;
 161         pOut += 2;
 162     }
 163
 164     /* Update the delay buffer. */
 165     memcpy(delayBuf, temp + nIn*2, 46*sizeof(float));
 166 }