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 "avcodec.h" 28#include "ac3.h" 29#include "get_bits.h" 30 31#if CONFIG_HARDCODED_TABLES 32 33/** 34 * Starting frequency coefficient bin for each critical band. 35 */ 36static const uint8_t band_start_tab[51] = { 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 * Maps each frequency coefficient bin to the critical band that contains it. 46 */ 47static const uint8_t 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#else /* CONFIG_HARDCODED_TABLES */ 73static uint8_t band_start_tab[51]; 74static uint8_t bin_to_band_tab[253]; 75#endif 76 77static inline int calc_lowcomp1(int a, int b0, int b1, int c) 78{ 79 if ((b0 + 256) == b1) { 80 a = c; 81 } else if (b0 > b1) { 82 a = FFMAX(a - 64, 0); 83 } 84 return a; 85} 86 87static inline int calc_lowcomp(int a, int b0, int b1, int bin) 88{ 89 if (bin < 7) { 90 return calc_lowcomp1(a, b0, b1, 384); 91 } else if (bin < 20) { 92 return calc_lowcomp1(a, b0, b1, 320); 93 } else { 94 return FFMAX(a - 128, 0); 95 } 96} 97 98void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, 99 int16_t *band_psd) 100{ 101 int bin, band; 102 103 /* exponent mapping to PSD */ 104 for (bin = start; bin < end; bin++) { 105 psd[bin]=(3072 - (exp[bin] << 7)); 106 } 107 108 /* PSD integration */ 109 bin = start; 110 band = bin_to_band_tab[start]; 111 do { 112 int v = psd[bin++]; 113 int band_end = FFMIN(band_start_tab[band+1], end); 114 for (; bin < band_end; bin++) { 115 int max = FFMAX(v, psd[bin]); 116 /* logadd */ 117 int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255); 118 v = max + ff_ac3_log_add_tab[adr]; 119 } 120 band_psd[band++] = v; 121 } while (end > band_start_tab[band]); 122} 123 124int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, 125 int start, int end, int fast_gain, int is_lfe, 126 int dba_mode, int dba_nsegs, uint8_t *dba_offsets, 127 uint8_t *dba_lengths, uint8_t *dba_values, 128 int16_t *mask) 129{ 130 int16_t excite[50]; /* excitation */ 131 int band; 132 int band_start, band_end, begin, end1; 133 int lowcomp, fastleak, slowleak; 134 135 /* excitation function */ 136 band_start = bin_to_band_tab[start]; 137 band_end = bin_to_band_tab[end-1] + 1; 138 139 if (band_start == 0) { 140 lowcomp = 0; 141 lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384); 142 excite[0] = band_psd[0] - fast_gain - lowcomp; 143 lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384); 144 excite[1] = band_psd[1] - fast_gain - lowcomp; 145 begin = 7; 146 for (band = 2; band < 7; band++) { 147 if (!(is_lfe && band == 6)) 148 lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384); 149 fastleak = band_psd[band] - fast_gain; 150 slowleak = band_psd[band] - s->slow_gain; 151 excite[band] = fastleak - lowcomp; 152 if (!(is_lfe && band == 6)) { 153 if (band_psd[band] <= band_psd[band+1]) { 154 begin = band + 1; 155 break; 156 } 157 } 158 } 159 160 end1 = FFMIN(band_end, 22); 161 for (band = begin; band < end1; band++) { 162 if (!(is_lfe && band == 6)) 163 lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band); 164 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); 165 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); 166 excite[band] = FFMAX(fastleak - lowcomp, slowleak); 167 } 168 begin = 22; 169 } else { 170 /* coupling channel */ 171 begin = band_start; 172 fastleak = (s->cpl_fast_leak << 8) + 768; 173 slowleak = (s->cpl_slow_leak << 8) + 768; 174 } 175 176 for (band = begin; band < band_end; band++) { 177 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); 178 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); 179 excite[band] = FFMAX(fastleak, slowleak); 180 } 181 182 /* compute masking curve */ 183 184 for (band = band_start; band < band_end; band++) { 185 int tmp = s->db_per_bit - band_psd[band]; 186 if (tmp > 0) { 187 excite[band] += tmp >> 2; 188 } 189 mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]); 190 } 191 192 /* delta bit allocation */ 193 194 if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) { 195 int i, seg, delta; 196 if (dba_nsegs >= 8) 197 return -1; 198 band = 0; 199 for (seg = 0; seg < dba_nsegs; seg++) { 200 band += dba_offsets[seg]; 201 if (band >= 50 || dba_lengths[seg] > 50-band) 202 return -1; 203 if (dba_values[seg] >= 4) { 204 delta = (dba_values[seg] - 3) << 7; 205 } else { 206 delta = (dba_values[seg] - 4) << 7; 207 } 208 for (i = 0; i < dba_lengths[seg]; i++) { 209 mask[band++] += delta; 210 } 211 } 212 } 213 return 0; 214} 215 216void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, 217 int snr_offset, int floor, 218 const uint8_t *bap_tab, uint8_t *bap) 219{ 220 int bin, band; 221 222 /* special case, if snr offset is -960, set all bap's to zero */ 223 if (snr_offset == -960) { 224 memset(bap, 0, 256); 225 return; 226 } 227 228 bin = start; 229 band = bin_to_band_tab[start]; 230 do { 231 int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor; 232 int band_end = FFMIN(band_start_tab[band+1], end); 233 for (; bin < band_end; bin++) { 234 int address = av_clip((psd[bin] - m) >> 5, 0, 63); 235 bap[bin] = bap_tab[address]; 236 } 237 } while (end > band_start_tab[band++]); 238} 239 240/* AC-3 bit allocation. The algorithm is the one described in the AC-3 241 spec. */ 242void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, 243 int8_t *exp, int start, int end, 244 int snr_offset, int fast_gain, int is_lfe, 245 int dba_mode, int dba_nsegs, 246 uint8_t *dba_offsets, uint8_t *dba_lengths, 247 uint8_t *dba_values) 248{ 249 int16_t psd[256]; /* scaled exponents */ 250 int16_t band_psd[50]; /* interpolated exponents */ 251 int16_t mask[50]; /* masking value */ 252 253 ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd); 254 255 ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe, 256 dba_mode, dba_nsegs, dba_offsets, dba_lengths, 257 dba_values, mask); 258 259 ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor, 260 ff_ac3_bap_tab, bap); 261} 262 263/** 264 * Initializes some tables. 265 * note: This function must remain thread safe because it is called by the 266 * AVParser init code. 267 */ 268av_cold void ac3_common_init(void) 269{ 270#if !CONFIG_HARDCODED_TABLES 271 /* compute bndtab and masktab from bandsz */ 272 int bin = 0, band; 273 for (band = 0; band < 50; band++) { 274 int band_end = bin + ff_ac3_critical_band_size_tab[band]; 275 band_start_tab[band] = bin; 276 while (bin < band_end) 277 bin_to_band_tab[bin++] = band; 278 } 279 band_start_tab[50] = bin; 280#endif /* !CONFIG_HARDCODED_TABLES */ 281} 282