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
calc_lowcomp1(int a, int b0, int b1, int c)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
calc_lowcomp(int a, int b0, int b1, int bin)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
ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, int16_t *band_psd)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
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)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 }
295