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/common.h"
28
29 #include "avcodec.h"
30 #include "ac3.h"
31
32 /**
33 * Starting frequency coefficient bin for each critical band.
34 */
35 const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = {
36 0, 1, 2, 3, 4, 5, 6, 7, 8, 9,
37 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,
38 20, 21, 22, 23, 24, 25, 26, 27, 28, 31,
39 34, 37, 40, 43, 46, 49, 55, 61, 67, 73,
40 79, 85, 97, 109, 121, 133, 157, 181, 205, 229, 253
41 };
42
43 /**
44 * Map each frequency coefficient bin to the critical band that contains it.
45 */
46 const uint8_t ff_ac3_bin_to_band_tab[253] = {
47 0,
48 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12,
49 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24,
50 25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30,
51 31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34,
52 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36,
53 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38,
54 39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40,
55 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41,
56 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42,
57 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43,
58 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44,
59 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
60 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45,
61 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
62 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46,
63 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
64 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47,
65 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
66 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48,
67 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49,
68 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49
69 };
70
calc_lowcomp1(int a,int b0,int b1,int c)71 static inline int calc_lowcomp1(int a, int b0, int b1, int c)
72 {
73 if ((b0 + 256) == b1) {
74 a = c;
75 } else if (b0 > b1) {
76 a = FFMAX(a - 64, 0);
77 }
78 return a;
79 }
80
calc_lowcomp(int a,int b0,int b1,int bin)81 static inline int calc_lowcomp(int a, int b0, int b1, int bin)
82 {
83 if (bin < 7) {
84 return calc_lowcomp1(a, b0, b1, 384);
85 } else if (bin < 20) {
86 return calc_lowcomp1(a, b0, b1, 320);
87 } else {
88 return FFMAX(a - 128, 0);
89 }
90 }
91
ff_ac3_bit_alloc_calc_psd(int8_t * exp,int start,int end,int16_t * psd,int16_t * band_psd)92 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
93 int16_t *band_psd)
94 {
95 int bin, band;
96
97 /* exponent mapping to PSD */
98 for (bin = start; bin < end; bin++) {
99 psd[bin]=(3072 - (exp[bin] << 7));
100 }
101
102 /* PSD integration */
103 bin = start;
104 band = ff_ac3_bin_to_band_tab[start];
105 do {
106 int v = psd[bin++];
107 int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end);
108 for (; bin < band_end; bin++) {
109 int max = FFMAX(v, psd[bin]);
110 /* logadd */
111 int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
112 v = max + ff_ac3_log_add_tab[adr];
113 }
114 band_psd[band++] = v;
115 } while (end > ff_ac3_band_start_tab[band]);
116 }
117
ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters * s,int16_t * band_psd,int start,int end,int fast_gain,int is_lfe,int dba_mode,int dba_nsegs,uint8_t * dba_offsets,uint8_t * dba_lengths,uint8_t * dba_values,int16_t * mask)118 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
119 int start, int end, int fast_gain, int is_lfe,
120 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
121 uint8_t *dba_lengths, uint8_t *dba_values,
122 int16_t *mask)
123 {
124 int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */
125 int band;
126 int band_start, band_end, begin, end1;
127 int lowcomp, fastleak, slowleak;
128
129 if (end <= 0)
130 return AVERROR_INVALIDDATA;
131
132 /* excitation function */
133 band_start = ff_ac3_bin_to_band_tab[start];
134 band_end = ff_ac3_bin_to_band_tab[end-1] + 1;
135
136 if (band_start == 0) {
137 lowcomp = 0;
138 lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
139 excite[0] = band_psd[0] - fast_gain - lowcomp;
140 lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
141 excite[1] = band_psd[1] - fast_gain - lowcomp;
142 begin = 7;
143 for (band = 2; band < 7; band++) {
144 if (!(is_lfe && band == 6))
145 lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384);
146 fastleak = band_psd[band] - fast_gain;
147 slowleak = band_psd[band] - s->slow_gain;
148 excite[band] = fastleak - lowcomp;
149 if (!(is_lfe && band == 6)) {
150 if (band_psd[band] <= band_psd[band+1]) {
151 begin = band + 1;
152 break;
153 }
154 }
155 }
156
157 end1 = FFMIN(band_end, 22);
158 for (band = begin; band < end1; band++) {
159 if (!(is_lfe && band == 6))
160 lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band);
161 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
162 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
163 excite[band] = FFMAX(fastleak - lowcomp, slowleak);
164 }
165 begin = 22;
166 } else {
167 /* coupling channel */
168 begin = band_start;
169 fastleak = (s->cpl_fast_leak << 8) + 768;
170 slowleak = (s->cpl_slow_leak << 8) + 768;
171 }
172
173 for (band = begin; band < band_end; band++) {
174 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
175 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
176 excite[band] = FFMAX(fastleak, slowleak);
177 }
178
179 /* compute masking curve */
180
181 for (band = band_start; band < band_end; band++) {
182 int tmp = s->db_per_bit - band_psd[band];
183 if (tmp > 0) {
184 excite[band] += tmp >> 2;
185 }
186 mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]);
187 }
188
189 /* delta bit allocation */
190
191 if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
192 int i, seg, delta;
193 if (dba_nsegs > 8)
194 return -1;
195 band = band_start;
196 for (seg = 0; seg < dba_nsegs; seg++) {
197 band += dba_offsets[seg];
198 if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band)
199 return -1;
200 if (dba_values[seg] >= 4) {
201 delta = (dba_values[seg] - 3) * 128;
202 } else {
203 delta = (dba_values[seg] - 4) * 128;
204 }
205 for (i = 0; i < dba_lengths[seg]; i++) {
206 mask[band++] += delta;
207 }
208 }
209 }
210 return 0;
211 }
212