/* * 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 "libavutil/common.h" #include "avcodec.h" #include "ac3.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 }; /** * 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 }; 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; if (end <= 0) return AVERROR_INVALIDDATA; /* 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) * 128; } else { delta = (dba_values[seg] - 4) * 128; } for (i = 0; i < dba_lengths[seg]; i++) { mask[band++] += delta; } } } return 0; }