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Diffstat (limited to 'ffmpeg1/libavcodec/ac3.c')
| -rw-r--r-- | ffmpeg1/libavcodec/ac3.c | 231 |
1 files changed, 231 insertions, 0 deletions
diff --git a/ffmpeg1/libavcodec/ac3.c b/ffmpeg1/libavcodec/ac3.c new file mode 100644 index 0000000..29e132f --- /dev/null +++ b/ffmpeg1/libavcodec/ac3.c @@ -0,0 +1,231 @@ +/* + * Common code between the AC-3 encoder and decoder + * Copyright (c) 2000 Fabrice Bellard + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/** + * @file + * Common code between the AC-3 encoder and decoder. + */ + +#include "avcodec.h" +#include "ac3.h" +#include "get_bits.h" + +/** + * Starting frequency coefficient bin for each critical band. + */ +const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] = { + 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, + 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, + 20, 21, 22, 23, 24, 25, 26, 27, 28, 31, + 34, 37, 40, 43, 46, 49, 55, 61, 67, 73, + 79, 85, 97, 109, 121, 133, 157, 181, 205, 229, 253 +}; + +#if CONFIG_HARDCODED_TABLES + +/** + * Map each frequency coefficient bin to the critical band that contains it. + */ +const uint8_t ff_ac3_bin_to_band_tab[253] = { + 0, + 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, + 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, + 25, 26, 27, 28, 28, 28, 29, 29, 29, 30, 30, 30, + 31, 31, 31, 32, 32, 32, 33, 33, 33, 34, 34, 34, + 35, 35, 35, 35, 35, 35, 36, 36, 36, 36, 36, 36, + 37, 37, 37, 37, 37, 37, 38, 38, 38, 38, 38, 38, + 39, 39, 39, 39, 39, 39, 40, 40, 40, 40, 40, 40, + 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, 41, + 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, 42, + 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, 43, + 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, 44, + 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, + 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, 45, + 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, + 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, 46, + 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, + 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, 47, + 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, + 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, 48, + 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, + 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49, 49 +}; + +#else /* CONFIG_HARDCODED_TABLES */ +uint8_t ff_ac3_bin_to_band_tab[253]; +#endif + +static inline int calc_lowcomp1(int a, int b0, int b1, int c) +{ + if ((b0 + 256) == b1) { + a = c; + } else if (b0 > b1) { + a = FFMAX(a - 64, 0); + } + return a; +} + +static inline int calc_lowcomp(int a, int b0, int b1, int bin) +{ + if (bin < 7) { + return calc_lowcomp1(a, b0, b1, 384); + } else if (bin < 20) { + return calc_lowcomp1(a, b0, b1, 320); + } else { + return FFMAX(a - 128, 0); + } +} + +void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd, + int16_t *band_psd) +{ + int bin, band; + + /* exponent mapping to PSD */ + for (bin = start; bin < end; bin++) { + psd[bin]=(3072 - (exp[bin] << 7)); + } + + /* PSD integration */ + bin = start; + band = ff_ac3_bin_to_band_tab[start]; + do { + int v = psd[bin++]; + int band_end = FFMIN(ff_ac3_band_start_tab[band+1], end); + for (; bin < band_end; bin++) { + int max = FFMAX(v, psd[bin]); + /* logadd */ + int adr = FFMIN(max - ((v + psd[bin] + 1) >> 1), 255); + v = max + ff_ac3_log_add_tab[adr]; + } + band_psd[band++] = v; + } while (end > ff_ac3_band_start_tab[band]); +} + +int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd, + int start, int end, int fast_gain, int is_lfe, + int dba_mode, int dba_nsegs, uint8_t *dba_offsets, + uint8_t *dba_lengths, uint8_t *dba_values, + int16_t *mask) +{ + int16_t excite[AC3_CRITICAL_BANDS]; /* excitation */ + int band; + int band_start, band_end, begin, end1; + int lowcomp, fastleak, slowleak; + + /* excitation function */ + band_start = ff_ac3_bin_to_band_tab[start]; + band_end = ff_ac3_bin_to_band_tab[end-1] + 1; + + if (band_start == 0) { + lowcomp = 0; + lowcomp = calc_lowcomp1(lowcomp, band_psd[0], band_psd[1], 384); + excite[0] = band_psd[0] - fast_gain - lowcomp; + lowcomp = calc_lowcomp1(lowcomp, band_psd[1], band_psd[2], 384); + excite[1] = band_psd[1] - fast_gain - lowcomp; + begin = 7; + for (band = 2; band < 7; band++) { + if (!(is_lfe && band == 6)) + lowcomp = calc_lowcomp1(lowcomp, band_psd[band], band_psd[band+1], 384); + fastleak = band_psd[band] - fast_gain; + slowleak = band_psd[band] - s->slow_gain; + excite[band] = fastleak - lowcomp; + if (!(is_lfe && band == 6)) { + if (band_psd[band] <= band_psd[band+1]) { + begin = band + 1; + break; + } + } + } + + end1 = FFMIN(band_end, 22); + for (band = begin; band < end1; band++) { + if (!(is_lfe && band == 6)) + lowcomp = calc_lowcomp(lowcomp, band_psd[band], band_psd[band+1], band); + fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); + slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); + excite[band] = FFMAX(fastleak - lowcomp, slowleak); + } + begin = 22; + } else { + /* coupling channel */ + begin = band_start; + fastleak = (s->cpl_fast_leak << 8) + 768; + slowleak = (s->cpl_slow_leak << 8) + 768; + } + + for (band = begin; band < band_end; band++) { + fastleak = FFMAX(fastleak - s->fast_decay, band_psd[band] - fast_gain); + slowleak = FFMAX(slowleak - s->slow_decay, band_psd[band] - s->slow_gain); + excite[band] = FFMAX(fastleak, slowleak); + } + + /* compute masking curve */ + + for (band = band_start; band < band_end; band++) { + int tmp = s->db_per_bit - band_psd[band]; + if (tmp > 0) { + excite[band] += tmp >> 2; + } + mask[band] = FFMAX(ff_ac3_hearing_threshold_tab[band >> s->sr_shift][s->sr_code], excite[band]); + } + + /* delta bit allocation */ + + if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) { + int i, seg, delta; + if (dba_nsegs > 8) + return -1; + band = band_start; + for (seg = 0; seg < dba_nsegs; seg++) { + band += dba_offsets[seg]; + if (band >= AC3_CRITICAL_BANDS || dba_lengths[seg] > AC3_CRITICAL_BANDS-band) + return -1; + if (dba_values[seg] >= 4) { + delta = (dba_values[seg] - 3) << 7; + } else { + delta = (dba_values[seg] - 4) << 7; + } + for (i = 0; i < dba_lengths[seg]; i++) { + mask[band++] += delta; + } + } + } + return 0; +} + +/** + * Initialize some tables. + * note: This function must remain thread safe because it is called by the + * AVParser init code. + */ +av_cold void ff_ac3_common_init(void) +{ +#if !CONFIG_HARDCODED_TABLES + /* compute ff_ac3_bin_to_band_tab from ff_ac3_band_start_tab */ + int bin = 0, band; + for (band = 0; band < AC3_CRITICAL_BANDS; band++) { + int band_end = ff_ac3_band_start_tab[band+1]; + while (bin < band_end) + ff_ac3_bin_to_band_tab[bin++] = band; + } +#endif /* !CONFIG_HARDCODED_TABLES */ +} |