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"
38 #include "audioconvert.h"
41 #ifndef CONFIG_AC3ENC_FLOAT
42 #define CONFIG_AC3ENC_FLOAT 0
46 /** Maximum number of exponent groups. +1 for separate DC exponent. */
47 #define AC3_MAX_EXP_GROUPS 85
49 /* stereo rematrixing algorithms */
50 #define AC3_REMATRIXING_IS_STATIC 0x1
51 #define AC3_REMATRIXING_SUMS 0
52 #define AC3_REMATRIXING_NONE 1
53 #define AC3_REMATRIXING_ALWAYS 3
55 /** Scale a float value by 2^bits and convert to an integer. */
56 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
59 #if CONFIG_AC3ENC_FLOAT
60 #include "ac3enc_float.h"
62 #include "ac3enc_fixed.h"
67 * Data for a single audio block.
69 typedef struct AC3Block {
70 uint8_t **bap; ///< bit allocation pointers (bap)
71 CoefType **mdct_coef; ///< MDCT coefficients
72 int32_t **fixed_coef; ///< fixed-point MDCT coefficients
73 uint8_t **exp; ///< original exponents
74 uint8_t **grouped_exp; ///< grouped exponents
75 int16_t **psd; ///< psd per frequency bin
76 int16_t **band_psd; ///< psd per critical band
77 int16_t **mask; ///< masking curve
78 uint16_t **qmant; ///< quantized mantissas
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 AC3DSPContext ac3dsp; ///< AC-3 optimized functions
91 AC3MDCTContext mdct; ///< MDCT context
93 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
95 int bitstream_id; ///< bitstream id (bsid)
96 int bitstream_mode; ///< bitstream mode (bsmod)
98 int bit_rate; ///< target bit rate, in bits-per-second
99 int sample_rate; ///< sampling frequency, in Hz
101 int frame_size_min; ///< minimum frame size in case rounding is necessary
102 int frame_size; ///< current frame size in bytes
103 int frame_size_code; ///< frame size code (frmsizecod)
105 int bits_written; ///< bit count (used to avg. bitrate)
106 int samples_written; ///< sample count (used to avg. bitrate)
108 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
109 int channels; ///< total number of channels (nchans)
110 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
111 int lfe_channel; ///< channel index of the LFE channel
112 int channel_mode; ///< channel mode (acmod)
113 const uint8_t *channel_map; ///< channel map used to reorder channels
115 int cutoff; ///< user-specified cutoff frequency, in Hz
116 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
117 int nb_coefs[AC3_MAX_CHANNELS];
119 int rematrixing; ///< determines how rematrixing strategy is calculated
121 /* bitrate allocation control */
122 int slow_gain_code; ///< slow gain code (sgaincod)
123 int slow_decay_code; ///< slow decay code (sdcycod)
124 int fast_decay_code; ///< fast decay code (fdcycod)
125 int db_per_bit_code; ///< dB/bit code (dbpbcod)
126 int floor_code; ///< floor code (floorcod)
127 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
128 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
129 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
130 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
131 int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
132 int frame_bits; ///< all frame bits except exponents and mantissas
133 int exponent_bits; ///< number of bits used for exponents
135 /* mantissa encoding */
136 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
137 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
139 SampleType **planar_samples;
141 uint8_t *bap1_buffer;
142 CoefType *mdct_coef_buffer;
143 int32_t *fixed_coef_buffer;
145 uint8_t *grouped_exp_buffer;
147 int16_t *band_psd_buffer;
148 int16_t *mask_buffer;
149 uint16_t *qmant_buffer;
151 uint8_t exp_strategy[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< exponent strategies
153 DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
157 /* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */
159 static av_cold void mdct_end(AC3MDCTContext *mdct);
161 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
164 static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in);
166 static void apply_window(DSPContext *dsp, SampleType *output, const SampleType *input,
167 const SampleType *window, int n);
169 static int normalize_samples(AC3EncodeContext *s);
171 static void scale_coefficients(AC3EncodeContext *s);
175 * LUT for number of exponent groups.
176 * exponent_group_tab[exponent strategy-1][number of coefficients]
178 static uint8_t exponent_group_tab[3][256];
182 * List of supported channel layouts.
184 static const int64_t ac3_channel_layouts[] = {
188 AV_CH_LAYOUT_SURROUND,
191 AV_CH_LAYOUT_4POINT0,
192 AV_CH_LAYOUT_5POINT0,
193 AV_CH_LAYOUT_5POINT0_BACK,
194 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
195 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
196 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
197 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
198 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
199 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
200 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
201 AV_CH_LAYOUT_5POINT1,
202 AV_CH_LAYOUT_5POINT1_BACK,
208 * Adjust the frame size to make the average bit rate match the target bit rate.
209 * This is only needed for 11025, 22050, and 44100 sample rates.
211 static void adjust_frame_size(AC3EncodeContext *s)
213 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
214 s->bits_written -= s->bit_rate;
215 s->samples_written -= s->sample_rate;
217 s->frame_size = s->frame_size_min +
218 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
219 s->bits_written += s->frame_size * 8;
220 s->samples_written += AC3_FRAME_SIZE;
225 * Deinterleave input samples.
226 * Channels are reordered from FFmpeg's default order to AC-3 order.
228 static void deinterleave_input_samples(AC3EncodeContext *s,
229 const SampleType *samples)
233 /* deinterleave and remap input samples */
234 for (ch = 0; ch < s->channels; ch++) {
235 const SampleType *sptr;
238 /* copy last 256 samples of previous frame to the start of the current frame */
239 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
240 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
244 sptr = samples + s->channel_map[ch];
245 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
246 s->planar_samples[ch][i] = *sptr;
254 * Apply the MDCT to input samples to generate frequency coefficients.
255 * This applies the KBD window and normalizes the input to reduce precision
256 * loss due to fixed-point calculations.
258 static void apply_mdct(AC3EncodeContext *s)
262 for (ch = 0; ch < s->channels; ch++) {
263 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
264 AC3Block *block = &s->blocks[blk];
265 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
267 apply_window(&s->dsp, s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
269 block->exp_shift[ch] = normalize_samples(s);
271 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
278 * Initialize stereo rematrixing.
279 * If the strategy does not change for each frame, set the rematrixing flags.
281 static void rematrixing_init(AC3EncodeContext *s)
283 if (s->channel_mode == AC3_CHMODE_STEREO)
284 s->rematrixing = AC3_REMATRIXING_SUMS;
286 s->rematrixing = AC3_REMATRIXING_NONE;
287 /* NOTE: AC3_REMATRIXING_ALWAYS might be used in
288 the future in conjunction with channel coupling. */
290 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC) {
291 int flag = (s->rematrixing == AC3_REMATRIXING_ALWAYS);
292 s->blocks[0].new_rematrixing_strategy = 1;
293 memset(s->blocks[0].rematrixing_flags, flag,
294 sizeof(s->blocks[0].rematrixing_flags));
300 * Determine rematrixing flags for each block and band.
302 static void compute_rematrixing_strategy(AC3EncodeContext *s)
306 AC3Block *block, *block0;
308 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC)
311 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
313 s->blocks[0].new_rematrixing_strategy = 1;
314 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
315 block = &s->blocks[blk];
316 for (bnd = 0; bnd < 4; bnd++) {
317 /* calculate calculate sum of squared coeffs for one band in one block */
318 int start = ff_ac3_rematrix_band_tab[bnd];
319 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
320 CoefSumType sum[4] = {0,};
321 for (i = start; i < end; i++) {
322 CoefType lt = block->mdct_coef[0][i];
323 CoefType rt = block->mdct_coef[1][i];
324 CoefType md = lt + rt;
325 CoefType sd = lt - rt;
332 /* compare sums to determine if rematrixing will be used for this band */
333 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
334 block->rematrixing_flags[bnd] = 1;
336 block->rematrixing_flags[bnd] = 0;
338 /* determine if new rematrixing flags will be sent */
340 !block->new_rematrixing_strategy &&
341 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
342 block->new_rematrixing_strategy = 1;
351 * Apply stereo rematrixing to coefficients based on rematrixing flags.
353 static void apply_rematrixing(AC3EncodeContext *s)
360 if (s->rematrixing == AC3_REMATRIXING_NONE)
363 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
365 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
366 AC3Block *block = &s->blocks[blk];
367 if (block->new_rematrixing_strategy)
368 flags = block->rematrixing_flags;
369 for (bnd = 0; bnd < 4; bnd++) {
371 start = ff_ac3_rematrix_band_tab[bnd];
372 end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
373 for (i = start; i < end; i++) {
374 int32_t lt = block->fixed_coef[0][i];
375 int32_t rt = block->fixed_coef[1][i];
376 block->fixed_coef[0][i] = (lt + rt) >> 1;
377 block->fixed_coef[1][i] = (lt - rt) >> 1;
386 * Initialize exponent tables.
388 static av_cold void exponent_init(AC3EncodeContext *s)
391 for (i = 73; i < 256; i++) {
392 exponent_group_tab[0][i] = (i - 1) / 3;
393 exponent_group_tab[1][i] = (i + 2) / 6;
394 exponent_group_tab[2][i] = (i + 8) / 12;
397 exponent_group_tab[0][7] = 2;
402 * Extract exponents from the MDCT coefficients.
403 * This takes into account the normalization that was done to the input samples
404 * by adjusting the exponents by the exponent shift values.
406 static void extract_exponents(AC3EncodeContext *s)
410 for (ch = 0; ch < s->channels; ch++) {
411 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
412 AC3Block *block = &s->blocks[blk];
413 uint8_t *exp = block->exp[ch];
414 int32_t *coef = block->fixed_coef[ch];
415 int exp_shift = block->exp_shift[ch];
416 for (i = 0; i < AC3_MAX_COEFS; i++) {
418 int v = abs(coef[i]);
422 e = 23 - av_log2(v) + exp_shift;
436 * Exponent Difference Threshold.
437 * New exponents are sent if their SAD exceed this number.
439 #define EXP_DIFF_THRESHOLD 500
443 * Calculate exponent strategies for all blocks in a single channel.
445 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
451 /* estimate if the exponent variation & decide if they should be
452 reused in the next frame */
453 exp_strategy[0] = EXP_NEW;
454 exp += AC3_MAX_COEFS;
455 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
456 exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
457 if (exp_diff > EXP_DIFF_THRESHOLD)
458 exp_strategy[blk] = EXP_NEW;
460 exp_strategy[blk] = EXP_REUSE;
461 exp += AC3_MAX_COEFS;
464 /* now select the encoding strategy type : if exponents are often
465 recoded, we use a coarse encoding */
467 while (blk < AC3_MAX_BLOCKS) {
469 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
471 switch (blk1 - blk) {
472 case 1: exp_strategy[blk] = EXP_D45; break;
474 case 3: exp_strategy[blk] = EXP_D25; break;
475 default: exp_strategy[blk] = EXP_D15; break;
483 * Calculate exponent strategies for all channels.
484 * Array arrangement is reversed to simplify the per-channel calculation.
486 static void compute_exp_strategy(AC3EncodeContext *s)
490 for (ch = 0; ch < s->fbw_channels; ch++) {
491 compute_exp_strategy_ch(s, s->exp_strategy[ch], s->blocks[0].exp[ch]);
495 s->exp_strategy[ch][0] = EXP_D15;
496 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
497 s->exp_strategy[ch][blk] = EXP_REUSE;
503 * Update the exponents so that they are the ones the decoder will decode.
505 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
509 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
511 /* for each group, compute the minimum exponent */
512 switch(exp_strategy) {
514 for (i = 1, k = 1; i <= nb_groups; i++) {
515 uint8_t exp_min = exp[k];
516 if (exp[k+1] < exp_min)
523 for (i = 1, k = 1; i <= nb_groups; i++) {
524 uint8_t exp_min = exp[k];
525 if (exp[k+1] < exp_min)
527 if (exp[k+2] < exp_min)
529 if (exp[k+3] < exp_min)
537 /* constraint for DC exponent */
541 /* decrease the delta between each groups to within 2 so that they can be
542 differentially encoded */
543 for (i = 1; i <= nb_groups; i++)
544 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
547 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
549 /* now we have the exponent values the decoder will see */
550 switch (exp_strategy) {
552 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
553 uint8_t exp1 = exp[i];
559 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
560 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
569 * Encode exponents from original extracted form to what the decoder will see.
570 * This copies and groups exponents based on exponent strategy and reduces
571 * deltas between adjacent exponent groups so that they can be differentially
574 static void encode_exponents(AC3EncodeContext *s)
577 uint8_t *exp, *exp1, *exp_strategy;
578 int nb_coefs, num_reuse_blocks;
580 for (ch = 0; ch < s->channels; ch++) {
581 exp = s->blocks[0].exp[ch];
582 exp_strategy = s->exp_strategy[ch];
583 nb_coefs = s->nb_coefs[ch];
586 while (blk < AC3_MAX_BLOCKS) {
589 /* count the number of EXP_REUSE blocks after the current block */
590 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
592 num_reuse_blocks = blk1 - blk - 1;
594 /* for the EXP_REUSE case we select the min of the exponents */
595 s->ac3dsp.ac3_exponent_min(exp, num_reuse_blocks, nb_coefs);
597 encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]);
599 /* copy encoded exponents for reuse case */
600 exp1 = exp + AC3_MAX_COEFS;
601 while (blk < blk1-1) {
602 memcpy(exp1, exp, nb_coefs * sizeof(*exp));
603 exp1 += AC3_MAX_COEFS;
615 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
616 * varies depending on exponent strategy and bandwidth.
618 static void group_exponents(AC3EncodeContext *s)
621 int group_size, nb_groups, bit_count;
623 int delta0, delta1, delta2;
627 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
628 AC3Block *block = &s->blocks[blk];
629 for (ch = 0; ch < s->channels; ch++) {
630 int exp_strategy = s->exp_strategy[ch][blk];
631 if (exp_strategy == EXP_REUSE)
633 group_size = exp_strategy + (exp_strategy == EXP_D45);
634 nb_groups = exponent_group_tab[exp_strategy-1][s->nb_coefs[ch]];
635 bit_count += 4 + (nb_groups * 7);
640 block->grouped_exp[ch][0] = exp1;
642 /* remaining exponents are delta encoded */
643 for (i = 1; i <= nb_groups; i++) {
644 /* merge three delta in one code */
648 delta0 = exp1 - exp0 + 2;
653 delta1 = exp1 - exp0 + 2;
658 delta2 = exp1 - exp0 + 2;
660 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
665 s->exponent_bits = bit_count;
670 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
671 * Extract exponents from MDCT coefficients, calculate exponent strategies,
672 * and encode final exponents.
674 static void process_exponents(AC3EncodeContext *s)
676 extract_exponents(s);
678 compute_exp_strategy(s);
689 * Count frame bits that are based solely on fixed parameters.
690 * This only has to be run once when the encoder is initialized.
692 static void count_frame_bits_fixed(AC3EncodeContext *s)
694 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
699 * no dynamic range codes
700 * no channel coupling
701 * bit allocation parameters do not change between blocks
702 * SNR offsets do not change between blocks
703 * no delta bit allocation
710 frame_bits += frame_bits_inc[s->channel_mode];
713 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
714 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
715 if (s->channel_mode == AC3_CHMODE_STEREO) {
716 frame_bits++; /* rematstr */
718 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
720 frame_bits++; /* lfeexpstr */
721 frame_bits++; /* baie */
722 frame_bits++; /* snr */
723 frame_bits += 2; /* delta / skip */
725 frame_bits++; /* cplinu for block 0 */
727 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
729 /* (fsnoffset[4] + fgaincod[4]) * c */
730 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
732 /* auxdatae, crcrsv */
738 s->frame_bits_fixed = frame_bits;
743 * Initialize bit allocation.
744 * Set default parameter codes and calculate parameter values.
746 static void bit_alloc_init(AC3EncodeContext *s)
750 /* init default parameters */
751 s->slow_decay_code = 2;
752 s->fast_decay_code = 1;
753 s->slow_gain_code = 1;
754 s->db_per_bit_code = 3;
756 for (ch = 0; ch < s->channels; ch++)
757 s->fast_gain_code[ch] = 4;
759 /* initial snr offset */
760 s->coarse_snr_offset = 40;
762 /* compute real values */
763 /* currently none of these values change during encoding, so we can just
764 set them once at initialization */
765 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
766 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
767 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
768 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
769 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
771 count_frame_bits_fixed(s);
776 * Count the bits used to encode the frame, minus exponents and mantissas.
777 * Bits based on fixed parameters have already been counted, so now we just
778 * have to add the bits based on parameters that change during encoding.
780 static void count_frame_bits(AC3EncodeContext *s)
785 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
786 /* stereo rematrixing */
787 if (s->channel_mode == AC3_CHMODE_STEREO &&
788 s->blocks[blk].new_rematrixing_strategy) {
792 for (ch = 0; ch < s->fbw_channels; ch++) {
793 if (s->exp_strategy[ch][blk] != EXP_REUSE)
794 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
797 s->frame_bits = s->frame_bits_fixed + frame_bits;
802 * Calculate the number of bits needed to encode a set of mantissas.
804 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
809 for (i = 0; i < nb_coefs; i++) {
812 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
814 } else if (b <= 13) {
815 // bap=5 to bap=13 use (bap-1) bits
818 // bap=14 uses 14 bits and bap=15 uses 16 bits
819 bits += (b == 14) ? 14 : 16;
827 * Finalize the mantissa bit count by adding in the grouped mantissas.
829 static int compute_mantissa_size_final(int mant_cnt[5])
831 // bap=1 : 3 mantissas in 5 bits
832 int bits = (mant_cnt[1] / 3) * 5;
833 // bap=2 : 3 mantissas in 7 bits
834 // bap=4 : 2 mantissas in 7 bits
835 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
836 // bap=3 : each mantissa is 3 bits
837 bits += mant_cnt[3] * 3;
843 * Calculate masking curve based on the final exponents.
844 * Also calculate the power spectral densities to use in future calculations.
846 static void bit_alloc_masking(AC3EncodeContext *s)
850 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
851 AC3Block *block = &s->blocks[blk];
852 for (ch = 0; ch < s->channels; ch++) {
853 /* We only need psd and mask for calculating bap.
854 Since we currently do not calculate bap when exponent
855 strategy is EXP_REUSE we do not need to calculate psd or mask. */
856 if (s->exp_strategy[ch][blk] != EXP_REUSE) {
857 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
859 block->psd[ch], block->band_psd[ch]);
860 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
862 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
863 ch == s->lfe_channel,
864 DBA_NONE, 0, NULL, NULL, NULL,
873 * Ensure that bap for each block and channel point to the current bap_buffer.
874 * They may have been switched during the bit allocation search.
876 static void reset_block_bap(AC3EncodeContext *s)
879 if (s->blocks[0].bap[0] == s->bap_buffer)
881 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
882 for (ch = 0; ch < s->channels; ch++) {
883 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
890 * Run the bit allocation with a given SNR offset.
891 * This calculates the bit allocation pointers that will be used to determine
892 * the quantization of each mantissa.
893 * @return the number of bits needed for mantissas if the given SNR offset is
896 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
902 snr_offset = (snr_offset - 240) << 2;
906 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
907 AC3Block *block = &s->blocks[blk];
908 // initialize grouped mantissa counts. these are set so that they are
909 // padded to the next whole group size when bits are counted in
910 // compute_mantissa_size_final
911 mant_cnt[0] = mant_cnt[3] = 0;
912 mant_cnt[1] = mant_cnt[2] = 2;
914 for (ch = 0; ch < s->channels; ch++) {
915 /* Currently the only bit allocation parameters which vary across
916 blocks within a frame are the exponent values. We can take
917 advantage of that by reusing the bit allocation pointers
918 whenever we reuse exponents. */
919 if (s->exp_strategy[ch][blk] == EXP_REUSE) {
920 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
922 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
923 s->nb_coefs[ch], snr_offset,
924 s->bit_alloc.floor, ff_ac3_bap_tab,
927 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
929 mantissa_bits += compute_mantissa_size_final(mant_cnt);
931 return mantissa_bits;
936 * Constant bitrate bit allocation search.
937 * Find the largest SNR offset that will allow data to fit in the frame.
939 static int cbr_bit_allocation(AC3EncodeContext *s)
943 int snr_offset, snr_incr;
945 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
947 snr_offset = s->coarse_snr_offset << 4;
949 /* if previous frame SNR offset was 1023, check if current frame can also
950 use SNR offset of 1023. if so, skip the search. */
951 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
952 if (bit_alloc(s, 1023) <= bits_left)
956 while (snr_offset >= 0 &&
957 bit_alloc(s, snr_offset) > bits_left) {
961 return AVERROR(EINVAL);
963 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
964 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
965 while (snr_offset + snr_incr <= 1023 &&
966 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
967 snr_offset += snr_incr;
968 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
971 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
974 s->coarse_snr_offset = snr_offset >> 4;
975 for (ch = 0; ch < s->channels; ch++)
976 s->fine_snr_offset[ch] = snr_offset & 0xF;
983 * Downgrade exponent strategies to reduce the bits used by the exponents.
984 * This is a fallback for when bit allocation fails with the normal exponent
985 * strategies. Each time this function is run it only downgrades the
986 * strategy in 1 channel of 1 block.
987 * @return non-zero if downgrade was unsuccessful
989 static int downgrade_exponents(AC3EncodeContext *s)
993 for (ch = 0; ch < s->fbw_channels; ch++) {
994 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
995 if (s->exp_strategy[ch][blk] == EXP_D15) {
996 s->exp_strategy[ch][blk] = EXP_D25;
1001 for (ch = 0; ch < s->fbw_channels; ch++) {
1002 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1003 if (s->exp_strategy[ch][blk] == EXP_D25) {
1004 s->exp_strategy[ch][blk] = EXP_D45;
1009 for (ch = 0; ch < s->fbw_channels; ch++) {
1010 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1011 the block number > 0 */
1012 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1013 if (s->exp_strategy[ch][blk] > EXP_REUSE) {
1014 s->exp_strategy[ch][blk] = EXP_REUSE;
1024 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1025 * This is a second fallback for when bit allocation still fails after exponents
1026 * have been downgraded.
1027 * @return non-zero if bandwidth reduction was unsuccessful
1029 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1033 if (s->bandwidth_code[0] > min_bw_code) {
1034 for (ch = 0; ch < s->fbw_channels; ch++) {
1035 s->bandwidth_code[ch]--;
1036 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1045 * Perform bit allocation search.
1046 * Finds the SNR offset value that maximizes quality and fits in the specified
1047 * frame size. Output is the SNR offset and a set of bit allocation pointers
1048 * used to quantize the mantissas.
1050 static int compute_bit_allocation(AC3EncodeContext *s)
1054 count_frame_bits(s);
1056 bit_alloc_masking(s);
1058 ret = cbr_bit_allocation(s);
1060 /* fallback 1: downgrade exponents */
1061 if (!downgrade_exponents(s)) {
1062 extract_exponents(s);
1063 encode_exponents(s);
1065 ret = compute_bit_allocation(s);
1069 /* fallback 2: reduce bandwidth */
1070 /* only do this if the user has not specified a specific cutoff
1072 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1073 process_exponents(s);
1074 ret = compute_bit_allocation(s);
1078 /* fallbacks were not enough... */
1087 * Symmetric quantization on 'levels' levels.
1089 static inline int sym_quant(int c, int e, int levels)
1094 v = (levels * (c << e)) >> 24;
1096 v = (levels >> 1) + v;
1098 v = (levels * ((-c) << e)) >> 24;
1100 v = (levels >> 1) - v;
1102 assert(v >= 0 && v < levels);
1108 * Asymmetric quantization on 2^qbits levels.
1110 static inline int asym_quant(int c, int e, int qbits)
1114 lshift = e + qbits - 24;
1121 m = (1 << (qbits-1));
1125 return v & ((1 << qbits)-1);
1130 * Quantize a set of mantissas for a single channel in a single block.
1132 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1133 int8_t exp_shift, uint8_t *exp,
1134 uint8_t *bap, uint16_t *qmant, int n)
1138 for (i = 0; i < n; i++) {
1140 int c = fixed_coef[i];
1141 int e = exp[i] - exp_shift;
1148 v = sym_quant(c, e, 3);
1149 switch (s->mant1_cnt) {
1151 s->qmant1_ptr = &qmant[i];
1156 *s->qmant1_ptr += 3 * v;
1161 *s->qmant1_ptr += v;
1168 v = sym_quant(c, e, 5);
1169 switch (s->mant2_cnt) {
1171 s->qmant2_ptr = &qmant[i];
1176 *s->qmant2_ptr += 5 * v;
1181 *s->qmant2_ptr += v;
1188 v = sym_quant(c, e, 7);
1191 v = sym_quant(c, e, 11);
1192 switch (s->mant4_cnt) {
1194 s->qmant4_ptr = &qmant[i];
1199 *s->qmant4_ptr += v;
1206 v = sym_quant(c, e, 15);
1209 v = asym_quant(c, e, 14);
1212 v = asym_quant(c, e, 16);
1215 v = asym_quant(c, e, b - 1);
1224 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1226 static void quantize_mantissas(AC3EncodeContext *s)
1231 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1232 AC3Block *block = &s->blocks[blk];
1233 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1234 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1236 for (ch = 0; ch < s->channels; ch++) {
1237 quantize_mantissas_blk_ch(s, block->fixed_coef[ch], block->exp_shift[ch],
1238 block->exp[ch], block->bap[ch],
1239 block->qmant[ch], s->nb_coefs[ch]);
1246 * Write the AC-3 frame header to the output bitstream.
1248 static void output_frame_header(AC3EncodeContext *s)
1250 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1251 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1252 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1253 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1254 put_bits(&s->pb, 5, s->bitstream_id);
1255 put_bits(&s->pb, 3, s->bitstream_mode);
1256 put_bits(&s->pb, 3, s->channel_mode);
1257 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1258 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1259 if (s->channel_mode & 0x04)
1260 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1261 if (s->channel_mode == AC3_CHMODE_STEREO)
1262 put_bits(&s->pb, 2, 0); /* surround not indicated */
1263 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1264 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1265 put_bits(&s->pb, 1, 0); /* no compression control word */
1266 put_bits(&s->pb, 1, 0); /* no lang code */
1267 put_bits(&s->pb, 1, 0); /* no audio production info */
1268 put_bits(&s->pb, 1, 0); /* no copyright */
1269 put_bits(&s->pb, 1, 1); /* original bitstream */
1270 put_bits(&s->pb, 1, 0); /* no time code 1 */
1271 put_bits(&s->pb, 1, 0); /* no time code 2 */
1272 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1277 * Write one audio block to the output bitstream.
1279 static void output_audio_block(AC3EncodeContext *s, int blk)
1281 int ch, i, baie, rbnd;
1282 AC3Block *block = &s->blocks[blk];
1284 /* block switching */
1285 for (ch = 0; ch < s->fbw_channels; ch++)
1286 put_bits(&s->pb, 1, 0);
1289 for (ch = 0; ch < s->fbw_channels; ch++)
1290 put_bits(&s->pb, 1, 1);
1292 /* dynamic range codes */
1293 put_bits(&s->pb, 1, 0);
1295 /* channel coupling */
1297 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1298 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1300 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1303 /* stereo rematrixing */
1304 if (s->channel_mode == AC3_CHMODE_STEREO) {
1305 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1306 if (block->new_rematrixing_strategy) {
1307 /* rematrixing flags */
1308 for (rbnd = 0; rbnd < 4; rbnd++)
1309 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1313 /* exponent strategy */
1314 for (ch = 0; ch < s->fbw_channels; ch++)
1315 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
1317 put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
1320 for (ch = 0; ch < s->fbw_channels; ch++) {
1321 if (s->exp_strategy[ch][blk] != EXP_REUSE)
1322 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1326 for (ch = 0; ch < s->channels; ch++) {
1329 if (s->exp_strategy[ch][blk] == EXP_REUSE)
1333 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1335 /* exponent groups */
1336 nb_groups = exponent_group_tab[s->exp_strategy[ch][blk]-1][s->nb_coefs[ch]];
1337 for (i = 1; i <= nb_groups; i++)
1338 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1340 /* gain range info */
1341 if (ch != s->lfe_channel)
1342 put_bits(&s->pb, 2, 0);
1345 /* bit allocation info */
1347 put_bits(&s->pb, 1, baie);
1349 put_bits(&s->pb, 2, s->slow_decay_code);
1350 put_bits(&s->pb, 2, s->fast_decay_code);
1351 put_bits(&s->pb, 2, s->slow_gain_code);
1352 put_bits(&s->pb, 2, s->db_per_bit_code);
1353 put_bits(&s->pb, 3, s->floor_code);
1357 put_bits(&s->pb, 1, baie);
1359 put_bits(&s->pb, 6, s->coarse_snr_offset);
1360 for (ch = 0; ch < s->channels; ch++) {
1361 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1362 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1366 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1367 put_bits(&s->pb, 1, 0); /* no data to skip */
1370 for (ch = 0; ch < s->channels; ch++) {
1372 for (i = 0; i < s->nb_coefs[ch]; i++) {
1373 q = block->qmant[ch][i];
1374 b = block->bap[ch][i];
1377 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1378 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1379 case 3: put_bits(&s->pb, 3, q); break;
1380 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1381 case 14: put_bits(&s->pb, 14, q); break;
1382 case 15: put_bits(&s->pb, 16, q); break;
1383 default: put_bits(&s->pb, b-1, q); break;
1390 /** CRC-16 Polynomial */
1391 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1394 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1411 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1417 r = mul_poly(r, a, poly);
1418 a = mul_poly(a, a, poly);
1426 * Fill the end of the frame with 0's and compute the two CRCs.
1428 static void output_frame_end(AC3EncodeContext *s)
1430 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1431 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1434 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1436 /* pad the remainder of the frame with zeros */
1437 flush_put_bits(&s->pb);
1439 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1440 assert(pad_bytes >= 0);
1442 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1445 /* this is not so easy because it is at the beginning of the data... */
1446 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1447 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1448 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1449 AV_WB16(frame + 2, crc1);
1452 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1453 s->frame_size - frame_size_58 - 3);
1454 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1455 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1456 if (crc2 == 0x770B) {
1457 frame[s->frame_size - 3] ^= 0x1;
1458 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1460 crc2 = av_bswap16(crc2);
1461 AV_WB16(frame + s->frame_size - 2, crc2);
1466 * Write the frame to the output bitstream.
1468 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1472 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1474 output_frame_header(s);
1476 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1477 output_audio_block(s, blk);
1479 output_frame_end(s);
1484 * Encode a single AC-3 frame.
1486 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1487 int buf_size, void *data)
1489 AC3EncodeContext *s = avctx->priv_data;
1490 const SampleType *samples = data;
1493 if (s->bit_alloc.sr_code == 1)
1494 adjust_frame_size(s);
1496 deinterleave_input_samples(s, samples);
1500 compute_rematrixing_strategy(s);
1502 scale_coefficients(s);
1504 apply_rematrixing(s);
1506 process_exponents(s);
1508 ret = compute_bit_allocation(s);
1510 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1514 quantize_mantissas(s);
1516 output_frame(s, frame);
1518 return s->frame_size;
1523 * Finalize encoding and free any memory allocated by the encoder.
1525 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1528 AC3EncodeContext *s = avctx->priv_data;
1530 for (ch = 0; ch < s->channels; ch++)
1531 av_freep(&s->planar_samples[ch]);
1532 av_freep(&s->planar_samples);
1533 av_freep(&s->bap_buffer);
1534 av_freep(&s->bap1_buffer);
1535 av_freep(&s->mdct_coef_buffer);
1536 av_freep(&s->fixed_coef_buffer);
1537 av_freep(&s->exp_buffer);
1538 av_freep(&s->grouped_exp_buffer);
1539 av_freep(&s->psd_buffer);
1540 av_freep(&s->band_psd_buffer);
1541 av_freep(&s->mask_buffer);
1542 av_freep(&s->qmant_buffer);
1543 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1544 AC3Block *block = &s->blocks[blk];
1545 av_freep(&block->bap);
1546 av_freep(&block->mdct_coef);
1547 av_freep(&block->fixed_coef);
1548 av_freep(&block->exp);
1549 av_freep(&block->grouped_exp);
1550 av_freep(&block->psd);
1551 av_freep(&block->band_psd);
1552 av_freep(&block->mask);
1553 av_freep(&block->qmant);
1558 av_freep(&avctx->coded_frame);
1564 * Set channel information during initialization.
1566 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1567 int64_t *channel_layout)
1571 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1572 return AVERROR(EINVAL);
1573 if ((uint64_t)*channel_layout > 0x7FF)
1574 return AVERROR(EINVAL);
1575 ch_layout = *channel_layout;
1577 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1578 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1579 return AVERROR(EINVAL);
1581 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1582 s->channels = channels;
1583 s->fbw_channels = channels - s->lfe_on;
1584 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1586 ch_layout -= AV_CH_LOW_FREQUENCY;
1588 switch (ch_layout) {
1589 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1590 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1591 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1592 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1593 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1594 case AV_CH_LAYOUT_QUAD:
1595 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1596 case AV_CH_LAYOUT_5POINT0:
1597 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1599 return AVERROR(EINVAL);
1602 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1603 *channel_layout = ch_layout;
1605 *channel_layout |= AV_CH_LOW_FREQUENCY;
1611 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1615 /* validate channel layout */
1616 if (!avctx->channel_layout) {
1617 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1618 "encoder will guess the layout, but it "
1619 "might be incorrect.\n");
1621 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1623 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1627 /* validate sample rate */
1628 for (i = 0; i < 9; i++) {
1629 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1633 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1634 return AVERROR(EINVAL);
1636 s->sample_rate = avctx->sample_rate;
1637 s->bit_alloc.sr_shift = i % 3;
1638 s->bit_alloc.sr_code = i / 3;
1640 /* validate bit rate */
1641 for (i = 0; i < 19; i++) {
1642 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1646 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1647 return AVERROR(EINVAL);
1649 s->bit_rate = avctx->bit_rate;
1650 s->frame_size_code = i << 1;
1652 /* validate cutoff */
1653 if (avctx->cutoff < 0) {
1654 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1655 return AVERROR(EINVAL);
1657 s->cutoff = avctx->cutoff;
1658 if (s->cutoff > (s->sample_rate >> 1))
1659 s->cutoff = s->sample_rate >> 1;
1666 * Set bandwidth for all channels.
1667 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1668 * default value will be used.
1670 static av_cold void set_bandwidth(AC3EncodeContext *s)
1675 /* calculate bandwidth based on user-specified cutoff frequency */
1677 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1678 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1680 /* use default bandwidth setting */
1681 /* XXX: should compute the bandwidth according to the frame
1682 size, so that we avoid annoying high frequency artifacts */
1686 /* set number of coefficients for each channel */
1687 for (ch = 0; ch < s->fbw_channels; ch++) {
1688 s->bandwidth_code[ch] = bw_code;
1689 s->nb_coefs[ch] = bw_code * 3 + 73;
1692 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1696 static av_cold int allocate_buffers(AVCodecContext *avctx)
1699 AC3EncodeContext *s = avctx->priv_data;
1701 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1703 for (ch = 0; ch < s->channels; ch++) {
1704 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1705 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1708 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1709 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1710 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1711 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1712 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1713 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1714 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1715 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1716 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1717 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1718 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1719 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1720 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1721 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1722 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1723 64 * sizeof(*s->mask_buffer), alloc_fail);
1724 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1725 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1726 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1727 AC3Block *block = &s->blocks[blk];
1728 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1730 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1732 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1734 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1736 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1738 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1740 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1742 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1745 for (ch = 0; ch < s->channels; ch++) {
1746 /* arrangement: block, channel, coeff */
1747 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1748 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1749 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1750 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1751 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1752 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1753 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1755 /* arrangement: channel, block, coeff */
1756 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)];
1760 if (CONFIG_AC3ENC_FLOAT) {
1761 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1762 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1763 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1764 AC3Block *block = &s->blocks[blk];
1765 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1766 sizeof(*block->fixed_coef), alloc_fail);
1767 for (ch = 0; ch < s->channels; ch++)
1768 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1771 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1772 AC3Block *block = &s->blocks[blk];
1773 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1774 sizeof(*block->fixed_coef), alloc_fail);
1775 for (ch = 0; ch < s->channels; ch++)
1776 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1782 return AVERROR(ENOMEM);
1787 * Initialize the encoder.
1789 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1791 AC3EncodeContext *s = avctx->priv_data;
1792 int ret, frame_size_58;
1794 avctx->frame_size = AC3_FRAME_SIZE;
1796 ff_ac3_common_init();
1798 ret = validate_options(avctx, s);
1802 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1803 s->bitstream_mode = 0; /* complete main audio service */
1805 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1806 s->bits_written = 0;
1807 s->samples_written = 0;
1808 s->frame_size = s->frame_size_min;
1810 /* calculate crc_inv for both possible frame sizes */
1811 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1812 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1813 if (s->bit_alloc.sr_code == 1) {
1814 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1815 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1820 rematrixing_init(s);
1826 ret = mdct_init(avctx, &s->mdct, 9);
1830 ret = allocate_buffers(avctx);
1834 avctx->coded_frame= avcodec_alloc_frame();
1836 dsputil_init(&s->dsp, avctx);
1837 ff_ac3dsp_init(&s->ac3dsp);
1841 ac3_encode_close(avctx);