2 * The simplest AC-3 encoder
3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
5 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 * The simplest AC-3 encoder.
31 #include "libavcore/audioconvert.h"
32 #include "libavutil/crc.h"
37 #include "audioconvert.h"
40 #ifndef CONFIG_AC3ENC_FLOAT
41 #define CONFIG_AC3ENC_FLOAT 0
45 /** Maximum number of exponent groups. +1 for separate DC exponent. */
46 #define AC3_MAX_EXP_GROUPS 85
48 /* stereo rematrixing algorithms */
49 #define AC3_REMATRIXING_IS_STATIC 0x1
50 #define AC3_REMATRIXING_SUMS 0
51 #define AC3_REMATRIXING_NONE 1
52 #define AC3_REMATRIXING_ALWAYS 3
54 /** Scale a float value by 2^bits and convert to an integer. */
55 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
58 #if CONFIG_AC3ENC_FLOAT
59 #include "ac3enc_float.h"
61 #include "ac3enc_fixed.h"
66 * Data for a single audio block.
68 typedef struct AC3Block {
69 uint8_t **bap; ///< bit allocation pointers (bap)
70 CoefType **mdct_coef; ///< MDCT coefficients
71 int32_t **fixed_coef; ///< fixed-point MDCT coefficients
72 uint8_t **exp; ///< original exponents
73 uint8_t **grouped_exp; ///< grouped exponents
74 int16_t **psd; ///< psd per frequency bin
75 int16_t **band_psd; ///< psd per critical band
76 int16_t **mask; ///< masking curve
77 uint16_t **qmant; ///< quantized mantissas
78 uint8_t exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
79 int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values
80 uint8_t new_rematrixing_strategy; ///< send new rematrixing flags in this block
81 uint8_t rematrixing_flags[4]; ///< rematrixing flags
85 * AC-3 encoder private context.
87 typedef struct AC3EncodeContext {
88 PutBitContext pb; ///< bitstream writer context
90 AC3MDCTContext mdct; ///< MDCT context
92 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
94 int bitstream_id; ///< bitstream id (bsid)
95 int bitstream_mode; ///< bitstream mode (bsmod)
97 int bit_rate; ///< target bit rate, in bits-per-second
98 int sample_rate; ///< sampling frequency, in Hz
100 int frame_size_min; ///< minimum frame size in case rounding is necessary
101 int frame_size; ///< current frame size in bytes
102 int frame_size_code; ///< frame size code (frmsizecod)
104 int bits_written; ///< bit count (used to avg. bitrate)
105 int samples_written; ///< sample count (used to avg. bitrate)
107 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
108 int channels; ///< total number of channels (nchans)
109 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
110 int lfe_channel; ///< channel index of the LFE channel
111 int channel_mode; ///< channel mode (acmod)
112 const uint8_t *channel_map; ///< channel map used to reorder channels
114 int cutoff; ///< user-specified cutoff frequency, in Hz
115 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
116 int nb_coefs[AC3_MAX_CHANNELS];
118 int rematrixing; ///< determines how rematrixing strategy is calculated
120 /* bitrate allocation control */
121 int slow_gain_code; ///< slow gain code (sgaincod)
122 int slow_decay_code; ///< slow decay code (sdcycod)
123 int fast_decay_code; ///< fast decay code (fdcycod)
124 int db_per_bit_code; ///< dB/bit code (dbpbcod)
125 int floor_code; ///< floor code (floorcod)
126 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
127 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
128 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
129 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
130 int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
131 int frame_bits; ///< all frame bits except exponents and mantissas
132 int exponent_bits; ///< number of bits used for exponents
134 /* mantissa encoding */
135 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
136 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
138 SampleType **planar_samples;
140 uint8_t *bap1_buffer;
141 CoefType *mdct_coef_buffer;
142 int32_t *fixed_coef_buffer;
144 uint8_t *grouped_exp_buffer;
146 int16_t *band_psd_buffer;
147 int16_t *mask_buffer;
148 uint16_t *qmant_buffer;
150 DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
154 /* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */
156 static av_cold void mdct_end(AC3MDCTContext *mdct);
158 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
161 static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in);
163 static void apply_window(SampleType *output, const SampleType *input,
164 const SampleType *window, int n);
166 static int normalize_samples(AC3EncodeContext *s);
168 static void scale_coefficients(AC3EncodeContext *s);
172 * LUT for number of exponent groups.
173 * exponent_group_tab[exponent strategy-1][number of coefficients]
175 static uint8_t exponent_group_tab[3][256];
179 * List of supported channel layouts.
181 static const int64_t ac3_channel_layouts[] = {
185 AV_CH_LAYOUT_SURROUND,
188 AV_CH_LAYOUT_4POINT0,
189 AV_CH_LAYOUT_5POINT0,
190 AV_CH_LAYOUT_5POINT0_BACK,
191 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
192 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
193 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
194 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
195 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
196 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
197 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
198 AV_CH_LAYOUT_5POINT1,
199 AV_CH_LAYOUT_5POINT1_BACK,
205 * Adjust the frame size to make the average bit rate match the target bit rate.
206 * This is only needed for 11025, 22050, and 44100 sample rates.
208 static void adjust_frame_size(AC3EncodeContext *s)
210 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
211 s->bits_written -= s->bit_rate;
212 s->samples_written -= s->sample_rate;
214 s->frame_size = s->frame_size_min +
215 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
216 s->bits_written += s->frame_size * 8;
217 s->samples_written += AC3_FRAME_SIZE;
222 * Deinterleave input samples.
223 * Channels are reordered from FFmpeg's default order to AC-3 order.
225 static void deinterleave_input_samples(AC3EncodeContext *s,
226 const SampleType *samples)
230 /* deinterleave and remap input samples */
231 for (ch = 0; ch < s->channels; ch++) {
232 const SampleType *sptr;
235 /* copy last 256 samples of previous frame to the start of the current frame */
236 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
237 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
241 sptr = samples + s->channel_map[ch];
242 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
243 s->planar_samples[ch][i] = *sptr;
251 * Apply the MDCT to input samples to generate frequency coefficients.
252 * This applies the KBD window and normalizes the input to reduce precision
253 * loss due to fixed-point calculations.
255 static void apply_mdct(AC3EncodeContext *s)
259 for (ch = 0; ch < s->channels; ch++) {
260 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
261 AC3Block *block = &s->blocks[blk];
262 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
264 apply_window(s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
266 block->exp_shift[ch] = normalize_samples(s);
268 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
275 * Initialize stereo rematrixing.
276 * If the strategy does not change for each frame, set the rematrixing flags.
278 static void rematrixing_init(AC3EncodeContext *s)
280 if (s->channel_mode == AC3_CHMODE_STEREO)
281 s->rematrixing = AC3_REMATRIXING_SUMS;
283 s->rematrixing = AC3_REMATRIXING_NONE;
284 /* NOTE: AC3_REMATRIXING_ALWAYS might be used in
285 the future in conjunction with channel coupling. */
287 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC) {
288 int flag = (s->rematrixing == AC3_REMATRIXING_ALWAYS);
289 s->blocks[0].new_rematrixing_strategy = 1;
290 memset(s->blocks[0].rematrixing_flags, flag,
291 sizeof(s->blocks[0].rematrixing_flags));
297 * Determine rematrixing flags for each block and band.
299 static void compute_rematrixing_strategy(AC3EncodeContext *s)
303 AC3Block *block, *block0;
305 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC)
308 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
310 s->blocks[0].new_rematrixing_strategy = 1;
311 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
312 block = &s->blocks[blk];
313 for (bnd = 0; bnd < 4; bnd++) {
314 /* calculate calculate sum of squared coeffs for one band in one block */
315 int start = ff_ac3_rematrix_band_tab[bnd];
316 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
317 CoefSumType sum[4] = {0,};
318 for (i = start; i < end; i++) {
319 CoefType lt = block->mdct_coef[0][i];
320 CoefType rt = block->mdct_coef[1][i];
321 CoefType md = lt + rt;
322 CoefType sd = lt - rt;
329 /* compare sums to determine if rematrixing will be used for this band */
330 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
331 block->rematrixing_flags[bnd] = 1;
333 block->rematrixing_flags[bnd] = 0;
335 /* determine if new rematrixing flags will be sent */
337 !block->new_rematrixing_strategy &&
338 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
339 block->new_rematrixing_strategy = 1;
348 * Apply stereo rematrixing to coefficients based on rematrixing flags.
350 static void apply_rematrixing(AC3EncodeContext *s)
357 if (s->rematrixing == AC3_REMATRIXING_NONE)
360 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
362 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
363 AC3Block *block = &s->blocks[blk];
364 if (block->new_rematrixing_strategy)
365 flags = block->rematrixing_flags;
366 for (bnd = 0; bnd < 4; bnd++) {
368 start = ff_ac3_rematrix_band_tab[bnd];
369 end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
370 for (i = start; i < end; i++) {
371 int32_t lt = block->fixed_coef[0][i];
372 int32_t rt = block->fixed_coef[1][i];
373 block->fixed_coef[0][i] = (lt + rt) >> 1;
374 block->fixed_coef[1][i] = (lt - rt) >> 1;
383 * Initialize exponent tables.
385 static av_cold void exponent_init(AC3EncodeContext *s)
388 for (i = 73; i < 256; i++) {
389 exponent_group_tab[0][i] = (i - 1) / 3;
390 exponent_group_tab[1][i] = (i + 2) / 6;
391 exponent_group_tab[2][i] = (i + 8) / 12;
394 exponent_group_tab[0][7] = 2;
399 * Extract exponents from the MDCT coefficients.
400 * This takes into account the normalization that was done to the input samples
401 * by adjusting the exponents by the exponent shift values.
403 static void extract_exponents(AC3EncodeContext *s)
407 for (ch = 0; ch < s->channels; ch++) {
408 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
409 AC3Block *block = &s->blocks[blk];
410 uint8_t *exp = block->exp[ch];
411 int32_t *coef = block->fixed_coef[ch];
412 int exp_shift = block->exp_shift[ch];
413 for (i = 0; i < AC3_MAX_COEFS; i++) {
415 int v = abs(coef[i]);
419 e = 23 - av_log2(v) + exp_shift;
433 * Exponent Difference Threshold.
434 * New exponents are sent if their SAD exceed this number.
436 #define EXP_DIFF_THRESHOLD 1000
440 * Calculate exponent strategies for all blocks in a single channel.
442 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
448 /* estimate if the exponent variation & decide if they should be
449 reused in the next frame */
450 exp_strategy[0] = EXP_NEW;
451 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
452 exp_diff = s->dsp.sad[0](NULL, exp[blk], exp[blk-1], 16, 16);
453 if (exp_diff > EXP_DIFF_THRESHOLD)
454 exp_strategy[blk] = EXP_NEW;
456 exp_strategy[blk] = EXP_REUSE;
460 /* now select the encoding strategy type : if exponents are often
461 recoded, we use a coarse encoding */
463 while (blk < AC3_MAX_BLOCKS) {
465 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
467 switch (blk1 - blk) {
468 case 1: exp_strategy[blk] = EXP_D45; break;
470 case 3: exp_strategy[blk] = EXP_D25; break;
471 default: exp_strategy[blk] = EXP_D15; break;
479 * Calculate exponent strategies for all channels.
480 * Array arrangement is reversed to simplify the per-channel calculation.
482 static void compute_exp_strategy(AC3EncodeContext *s)
484 uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
485 uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
488 for (ch = 0; ch < s->fbw_channels; ch++) {
489 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
490 exp1[ch][blk] = s->blocks[blk].exp[ch];
491 exp_str1[ch][blk] = s->blocks[blk].exp_strategy[ch];
494 compute_exp_strategy_ch(s, exp_str1[ch], exp1[ch]);
496 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
497 s->blocks[blk].exp_strategy[ch] = exp_str1[ch][blk];
501 s->blocks[0].exp_strategy[ch] = EXP_D15;
502 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
503 s->blocks[blk].exp_strategy[ch] = EXP_REUSE;
509 * Set each encoded exponent in a block to the minimum of itself and the
510 * exponent in the same frequency bin of a following block.
511 * exp[i] = min(exp[i], exp1[i]
513 static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
516 for (i = 0; i < n; i++) {
517 if (exp1[i] < exp[i])
524 * Update the exponents so that they are the ones the decoder will decode.
526 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
530 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
532 /* for each group, compute the minimum exponent */
533 switch(exp_strategy) {
535 for (i = 1, k = 1; i <= nb_groups; i++) {
536 uint8_t exp_min = exp[k];
537 if (exp[k+1] < exp_min)
544 for (i = 1, k = 1; i <= nb_groups; i++) {
545 uint8_t exp_min = exp[k];
546 if (exp[k+1] < exp_min)
548 if (exp[k+2] < exp_min)
550 if (exp[k+3] < exp_min)
558 /* constraint for DC exponent */
562 /* decrease the delta between each groups to within 2 so that they can be
563 differentially encoded */
564 for (i = 1; i <= nb_groups; i++)
565 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
568 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
570 /* now we have the exponent values the decoder will see */
571 switch (exp_strategy) {
573 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
574 uint8_t exp1 = exp[i];
580 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
581 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
590 * Encode exponents from original extracted form to what the decoder will see.
591 * This copies and groups exponents based on exponent strategy and reduces
592 * deltas between adjacent exponent groups so that they can be differentially
595 static void encode_exponents(AC3EncodeContext *s)
597 int blk, blk1, blk2, ch;
598 AC3Block *block, *block1, *block2;
600 for (ch = 0; ch < s->channels; ch++) {
602 block = &s->blocks[0];
603 while (blk < AC3_MAX_BLOCKS) {
606 /* for the EXP_REUSE case we select the min of the exponents */
607 while (blk1 < AC3_MAX_BLOCKS && block1->exp_strategy[ch] == EXP_REUSE) {
608 exponent_min(block->exp[ch], block1->exp[ch], s->nb_coefs[ch]);
612 encode_exponents_blk_ch(block->exp[ch], s->nb_coefs[ch],
613 block->exp_strategy[ch]);
614 /* copy encoded exponents for reuse case */
616 for (blk2 = blk+1; blk2 < blk1; blk2++, block2++) {
617 memcpy(block2->exp[ch], block->exp[ch],
618 s->nb_coefs[ch] * sizeof(uint8_t));
629 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
630 * varies depending on exponent strategy and bandwidth.
632 static void group_exponents(AC3EncodeContext *s)
635 int group_size, nb_groups, bit_count;
637 int delta0, delta1, delta2;
641 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
642 AC3Block *block = &s->blocks[blk];
643 for (ch = 0; ch < s->channels; ch++) {
644 if (block->exp_strategy[ch] == EXP_REUSE) {
647 group_size = block->exp_strategy[ch] + (block->exp_strategy[ch] == EXP_D45);
648 nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]];
649 bit_count += 4 + (nb_groups * 7);
654 block->grouped_exp[ch][0] = exp1;
656 /* remaining exponents are delta encoded */
657 for (i = 1; i <= nb_groups; i++) {
658 /* merge three delta in one code */
662 delta0 = exp1 - exp0 + 2;
667 delta1 = exp1 - exp0 + 2;
672 delta2 = exp1 - exp0 + 2;
674 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
679 s->exponent_bits = bit_count;
684 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
685 * Extract exponents from MDCT coefficients, calculate exponent strategies,
686 * and encode final exponents.
688 static void process_exponents(AC3EncodeContext *s)
690 extract_exponents(s);
692 compute_exp_strategy(s);
701 * Count frame bits that are based solely on fixed parameters.
702 * This only has to be run once when the encoder is initialized.
704 static void count_frame_bits_fixed(AC3EncodeContext *s)
706 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
711 * no dynamic range codes
712 * no channel coupling
713 * bit allocation parameters do not change between blocks
714 * SNR offsets do not change between blocks
715 * no delta bit allocation
722 frame_bits += frame_bits_inc[s->channel_mode];
725 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
726 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
727 if (s->channel_mode == AC3_CHMODE_STEREO) {
728 frame_bits++; /* rematstr */
730 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
732 frame_bits++; /* lfeexpstr */
733 frame_bits++; /* baie */
734 frame_bits++; /* snr */
735 frame_bits += 2; /* delta / skip */
737 frame_bits++; /* cplinu for block 0 */
739 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
741 /* (fsnoffset[4] + fgaincod[4]) * c */
742 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
744 /* auxdatae, crcrsv */
750 s->frame_bits_fixed = frame_bits;
755 * Initialize bit allocation.
756 * Set default parameter codes and calculate parameter values.
758 static void bit_alloc_init(AC3EncodeContext *s)
762 /* init default parameters */
763 s->slow_decay_code = 2;
764 s->fast_decay_code = 1;
765 s->slow_gain_code = 1;
766 s->db_per_bit_code = 3;
768 for (ch = 0; ch < s->channels; ch++)
769 s->fast_gain_code[ch] = 4;
771 /* initial snr offset */
772 s->coarse_snr_offset = 40;
774 /* compute real values */
775 /* currently none of these values change during encoding, so we can just
776 set them once at initialization */
777 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
778 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
779 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
780 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
781 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
783 count_frame_bits_fixed(s);
788 * Count the bits used to encode the frame, minus exponents and mantissas.
789 * Bits based on fixed parameters have already been counted, so now we just
790 * have to add the bits based on parameters that change during encoding.
792 static void count_frame_bits(AC3EncodeContext *s)
797 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
798 uint8_t *exp_strategy = s->blocks[blk].exp_strategy;
800 /* stereo rematrixing */
801 if (s->channel_mode == AC3_CHMODE_STEREO &&
802 s->blocks[blk].new_rematrixing_strategy) {
806 for (ch = 0; ch < s->fbw_channels; ch++) {
807 if (exp_strategy[ch] != EXP_REUSE)
808 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
811 s->frame_bits = s->frame_bits_fixed + frame_bits;
816 * Calculate the number of bits needed to encode a set of mantissas.
818 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
823 for (i = 0; i < nb_coefs; i++) {
826 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
828 } else if (b <= 13) {
829 // bap=5 to bap=13 use (bap-1) bits
832 // bap=14 uses 14 bits and bap=15 uses 16 bits
833 bits += (b == 14) ? 14 : 16;
841 * Finalize the mantissa bit count by adding in the grouped mantissas.
843 static int compute_mantissa_size_final(int mant_cnt[5])
845 // bap=1 : 3 mantissas in 5 bits
846 int bits = (mant_cnt[1] / 3) * 5;
847 // bap=2 : 3 mantissas in 7 bits
848 // bap=4 : 2 mantissas in 7 bits
849 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
850 // bap=3 : each mantissa is 3 bits
851 bits += mant_cnt[3] * 3;
857 * Calculate masking curve based on the final exponents.
858 * Also calculate the power spectral densities to use in future calculations.
860 static void bit_alloc_masking(AC3EncodeContext *s)
864 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
865 AC3Block *block = &s->blocks[blk];
866 for (ch = 0; ch < s->channels; ch++) {
867 /* We only need psd and mask for calculating bap.
868 Since we currently do not calculate bap when exponent
869 strategy is EXP_REUSE we do not need to calculate psd or mask. */
870 if (block->exp_strategy[ch] != EXP_REUSE) {
871 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
873 block->psd[ch], block->band_psd[ch]);
874 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
876 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
877 ch == s->lfe_channel,
878 DBA_NONE, 0, NULL, NULL, NULL,
887 * Ensure that bap for each block and channel point to the current bap_buffer.
888 * They may have been switched during the bit allocation search.
890 static void reset_block_bap(AC3EncodeContext *s)
893 if (s->blocks[0].bap[0] == s->bap_buffer)
895 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
896 for (ch = 0; ch < s->channels; ch++) {
897 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
904 * Run the bit allocation with a given SNR offset.
905 * This calculates the bit allocation pointers that will be used to determine
906 * the quantization of each mantissa.
907 * @return the number of bits needed for mantissas if the given SNR offset is
910 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
916 snr_offset = (snr_offset - 240) << 2;
920 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
921 AC3Block *block = &s->blocks[blk];
922 // initialize grouped mantissa counts. these are set so that they are
923 // padded to the next whole group size when bits are counted in
924 // compute_mantissa_size_final
925 mant_cnt[0] = mant_cnt[3] = 0;
926 mant_cnt[1] = mant_cnt[2] = 2;
928 for (ch = 0; ch < s->channels; ch++) {
929 /* Currently the only bit allocation parameters which vary across
930 blocks within a frame are the exponent values. We can take
931 advantage of that by reusing the bit allocation pointers
932 whenever we reuse exponents. */
933 if (block->exp_strategy[ch] == EXP_REUSE) {
934 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
936 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
937 s->nb_coefs[ch], snr_offset,
938 s->bit_alloc.floor, ff_ac3_bap_tab,
941 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
943 mantissa_bits += compute_mantissa_size_final(mant_cnt);
945 return mantissa_bits;
950 * Constant bitrate bit allocation search.
951 * Find the largest SNR offset that will allow data to fit in the frame.
953 static int cbr_bit_allocation(AC3EncodeContext *s)
957 int snr_offset, snr_incr;
959 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
961 snr_offset = s->coarse_snr_offset << 4;
963 /* if previous frame SNR offset was 1023, check if current frame can also
964 use SNR offset of 1023. if so, skip the search. */
965 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
966 if (bit_alloc(s, 1023) <= bits_left)
970 while (snr_offset >= 0 &&
971 bit_alloc(s, snr_offset) > bits_left) {
975 return AVERROR(EINVAL);
977 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
978 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
979 while (snr_offset + snr_incr <= 1023 &&
980 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
981 snr_offset += snr_incr;
982 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
985 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
988 s->coarse_snr_offset = snr_offset >> 4;
989 for (ch = 0; ch < s->channels; ch++)
990 s->fine_snr_offset[ch] = snr_offset & 0xF;
997 * Downgrade exponent strategies to reduce the bits used by the exponents.
998 * This is a fallback for when bit allocation fails with the normal exponent
999 * strategies. Each time this function is run it only downgrades the
1000 * strategy in 1 channel of 1 block.
1001 * @return non-zero if downgrade was unsuccessful
1003 static int downgrade_exponents(AC3EncodeContext *s)
1007 for (ch = 0; ch < s->fbw_channels; ch++) {
1008 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1009 if (s->blocks[blk].exp_strategy[ch] == EXP_D15) {
1010 s->blocks[blk].exp_strategy[ch] = EXP_D25;
1015 for (ch = 0; ch < s->fbw_channels; ch++) {
1016 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1017 if (s->blocks[blk].exp_strategy[ch] == EXP_D25) {
1018 s->blocks[blk].exp_strategy[ch] = EXP_D45;
1023 for (ch = 0; ch < s->fbw_channels; ch++) {
1024 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1025 the block number > 0 */
1026 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1027 if (s->blocks[blk].exp_strategy[ch] > EXP_REUSE) {
1028 s->blocks[blk].exp_strategy[ch] = EXP_REUSE;
1038 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1039 * This is a second fallback for when bit allocation still fails after exponents
1040 * have been downgraded.
1041 * @return non-zero if bandwidth reduction was unsuccessful
1043 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1047 if (s->bandwidth_code[0] > min_bw_code) {
1048 for (ch = 0; ch < s->fbw_channels; ch++) {
1049 s->bandwidth_code[ch]--;
1050 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1059 * Perform bit allocation search.
1060 * Finds the SNR offset value that maximizes quality and fits in the specified
1061 * frame size. Output is the SNR offset and a set of bit allocation pointers
1062 * used to quantize the mantissas.
1064 static int compute_bit_allocation(AC3EncodeContext *s)
1068 count_frame_bits(s);
1070 bit_alloc_masking(s);
1072 ret = cbr_bit_allocation(s);
1074 /* fallback 1: downgrade exponents */
1075 if (!downgrade_exponents(s)) {
1076 extract_exponents(s);
1077 encode_exponents(s);
1079 ret = compute_bit_allocation(s);
1083 /* fallback 2: reduce bandwidth */
1084 /* only do this if the user has not specified a specific cutoff
1086 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1087 process_exponents(s);
1088 ret = compute_bit_allocation(s);
1092 /* fallbacks were not enough... */
1101 * Symmetric quantization on 'levels' levels.
1103 static inline int sym_quant(int c, int e, int levels)
1108 v = (levels * (c << e)) >> 24;
1110 v = (levels >> 1) + v;
1112 v = (levels * ((-c) << e)) >> 24;
1114 v = (levels >> 1) - v;
1116 assert(v >= 0 && v < levels);
1122 * Asymmetric quantization on 2^qbits levels.
1124 static inline int asym_quant(int c, int e, int qbits)
1128 lshift = e + qbits - 24;
1135 m = (1 << (qbits-1));
1139 return v & ((1 << qbits)-1);
1144 * Quantize a set of mantissas for a single channel in a single block.
1146 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1147 int8_t exp_shift, uint8_t *exp,
1148 uint8_t *bap, uint16_t *qmant, int n)
1152 for (i = 0; i < n; i++) {
1154 int c = fixed_coef[i];
1155 int e = exp[i] - exp_shift;
1162 v = sym_quant(c, e, 3);
1163 switch (s->mant1_cnt) {
1165 s->qmant1_ptr = &qmant[i];
1170 *s->qmant1_ptr += 3 * v;
1175 *s->qmant1_ptr += v;
1182 v = sym_quant(c, e, 5);
1183 switch (s->mant2_cnt) {
1185 s->qmant2_ptr = &qmant[i];
1190 *s->qmant2_ptr += 5 * v;
1195 *s->qmant2_ptr += v;
1202 v = sym_quant(c, e, 7);
1205 v = sym_quant(c, e, 11);
1206 switch (s->mant4_cnt) {
1208 s->qmant4_ptr = &qmant[i];
1213 *s->qmant4_ptr += v;
1220 v = sym_quant(c, e, 15);
1223 v = asym_quant(c, e, 14);
1226 v = asym_quant(c, e, 16);
1229 v = asym_quant(c, e, b - 1);
1238 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1240 static void quantize_mantissas(AC3EncodeContext *s)
1245 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1246 AC3Block *block = &s->blocks[blk];
1247 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1248 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1250 for (ch = 0; ch < s->channels; ch++) {
1251 quantize_mantissas_blk_ch(s, block->fixed_coef[ch], block->exp_shift[ch],
1252 block->exp[ch], block->bap[ch],
1253 block->qmant[ch], s->nb_coefs[ch]);
1260 * Write the AC-3 frame header to the output bitstream.
1262 static void output_frame_header(AC3EncodeContext *s)
1264 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1265 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1266 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1267 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1268 put_bits(&s->pb, 5, s->bitstream_id);
1269 put_bits(&s->pb, 3, s->bitstream_mode);
1270 put_bits(&s->pb, 3, s->channel_mode);
1271 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1272 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1273 if (s->channel_mode & 0x04)
1274 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1275 if (s->channel_mode == AC3_CHMODE_STEREO)
1276 put_bits(&s->pb, 2, 0); /* surround not indicated */
1277 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1278 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1279 put_bits(&s->pb, 1, 0); /* no compression control word */
1280 put_bits(&s->pb, 1, 0); /* no lang code */
1281 put_bits(&s->pb, 1, 0); /* no audio production info */
1282 put_bits(&s->pb, 1, 0); /* no copyright */
1283 put_bits(&s->pb, 1, 1); /* original bitstream */
1284 put_bits(&s->pb, 1, 0); /* no time code 1 */
1285 put_bits(&s->pb, 1, 0); /* no time code 2 */
1286 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1291 * Write one audio block to the output bitstream.
1293 static void output_audio_block(AC3EncodeContext *s, int block_num)
1295 int ch, i, baie, rbnd;
1296 AC3Block *block = &s->blocks[block_num];
1298 /* block switching */
1299 for (ch = 0; ch < s->fbw_channels; ch++)
1300 put_bits(&s->pb, 1, 0);
1303 for (ch = 0; ch < s->fbw_channels; ch++)
1304 put_bits(&s->pb, 1, 1);
1306 /* dynamic range codes */
1307 put_bits(&s->pb, 1, 0);
1309 /* channel coupling */
1311 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1312 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1314 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1317 /* stereo rematrixing */
1318 if (s->channel_mode == AC3_CHMODE_STEREO) {
1319 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1320 if (block->new_rematrixing_strategy) {
1321 /* rematrixing flags */
1322 for (rbnd = 0; rbnd < 4; rbnd++)
1323 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1327 /* exponent strategy */
1328 for (ch = 0; ch < s->fbw_channels; ch++)
1329 put_bits(&s->pb, 2, block->exp_strategy[ch]);
1331 put_bits(&s->pb, 1, block->exp_strategy[s->lfe_channel]);
1334 for (ch = 0; ch < s->fbw_channels; ch++) {
1335 if (block->exp_strategy[ch] != EXP_REUSE)
1336 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1340 for (ch = 0; ch < s->channels; ch++) {
1343 if (block->exp_strategy[ch] == EXP_REUSE)
1347 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1349 /* exponent groups */
1350 nb_groups = exponent_group_tab[block->exp_strategy[ch]-1][s->nb_coefs[ch]];
1351 for (i = 1; i <= nb_groups; i++)
1352 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1354 /* gain range info */
1355 if (ch != s->lfe_channel)
1356 put_bits(&s->pb, 2, 0);
1359 /* bit allocation info */
1360 baie = (block_num == 0);
1361 put_bits(&s->pb, 1, baie);
1363 put_bits(&s->pb, 2, s->slow_decay_code);
1364 put_bits(&s->pb, 2, s->fast_decay_code);
1365 put_bits(&s->pb, 2, s->slow_gain_code);
1366 put_bits(&s->pb, 2, s->db_per_bit_code);
1367 put_bits(&s->pb, 3, s->floor_code);
1371 put_bits(&s->pb, 1, baie);
1373 put_bits(&s->pb, 6, s->coarse_snr_offset);
1374 for (ch = 0; ch < s->channels; ch++) {
1375 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1376 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1380 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1381 put_bits(&s->pb, 1, 0); /* no data to skip */
1384 for (ch = 0; ch < s->channels; ch++) {
1386 for (i = 0; i < s->nb_coefs[ch]; i++) {
1387 q = block->qmant[ch][i];
1388 b = block->bap[ch][i];
1391 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1392 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1393 case 3: put_bits(&s->pb, 3, q); break;
1394 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1395 case 14: put_bits(&s->pb, 14, q); break;
1396 case 15: put_bits(&s->pb, 16, q); break;
1397 default: put_bits(&s->pb, b-1, q); break;
1404 /** CRC-16 Polynomial */
1405 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1408 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1425 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1431 r = mul_poly(r, a, poly);
1432 a = mul_poly(a, a, poly);
1440 * Fill the end of the frame with 0's and compute the two CRCs.
1442 static void output_frame_end(AC3EncodeContext *s)
1444 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1445 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1448 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1450 /* pad the remainder of the frame with zeros */
1451 flush_put_bits(&s->pb);
1453 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1454 assert(pad_bytes >= 0);
1456 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1459 /* this is not so easy because it is at the beginning of the data... */
1460 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1461 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1462 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1463 AV_WB16(frame + 2, crc1);
1466 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1467 s->frame_size - frame_size_58 - 3);
1468 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1469 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1470 if (crc2 == 0x770B) {
1471 frame[s->frame_size - 3] ^= 0x1;
1472 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1474 crc2 = av_bswap16(crc2);
1475 AV_WB16(frame + s->frame_size - 2, crc2);
1480 * Write the frame to the output bitstream.
1482 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1486 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1488 output_frame_header(s);
1490 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1491 output_audio_block(s, blk);
1493 output_frame_end(s);
1498 * Encode a single AC-3 frame.
1500 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1501 int buf_size, void *data)
1503 AC3EncodeContext *s = avctx->priv_data;
1504 const SampleType *samples = data;
1507 if (s->bit_alloc.sr_code == 1)
1508 adjust_frame_size(s);
1510 deinterleave_input_samples(s, samples);
1514 compute_rematrixing_strategy(s);
1516 scale_coefficients(s);
1518 apply_rematrixing(s);
1520 process_exponents(s);
1522 ret = compute_bit_allocation(s);
1524 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1528 quantize_mantissas(s);
1530 output_frame(s, frame);
1532 return s->frame_size;
1537 * Finalize encoding and free any memory allocated by the encoder.
1539 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1542 AC3EncodeContext *s = avctx->priv_data;
1544 for (ch = 0; ch < s->channels; ch++)
1545 av_freep(&s->planar_samples[ch]);
1546 av_freep(&s->planar_samples);
1547 av_freep(&s->bap_buffer);
1548 av_freep(&s->bap1_buffer);
1549 av_freep(&s->mdct_coef_buffer);
1550 av_freep(&s->fixed_coef_buffer);
1551 av_freep(&s->exp_buffer);
1552 av_freep(&s->grouped_exp_buffer);
1553 av_freep(&s->psd_buffer);
1554 av_freep(&s->band_psd_buffer);
1555 av_freep(&s->mask_buffer);
1556 av_freep(&s->qmant_buffer);
1557 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1558 AC3Block *block = &s->blocks[blk];
1559 av_freep(&block->bap);
1560 av_freep(&block->mdct_coef);
1561 av_freep(&block->fixed_coef);
1562 av_freep(&block->exp);
1563 av_freep(&block->grouped_exp);
1564 av_freep(&block->psd);
1565 av_freep(&block->band_psd);
1566 av_freep(&block->mask);
1567 av_freep(&block->qmant);
1572 av_freep(&avctx->coded_frame);
1578 * Set channel information during initialization.
1580 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1581 int64_t *channel_layout)
1585 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1586 return AVERROR(EINVAL);
1587 if ((uint64_t)*channel_layout > 0x7FF)
1588 return AVERROR(EINVAL);
1589 ch_layout = *channel_layout;
1591 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1592 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1593 return AVERROR(EINVAL);
1595 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1596 s->channels = channels;
1597 s->fbw_channels = channels - s->lfe_on;
1598 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1600 ch_layout -= AV_CH_LOW_FREQUENCY;
1602 switch (ch_layout) {
1603 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1604 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1605 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1606 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1607 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1608 case AV_CH_LAYOUT_QUAD:
1609 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1610 case AV_CH_LAYOUT_5POINT0:
1611 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1613 return AVERROR(EINVAL);
1616 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1617 *channel_layout = ch_layout;
1619 *channel_layout |= AV_CH_LOW_FREQUENCY;
1625 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1629 /* validate channel layout */
1630 if (!avctx->channel_layout) {
1631 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1632 "encoder will guess the layout, but it "
1633 "might be incorrect.\n");
1635 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1637 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1641 /* validate sample rate */
1642 for (i = 0; i < 9; i++) {
1643 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1647 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1648 return AVERROR(EINVAL);
1650 s->sample_rate = avctx->sample_rate;
1651 s->bit_alloc.sr_shift = i % 3;
1652 s->bit_alloc.sr_code = i / 3;
1654 /* validate bit rate */
1655 for (i = 0; i < 19; i++) {
1656 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1660 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1661 return AVERROR(EINVAL);
1663 s->bit_rate = avctx->bit_rate;
1664 s->frame_size_code = i << 1;
1666 /* validate cutoff */
1667 if (avctx->cutoff < 0) {
1668 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1669 return AVERROR(EINVAL);
1671 s->cutoff = avctx->cutoff;
1672 if (s->cutoff > (s->sample_rate >> 1))
1673 s->cutoff = s->sample_rate >> 1;
1680 * Set bandwidth for all channels.
1681 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1682 * default value will be used.
1684 static av_cold void set_bandwidth(AC3EncodeContext *s)
1689 /* calculate bandwidth based on user-specified cutoff frequency */
1691 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1692 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1694 /* use default bandwidth setting */
1695 /* XXX: should compute the bandwidth according to the frame
1696 size, so that we avoid annoying high frequency artifacts */
1700 /* set number of coefficients for each channel */
1701 for (ch = 0; ch < s->fbw_channels; ch++) {
1702 s->bandwidth_code[ch] = bw_code;
1703 s->nb_coefs[ch] = bw_code * 3 + 73;
1706 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1710 static av_cold int allocate_buffers(AVCodecContext *avctx)
1713 AC3EncodeContext *s = avctx->priv_data;
1715 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1717 for (ch = 0; ch < s->channels; ch++) {
1718 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1719 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1722 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1723 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1724 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1725 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1726 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1727 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1728 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1729 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1730 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1731 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1732 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1733 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1734 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1735 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1736 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1737 64 * sizeof(*s->mask_buffer), alloc_fail);
1738 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1739 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1740 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1741 AC3Block *block = &s->blocks[blk];
1742 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1744 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1746 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1748 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1750 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1752 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1754 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1756 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1759 for (ch = 0; ch < s->channels; ch++) {
1760 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1761 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1762 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1763 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1764 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1765 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1766 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1767 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1771 if (CONFIG_AC3ENC_FLOAT) {
1772 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1773 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1774 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1775 AC3Block *block = &s->blocks[blk];
1776 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1777 sizeof(*block->fixed_coef), alloc_fail);
1778 for (ch = 0; ch < s->channels; ch++)
1779 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1782 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1783 AC3Block *block = &s->blocks[blk];
1784 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1785 sizeof(*block->fixed_coef), alloc_fail);
1786 for (ch = 0; ch < s->channels; ch++)
1787 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1793 return AVERROR(ENOMEM);
1798 * Initialize the encoder.
1800 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1802 AC3EncodeContext *s = avctx->priv_data;
1803 int ret, frame_size_58;
1805 avctx->frame_size = AC3_FRAME_SIZE;
1809 ret = validate_options(avctx, s);
1813 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1814 s->bitstream_mode = 0; /* complete main audio service */
1816 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1817 s->bits_written = 0;
1818 s->samples_written = 0;
1819 s->frame_size = s->frame_size_min;
1821 /* calculate crc_inv for both possible frame sizes */
1822 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1823 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1824 if (s->bit_alloc.sr_code == 1) {
1825 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1826 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1831 rematrixing_init(s);
1837 ret = mdct_init(avctx, &s->mdct, 9);
1841 ret = allocate_buffers(avctx);
1845 avctx->coded_frame= avcodec_alloc_frame();
1847 dsputil_init(&s->dsp, avctx);
1851 ac3_encode_close(avctx);