ac3: detect dba errors and prevent writing past end of array
[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 ac3.c
24 * Common code between the AC-3 encoder and decoder.
25 */
26
27 #include "avcodec.h"
28 #include "ac3.h"
29 #include "bitstream.h"
30
31 static uint8_t band_start_tab[51];
32 static uint8_t bin_to_band_tab[253];
33
34 static inline int calc_lowcomp1(int a, int b0, int b1, int c)
35 {
36 if ((b0 + 256) == b1) {
37 a = c;
38 } else if (b0 > b1) {
39 a = FFMAX(a - 64, 0);
40 }
41 return a;
42 }
43
44 static inline int calc_lowcomp(int a, int b0, int b1, int bin)
45 {
46 if (bin < 7) {
47 return calc_lowcomp1(a, b0, b1, 384);
48 } else if (bin < 20) {
49 return calc_lowcomp1(a, b0, b1, 320);
50 } else {
51 return FFMAX(a - 128, 0);
52 }
53 }
54
55 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
56 int16_t *band_psd)
57 {
58 int bin, i, j, k, end1, v;
59
60 /* exponent mapping to PSD */
61 for(bin=start;bin<end;bin++) {
62 psd[bin]=(3072 - (exp[bin] << 7));
63 }
64
65 /* PSD integration */
66 j=start;
67 k=bin_to_band_tab[start];
68 do {
69 v=psd[j];
70 j++;
71 end1 = FFMIN(band_start_tab[k+1], end);
72 for(i=j;i<end1;i++) {
73 /* logadd */
74 int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255);
75 v = FFMAX(v, psd[j]) + ff_ac3_log_add_tab[adr];
76 j++;
77 }
78 band_psd[k]=v;
79 k++;
80 } while (end > band_start_tab[k]);
81 }
82
83 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
84 int start, int end, int fast_gain, int is_lfe,
85 int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
86 uint8_t *dba_lengths, uint8_t *dba_values,
87 int16_t *mask)
88 {
89 int16_t excite[50]; /* excitation */
90 int bin, k;
91 int bndstrt, bndend, begin, end1, tmp;
92 int lowcomp, fastleak, slowleak;
93
94 /* excitation function */
95 bndstrt = bin_to_band_tab[start];
96 bndend = bin_to_band_tab[end-1] + 1;
97
98 if (bndstrt == 0) {
99 lowcomp = 0;
100 lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
101 excite[0] = band_psd[0] - fast_gain - lowcomp;
102 lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
103 excite[1] = band_psd[1] - fast_gain - lowcomp;
104 begin = 7;
105 for (bin = 2; bin < 7; bin++) {
106 if (!(is_lfe && bin == 6))
107 lowcomp = calc_lowcomp1(lowcomp, band_psd[bin], band_psd[bin+1], 384);
108 fastleak = band_psd[bin] - fast_gain;
109 slowleak = band_psd[bin] - s->slow_gain;
110 excite[bin] = fastleak - lowcomp;
111 if (!(is_lfe && bin == 6)) {
112 if (band_psd[bin] <= band_psd[bin+1]) {
113 begin = bin + 1;
114 break;
115 }
116 }
117 }
118
119 end1=bndend;
120 if (end1 > 22) end1=22;
121
122 for (bin = begin; bin < end1; bin++) {
123 if (!(is_lfe && bin == 6))
124 lowcomp = calc_lowcomp(lowcomp, band_psd[bin], band_psd[bin+1], bin);
125
126 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
127 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
128 excite[bin] = FFMAX(fastleak - lowcomp, slowleak);
129 }
130 begin = 22;
131 } else {
132 /* coupling channel */
133 begin = bndstrt;
134
135 fastleak = (s->cpl_fast_leak << 8) + 768;
136 slowleak = (s->cpl_slow_leak << 8) + 768;
137 }
138
139 for (bin = begin; bin < bndend; bin++) {
140 fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain);
141 slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain);
142 excite[bin] = FFMAX(fastleak, slowleak);
143 }
144
145 /* compute masking curve */
146
147 for (bin = bndstrt; bin < bndend; bin++) {
148 tmp = s->db_per_bit - band_psd[bin];
149 if (tmp > 0) {
150 excite[bin] += tmp >> 2;
151 }
152 mask[bin] = FFMAX(ff_ac3_hearing_threshold_tab[bin >> s->sr_shift][s->sr_code], excite[bin]);
153 }
154
155 /* delta bit allocation */
156
157 if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
158 int band, seg, delta;
159 if (dba_nsegs >= 8)
160 return -1;
161 band = 0;
162 for (seg = 0; seg < dba_nsegs; seg++) {
163 band += dba_offsets[seg];
164 if (band >= 50 || dba_lengths[seg] > 50-band)
165 return -1;
166 if (dba_values[seg] >= 4) {
167 delta = (dba_values[seg] - 3) << 7;
168 } else {
169 delta = (dba_values[seg] - 4) << 7;
170 }
171 for (k = 0; k < dba_lengths[seg]; k++) {
172 mask[band] += delta;
173 band++;
174 }
175 }
176 }
177 return 0;
178 }
179
180 void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
181 int snr_offset, int floor,
182 const uint8_t *bap_tab, uint8_t *bap)
183 {
184 int i, j, k, end1, v, address;
185
186 /* special case, if snr offset is -960, set all bap's to zero */
187 if(snr_offset == -960) {
188 memset(bap, 0, 256);
189 return;
190 }
191
192 i = start;
193 j = bin_to_band_tab[start];
194 do {
195 v = (FFMAX(mask[j] - snr_offset - floor, 0) & 0x1FE0) + floor;
196 end1 = FFMIN(band_start_tab[j] + ff_ac3_critical_band_size_tab[j], end);
197 for (k = i; k < end1; k++) {
198 address = av_clip((psd[i] - v) >> 5, 0, 63);
199 bap[i] = bap_tab[address];
200 i++;
201 }
202 } while (end > band_start_tab[j++]);
203 }
204
205 /* AC-3 bit allocation. The algorithm is the one described in the AC-3
206 spec. */
207 void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
208 int8_t *exp, int start, int end,
209 int snr_offset, int fast_gain, int is_lfe,
210 int dba_mode, int dba_nsegs,
211 uint8_t *dba_offsets, uint8_t *dba_lengths,
212 uint8_t *dba_values)
213 {
214 int16_t psd[256]; /* scaled exponents */
215 int16_t band_psd[50]; /* interpolated exponents */
216 int16_t mask[50]; /* masking value */
217
218 ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd);
219
220 ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe,
221 dba_mode, dba_nsegs, dba_offsets, dba_lengths, dba_values,
222 mask);
223
224 ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor,
225 ff_ac3_bap_tab, bap);
226 }
227
228 /**
229 * Initializes some tables.
230 * note: This function must remain thread safe because it is called by the
231 * AVParser init code.
232 */
233 av_cold void ac3_common_init(void)
234 {
235 int i, j, k, l, v;
236 /* compute bndtab and masktab from bandsz */
237 k = 0;
238 l = 0;
239 for(i=0;i<50;i++) {
240 band_start_tab[i] = l;
241 v = ff_ac3_critical_band_size_tab[i];
242 for(j=0;j<v;j++) bin_to_band_tab[k++]=i;
243 l += v;
244 }
245 band_start_tab[50] = l;
246 }