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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 | /** | |
32 | * Starting frequency coefficient bin for each critical band. | |
33 | */ | |
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 | |
40 | }; | |
41 | ||
42 | #if CONFIG_HARDCODED_TABLES | |
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 | #else /* CONFIG_HARDCODED_TABLES */ | |
73 | uint8_t ff_ac3_bin_to_band_tab[253]; | |
74 | #endif | |
75 | ||
76 | static inline int calc_lowcomp1(int a, int b0, int b1, int c) | |
77 | { | |
78 | if ((b0 + 256) == b1) { | |
79 | a = c; | |
80 | } else if (b0 > b1) { | |
81 | a = FFMAX(a - 64, 0); | |
82 | } | |
83 | return a; | |
84 | } | |
85 | ||
86 | static inline int calc_lowcomp(int a, int b0, int b1, int bin) | |
87 | { | |
88 | if (bin < 7) { | |
89 | return calc_lowcomp1(a, b0, b1, 384); | |
90 | } else if (bin < 20) { | |
91 | return calc_lowcomp1(a, b0, b1, 320); | |
92 | } else { | |
93 | return FFMAX(a - 128, 0); | |
94 | } | |
95 | } | |
96 | ||
97 | void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, | |
98 | int16_t *band_psd) | |
99 | { | |
100 | int bin, band; | |
101 | ||
102 | /* exponent mapping to PSD */ | |
103 | for (bin = start; bin < end; bin++) { | |
104 | psd[bin]=(3072 - (exp[bin] << 7)); | |
105 | } | |
106 | ||
107 | /* PSD integration */ | |
108 | bin = start; | |
109 | band = ff_ac3_bin_to_band_tab[start]; | |
110 | do { | |
111 | int v = psd[bin++]; | |
112 | int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end); | |
113 | for (; bin < band_end; bin++) { | |
114 | int max = FFMAX(v, psd[bin]); | |
115 | /* logadd */ | |
116 | int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255); | |
117 | v = max + ff_ac3_log_add_tab[adr]; | |
118 | } | |
119 | band_psd[band++] = v; | |
120 | } while (end > ff_ac3_band_start_tab[band]); | |
121 | } | |
122 | ||
123 | int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, | |
124 | int start, int end, int fast_gain, int is_lfe, | |
125 | int dba_mode, int dba_nsegs, uint8_t *dba_offsets, | |
126 | uint8_t *dba_lengths, uint8_t *dba_values, | |
127 | int16_t *mask) | |
128 | { | |
129 | int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */ | |
130 | int band; | |
131 | int band_start, band_end, begin, end1; | |
132 | int lowcomp, fastleak, slowleak; | |
133 | ||
134 | /* excitation function */ | |
135 | band_start = ff_ac3_bin_to_band_tab[start]; | |
136 | band_end = ff_ac3_bin_to_band_tab[end-1] + 1; | |
137 | ||
138 | if (band_start == 0) { | |
139 | lowcomp = 0; | |
140 | lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384); | |
141 | excite[0] = band_psd[0] - fast_gain - lowcomp; | |
142 | lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384); | |
143 | excite[1] = band_psd[1] - fast_gain - lowcomp; | |
144 | begin = 7; | |
145 | for (band = 2; band < 7; band++) { | |
146 | if (!(is_lfe && band == 6)) | |
147 | lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384); | |
148 | fastleak = band_psd[band] - fast_gain; | |
149 | slowleak = band_psd[band] - s->slow_gain; | |
150 | excite[band] = fastleak - lowcomp; | |
151 | if (!(is_lfe && band == 6)) { | |
152 | if (band_psd[band] <= band_psd[band+1]) { | |
153 | begin = band + 1; | |
154 | break; | |
155 | } | |
156 | } | |
157 | } | |
158 | ||
159 | end1 = FFMIN(band_end, 22); | |
160 | for (band = begin; band < end1; band++) { | |
161 | if (!(is_lfe && band == 6)) | |
162 | lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band); | |
163 | fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); | |
164 | slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); | |
165 | excite[band] = FFMAX(fastleak - lowcomp, slowleak); | |
166 | } | |
167 | begin = 22; | |
168 | } else { | |
169 | /* coupling channel */ | |
170 | begin = band_start; | |
171 | fastleak = (s->cpl_fast_leak << 8) + 768; | |
172 | slowleak = (s->cpl_slow_leak << 8) + 768; | |
173 | } | |
174 | ||
175 | for (band = begin; band < band_end; band++) { | |
176 | fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); | |
177 | slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); | |
178 | excite[band] = FFMAX(fastleak, slowleak); | |
179 | } | |
180 | ||
181 | /* compute masking curve */ | |
182 | ||
183 | for (band = band_start; band < band_end; band++) { | |
184 | int tmp = s->db_per_bit - band_psd[band]; | |
185 | if (tmp > 0) { | |
186 | excite[band] += tmp >> 2; | |
187 | } | |
188 | mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]); | |
189 | } | |
190 | ||
191 | /* delta bit allocation */ | |
192 | ||
193 | if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) { | |
194 | int i, seg, delta; | |
195 | if (dba_nsegs > 8) | |
196 | return -1; | |
197 | band = band_start; | |
198 | for (seg = 0; seg < dba_nsegs; seg++) { | |
199 | band += dba_offsets[seg]; | |
200 | if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band) | |
201 | return -1; | |
202 | if (dba_values[seg] >= 4) { | |
203 | delta = (dba_values[seg] - 3) << 7; | |
204 | } else { | |
205 | delta = (dba_values[seg] - 4) << 7; | |
206 | } | |
207 | for (i = 0; i < dba_lengths[seg]; i++) { | |
208 | mask[band++] += delta; | |
209 | } | |
210 | } | |
211 | } | |
212 | return 0; | |
213 | } | |
214 | ||
215 | /** | |
216 | * Initialize some tables. | |
217 | * note: This function must remain thread safe because it is called by the | |
218 | * AVParser init code. | |
219 | */ | |
220 | av_cold void ff_ac3_common_init(void) | |
221 | { | |
222 | #if !CONFIG_HARDCODED_TABLES | |
223 | /* compute ff_ac3_bin_to_band_tab from ff_ac3_band_start_tab */ | |
224 | int bin = 0, band; | |
225 | for (band = 0; band < AC3_CRITICAL_BANDS; band++) { | |
226 | int band_end = ff_ac3_band_start_tab[band+1]; | |
227 | while (bin < band_end) | |
228 | ff_ac3_bin_to_band_tab[bin++] = band; | |
229 | } | |
230 | #endif /* !CONFIG_HARDCODED_TABLES */ | |
231 | } |