/* * 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;}