libavcodec/ac3.c

   1 /*
   2  * Common code between the AC-3 encoder and decoder
   3  * Copyright (c) 2000 Fabrice Bellard
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * Common code between the AC-3 encoder and decoder.
  25  */
  26
  27 #include "libavutil/error.h"
  28 #include "libavutil/macros.h"
  29
  30 #include "ac3.h"
  31 #include "ac3defs.h"
  32
  33 /**
  34  * Starting frequency coefficient bin for each critical band.
  35  */
  36 const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = {
  37       0,  1,   2,   3,   4,   5,   6,   7,   8,   9,
  38      10,  11, 12,  13,  14,  15,  16,  17,  18,  19,
  39      20,  21, 22,  23,  24,  25,  26,  27,  28,  31,
  40      34,  37, 40,  43,  46,  49,  55,  61,  67,  73,
  41      79,  85, 97, 109, 121, 133, 157, 181, 205, 229, 253
  42 };
  43
  44 /**
  45  * Map each frequency coefficient bin to the critical band that contains it.
  46  */
  47 const uint8_t ff_ac3_bin_to_band_tab[253] = {
  48      0,
  49      1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12,
  50     13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
  51     25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30,
  52     31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34,
  53     35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36,
  54     37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38,
  55     39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40,
  56     41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
  57     42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
  58     43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43,
  59     44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44,
  60     45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
  61     45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
  62     46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
  63     46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
  64     47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
  65     47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
  66     48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
  67     48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
  68     49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,
  69     49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49
  70 };
  71
  72 static const uint8_t ac3_log_add_tab[260]= {
  73 0x40,0x3f,0x3e,0x3d,0x3c,0x3b,0x3a,0x39,0x38,0x37,
  74 0x36,0x35,0x34,0x34,0x33,0x32,0x31,0x30,0x2f,0x2f,
  75 0x2e,0x2d,0x2c,0x2c,0x2b,0x2a,0x29,0x29,0x28,0x27,
  76 0x26,0x26,0x25,0x24,0x24,0x23,0x23,0x22,0x21,0x21,
  77 0x20,0x20,0x1f,0x1e,0x1e,0x1d,0x1d,0x1c,0x1c,0x1b,
  78 0x1b,0x1a,0x1a,0x19,0x19,0x18,0x18,0x17,0x17,0x16,
  79 0x16,0x15,0x15,0x15,0x14,0x14,0x13,0x13,0x13,0x12,
  80 0x12,0x12,0x11,0x11,0x11,0x10,0x10,0x10,0x0f,0x0f,
  81 0x0f,0x0e,0x0e,0x0e,0x0d,0x0d,0x0d,0x0d,0x0c,0x0c,
  82 0x0c,0x0c,0x0b,0x0b,0x0b,0x0b,0x0a,0x0a,0x0a,0x0a,
  83 0x0a,0x09,0x09,0x09,0x09,0x09,0x08,0x08,0x08,0x08,
  84 0x08,0x08,0x07,0x07,0x07,0x07,0x07,0x07,0x06,0x06,
  85 0x06,0x06,0x06,0x06,0x06,0x06,0x05,0x05,0x05,0x05,
  86 0x05,0x05,0x05,0x05,0x04,0x04,0x04,0x04,0x04,0x04,
  87 0x04,0x04,0x04,0x04,0x04,0x03,0x03,0x03,0x03,0x03,
  88 0x03,0x03,0x03,0x03,0x03,0x03,0x03,0x03,0x03,0x02,
  89 0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,
  90 0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x02,0x01,0x01,
  91 0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,
  92 0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,
  93 0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,
  94 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  95 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  96 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  97 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  98 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,
  99 };
 100
 101 static const uint16_t ac3_hearing_threshold_tab[AC3_CRITICAL_BANDS][3]= {
 102 { 0x04d0,0x04f0,0x0580 },
 103 { 0x04d0,0x04f0,0x0580 },
 104 { 0x0440,0x0460,0x04b0 },
 105 { 0x0400,0x0410,0x0450 },
 106 { 0x03e0,0x03e0,0x0420 },
 107 { 0x03c0,0x03d0,0x03f0 },
 108 { 0x03b0,0x03c0,0x03e0 },
 109 { 0x03b0,0x03b0,0x03d0 },
 110 { 0x03a0,0x03b0,0x03c0 },
 111 { 0x03a0,0x03a0,0x03b0 },
 112 { 0x03a0,0x03a0,0x03b0 },
 113 { 0x03a0,0x03a0,0x03b0 },
 114 { 0x03a0,0x03a0,0x03a0 },
 115 { 0x0390,0x03a0,0x03a0 },
 116 { 0x0390,0x0390,0x03a0 },
 117 { 0x0390,0x0390,0x03a0 },
 118 { 0x0380,0x0390,0x03a0 },
 119 { 0x0380,0x0380,0x03a0 },
 120 { 0x0370,0x0380,0x03a0 },
 121 { 0x0370,0x0380,0x03a0 },
 122 { 0x0360,0x0370,0x0390 },
 123 { 0x0360,0x0370,0x0390 },
 124 { 0x0350,0x0360,0x0390 },
 125 { 0x0350,0x0360,0x0390 },
 126 { 0x0340,0x0350,0x0380 },
 127 { 0x0340,0x0350,0x0380 },
 128 { 0x0330,0x0340,0x0380 },
 129 { 0x0320,0x0340,0x0370 },
 130 { 0x0310,0x0320,0x0360 },
 131 { 0x0300,0x0310,0x0350 },
 132 { 0x02f0,0x0300,0x0340 },
 133 { 0x02f0,0x02f0,0x0330 },
 134 { 0x02f0,0x02f0,0x0320 },
 135 { 0x02f0,0x02f0,0x0310 },
 136 { 0x0300,0x02f0,0x0300 },
 137 { 0x0310,0x0300,0x02f0 },
 138 { 0x0340,0x0320,0x02f0 },
 139 { 0x0390,0x0350,0x02f0 },
 140 { 0x03e0,0x0390,0x0300 },
 141 { 0x0420,0x03e0,0x0310 },
 142 { 0x0460,0x0420,0x0330 },
 143 { 0x0490,0x0450,0x0350 },
 144 { 0x04a0,0x04a0,0x03c0 },
 145 { 0x0460,0x0490,0x0410 },
 146 { 0x0440,0x0460,0x0470 },
 147 { 0x0440,0x0440,0x04a0 },
 148 { 0x0520,0x0480,0x0460 },
 149 { 0x0800,0x0630,0x0440 },
 150 { 0x0840,0x0840,0x0450 },
 151 { 0x0840,0x0840,0x04e0 },
 152 };
 153
 154 static inline int calc_lowcomp1(int a, int b0, int b1, int c)
 155 {
 156     if ((b0 + 256) == b1) {
 157         a = c;
 158     } else if (b0 > b1) {
 159         a = FFMAX(a - 64, 0);
 160     }
 161     return a;
 162 }
 163
 164 static inline int calc_lowcomp(int a, int b0, int b1, int bin)
 165 {
 166     if (bin < 7) {
 167         return calc_lowcomp1(a, b0, b1, 384);
 168     } else if (bin < 20) {
 169         return calc_lowcomp1(a, b0, b1, 320);
 170     } else {
 171         return FFMAX(a - 128, 0);
 172     }
 173 }
 174
 175 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
 176                                int16_t *band_psd)
 177 {
 178     int bin, band;
 179
 180     /* exponent mapping to PSD */
 181     for (bin = start; bin < end; bin++) {
 182         psd[bin]=(3072 - (exp[bin] << 7));
 183     }
 184
 185     /* PSD integration */
 186     bin  = start;
 187     band = ff_ac3_bin_to_band_tab[start];
 188     do {
 189         int v = psd[bin++];
 190         int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end);
 191         for (; bin < band_end; bin++) {
 192             int max = FFMAX(v, psd[bin]);
 193             /* logadd */
 194             int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
 195             v = max + ac3_log_add_tab[adr];
 196         }
 197         band_psd[band++] = v;
 198     } while (end > ff_ac3_band_start_tab[band]);
 199 }
 200
 201 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
 202                                int start, int end, int fast_gain, int is_lfe,
 203                                int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
 204                                uint8_t *dba_lengths, uint8_t *dba_values,
 205                                int16_t *mask)
 206 {
 207     int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */
 208     int band;
 209     int band_start, band_end, begin, end1;
 210     int lowcomp, fastleak, slowleak;
 211
 212     if (end <= 0)
 213         return AVERROR_INVALIDDATA;
 214
 215     /* excitation function */
 216     band_start = ff_ac3_bin_to_band_tab[start];
 217     band_end   = ff_ac3_bin_to_band_tab[end-1] + 1;
 218
 219     if (band_start == 0) {
 220         lowcomp = 0;
 221         lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
 222         excite[0] = band_psd[0] - fast_gain - lowcomp;
 223         lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
 224         excite[1] = band_psd[1] - fast_gain - lowcomp;
 225         begin = 7;
 226         for (band = 2; band < 7; band++) {
 227             if (!(is_lfe && band == 6))
 228                 lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384);
 229             fastleak = band_psd[band] - fast_gain;
 230             slowleak = band_psd[band] - s->slow_gain;
 231             excite[band] = fastleak - lowcomp;
 232             if (!(is_lfe && band == 6)) {
 233                 if (band_psd[band] <= band_psd[band+1]) {
 234                     begin = band + 1;
 235                     break;
 236                 }
 237             }
 238         }
 239
 240         end1 = FFMIN(band_end, 22);
 241         for (band = begin; band < end1; band++) {
 242             if (!(is_lfe && band == 6))
 243                 lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band);
 244             fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
 245             slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
 246             excite[band] = FFMAX(fastleak - lowcomp, slowleak);
 247         }
 248         begin = 22;
 249     } else {
 250         /* coupling channel */
 251         begin = band_start;
 252         fastleak = (s->cpl_fast_leak << 8) + 768;
 253         slowleak = (s->cpl_slow_leak << 8) + 768;
 254     }
 255
 256     for (band = begin; band < band_end; band++) {
 257         fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
 258         slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
 259         excite[band] = FFMAX(fastleak, slowleak);
 260     }
 261
 262     /* compute masking curve */
 263
 264     for (band = band_start; band < band_end; band++) {
 265         int tmp = s->db_per_bit - band_psd[band];
 266         if (tmp > 0) {
 267             excite[band] += tmp >> 2;
 268         }
 269         mask[band] = FFMAX(ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]);
 270     }
 271
 272     /* delta bit allocation */
 273
 274     if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
 275         int i, seg, delta;
 276         if (dba_nsegs > 8)
 277             return -1;
 278         band = band_start;
 279         for (seg = 0; seg < dba_nsegs; seg++) {
 280             band += dba_offsets[seg];
 281             if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band)
 282                 return -1;
 283             if (dba_values[seg] >= 4) {
 284                 delta = (dba_values[seg] - 3) * 128;
 285             } else {
 286                 delta = (dba_values[seg] - 4) * 128;
 287             }
 288             for (i = 0; i < dba_lengths[seg]; i++) {
 289                 mask[band++] += delta;
 290             }
 291         }
 292     }
 293     return 0;
 294 }