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#if CONFIG_HARDCODED_TABLES
32
33/**
34 * Starting frequency coefficient bin for each critical band.
35 */
36static 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 */
47static 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 */
73static uint8_t band_start_tab[51];
74static uint8_t bin_to_band_tab[253];
75#endif
76
77static 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
87static 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
98void 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            int max = FFMAX(v, psd[bin]);
116            /* logadd */
117            int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255);
118            v = max + ff_ac3_log_add_tab[adr];
119        }
120        band_psd[band++] = v;
121    } while (end > band_start_tab[band]);
122}
123
124int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
125                               int start, int end, int fast_gain, int is_lfe,
126                               int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
127                               uint8_t *dba_lengths, uint8_t *dba_values,
128                               int16_t *mask)
129{
130    int16_t excite[50]; /* excitation */
131    int band;
132    int band_start, band_end, begin, end1;
133    int lowcomp, fastleak, slowleak;
134
135    /* excitation function */
136    band_start = bin_to_band_tab[start];
137    band_end   = bin_to_band_tab[end-1] + 1;
138
139    if (band_start == 0) {
140        lowcomp = 0;
141        lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384);
142        excite[0] = band_psd[0] - fast_gain - lowcomp;
143        lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384);
144        excite[1] = band_psd[1] - fast_gain - lowcomp;
145        begin = 7;
146        for (band = 2; band < 7; band++) {
147            if (!(is_lfe && band == 6))
148                lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384);
149            fastleak = band_psd[band] - fast_gain;
150            slowleak = band_psd[band] - s->slow_gain;
151            excite[band] = fastleak - lowcomp;
152            if (!(is_lfe && band == 6)) {
153                if (band_psd[band] <= band_psd[band+1]) {
154                    begin = band + 1;
155                    break;
156                }
157            }
158        }
159
160        end1 = FFMIN(band_end, 22);
161        for (band = begin; band < end1; band++) {
162            if (!(is_lfe && band == 6))
163                lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band);
164            fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
165            slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
166            excite[band] = FFMAX(fastleak - lowcomp, slowleak);
167        }
168        begin = 22;
169    } else {
170        /* coupling channel */
171        begin = band_start;
172        fastleak = (s->cpl_fast_leak << 8) + 768;
173        slowleak = (s->cpl_slow_leak << 8) + 768;
174    }
175
176    for (band = begin; band < band_end; band++) {
177        fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain);
178        slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain);
179        excite[band] = FFMAX(fastleak, slowleak);
180    }
181
182    /* compute masking curve */
183
184    for (band = band_start; band < band_end; band++) {
185        int tmp = s->db_per_bit - band_psd[band];
186        if (tmp > 0) {
187            excite[band] += tmp >> 2;
188        }
189        mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]);
190    }
191
192    /* delta bit allocation */
193
194    if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) {
195        int i, seg, delta;
196        if (dba_nsegs >= 8)
197            return -1;
198        band = 0;
199        for (seg = 0; seg < dba_nsegs; seg++) {
200            band += dba_offsets[seg];
201            if (band >= 50 || dba_lengths[seg] > 50-band)
202                return -1;
203            if (dba_values[seg] >= 4) {
204                delta = (dba_values[seg] - 3) << 7;
205            } else {
206                delta = (dba_values[seg] - 4) << 7;
207            }
208            for (i = 0; i < dba_lengths[seg]; i++) {
209                mask[band++] += delta;
210            }
211        }
212    }
213    return 0;
214}
215
216void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
217                               int snr_offset, int floor,
218                               const uint8_t *bap_tab, uint8_t *bap)
219{
220    int bin, band;
221
222    /* special case, if snr offset is -960, set all bap's to zero */
223    if (snr_offset == -960) {
224        memset(bap, 0, 256);
225        return;
226    }
227
228    bin  = start;
229    band = bin_to_band_tab[start];
230    do {
231        int m = (FFMAX(mask[band] - snr_offset - floor, 0) & 0x1FE0) + floor;
232        int band_end = FFMIN(band_start_tab[band+1], end);
233        for (; bin < band_end; bin++) {
234            int address = av_clip((psd[bin] - m) >> 5, 0, 63);
235            bap[bin] = bap_tab[address];
236        }
237    } while (end > band_start_tab[band++]);
238}
239
240/* AC-3 bit allocation. The algorithm is the one described in the AC-3
241   spec. */
242void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
243                                   int8_t *exp, int start, int end,
244                                   int snr_offset, int fast_gain, int is_lfe,
245                                   int dba_mode, int dba_nsegs,
246                                   uint8_t *dba_offsets, uint8_t *dba_lengths,
247                                   uint8_t *dba_values)
248{
249    int16_t psd[256];   /* scaled exponents */
250    int16_t band_psd[50]; /* interpolated exponents */
251    int16_t mask[50];   /* masking value */
252
253    ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd);
254
255    ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe,
256                               dba_mode, dba_nsegs, dba_offsets, dba_lengths,
257                               dba_values, mask);
258
259    ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor,
260                              ff_ac3_bap_tab, bap);
261}
262
263/**
264 * Initializes some tables.
265 * note: This function must remain thread safe because it is called by the
266 *       AVParser init code.
267 */
268av_cold void ac3_common_init(void)
269{
270#if !CONFIG_HARDCODED_TABLES
271    /* compute bndtab and masktab from bandsz */
272    int bin = 0, band;
273    for (band = 0; band < 50; band++) {
274        int band_end = bin + ff_ac3_critical_band_size_tab[band];
275        band_start_tab[band] = bin;
276        while (bin < band_end)
277            bin_to_band_tab[bin++] = band;
278    }
279    band_start_tab[50] = bin;
280#endif /* !CONFIG_HARDCODED_TABLES */
281}
282