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231 lines
7.8 KiB
231 lines
7.8 KiB
/* |
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* Common code between the AC-3 encoder and decoder |
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* Copyright (c) 2000 Fabrice Bellard |
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* |
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* This file is part of FFmpeg. |
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* |
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* FFmpeg is free software; you can redistribute it and/or |
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* modify it under the terms of the GNU Lesser General Public |
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* License as published by the Free Software Foundation; either |
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* version 2.1 of the License, or (at your option) any later version. |
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* |
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* FFmpeg is distributed in the hope that it will be useful, |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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* Lesser General Public License for more details. |
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* |
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* You should have received a copy of the GNU Lesser General Public |
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* License along with FFmpeg; if not, write to the Free Software |
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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*/ |
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/** |
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* @file |
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* Common code between the AC-3 encoder and decoder. |
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*/ |
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#include "avcodec.h" |
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#include "ac3.h" |
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#include "get_bits.h" |
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/** |
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* Starting frequency coefficient bin for each critical band. |
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*/ |
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const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = { |
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, |
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10, 11, 12, 13, 14, 15, 16, 17, 18, 19, |
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20, 21, 22, 23, 24, 25, 26, 27, 28, 31, |
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34, 37, 40, 43, 46, 49, 55, 61, 67, 73, |
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79, 85, 97, 109, 121, 133, 157, 181, 205, 229, 253 |
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}; |
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#if CONFIG_HARDCODED_TABLES |
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/** |
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* Map each frequency coefficient bin to the critical band that contains it. |
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*/ |
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const uint8_t ff_ac3_bin_to_band_tab[253] = { |
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0, |
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1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, |
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13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, |
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25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30, |
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31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34, |
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35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36, |
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37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38, |
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39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40, |
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41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, |
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42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, |
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43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, |
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44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, |
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45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, |
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45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, |
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46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, |
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46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, |
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47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, |
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47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, |
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48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, |
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48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, |
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49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, |
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49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49 |
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}; |
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#else /* CONFIG_HARDCODED_TABLES */ |
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uint8_t ff_ac3_bin_to_band_tab[253]; |
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#endif |
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static inline int calc_lowcomp1(int a, int b0, int b1, int c) |
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{ |
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if ((b0 + 256) == b1) { |
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a = c; |
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} else if (b0 > b1) { |
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a = FFMAX(a - 64, 0); |
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} |
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return a; |
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} |
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static inline int calc_lowcomp(int a, int b0, int b1, int bin) |
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{ |
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if (bin < 7) { |
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return calc_lowcomp1(a, b0, b1, 384); |
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} else if (bin < 20) { |
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return calc_lowcomp1(a, b0, b1, 320); |
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} else { |
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return FFMAX(a - 128, 0); |
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} |
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} |
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void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, |
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int16_t *band_psd) |
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{ |
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int bin, band; |
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/* exponent mapping to PSD */ |
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for (bin = start; bin < end; bin++) { |
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psd[bin]=(3072 - (exp[bin] << 7)); |
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} |
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/* PSD integration */ |
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bin = start; |
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band = ff_ac3_bin_to_band_tab[start]; |
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do { |
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int v = psd[bin++]; |
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int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end); |
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for (; bin < band_end; bin++) { |
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int max = FFMAX(v, psd[bin]); |
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/* logadd */ |
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int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255); |
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v = max + ff_ac3_log_add_tab[adr]; |
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} |
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band_psd[band++] = v; |
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} while (end > ff_ac3_band_start_tab[band]); |
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} |
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int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, |
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int start, int end, int fast_gain, int is_lfe, |
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int dba_mode, int dba_nsegs, uint8_t *dba_offsets, |
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uint8_t *dba_lengths, uint8_t *dba_values, |
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int16_t *mask) |
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{ |
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int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */ |
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int band; |
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int band_start, band_end, begin, end1; |
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int lowcomp, fastleak, slowleak; |
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/* excitation function */ |
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band_start = ff_ac3_bin_to_band_tab[start]; |
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band_end = ff_ac3_bin_to_band_tab[end-1] + 1; |
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if (band_start == 0) { |
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lowcomp = 0; |
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lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384); |
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excite[0] = band_psd[0] - fast_gain - lowcomp; |
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lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384); |
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excite[1] = band_psd[1] - fast_gain - lowcomp; |
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begin = 7; |
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for (band = 2; band < 7; band++) { |
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if (!(is_lfe && band == 6)) |
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lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384); |
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fastleak = band_psd[band] - fast_gain; |
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slowleak = band_psd[band] - s->slow_gain; |
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excite[band] = fastleak - lowcomp; |
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if (!(is_lfe && band == 6)) { |
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if (band_psd[band] <= band_psd[band+1]) { |
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begin = band + 1; |
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break; |
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} |
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} |
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} |
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end1 = FFMIN(band_end, 22); |
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for (band = begin; band < end1; band++) { |
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if (!(is_lfe && band == 6)) |
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lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band); |
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fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); |
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slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); |
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excite[band] = FFMAX(fastleak - lowcomp, slowleak); |
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} |
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begin = 22; |
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} else { |
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/* coupling channel */ |
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begin = band_start; |
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fastleak = (s->cpl_fast_leak << 8) + 768; |
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slowleak = (s->cpl_slow_leak << 8) + 768; |
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} |
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for (band = begin; band < band_end; band++) { |
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fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); |
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slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); |
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excite[band] = FFMAX(fastleak, slowleak); |
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} |
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/* compute masking curve */ |
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for (band = band_start; band < band_end; band++) { |
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int tmp = s->db_per_bit - band_psd[band]; |
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if (tmp > 0) { |
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excite[band] += tmp >> 2; |
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} |
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mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]); |
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} |
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/* delta bit allocation */ |
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if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) { |
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int i, seg, delta; |
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if (dba_nsegs > 8) |
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return -1; |
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band = band_start; |
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for (seg = 0; seg < dba_nsegs; seg++) { |
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band += dba_offsets[seg]; |
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if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band) |
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return -1; |
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if (dba_values[seg] >= 4) { |
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delta = (dba_values[seg] - 3) << 7; |
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} else { |
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delta = (dba_values[seg] - 4) << 7; |
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} |
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for (i = 0; i < dba_lengths[seg]; i++) { |
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mask[band++] += delta; |
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} |
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} |
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} |
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return 0; |
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} |
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/** |
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* Initialize some tables. |
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* note: This function must remain thread safe because it is called by the |
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* AVParser init code. |
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*/ |
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av_cold void ff_ac3_common_init(void) |
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{ |
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#if !CONFIG_HARDCODED_TABLES |
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/* compute ff_ac3_bin_to_band_tab from ff_ac3_band_start_tab */ |
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int bin = 0, band; |
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for (band = 0; band < AC3_CRITICAL_BANDS; band++) { |
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int band_end = ff_ac3_band_start_tab[band+1]; |
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while (bin < band_end) |
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ff_ac3_bin_to_band_tab[bin++] = band; |
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} |
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#endif /* !CONFIG_HARDCODED_TABLES */ |
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}
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