Move some variable declarations to inside of loops.
[libav.git] / libavcodec / ac3.c
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 libavcodec/ac3.c
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 */
36 static 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 */
47 static 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 */
73 static uint8_t band_start_tab[51];
74 static uint8_t bin_to_band_tab[253];
75 #endif
76
77 static 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
87 static 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
98 void 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 /* logadd */
116 int adr = FFMIN(FFABS(v - psd[bin]) >> 1, 255);
117 v = FFMAX(v, psd[bin]) + ff_ac3_log_add_tab[adr];
118 }
119 band_psd[band++] = v;
120 } while (end > 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[50]; /* excitation */
130 int band;
131 int band_start, band_end, begin, end1;
132 int lowcomp, fastleak, slowleak;
133
134 /* excitation function */
135 band_start = bin_to_band_tab[start];
136 band_end = 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 = 0;
198 for (seg = 0; seg < dba_nsegs; seg++) {
199 band += dba_offsets[seg];
200 if (band >= 50 || dba_lengths[seg] > 50-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 void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
216 int snr_offset, int floor,
217 const uint8_t *bap_tab, uint8_t *bap)
218 {
219 int i, j;
220
221 /* special case, if snr offset is -960, set all bap's to zero */
222 if (snr_offset == -960) {
223 memset(bap, 0, 256);
224 return;
225 }
226
227 i = start;
228 j = bin_to_band_tab[start];
229 do {
230 int v = (FFMAX(mask[j] - snr_offset - floor, 0) & 0x1FE0) + floor;
231 int end1 = FFMIN(band_start_tab[j] + ff_ac3_critical_band_size_tab[j], end);
232 for (; i < end1; i++) {
233 int address = av_clip((psd[i] - v) >> 5, 0, 63);
234 bap[i] = bap_tab[address];
235 }
236 } while (end > band_start_tab[j++]);
237 }
238
239 /* AC-3 bit allocation. The algorithm is the one described in the AC-3
240 spec. */
241 void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
242 int8_t *exp, int start, int end,
243 int snr_offset, int fast_gain, int is_lfe,
244 int dba_mode, int dba_nsegs,
245 uint8_t *dba_offsets, uint8_t *dba_lengths,
246 uint8_t *dba_values)
247 {
248 int16_t psd[256]; /* scaled exponents */
249 int16_t band_psd[50]; /* interpolated exponents */
250 int16_t mask[50]; /* masking value */
251
252 ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd);
253
254 ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe,
255 dba_mode, dba_nsegs, dba_offsets, dba_lengths,
256 dba_values, mask);
257
258 ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor,
259 ff_ac3_bap_tab, bap);
260 }
261
262 /**
263 * Initializes some tables.
264 * note: This function must remain thread safe because it is called by the
265 * AVParser init code.
266 */
267 av_cold void ac3_common_init(void)
268 {
269 #if !CONFIG_HARDCODED_TABLES
270 /* compute bndtab and masktab from bandsz */
271 int bin = 0, band;
272 for (band = 0; band < 50; band++) {
273 int band_end = bin + ff_ac3_critical_band_size_tab[band];
274 band_start_tab[band] = bin;
275 while (bin < band_end)
276 bin_to_band_tab[bin++] = band;
277 }
278 band_start_tab[50] = bin;
279 #endif /* !CONFIG_HARDCODED_TABLES */
280 }