2 * Common code between the AC-3 encoder and decoder
3 * Copyright (c) 2000 Fabrice Bellard
5 * This file is part of FFmpeg.
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.
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.
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
24 * Common code between the AC-3 encoder and decoder.
32 * Starting frequency coefficient bin for each critical band.
34 const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = {
35 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
36 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
37 20, 21, 22, 23, 24, 25, 26, 27, 28, 31,
38 34, 37, 40, 43, 46, 49, 55, 61, 67, 73,
39 79, 85, 97, 109, 121, 133, 157, 181, 205, 229, 253
43 * Map each frequency coefficient bin to the critical band that contains it.
45 const uint8_t ff_ac3_bin_to_band_tab[253] = {
47 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
48 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
49 25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30,
50 31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34,
51 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36,
52 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38,
53 39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40,
54 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
55 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
56 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43,
57 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44,
58 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
59 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
60 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
61 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
62 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
63 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
64 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
65 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
66 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,
67 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49
70 static inline int calc_lowcomp1(int a, int b0, int b1, int c)
72 if ((b0 + 256) == b1) {
80 static inline int calc_lowcomp(int a, int b0, int b1, int bin)
83 return calc_lowcomp1(a, b0, b1, 384);
84 } else if (bin < 20) {
85 return calc_lowcomp1(a, b0, b1, 320);
87 return FFMAX(a - 128, 0);
91 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
96 /* exponent mapping to PSD */
97 for (bin = start; bin < end; bin++) {
98 psd[bin]=(3072 - (exp[bin] << 7));
101 /* PSD integration */
103 band = ff_ac3_bin_to_band_tab[start];
106 int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end);
107 for (; bin < band_end; bin++) {
108 int max = FFMAX(v, psd[bin]);
110 int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
111 v = max + ff_ac3_log_add_tab[adr];
113 band_psd[band++] = v;
114 } while (end > ff_ac3_band_start_tab[band]);
117 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
118 int start, int end, int fast_gain, int is_lfe,
119 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
120 uint8_t *dba_lengths, uint8_t *dba_values,
123 int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */
125 int band_start, band_end, begin, end1;
126 int lowcomp, fastleak, slowleak;
129 return AVERROR_INVALIDDATA;
131 /* excitation function */
132 band_start = ff_ac3_bin_to_band_tab[start];
133 band_end = ff_ac3_bin_to_band_tab[end-1] + 1;
135 if (band_start == 0) {
137 lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
138 excite[0] = band_psd[0] - fast_gain - lowcomp;
139 lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
140 excite[1] = band_psd[1] - fast_gain - lowcomp;
142 for (band = 2; band < 7; band++) {
143 if (!(is_lfe && band == 6))
144 lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384);
145 fastleak = band_psd[band] - fast_gain;
146 slowleak = band_psd[band] - s->slow_gain;
147 excite[band] = fastleak - lowcomp;
148 if (!(is_lfe && band == 6)) {
149 if (band_psd[band] <= band_psd[band+1]) {
156 end1 = FFMIN(band_end, 22);
157 for (band = begin; band < end1; band++) {
158 if (!(is_lfe && band == 6))
159 lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band);
160 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
161 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
162 excite[band] = FFMAX(fastleak - lowcomp, slowleak);
166 /* coupling channel */
168 fastleak = (s->cpl_fast_leak << 8) + 768;
169 slowleak = (s->cpl_slow_leak << 8) + 768;
172 for (band = begin; band < band_end; band++) {
173 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
174 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
175 excite[band] = FFMAX(fastleak, slowleak);
178 /* compute masking curve */
180 for (band = band_start; band < band_end; band++) {
181 int tmp = s->db_per_bit - band_psd[band];
183 excite[band] += tmp >> 2;
185 mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]);
188 /* delta bit allocation */
190 if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
195 for (seg = 0; seg < dba_nsegs; seg++) {
196 band += dba_offsets[seg];
197 if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band)
199 if (dba_values[seg] >= 4) {
200 delta = (dba_values[seg] - 3) * 128;
202 delta = (dba_values[seg] - 4) * 128;
204 for (i = 0; i < dba_lengths[seg]; i++) {
205 mask[band++] += delta;