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Diffstat (limited to 'contrib/ffmpeg/libavcodec/ac3.c')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/ac3.c | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/ac3.c b/contrib/ffmpeg/libavcodec/ac3.c new file mode 100644 index 000000000..cc80277bc --- /dev/null +++ b/contrib/ffmpeg/libavcodec/ac3.c @@ -0,0 +1,239 @@ +/* + * Common code between AC3 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 ac3.c + * Common code between AC3 encoder and decoder. + */ + +#include "avcodec.h" +#include "ac3.h" +#include "bitstream.h" + +static uint8_t band_start_tab[51]; +static uint8_t bin_to_band_tab[253]; + +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, i, j, k, end1, v; + + /* exponent mapping to PSD */ + for(bin=start;bin<end;bin++) { + psd[bin]=(3072 - (exp[bin] << 7)); + } + + /* PSD integration */ + j=start; + k=bin_to_band_tab[start]; + do { + v=psd[j]; + j++; + end1 = FFMIN(band_start_tab[k+1], end); + for(i=j;i<end1;i++) { + /* logadd */ + int adr = FFMIN(FFABS(v - psd[j]) >> 1, 255); + v = FFMAX(v, psd[j]) + ff_ac3_log_add_tab[adr]; + j++; + } + band_psd[k]=v; + k++; + } while (end > band_start_tab[k]); +} + +void 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[50]; /* excitation */ + int bin, k; + int bndstrt, bndend, begin, end1, tmp; + int lowcomp, fastleak, slowleak; + + /* excitation function */ + bndstrt = bin_to_band_tab[start]; + bndend = bin_to_band_tab[end-1] + 1; + + if (bndstrt == 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 (bin = 2; bin < 7; bin++) { + if (!(is_lfe && bin == 6)) + lowcomp = calc_lowcomp1(lowcomp, band_psd[bin], band_psd[bin+1], 384); + fastleak = band_psd[bin] - fast_gain; + slowleak = band_psd[bin] - s->slow_gain; + excite[bin] = fastleak - lowcomp; + if (!(is_lfe && bin == 6)) { + if (band_psd[bin] <= band_psd[bin+1]) { + begin = bin + 1; + break; + } + } + } + + end1=bndend; + if (end1 > 22) end1=22; + + for (bin = begin; bin < end1; bin++) { + if (!(is_lfe && bin == 6)) + lowcomp = calc_lowcomp(lowcomp, band_psd[bin], band_psd[bin+1], bin); + + fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain); + slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain); + excite[bin] = FFMAX(fastleak - lowcomp, slowleak); + } + begin = 22; + } else { + /* coupling channel */ + begin = bndstrt; + + fastleak = (s->cpl_fast_leak << 8) + 768; + slowleak = (s->cpl_slow_leak << 8) + 768; + } + + for (bin = begin; bin < bndend; bin++) { + fastleak = FFMAX(fastleak - s->fast_decay, band_psd[bin] - fast_gain); + slowleak = FFMAX(slowleak - s->slow_decay, band_psd[bin] - s->slow_gain); + excite[bin] = FFMAX(fastleak, slowleak); + } + + /* compute masking curve */ + + for (bin = bndstrt; bin < bndend; bin++) { + tmp = s->db_per_bit - band_psd[bin]; + if (tmp > 0) { + excite[bin] += tmp >> 2; + } + mask[bin] = FFMAX(ff_ac3_hearing_threshold_tab[bin >> s->sr_shift][s->sr_code], excite[bin]); + } + + /* delta bit allocation */ + + if (dba_mode == DBA_REUSE || dba_mode == DBA_NEW) { + int band, seg, delta; + band = 0; + for (seg = 0; seg < dba_nsegs; seg++) { + band += dba_offsets[seg]; + if (dba_values[seg] >= 4) { + delta = (dba_values[seg] - 3) << 7; + } else { + delta = (dba_values[seg] - 4) << 7; + } + for (k = 0; k < dba_lengths[seg]; k++) { + mask[band] += delta; + band++; + } + } + } +} + +void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end, + int snr_offset, int floor, uint8_t *bap) +{ + int i, j, k, end1, v, address; + + /* special case, if snr offset is -960, set all bap's to zero */ + if(snr_offset == -960) { + memset(bap, 0, 256); + return; + } + + i = start; + j = bin_to_band_tab[start]; + do { + v = (FFMAX(mask[j] - snr_offset - floor, 0) & 0x1FE0) + floor; + end1 = FFMIN(band_start_tab[j] + ff_ac3_critical_band_size_tab[j], end); + for (k = i; k < end1; k++) { + address = av_clip((psd[i] - v) >> 5, 0, 63); + bap[i] = ff_ac3_bap_tab[address]; + i++; + } + } while (end > band_start_tab[j++]); +} + +/* AC3 bit allocation. The algorithm is the one described in the AC3 + spec. */ +void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap, + int8_t *exp, int start, int end, + int snr_offset, 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 psd[256]; /* scaled exponents */ + int16_t band_psd[50]; /* interpolated exponents */ + int16_t mask[50]; /* masking value */ + + ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, band_psd); + + ff_ac3_bit_alloc_calc_mask(s, band_psd, start, end, fast_gain, is_lfe, + dba_mode, dba_nsegs, dba_offsets, dba_lengths, dba_values, + mask); + + ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snr_offset, s->floor, bap); +} + +/** + * Initializes some tables. + * note: This function must remain thread safe because it is called by the + * AVParser init code. + */ +void ac3_common_init(void) +{ + int i, j, k, l, v; + /* compute bndtab and masktab from bandsz */ + k = 0; + l = 0; + for(i=0;i<50;i++) { + band_start_tab[i] = l; + v = ff_ac3_critical_band_size_tab[i]; + for(j=0;j<v;j++) bin_to_band_tab[k++]=i; + l += v; + } + band_start_tab[50] = l; +} |