/* * The simplest AC-3 encoder * Copyright (c) 2000 Fabrice Bellard * Copyright (c) 2006-2010 Justin Ruggles * Copyright (c) 2006-2010 Prakash Punnoor * * 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 * The simplest AC-3 encoder. */ //#define DEBUG #include "libavcore/audioconvert.h" #include "libavutil/crc.h" #include "avcodec.h" #include "put_bits.h" #include "dsputil.h" #include "ac3.h" #include "audioconvert.h" /** Maximum number of exponent groups. +1 for separate DC exponent. */ #define AC3_MAX_EXP_GROUPS 85 /** Scale a float value by 2^bits and convert to an integer. */ #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits))) /** Scale a float value by 2^15, convert to an integer, and clip to range -32767..32767. */ #define FIX15(a) av_clip(SCALE_FLOAT(a, 15), -32767, 32767) /** * Compex number. * Used in fixed-point MDCT calculation. */ typedef struct IComplex { int16_t re,im; } IComplex; typedef struct AC3MDCTContext { AVCodecContext *avctx; ///< parent context for av_log() int nbits; ///< log2(transform size) int16_t *costab; ///< FFT cos table int16_t *sintab; ///< FFT sin table int16_t *xcos1; ///< MDCT cos table int16_t *xsin1; ///< MDCT sin table int16_t *rot_tmp; ///< temp buffer for pre-rotated samples IComplex *cplx_tmp; ///< temp buffer for complex pre-rotated samples } AC3MDCTContext; /** * Data for a single audio block. */ typedef struct AC3Block { uint8_t **bap; ///< bit allocation pointers (bap) int32_t **mdct_coef; ///< MDCT coefficients uint8_t **exp; ///< original exponents uint8_t **grouped_exp; ///< grouped exponents int16_t **psd; ///< psd per frequency bin int16_t **band_psd; ///< psd per critical band int16_t **mask; ///< masking curve uint16_t **qmant; ///< quantized mantissas uint8_t exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values } AC3Block; /** * AC-3 encoder private context. */ typedef struct AC3EncodeContext { PutBitContext pb; ///< bitstream writer context DSPContext dsp; AC3MDCTContext mdct; ///< MDCT context AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info int bitstream_id; ///< bitstream id (bsid) int bitstream_mode; ///< bitstream mode (bsmod) int bit_rate; ///< target bit rate, in bits-per-second int sample_rate; ///< sampling frequency, in Hz int frame_size_min; ///< minimum frame size in case rounding is necessary int frame_size; ///< current frame size in bytes int frame_size_code; ///< frame size code (frmsizecod) uint16_t crc_inv[2]; int bits_written; ///< bit count (used to avg. bitrate) int samples_written; ///< sample count (used to avg. bitrate) int fbw_channels; ///< number of full-bandwidth channels (nfchans) int channels; ///< total number of channels (nchans) int lfe_on; ///< indicates if there is an LFE channel (lfeon) int lfe_channel; ///< channel index of the LFE channel int channel_mode; ///< channel mode (acmod) const uint8_t *channel_map; ///< channel map used to reorder channels int cutoff; ///< user-specified cutoff frequency, in Hz int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod) int nb_coefs[AC3_MAX_CHANNELS]; /* bitrate allocation control */ int slow_gain_code; ///< slow gain code (sgaincod) int slow_decay_code; ///< slow decay code (sdcycod) int fast_decay_code; ///< fast decay code (fdcycod) int db_per_bit_code; ///< dB/bit code (dbpbcod) int floor_code; ///< floor code (floorcod) AC3BitAllocParameters bit_alloc; ///< bit allocation parameters int coarse_snr_offset; ///< coarse SNR offsets (csnroffst) int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod) int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst) int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters int frame_bits; ///< all frame bits except exponents and mantissas int exponent_bits; ///< number of bits used for exponents /* mantissa encoding */ int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4 int16_t **planar_samples; uint8_t *bap_buffer; uint8_t *bap1_buffer; int32_t *mdct_coef_buffer; uint8_t *exp_buffer; uint8_t *grouped_exp_buffer; int16_t *psd_buffer; int16_t *band_psd_buffer; int16_t *mask_buffer; uint16_t *qmant_buffer; DECLARE_ALIGNED(16, int16_t, windowed_samples)[AC3_WINDOW_SIZE]; } AC3EncodeContext; /** * LUT for number of exponent groups. * exponent_group_tab[exponent strategy-1][number of coefficients] */ uint8_t exponent_group_tab[3][256]; /** * Adjust the frame size to make the average bit rate match the target bit rate. * This is only needed for 11025, 22050, and 44100 sample rates. */ static void adjust_frame_size(AC3EncodeContext *s) { while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) { s->bits_written -= s->bit_rate; s->samples_written -= s->sample_rate; } s->frame_size = s->frame_size_min + 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate); s->bits_written += s->frame_size * 8; s->samples_written += AC3_FRAME_SIZE; } /** * Deinterleave input samples. * Channels are reordered from FFmpeg's default order to AC-3 order. */ static void deinterleave_input_samples(AC3EncodeContext *s, const int16_t *samples) { int ch, i; /* deinterleave and remap input samples */ for (ch = 0; ch < s->channels; ch++) { const int16_t *sptr; int sinc; /* copy last 256 samples of previous frame to the start of the current frame */ memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE], AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0])); /* deinterleave */ sinc = s->channels; sptr = samples + s->channel_map[ch]; for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) { s->planar_samples[ch][i] = *sptr; sptr += sinc; } } } /** * Finalize MDCT and free allocated memory. */ static av_cold void mdct_end(AC3MDCTContext *mdct) { mdct->nbits = 0; av_freep(&mdct->costab); av_freep(&mdct->sintab); av_freep(&mdct->xcos1); av_freep(&mdct->xsin1); av_freep(&mdct->rot_tmp); av_freep(&mdct->cplx_tmp); } /** * Initialize FFT tables. * @param ln log2(FFT size) */ static av_cold int fft_init(AC3MDCTContext *mdct, int ln) { int i, n, n2; float alpha; n = 1 << ln; n2 = n >> 1; FF_ALLOC_OR_GOTO(mdct->avctx, mdct->costab, n2 * sizeof(*mdct->costab), fft_alloc_fail); FF_ALLOC_OR_GOTO(mdct->avctx, mdct->sintab, n2 * sizeof(*mdct->sintab), fft_alloc_fail); for (i = 0; i < n2; i++) { alpha = 2.0 * M_PI * i / n; mdct->costab[i] = FIX15(cos(alpha)); mdct->sintab[i] = FIX15(sin(alpha)); } return 0; fft_alloc_fail: mdct_end(mdct); return AVERROR(ENOMEM); } /** * Initialize MDCT tables. * @param nbits log2(MDCT size) */ static av_cold int mdct_init(AC3MDCTContext *mdct, int nbits) { int i, n, n4, ret; n = 1 << nbits; n4 = n >> 2; mdct->nbits = nbits; ret = fft_init(mdct, nbits - 2); if (ret) return ret; FF_ALLOC_OR_GOTO(mdct->avctx, mdct->xcos1, n4 * sizeof(*mdct->xcos1), mdct_alloc_fail); FF_ALLOC_OR_GOTO(mdct->avctx, mdct->xsin1 , n4 * sizeof(*mdct->xsin1), mdct_alloc_fail); FF_ALLOC_OR_GOTO(mdct->avctx, mdct->rot_tmp, n * sizeof(*mdct->rot_tmp), mdct_alloc_fail); FF_ALLOC_OR_GOTO(mdct->avctx, mdct->cplx_tmp, n4 * sizeof(*mdct->cplx_tmp), mdct_alloc_fail); for (i = 0; i < n4; i++) { float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n; mdct->xcos1[i] = FIX15(-cos(alpha)); mdct->xsin1[i] = FIX15(-sin(alpha)); } return 0; mdct_alloc_fail: mdct_end(mdct); return AVERROR(ENOMEM); } /** Butterfly op */ #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \ { \ int ax, ay, bx, by; \ bx = pre1; \ by = pim1; \ ax = qre1; \ ay = qim1; \ pre = (bx + ax) >> 1; \ pim = (by + ay) >> 1; \ qre = (bx - ax) >> 1; \ qim = (by - ay) >> 1; \ } /** Complex multiply */ #define CMUL(pre, pim, are, aim, bre, bim) \ { \ pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \ pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \ } /** * Calculate a 2^n point complex FFT on 2^ln points. * @param z complex input/output samples * @param ln log2(FFT size) */ static void fft(AC3MDCTContext *mdct, IComplex *z, int ln) { int j, l, np, np2; int nblocks, nloops; register IComplex *p,*q; int tmp_re, tmp_im; np = 1 << ln; /* reverse */ for (j = 0; j < np; j++) { int k = av_reverse[j] >> (8 - ln); if (k < j) FFSWAP(IComplex, z[k], z[j]); } /* pass 0 */ p = &z[0]; j = np >> 1; do { BF(p[0].re, p[0].im, p[1].re, p[1].im, p[0].re, p[0].im, p[1].re, p[1].im); p += 2; } while (--j); /* pass 1 */ p = &z[0]; j = np >> 2; do { BF(p[0].re, p[0].im, p[2].re, p[2].im, p[0].re, p[0].im, p[2].re, p[2].im); BF(p[1].re, p[1].im, p[3].re, p[3].im, p[1].re, p[1].im, p[3].im, -p[3].re); p+=4; } while (--j); /* pass 2 .. ln-1 */ nblocks = np >> 3; nloops = 1 << 2; np2 = np >> 1; do { p = z; q = z + nloops; for (j = 0; j < nblocks; j++) { BF(p->re, p->im, q->re, q->im, p->re, p->im, q->re, q->im); p++; q++; for(l = nblocks; l < np2; l += nblocks) { CMUL(tmp_re, tmp_im, mdct->costab[l], -mdct->sintab[l], q->re, q->im); BF(p->re, p->im, q->re, q->im, p->re, p->im, tmp_re, tmp_im); p++; q++; } p += nloops; q += nloops; } nblocks = nblocks >> 1; nloops = nloops << 1; } while (nblocks); } /** * Calculate a 512-point MDCT * @param out 256 output frequency coefficients * @param in 512 windowed input audio samples */ static void mdct512(AC3MDCTContext *mdct, int32_t *out, int16_t *in) { int i, re, im, n, n2, n4; int16_t *rot = mdct->rot_tmp; IComplex *x = mdct->cplx_tmp; n = 1 << mdct->nbits; n2 = n >> 1; n4 = n >> 2; /* shift to simplify computations */ for (i = 0; i > 1; im = -((int)rot[n2+2*i] - (int)rot[n2-1-2*i]) >> 1; CMUL(x[i].re, x[i].im, re, im, -mdct->xcos1[i], mdct->xsin1[i]); } fft(mdct, x, mdct->nbits - 2); /* post rotation */ for (i = 0; i < n4; i++) { re = x[i].re; im = x[i].im; CMUL(out[n2-1-2*i], out[2*i], re, im, mdct->xsin1[i], mdct->xcos1[i]); } } /** * Apply KBD window to input samples prior to MDCT. */ static void apply_window(int16_t *output, const int16_t *input, const int16_t *window, int n) { int i; int n2 = n >> 1; for (i = 0; i < n2; i++) { output[i] = MUL16(input[i], window[i]) >> 15; output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15; } } /** * Calculate the log2() of the maximum absolute value in an array. * @param tab input array * @param n number of values in the array * @return log2(max(abs(tab[]))) */ static int log2_tab(int16_t *tab, int n) { int i, v; v = 0; for (i = 0; i < n; i++) v |= abs(tab[i]); return av_log2(v); } /** * Left-shift each value in an array by a specified amount. * @param tab input array * @param n number of values in the array * @param lshift left shift amount. a negative value means right shift. */ static void lshift_tab(int16_t *tab, int n, int lshift) { int i; if (lshift > 0) { for (i = 0; i < n; i++) tab[i] <<= lshift; } else if (lshift < 0) { lshift = -lshift; for (i = 0; i < n; i++) tab[i] >>= lshift; } } /** * Normalize the input samples to use the maximum available precision. * This assumes signed 16-bit input samples. Exponents are reduced by 9 to * match the 24-bit internal precision for MDCT coefficients. * * @return exponent shift */ static int normalize_samples(AC3EncodeContext *s) { int v = 14 - log2_tab(s->windowed_samples, AC3_WINDOW_SIZE); v = FFMAX(0, v); lshift_tab(s->windowed_samples, AC3_WINDOW_SIZE, v); return v - 9; } /** * Apply the MDCT to input samples to generate frequency coefficients. * This applies the KBD window and normalizes the input to reduce precision * loss due to fixed-point calculations. */ static void apply_mdct(AC3EncodeContext *s) { int blk, ch; for (ch = 0; ch < s->channels; ch++) { for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; const int16_t *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE]; apply_window(s->windowed_samples, input_samples, ff_ac3_window, AC3_WINDOW_SIZE); block->exp_shift[ch] = normalize_samples(s); mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples); } } } /** * Initialize exponent tables. */ static av_cold void exponent_init(AC3EncodeContext *s) { int i; for (i = 73; i < 256; i++) { exponent_group_tab[0][i] = (i - 1) / 3; exponent_group_tab[1][i] = (i + 2) / 6; exponent_group_tab[2][i] = (i + 8) / 12; } /* LFE */ exponent_group_tab[0][7] = 2; } /** * Extract exponents from the MDCT coefficients. * This takes into account the normalization that was done to the input samples * by adjusting the exponents by the exponent shift values. */ static void extract_exponents(AC3EncodeContext *s) { int blk, ch, i; for (ch = 0; ch < s->channels; ch++) { for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; for (i = 0; i < AC3_MAX_COEFS; i++) { int e; int v = abs(block->mdct_coef[ch][i]); if (v == 0) e = 24; else { e = 23 - av_log2(v) + block->exp_shift[ch]; if (e >= 24) { e = 24; block->mdct_coef[ch][i] = 0; } } block->exp[ch][i] = e; } } } } /** * Exponent Difference Threshold. * New exponents are sent if their SAD exceed this number. */ #define EXP_DIFF_THRESHOLD 1000 /** * Calculate exponent strategies for all blocks in a single channel. */ static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy, uint8_t **exp) { int blk, blk1; int exp_diff; /* estimate if the exponent variation & decide if they should be reused in the next frame */ exp_strategy[0] = EXP_NEW; for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) { exp_diff = s->dsp.sad[0](NULL, exp[blk], exp[blk-1], 16, 16); if (exp_diff > EXP_DIFF_THRESHOLD) exp_strategy[blk] = EXP_NEW; else exp_strategy[blk] = EXP_REUSE; } emms_c(); /* now select the encoding strategy type : if exponents are often recoded, we use a coarse encoding */ blk = 0; while (blk < AC3_MAX_BLOCKS) { blk1 = blk + 1; while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE) blk1++; switch (blk1 - blk) { case 1: exp_strategy[blk] = EXP_D45; break; case 2: case 3: exp_strategy[blk] = EXP_D25; break; default: exp_strategy[blk] = EXP_D15; break; } blk = blk1; } } /** * Calculate exponent strategies for all channels. * Array arrangement is reversed to simplify the per-channel calculation. */ static void compute_exp_strategy(AC3EncodeContext *s) { uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; int ch, blk; for (ch = 0; ch < s->fbw_channels; ch++) { for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { exp1[ch][blk] = s->blocks[blk].exp[ch]; exp_str1[ch][blk] = s->blocks[blk].exp_strategy[ch]; } compute_exp_strategy_ch(s, exp_str1[ch], exp1[ch]); for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) s->blocks[blk].exp_strategy[ch] = exp_str1[ch][blk]; } if (s->lfe_on) { ch = s->lfe_channel; s->blocks[0].exp_strategy[ch] = EXP_D15; for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) s->blocks[blk].exp_strategy[ch] = EXP_REUSE; } } /** * Set each encoded exponent in a block to the minimum of itself and the * exponent in the same frequency bin of a following block. * exp[i] = min(exp[i], exp1[i] */ static void exponent_min(uint8_t *exp, uint8_t *exp1, int n) { int i; for (i = 0; i < n; i++) { if (exp1[i] < exp[i]) exp[i] = exp1[i]; } } /** * Update the exponents so that they are the ones the decoder will decode. */ static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy) { int nb_groups, i, k; nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3; /* for each group, compute the minimum exponent */ switch(exp_strategy) { case EXP_D25: for (i = 1, k = 1; i <= nb_groups; i++) { uint8_t exp_min = exp[k]; if (exp[k+1] < exp_min) exp_min = exp[k+1]; exp[i] = exp_min; k += 2; } break; case EXP_D45: for (i = 1, k = 1; i <= nb_groups; i++) { uint8_t exp_min = exp[k]; if (exp[k+1] < exp_min) exp_min = exp[k+1]; if (exp[k+2] < exp_min) exp_min = exp[k+2]; if (exp[k+3] < exp_min) exp_min = exp[k+3]; exp[i] = exp_min; k += 4; } break; } /* constraint for DC exponent */ if (exp[0] > 15) exp[0] = 15; /* decrease the delta between each groups to within 2 so that they can be differentially encoded */ for (i = 1; i <= nb_groups; i++) exp[i] = FFMIN(exp[i], exp[i-1] + 2); i--; while (--i >= 0) exp[i] = FFMIN(exp[i], exp[i+1] + 2); /* now we have the exponent values the decoder will see */ switch (exp_strategy) { case EXP_D25: for (i = nb_groups, k = nb_groups * 2; i > 0; i--) { uint8_t exp1 = exp[i]; exp[k--] = exp1; exp[k--] = exp1; } break; case EXP_D45: for (i = nb_groups, k = nb_groups * 4; i > 0; i--) { exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i]; k -= 4; } break; } } /** * Encode exponents from original extracted form to what the decoder will see. * This copies and groups exponents based on exponent strategy and reduces * deltas between adjacent exponent groups so that they can be differentially * encoded. */ static void encode_exponents(AC3EncodeContext *s) { int blk, blk1, blk2, ch; AC3Block *block, *block1, *block2; for (ch = 0; ch < s->channels; ch++) { blk = 0; block = &s->blocks[0]; while (blk < AC3_MAX_BLOCKS) { blk1 = blk + 1; block1 = block + 1; /* for the EXP_REUSE case we select the min of the exponents */ while (blk1 < AC3_MAX_BLOCKS && block1->exp_strategy[ch] == EXP_REUSE) { exponent_min(block->exp[ch], block1->exp[ch], s->nb_coefs[ch]); blk1++; block1++; } encode_exponents_blk_ch(block->exp[ch], s->nb_coefs[ch], block->exp_strategy[ch]); /* copy encoded exponents for reuse case */ block2 = block + 1; for (blk2 = blk+1; blk2 < blk1; blk2++, block2++) { memcpy(block2->exp[ch], block->exp[ch], s->nb_coefs[ch] * sizeof(uint8_t)); } blk = blk1; block = block1; } } } /** * Group exponents. * 3 delta-encoded exponents are in each 7-bit group. The number of groups * varies depending on exponent strategy and bandwidth. */ static void group_exponents(AC3EncodeContext *s) { int blk, ch, i; int group_size, nb_groups, bit_count; uint8_t *p; int delta0, delta1, delta2; int exp0, exp1; bit_count = 0; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; for (ch = 0; ch < s->channels; ch++) { if (block->exp_strategy[ch] == EXP_REUSE) { continue; } group_size = block->exp_strategy[ch] + (block->exp_strategy[ch] == EXP_D45); nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]]; bit_count += 4 + (nb_groups * 7); p = block->exp[ch]; /* DC exponent */ exp1 = *p++; block->grouped_exp[ch][0] = exp1; /* remaining exponents are delta encoded */ for (i = 1; i <= nb_groups; i++) { /* merge three delta in one code */ exp0 = exp1; exp1 = p[0]; p += group_size; delta0 = exp1 - exp0 + 2; exp0 = exp1; exp1 = p[0]; p += group_size; delta1 = exp1 - exp0 + 2; exp0 = exp1; exp1 = p[0]; p += group_size; delta2 = exp1 - exp0 + 2; block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2; } } } s->exponent_bits = bit_count; } /** * Calculate final exponents from the supplied MDCT coefficients and exponent shift. * Extract exponents from MDCT coefficients, calculate exponent strategies, * and encode final exponents. */ static void process_exponents(AC3EncodeContext *s) { extract_exponents(s); compute_exp_strategy(s); encode_exponents(s); group_exponents(s); } /** * Count frame bits that are based solely on fixed parameters. * This only has to be run once when the encoder is initialized. */ static void count_frame_bits_fixed(AC3EncodeContext *s) { static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 }; int blk; int frame_bits; /* assumptions: * no dynamic range codes * no channel coupling * no rematrixing * bit allocation parameters do not change between blocks * SNR offsets do not change between blocks * no delta bit allocation * no skipped data * no auxilliary data */ /* header size */ frame_bits = 65; frame_bits += frame_bits_inc[s->channel_mode]; /* audio blocks */ for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */ if (s->channel_mode == AC3_CHMODE_STEREO) { frame_bits++; /* rematstr */ if (!blk) frame_bits += 4; } frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */ if (s->lfe_on) frame_bits++; /* lfeexpstr */ frame_bits++; /* baie */ frame_bits++; /* snr */ frame_bits += 2; /* delta / skip */ } frame_bits++; /* cplinu for block 0 */ /* bit alloc info */ /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */ /* csnroffset[6] */ /* (fsnoffset[4] + fgaincod[4]) * c */ frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3); /* auxdatae, crcrsv */ frame_bits += 2; /* CRC */ frame_bits += 16; s->frame_bits_fixed = frame_bits; } /** * Initialize bit allocation. * Set default parameter codes and calculate parameter values. */ static void bit_alloc_init(AC3EncodeContext *s) { int ch; /* init default parameters */ s->slow_decay_code = 2; s->fast_decay_code = 1; s->slow_gain_code = 1; s->db_per_bit_code = 3; s->floor_code = 4; for (ch = 0; ch < s->channels; ch++) s->fast_gain_code[ch] = 4; /* initial snr offset */ s->coarse_snr_offset = 40; /* compute real values */ /* currently none of these values change during encoding, so we can just set them once at initialization */ s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift; s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift; s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code]; s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code]; s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code]; count_frame_bits_fixed(s); } /** * Count the bits used to encode the frame, minus exponents and mantissas. * Bits based on fixed parameters have already been counted, so now we just * have to add the bits based on parameters that change during encoding. */ static void count_frame_bits(AC3EncodeContext *s) { int blk, ch; int frame_bits = 0; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { uint8_t *exp_strategy = s->blocks[blk].exp_strategy; for (ch = 0; ch < s->fbw_channels; ch++) { if (exp_strategy[ch] != EXP_REUSE) frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */ } } s->frame_bits = s->frame_bits_fixed + frame_bits; } /** * Calculate the number of bits needed to encode a set of mantissas. */ static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs) { int bits, b, i; bits = 0; for (i = 0; i < nb_coefs; i++) { b = bap[i]; if (b <= 4) { // bap=1 to bap=4 will be counted in compute_mantissa_size_final mant_cnt[b]++; } else if (b <= 13) { // bap=5 to bap=13 use (bap-1) bits bits += b - 1; } else { // bap=14 uses 14 bits and bap=15 uses 16 bits bits += (b == 14) ? 14 : 16; } } return bits; } /** * Finalize the mantissa bit count by adding in the grouped mantissas. */ static int compute_mantissa_size_final(int mant_cnt[5]) { // bap=1 : 3 mantissas in 5 bits int bits = (mant_cnt[1] / 3) * 5; // bap=2 : 3 mantissas in 7 bits // bap=4 : 2 mantissas in 7 bits bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7; // bap=3 : each mantissa is 3 bits bits += mant_cnt[3] * 3; return bits; } /** * Calculate masking curve based on the final exponents. * Also calculate the power spectral densities to use in future calculations. */ static void bit_alloc_masking(AC3EncodeContext *s) { int blk, ch; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; for (ch = 0; ch < s->channels; ch++) { /* We only need psd and mask for calculating bap. Since we currently do not calculate bap when exponent strategy is EXP_REUSE we do not need to calculate psd or mask. */ if (block->exp_strategy[ch] != EXP_REUSE) { ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0, s->nb_coefs[ch], block->psd[ch], block->band_psd[ch]); ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch], 0, s->nb_coefs[ch], ff_ac3_fast_gain_tab[s->fast_gain_code[ch]], ch == s->lfe_channel, DBA_NONE, 0, NULL, NULL, NULL, block->mask[ch]); } } } } /** * Ensure that bap for each block and channel point to the current bap_buffer. * They may have been switched during the bit allocation search. */ static void reset_block_bap(AC3EncodeContext *s) { int blk, ch; if (s->blocks[0].bap[0] == s->bap_buffer) return; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { for (ch = 0; ch < s->channels; ch++) { s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)]; } } } /** * Run the bit allocation with a given SNR offset. * This calculates the bit allocation pointers that will be used to determine * the quantization of each mantissa. * @return the number of bits needed for mantissas if the given SNR offset is * is used. */ static int bit_alloc(AC3EncodeContext *s, int snr_offset) { int blk, ch; int mantissa_bits; int mant_cnt[5]; snr_offset = (snr_offset - 240) << 2; reset_block_bap(s); mantissa_bits = 0; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; // initialize grouped mantissa counts. these are set so that they are // padded to the next whole group size when bits are counted in // compute_mantissa_size_final mant_cnt[0] = mant_cnt[3] = 0; mant_cnt[1] = mant_cnt[2] = 2; mant_cnt[4] = 1; for (ch = 0; ch < s->channels; ch++) { /* Currently the only bit allocation parameters which vary across blocks within a frame are the exponent values. We can take advantage of that by reusing the bit allocation pointers whenever we reuse exponents. */ if (block->exp_strategy[ch] == EXP_REUSE) { memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS); } else { ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0, s->nb_coefs[ch], snr_offset, s->bit_alloc.floor, ff_ac3_bap_tab, block->bap[ch]); } mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]); } mantissa_bits += compute_mantissa_size_final(mant_cnt); } return mantissa_bits; } /** * Constant bitrate bit allocation search. * Find the largest SNR offset that will allow data to fit in the frame. */ static int cbr_bit_allocation(AC3EncodeContext *s) { int ch; int bits_left; int snr_offset, snr_incr; bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits); snr_offset = s->coarse_snr_offset << 4; while (snr_offset >= 0 && bit_alloc(s, snr_offset) > bits_left) { snr_offset -= 64; } if (snr_offset < 0) return AVERROR(EINVAL); FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer); for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) { while (snr_offset + 64 <= 1023 && bit_alloc(s, snr_offset + snr_incr) <= bits_left) { snr_offset += snr_incr; FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer); } } FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer); reset_block_bap(s); s->coarse_snr_offset = snr_offset >> 4; for (ch = 0; ch < s->channels; ch++) s->fine_snr_offset[ch] = snr_offset & 0xF; return 0; } /** * Downgrade exponent strategies to reduce the bits used by the exponents. * This is a fallback for when bit allocation fails with the normal exponent * strategies. Each time this function is run it only downgrades the * strategy in 1 channel of 1 block. * @return non-zero if downgrade was unsuccessful */ static int downgrade_exponents(AC3EncodeContext *s) { int ch, blk; for (ch = 0; ch < s->fbw_channels; ch++) { for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) { if (s->blocks[blk].exp_strategy[ch] == EXP_D15) { s->blocks[blk].exp_strategy[ch] = EXP_D25; return 0; } } } for (ch = 0; ch < s->fbw_channels; ch++) { for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) { if (s->blocks[blk].exp_strategy[ch] == EXP_D25) { s->blocks[blk].exp_strategy[ch] = EXP_D45; return 0; } } } for (ch = 0; ch < s->fbw_channels; ch++) { /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if the block number > 0 */ for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) { if (s->blocks[blk].exp_strategy[ch] > EXP_REUSE) { s->blocks[blk].exp_strategy[ch] = EXP_REUSE; return 0; } } } return -1; } /** * Reduce the bandwidth to reduce the number of bits used for a given SNR offset. * This is a second fallback for when bit allocation still fails after exponents * have been downgraded. * @return non-zero if bandwidth reduction was unsuccessful */ static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code) { int ch; if (s->bandwidth_code[0] > min_bw_code) { for (ch = 0; ch < s->fbw_channels; ch++) { s->bandwidth_code[ch]--; s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73; } return 0; } return -1; } /** * Perform bit allocation search. * Finds the SNR offset value that maximizes quality and fits in the specified * frame size. Output is the SNR offset and a set of bit allocation pointers * used to quantize the mantissas. */ static int compute_bit_allocation(AC3EncodeContext *s) { int ret; count_frame_bits(s); bit_alloc_masking(s); ret = cbr_bit_allocation(s); while (ret) { /* fallback 1: downgrade exponents */ if (!downgrade_exponents(s)) { extract_exponents(s); encode_exponents(s); group_exponents(s); ret = compute_bit_allocation(s); continue; } /* fallback 2: reduce bandwidth */ /* only do this if the user has not specified a specific cutoff frequency */ if (!s->cutoff && !reduce_bandwidth(s, 0)) { process_exponents(s); ret = compute_bit_allocation(s); continue; } /* fallbacks were not enough... */ break; } return ret; } /** * Symmetric quantization on 'levels' levels. */ static inline int sym_quant(int c, int e, int levels) { int v; if (c >= 0) { v = (levels * (c << e)) >> 24; v = (v + 1) >> 1; v = (levels >> 1) + v; } else { v = (levels * ((-c) << e)) >> 24; v = (v + 1) >> 1; v = (levels >> 1) - v; } assert(v >= 0 && v < levels); return v; } /** * Asymmetric quantization on 2^qbits levels. */ static inline int asym_quant(int c, int e, int qbits) { int lshift, m, v; lshift = e + qbits - 24; if (lshift >= 0) v = c << lshift; else v = c >> (-lshift); /* rounding */ v = (v + 1) >> 1; m = (1 << (qbits-1)); if (v >= m) v = m - 1; assert(v >= -m); return v & ((1 << qbits)-1); } /** * Quantize a set of mantissas for a single channel in a single block. */ static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *mdct_coef, int8_t exp_shift, uint8_t *exp, uint8_t *bap, uint16_t *qmant, int n) { int i; for (i = 0; i < n; i++) { int v; int c = mdct_coef[i]; int e = exp[i] - exp_shift; int b = bap[i]; switch (b) { case 0: v = 0; break; case 1: v = sym_quant(c, e, 3); switch (s->mant1_cnt) { case 0: s->qmant1_ptr = &qmant[i]; v = 9 * v; s->mant1_cnt = 1; break; case 1: *s->qmant1_ptr += 3 * v; s->mant1_cnt = 2; v = 128; break; default: *s->qmant1_ptr += v; s->mant1_cnt = 0; v = 128; break; } break; case 2: v = sym_quant(c, e, 5); switch (s->mant2_cnt) { case 0: s->qmant2_ptr = &qmant[i]; v = 25 * v; s->mant2_cnt = 1; break; case 1: *s->qmant2_ptr += 5 * v; s->mant2_cnt = 2; v = 128; break; default: *s->qmant2_ptr += v; s->mant2_cnt = 0; v = 128; break; } break; case 3: v = sym_quant(c, e, 7); break; case 4: v = sym_quant(c, e, 11); switch (s->mant4_cnt) { case 0: s->qmant4_ptr = &qmant[i]; v = 11 * v; s->mant4_cnt = 1; break; default: *s->qmant4_ptr += v; s->mant4_cnt = 0; v = 128; break; } break; case 5: v = sym_quant(c, e, 15); break; case 14: v = asym_quant(c, e, 14); break; case 15: v = asym_quant(c, e, 16); break; default: v = asym_quant(c, e, b - 1); break; } qmant[i] = v; } } /** * Quantize mantissas using coefficients, exponents, and bit allocation pointers. */ static void quantize_mantissas(AC3EncodeContext *s) { int blk, ch; for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0; s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL; for (ch = 0; ch < s->channels; ch++) { quantize_mantissas_blk_ch(s, block->mdct_coef[ch], block->exp_shift[ch], block->exp[ch], block->bap[ch], block->qmant[ch], s->nb_coefs[ch]); } } } /** * Write the AC-3 frame header to the output bitstream. */ static void output_frame_header(AC3EncodeContext *s) { put_bits(&s->pb, 16, 0x0b77); /* frame header */ put_bits(&s->pb, 16, 0); /* crc1: will be filled later */ put_bits(&s->pb, 2, s->bit_alloc.sr_code); put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2); put_bits(&s->pb, 5, s->bitstream_id); put_bits(&s->pb, 3, s->bitstream_mode); put_bits(&s->pb, 3, s->channel_mode); if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO) put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */ if (s->channel_mode & 0x04) put_bits(&s->pb, 2, 1); /* XXX -6 dB */ if (s->channel_mode == AC3_CHMODE_STEREO) put_bits(&s->pb, 2, 0); /* surround not indicated */ put_bits(&s->pb, 1, s->lfe_on); /* LFE */ put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */ put_bits(&s->pb, 1, 0); /* no compression control word */ put_bits(&s->pb, 1, 0); /* no lang code */ put_bits(&s->pb, 1, 0); /* no audio production info */ put_bits(&s->pb, 1, 0); /* no copyright */ put_bits(&s->pb, 1, 1); /* original bitstream */ put_bits(&s->pb, 1, 0); /* no time code 1 */ put_bits(&s->pb, 1, 0); /* no time code 2 */ put_bits(&s->pb, 1, 0); /* no additional bit stream info */ } /** * Write one audio block to the output bitstream. */ static void output_audio_block(AC3EncodeContext *s, int block_num) { int ch, i, baie, rbnd; AC3Block *block = &s->blocks[block_num]; /* block switching */ for (ch = 0; ch < s->fbw_channels; ch++) put_bits(&s->pb, 1, 0); /* dither flags */ for (ch = 0; ch < s->fbw_channels; ch++) put_bits(&s->pb, 1, 1); /* dynamic range codes */ put_bits(&s->pb, 1, 0); /* channel coupling */ if (!block_num) { put_bits(&s->pb, 1, 1); /* coupling strategy present */ put_bits(&s->pb, 1, 0); /* no coupling strategy */ } else { put_bits(&s->pb, 1, 0); /* no new coupling strategy */ } /* stereo rematrixing */ if (s->channel_mode == AC3_CHMODE_STEREO) { if (!block_num) { /* first block must define rematrixing (rematstr) */ put_bits(&s->pb, 1, 1); /* dummy rematrixing rematflg(1:4)=0 */ for (rbnd = 0; rbnd < 4; rbnd++) put_bits(&s->pb, 1, 0); } else { /* no matrixing (but should be used in the future) */ put_bits(&s->pb, 1, 0); } } /* exponent strategy */ for (ch = 0; ch < s->fbw_channels; ch++) put_bits(&s->pb, 2, block->exp_strategy[ch]); if (s->lfe_on) put_bits(&s->pb, 1, block->exp_strategy[s->lfe_channel]); /* bandwidth */ for (ch = 0; ch < s->fbw_channels; ch++) { if (block->exp_strategy[ch] != EXP_REUSE) put_bits(&s->pb, 6, s->bandwidth_code[ch]); } /* exponents */ for (ch = 0; ch < s->channels; ch++) { int nb_groups; if (block->exp_strategy[ch] == EXP_REUSE) continue; /* DC exponent */ put_bits(&s->pb, 4, block->grouped_exp[ch][0]); /* exponent groups */ nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]]; for (i = 1; i <= nb_groups; i++) put_bits(&s->pb, 7, block->grouped_exp[ch][i]); /* gain range info */ if (ch != s->lfe_channel) put_bits(&s->pb, 2, 0); } /* bit allocation info */ baie = (block_num == 0); put_bits(&s->pb, 1, baie); if (baie) { put_bits(&s->pb, 2, s->slow_decay_code); put_bits(&s->pb, 2, s->fast_decay_code); put_bits(&s->pb, 2, s->slow_gain_code); put_bits(&s->pb, 2, s->db_per_bit_code); put_bits(&s->pb, 3, s->floor_code); } /* snr offset */ put_bits(&s->pb, 1, baie); if (baie) { put_bits(&s->pb, 6, s->coarse_snr_offset); for (ch = 0; ch < s->channels; ch++) { put_bits(&s->pb, 4, s->fine_snr_offset[ch]); put_bits(&s->pb, 3, s->fast_gain_code[ch]); } } put_bits(&s->pb, 1, 0); /* no delta bit allocation */ put_bits(&s->pb, 1, 0); /* no data to skip */ /* mantissas */ for (ch = 0; ch < s->channels; ch++) { int b, q; for (i = 0; i < s->nb_coefs[ch]; i++) { q = block->qmant[ch][i]; b = block->bap[ch][i]; switch (b) { case 0: break; case 1: if (q != 128) put_bits(&s->pb, 5, q); break; case 2: if (q != 128) put_bits(&s->pb, 7, q); break; case 3: put_bits(&s->pb, 3, q); break; case 4: if (q != 128) put_bits(&s->pb, 7, q); break; case 14: put_bits(&s->pb, 14, q); break; case 15: put_bits(&s->pb, 16, q); break; default: put_bits(&s->pb, b-1, q); break; } } } } /** CRC-16 Polynomial */ #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16)) static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly) { unsigned int c; c = 0; while (a) { if (a & 1) c ^= b; a = a >> 1; b = b << 1; if (b & (1 << 16)) b ^= poly; } return c; } static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly) { unsigned int r; r = 1; while (n) { if (n & 1) r = mul_poly(r, a, poly); a = mul_poly(a, a, poly); n >>= 1; } return r; } /** * Fill the end of the frame with 0's and compute the two CRCs. */ static void output_frame_end(AC3EncodeContext *s) { const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI); int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv; uint8_t *frame; frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1; /* pad the remainder of the frame with zeros */ flush_put_bits(&s->pb); frame = s->pb.buf; pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2; assert(pad_bytes >= 0); if (pad_bytes > 0) memset(put_bits_ptr(&s->pb), 0, pad_bytes); /* compute crc1 */ /* this is not so easy because it is at the beginning of the data... */ crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4)); crc_inv = s->crc_inv[s->frame_size > s->frame_size_min]; crc1 = mul_poly(crc_inv, crc1, CRC16_POLY); AV_WB16(frame + 2, crc1); /* compute crc2 */ crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58, s->frame_size - frame_size_58 - 3); crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1); /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */ if (crc2 == 0x770B) { frame[s->frame_size - 3] ^= 0x1; crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1); } crc2 = av_bswap16(crc2); AV_WB16(frame + s->frame_size - 2, crc2); } /** * Write the frame to the output bitstream. */ static void output_frame(AC3EncodeContext *s, unsigned char *frame) { int blk; init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE); output_frame_header(s); for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) output_audio_block(s, blk); output_frame_end(s); } /** * Encode a single AC-3 frame. */ static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame, int buf_size, void *data) { AC3EncodeContext *s = avctx->priv_data; const int16_t *samples = data; int ret; if (s->bit_alloc.sr_code == 1) adjust_frame_size(s); deinterleave_input_samples(s, samples); apply_mdct(s); process_exponents(s); ret = compute_bit_allocation(s); if (ret) { av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n"); return ret; } quantize_mantissas(s); output_frame(s, frame); return s->frame_size; } /** * Finalize encoding and free any memory allocated by the encoder. */ static av_cold int ac3_encode_close(AVCodecContext *avctx) { int blk, ch; AC3EncodeContext *s = avctx->priv_data; for (ch = 0; ch < s->channels; ch++) av_freep(&s->planar_samples[ch]); av_freep(&s->planar_samples); av_freep(&s->bap_buffer); av_freep(&s->bap1_buffer); av_freep(&s->mdct_coef_buffer); av_freep(&s->exp_buffer); av_freep(&s->grouped_exp_buffer); av_freep(&s->psd_buffer); av_freep(&s->band_psd_buffer); av_freep(&s->mask_buffer); av_freep(&s->qmant_buffer); for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; av_freep(&block->bap); av_freep(&block->mdct_coef); av_freep(&block->exp); av_freep(&block->grouped_exp); av_freep(&block->psd); av_freep(&block->band_psd); av_freep(&block->mask); av_freep(&block->qmant); } mdct_end(&s->mdct); av_freep(&avctx->coded_frame); return 0; } /** * Set channel information during initialization. */ static av_cold int set_channel_info(AC3EncodeContext *s, int channels, int64_t *channel_layout) { int ch_layout; if (channels < 1 || channels > AC3_MAX_CHANNELS) return AVERROR(EINVAL); if ((uint64_t)*channel_layout > 0x7FF) return AVERROR(EINVAL); ch_layout = *channel_layout; if (!ch_layout) ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL); if (av_get_channel_layout_nb_channels(ch_layout) != channels) return AVERROR(EINVAL); s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY); s->channels = channels; s->fbw_channels = channels - s->lfe_on; s->lfe_channel = s->lfe_on ? s->fbw_channels : -1; if (s->lfe_on) ch_layout -= AV_CH_LOW_FREQUENCY; switch (ch_layout) { case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break; case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break; case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break; case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break; case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break; case AV_CH_LAYOUT_QUAD: case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break; case AV_CH_LAYOUT_5POINT0: case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break; default: return AVERROR(EINVAL); } s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on]; *channel_layout = ch_layout; if (s->lfe_on) *channel_layout |= AV_CH_LOW_FREQUENCY; return 0; } static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s) { int i, ret; /* validate channel layout */ if (!avctx->channel_layout) { av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The " "encoder will guess the layout, but it " "might be incorrect.\n"); } ret = set_channel_info(s, avctx->channels, &avctx->channel_layout); if (ret) { av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n"); return ret; } /* validate sample rate */ for (i = 0; i < 9; i++) { if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate) break; } if (i == 9) { av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n"); return AVERROR(EINVAL); } s->sample_rate = avctx->sample_rate; s->bit_alloc.sr_shift = i % 3; s->bit_alloc.sr_code = i / 3; /* validate bit rate */ for (i = 0; i < 19; i++) { if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate) break; } if (i == 19) { av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n"); return AVERROR(EINVAL); } s->bit_rate = avctx->bit_rate; s->frame_size_code = i << 1; /* validate cutoff */ if (avctx->cutoff < 0) { av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n"); return AVERROR(EINVAL); } s->cutoff = avctx->cutoff; if (s->cutoff > (s->sample_rate >> 1)) s->cutoff = s->sample_rate >> 1; return 0; } /** * Set bandwidth for all channels. * The user can optionally supply a cutoff frequency. Otherwise an appropriate * default value will be used. */ static av_cold void set_bandwidth(AC3EncodeContext *s) { int ch, bw_code; if (s->cutoff) { /* calculate bandwidth based on user-specified cutoff frequency */ int fbw_coeffs; fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate; bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60); } else { /* use default bandwidth setting */ /* XXX: should compute the bandwidth according to the frame size, so that we avoid annoying high frequency artifacts */ bw_code = 50; } /* set number of coefficients for each channel */ for (ch = 0; ch < s->fbw_channels; ch++) { s->bandwidth_code[ch] = bw_code; s->nb_coefs[ch] = bw_code * 3 + 73; } if (s->lfe_on) s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */ } static av_cold int allocate_buffers(AVCodecContext *avctx) { int blk, ch; AC3EncodeContext *s = avctx->priv_data; FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples), alloc_fail); for (ch = 0; ch < s->channels; ch++) { FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch], (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples), alloc_fail); } FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels * 128 * sizeof(*s->grouped_exp_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels * 64 * sizeof(*s->band_psd_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels * 64 * sizeof(*s->mask_buffer), alloc_fail); FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels * AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail); for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) { AC3Block *block = &s->blocks[blk]; FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask), alloc_fail); FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant), alloc_fail); for (ch = 0; ch < s->channels; ch++) { block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)]; block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)]; block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)]; block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)]; block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)]; block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)]; block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)]; block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)]; } } return 0; alloc_fail: return AVERROR(ENOMEM); } /** * Initialize the encoder. */ static av_cold int ac3_encode_init(AVCodecContext *avctx) { AC3EncodeContext *s = avctx->priv_data; int ret, frame_size_58; avctx->frame_size = AC3_FRAME_SIZE; ac3_common_init(); ret = validate_options(avctx, s); if (ret) return ret; s->bitstream_id = 8 + s->bit_alloc.sr_shift; s->bitstream_mode = 0; /* complete main audio service */ s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code]; s->bits_written = 0; s->samples_written = 0; s->frame_size = s->frame_size_min; /* calculate crc_inv for both possible frame sizes */ frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1; s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY); if (s->bit_alloc.sr_code == 1) { frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1; s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY); } set_bandwidth(s); exponent_init(s); bit_alloc_init(s); s->mdct.avctx = avctx; ret = mdct_init(&s->mdct, 9); if (ret) goto init_fail; ret = allocate_buffers(avctx); if (ret) goto init_fail; avctx->coded_frame= avcodec_alloc_frame(); dsputil_init(&s->dsp, avctx); return 0; init_fail: ac3_encode_close(avctx); return ret; } #ifdef TEST /*************************************************************************/ /* TEST */ #include "libavutil/lfg.h" #define MDCT_NBITS 9 #define MDCT_SAMPLES (1 << MDCT_NBITS) #define FN (MDCT_SAMPLES/4) static void fft_test(AC3MDCTContext *mdct, AVLFG *lfg) { IComplex in[FN], in1[FN]; int k, n, i; float sum_re, sum_im, a; for (i = 0; i < FN; i++) { in[i].re = av_lfg_get(lfg) % 65535 - 32767; in[i].im = av_lfg_get(lfg) % 65535 - 32767; in1[i] = in[i]; } fft(mdct, in, 7); /* do it by hand */ for (k = 0; k < FN; k++) { sum_re = 0; sum_im = 0; for (n = 0; n < FN; n++) { a = -2 * M_PI * (n * k) / FN; sum_re += in1[n].re * cos(a) - in1[n].im * sin(a); sum_im += in1[n].re * sin(a) + in1[n].im * cos(a); } av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n", k, in[k].re, in[k].im, sum_re / FN, sum_im / FN); } } static void mdct_test(AC3MDCTContext *mdct, AVLFG *lfg) { int16_t input[MDCT_SAMPLES]; int32_t output[AC3_MAX_COEFS]; float input1[MDCT_SAMPLES]; float output1[AC3_MAX_COEFS]; float s, a, err, e, emax; int i, k, n; for (i = 0; i < MDCT_SAMPLES; i++) { input[i] = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10; input1[i] = input[i]; } mdct512(mdct, output, input); /* do it by hand */ for (k = 0; k < AC3_MAX_COEFS; k++) { s = 0; for (n = 0; n < MDCT_SAMPLES; n++) { a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES)); s += input1[n] * cos(a); } output1[k] = -2 * s / MDCT_SAMPLES; } err = 0; emax = 0; for (i = 0; i < AC3_MAX_COEFS; i++) { av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]); e = output[i] - output1[i]; if (e > emax) emax = e; err += e * e; } av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax); } int main(void) { AVLFG lfg; AC3MDCTContext mdct; mdct.avctx = NULL; av_log_set_level(AV_LOG_DEBUG); mdct_init(&mdct, 9); fft_test(&mdct, &lfg); mdct_test(&mdct, &lfg); return 0; } #endif /* TEST */ AVCodec ac3_encoder = { "ac3", AVMEDIA_TYPE_AUDIO, CODEC_ID_AC3, sizeof(AC3EncodeContext), ac3_encode_init, ac3_encode_frame, ac3_encode_close, NULL, .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE}, .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"), .channel_layouts = (const int64_t[]){ AV_CH_LAYOUT_MONO, AV_CH_LAYOUT_STEREO, AV_CH_LAYOUT_2_1, AV_CH_LAYOUT_SURROUND, AV_CH_LAYOUT_2_2, AV_CH_LAYOUT_QUAD, AV_CH_LAYOUT_4POINT0, AV_CH_LAYOUT_5POINT0, AV_CH_LAYOUT_5POINT0_BACK, (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY), (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY), AV_CH_LAYOUT_5POINT1, AV_CH_LAYOUT_5POINT1_BACK, 0 }, };