| /* |
| * 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; |
| } |
