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.
30 //#define ASSERT_LEVEL 2
32 #include "libavutil/audioconvert.h"
33 #include "libavutil/avassert.h"
34 #include "libavutil/crc.h"
40 #include "audioconvert.h"
43 #ifndef CONFIG_AC3ENC_FLOAT
44 #define CONFIG_AC3ENC_FLOAT 0
48 /** Maximum number of exponent groups. +1 for separate DC exponent. */
49 #define AC3_MAX_EXP_GROUPS 85
51 /* stereo rematrixing algorithms */
52 #define AC3_REMATRIXING_IS_STATIC 0x1
53 #define AC3_REMATRIXING_SUMS 0
54 #define AC3_REMATRIXING_NONE 1
55 #define AC3_REMATRIXING_ALWAYS 3
57 /** Scale a float value by 2^bits and convert to an integer. */
58 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
61 #if CONFIG_AC3ENC_FLOAT
62 #include "ac3enc_float.h"
64 #include "ac3enc_fixed.h"
69 * Data for a single audio block.
71 typedef struct AC3Block {
72 uint8_t **bap; ///< bit allocation pointers (bap)
73 CoefType **mdct_coef; ///< MDCT coefficients
74 int32_t **fixed_coef; ///< fixed-point MDCT coefficients
75 uint8_t **exp; ///< original exponents
76 uint8_t **grouped_exp; ///< grouped exponents
77 int16_t **psd; ///< psd per frequency bin
78 int16_t **band_psd; ///< psd per critical band
79 int16_t **mask; ///< masking curve
80 uint16_t **qmant; ///< quantized mantissas
81 uint8_t coeff_shift[AC3_MAX_CHANNELS]; ///< fixed-point coefficient shift values
82 uint8_t new_rematrixing_strategy; ///< send new rematrixing flags in this block
83 uint8_t rematrixing_flags[4]; ///< rematrixing flags
87 * AC-3 encoder private context.
89 typedef struct AC3EncodeContext {
90 PutBitContext pb; ///< bitstream writer context
92 AC3DSPContext ac3dsp; ///< AC-3 optimized functions
93 AC3MDCTContext mdct; ///< MDCT context
95 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
97 int bitstream_id; ///< bitstream id (bsid)
98 int bitstream_mode; ///< bitstream mode (bsmod)
100 int bit_rate; ///< target bit rate, in bits-per-second
101 int sample_rate; ///< sampling frequency, in Hz
103 int frame_size_min; ///< minimum frame size in case rounding is necessary
104 int frame_size; ///< current frame size in bytes
105 int frame_size_code; ///< frame size code (frmsizecod)
107 int bits_written; ///< bit count (used to avg. bitrate)
108 int samples_written; ///< sample count (used to avg. bitrate)
110 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
111 int channels; ///< total number of channels (nchans)
112 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
113 int lfe_channel; ///< channel index of the LFE channel
114 int channel_mode; ///< channel mode (acmod)
115 const uint8_t *channel_map; ///< channel map used to reorder channels
117 int cutoff; ///< user-specified cutoff frequency, in Hz
118 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
119 int nb_coefs[AC3_MAX_CHANNELS];
121 int rematrixing; ///< determines how rematrixing strategy is calculated
122 int num_rematrixing_bands; ///< number of rematrixing bands
124 /* bitrate allocation control */
125 int slow_gain_code; ///< slow gain code (sgaincod)
126 int slow_decay_code; ///< slow decay code (sdcycod)
127 int fast_decay_code; ///< fast decay code (fdcycod)
128 int db_per_bit_code; ///< dB/bit code (dbpbcod)
129 int floor_code; ///< floor code (floorcod)
130 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
131 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
132 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
133 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
134 int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
135 int frame_bits; ///< all frame bits except exponents and mantissas
136 int exponent_bits; ///< number of bits used for exponents
138 /* mantissa encoding */
139 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
140 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
142 SampleType **planar_samples;
144 uint8_t *bap1_buffer;
145 CoefType *mdct_coef_buffer;
146 int32_t *fixed_coef_buffer;
148 uint8_t *grouped_exp_buffer;
150 int16_t *band_psd_buffer;
151 int16_t *mask_buffer;
152 uint16_t *qmant_buffer;
154 uint8_t exp_strategy[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< exponent strategies
156 DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
160 /* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */
162 static av_cold void mdct_end(AC3MDCTContext *mdct);
164 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
167 static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in);
169 static void apply_window(DSPContext *dsp, SampleType *output, const SampleType *input,
170 const SampleType *window, int n);
172 static int normalize_samples(AC3EncodeContext *s);
174 static void scale_coefficients(AC3EncodeContext *s);
178 * LUT for number of exponent groups.
179 * exponent_group_tab[exponent strategy-1][number of coefficients]
181 static uint8_t exponent_group_tab[3][256];
185 * List of supported channel layouts.
187 static const int64_t ac3_channel_layouts[] = {
191 AV_CH_LAYOUT_SURROUND,
194 AV_CH_LAYOUT_4POINT0,
195 AV_CH_LAYOUT_5POINT0,
196 AV_CH_LAYOUT_5POINT0_BACK,
197 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
198 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
199 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
200 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
201 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
202 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
203 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
204 AV_CH_LAYOUT_5POINT1,
205 AV_CH_LAYOUT_5POINT1_BACK,
211 * Adjust the frame size to make the average bit rate match the target bit rate.
212 * This is only needed for 11025, 22050, and 44100 sample rates.
214 static void adjust_frame_size(AC3EncodeContext *s)
216 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
217 s->bits_written -= s->bit_rate;
218 s->samples_written -= s->sample_rate;
220 s->frame_size = s->frame_size_min +
221 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
222 s->bits_written += s->frame_size * 8;
223 s->samples_written += AC3_FRAME_SIZE;
228 * Deinterleave input samples.
229 * Channels are reordered from FFmpeg's default order to AC-3 order.
231 static void deinterleave_input_samples(AC3EncodeContext *s,
232 const SampleType *samples)
236 /* deinterleave and remap input samples */
237 for (ch = 0; ch < s->channels; ch++) {
238 const SampleType *sptr;
241 /* copy last 256 samples of previous frame to the start of the current frame */
242 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
243 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
247 sptr = samples + s->channel_map[ch];
248 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
249 s->planar_samples[ch][i] = *sptr;
257 * Apply the MDCT to input samples to generate frequency coefficients.
258 * This applies the KBD window and normalizes the input to reduce precision
259 * loss due to fixed-point calculations.
261 static void apply_mdct(AC3EncodeContext *s)
265 for (ch = 0; ch < s->channels; ch++) {
266 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
267 AC3Block *block = &s->blocks[blk];
268 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
270 apply_window(&s->dsp, s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
272 block->coeff_shift[ch] = normalize_samples(s);
274 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
281 * Initialize stereo rematrixing.
282 * If the strategy does not change for each frame, set the rematrixing flags.
284 static void rematrixing_init(AC3EncodeContext *s)
286 if (s->channel_mode == AC3_CHMODE_STEREO)
287 s->rematrixing = AC3_REMATRIXING_SUMS;
289 s->rematrixing = AC3_REMATRIXING_NONE;
290 /* NOTE: AC3_REMATRIXING_ALWAYS might be used in
291 the future in conjunction with channel coupling. */
293 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC) {
294 int flag = (s->rematrixing == AC3_REMATRIXING_ALWAYS);
295 s->blocks[0].new_rematrixing_strategy = 1;
296 memset(s->blocks[0].rematrixing_flags, flag,
297 sizeof(s->blocks[0].rematrixing_flags));
303 * Determine rematrixing flags for each block and band.
305 static void compute_rematrixing_strategy(AC3EncodeContext *s)
309 AC3Block *block, *block0;
311 s->num_rematrixing_bands = 4;
313 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC)
316 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
318 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
319 block = &s->blocks[blk];
320 block->new_rematrixing_strategy = !blk;
321 for (bnd = 0; bnd < s->num_rematrixing_bands; bnd++) {
322 /* calculate calculate sum of squared coeffs for one band in one block */
323 int start = ff_ac3_rematrix_band_tab[bnd];
324 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
325 CoefSumType sum[4] = {0,};
326 for (i = start; i < end; i++) {
327 CoefType lt = block->mdct_coef[0][i];
328 CoefType rt = block->mdct_coef[1][i];
329 CoefType md = lt + rt;
330 CoefType sd = lt - rt;
331 MAC_COEF(sum[0], lt, lt);
332 MAC_COEF(sum[1], rt, rt);
333 MAC_COEF(sum[2], md, md);
334 MAC_COEF(sum[3], sd, sd);
337 /* compare sums to determine if rematrixing will be used for this band */
338 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
339 block->rematrixing_flags[bnd] = 1;
341 block->rematrixing_flags[bnd] = 0;
343 /* determine if new rematrixing flags will be sent */
345 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
346 block->new_rematrixing_strategy = 1;
355 * Apply stereo rematrixing to coefficients based on rematrixing flags.
357 static void apply_rematrixing(AC3EncodeContext *s)
364 if (s->rematrixing == AC3_REMATRIXING_NONE)
367 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
369 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
370 AC3Block *block = &s->blocks[blk];
371 if (block->new_rematrixing_strategy)
372 flags = block->rematrixing_flags;
373 for (bnd = 0; bnd < s->num_rematrixing_bands; bnd++) {
375 start = ff_ac3_rematrix_band_tab[bnd];
376 end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
377 for (i = start; i < end; i++) {
378 int32_t lt = block->fixed_coef[0][i];
379 int32_t rt = block->fixed_coef[1][i];
380 block->fixed_coef[0][i] = (lt + rt) >> 1;
381 block->fixed_coef[1][i] = (lt - rt) >> 1;
390 * Initialize exponent tables.
392 static av_cold void exponent_init(AC3EncodeContext *s)
395 for (i = 73; i < 256; i++) {
396 exponent_group_tab[0][i] = (i - 1) / 3;
397 exponent_group_tab[1][i] = (i + 2) / 6;
398 exponent_group_tab[2][i] = (i + 8) / 12;
401 exponent_group_tab[0][7] = 2;
406 * Extract exponents from the MDCT coefficients.
407 * This takes into account the normalization that was done to the input samples
408 * by adjusting the exponents by the exponent shift values.
410 static void extract_exponents(AC3EncodeContext *s)
414 for (ch = 0; ch < s->channels; ch++) {
415 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
416 AC3Block *block = &s->blocks[blk];
417 uint8_t *exp = block->exp[ch];
418 int32_t *coef = block->fixed_coef[ch];
419 for (i = 0; i < AC3_MAX_COEFS; i++) {
421 int v = abs(coef[i]);
440 * Exponent Difference Threshold.
441 * New exponents are sent if their SAD exceed this number.
443 #define EXP_DIFF_THRESHOLD 500
447 * Calculate exponent strategies for all blocks in a single channel.
449 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
455 /* estimate if the exponent variation & decide if they should be
456 reused in the next frame */
457 exp_strategy[0] = EXP_NEW;
458 exp += AC3_MAX_COEFS;
459 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
460 exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
461 if (exp_diff > EXP_DIFF_THRESHOLD)
462 exp_strategy[blk] = EXP_NEW;
464 exp_strategy[blk] = EXP_REUSE;
465 exp += AC3_MAX_COEFS;
468 /* now select the encoding strategy type : if exponents are often
469 recoded, we use a coarse encoding */
471 while (blk < AC3_MAX_BLOCKS) {
473 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
475 switch (blk1 - blk) {
476 case 1: exp_strategy[blk] = EXP_D45; break;
478 case 3: exp_strategy[blk] = EXP_D25; break;
479 default: exp_strategy[blk] = EXP_D15; break;
487 * Calculate exponent strategies for all channels.
488 * Array arrangement is reversed to simplify the per-channel calculation.
490 static void compute_exp_strategy(AC3EncodeContext *s)
494 for (ch = 0; ch < s->fbw_channels; ch++) {
495 compute_exp_strategy_ch(s, s->exp_strategy[ch], s->blocks[0].exp[ch]);
499 s->exp_strategy[ch][0] = EXP_D15;
500 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
501 s->exp_strategy[ch][blk] = EXP_REUSE;
507 * Update the exponents so that they are the ones the decoder will decode.
509 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
513 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
515 /* for each group, compute the minimum exponent */
516 switch(exp_strategy) {
518 for (i = 1, k = 1; i <= nb_groups; i++) {
519 uint8_t exp_min = exp[k];
520 if (exp[k+1] < exp_min)
527 for (i = 1, k = 1; i <= nb_groups; i++) {
528 uint8_t exp_min = exp[k];
529 if (exp[k+1] < exp_min)
531 if (exp[k+2] < exp_min)
533 if (exp[k+3] < exp_min)
541 /* constraint for DC exponent */
545 /* decrease the delta between each groups to within 2 so that they can be
546 differentially encoded */
547 for (i = 1; i <= nb_groups; i++)
548 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
551 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
553 /* now we have the exponent values the decoder will see */
554 switch (exp_strategy) {
556 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
557 uint8_t exp1 = exp[i];
563 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
564 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
573 * Encode exponents from original extracted form to what the decoder will see.
574 * This copies and groups exponents based on exponent strategy and reduces
575 * deltas between adjacent exponent groups so that they can be differentially
578 static void encode_exponents(AC3EncodeContext *s)
581 uint8_t *exp, *exp1, *exp_strategy;
582 int nb_coefs, num_reuse_blocks;
584 for (ch = 0; ch < s->channels; ch++) {
585 exp = s->blocks[0].exp[ch];
586 exp_strategy = s->exp_strategy[ch];
587 nb_coefs = s->nb_coefs[ch];
590 while (blk < AC3_MAX_BLOCKS) {
593 /* count the number of EXP_REUSE blocks after the current block */
594 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
596 num_reuse_blocks = blk1 - blk - 1;
598 /* for the EXP_REUSE case we select the min of the exponents */
599 s->ac3dsp.ac3_exponent_min(exp, num_reuse_blocks, nb_coefs);
601 encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]);
603 /* copy encoded exponents for reuse case */
604 exp1 = exp + AC3_MAX_COEFS;
605 while (blk < blk1-1) {
606 memcpy(exp1, exp, nb_coefs * sizeof(*exp));
607 exp1 += AC3_MAX_COEFS;
619 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
620 * varies depending on exponent strategy and bandwidth.
622 static void group_exponents(AC3EncodeContext *s)
625 int group_size, nb_groups, bit_count;
627 int delta0, delta1, delta2;
631 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
632 AC3Block *block = &s->blocks[blk];
633 for (ch = 0; ch < s->channels; ch++) {
634 int exp_strategy = s->exp_strategy[ch][blk];
635 if (exp_strategy == EXP_REUSE)
637 group_size = exp_strategy + (exp_strategy == EXP_D45);
638 nb_groups = exponent_group_tab[exp_strategy-1][s->nb_coefs[ch]];
639 bit_count += 4 + (nb_groups * 7);
644 block->grouped_exp[ch][0] = exp1;
646 /* remaining exponents are delta encoded */
647 for (i = 1; i <= nb_groups; i++) {
648 /* merge three delta in one code */
652 delta0 = exp1 - exp0 + 2;
653 av_assert2(delta0 >= 0 && delta0 <= 4);
658 delta1 = exp1 - exp0 + 2;
659 av_assert2(delta1 >= 0 && delta1 <= 4);
664 delta2 = exp1 - exp0 + 2;
665 av_assert2(delta2 >= 0 && delta2 <= 4);
667 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
672 s->exponent_bits = bit_count;
677 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
678 * Extract exponents from MDCT coefficients, calculate exponent strategies,
679 * and encode final exponents.
681 static void process_exponents(AC3EncodeContext *s)
683 extract_exponents(s);
685 compute_exp_strategy(s);
696 * Count frame bits that are based solely on fixed parameters.
697 * This only has to be run once when the encoder is initialized.
699 static void count_frame_bits_fixed(AC3EncodeContext *s)
701 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
706 * no dynamic range codes
707 * no channel coupling
708 * bit allocation parameters do not change between blocks
709 * SNR offsets do not change between blocks
710 * no delta bit allocation
717 frame_bits += frame_bits_inc[s->channel_mode];
720 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
721 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
722 if (s->channel_mode == AC3_CHMODE_STEREO) {
723 frame_bits++; /* rematstr */
725 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
727 frame_bits++; /* lfeexpstr */
728 frame_bits++; /* baie */
729 frame_bits++; /* snr */
730 frame_bits += 2; /* delta / skip */
732 frame_bits++; /* cplinu for block 0 */
734 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
736 /* (fsnoffset[4] + fgaincod[4]) * c */
737 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
739 /* auxdatae, crcrsv */
745 s->frame_bits_fixed = frame_bits;
750 * Initialize bit allocation.
751 * Set default parameter codes and calculate parameter values.
753 static void bit_alloc_init(AC3EncodeContext *s)
757 /* init default parameters */
758 s->slow_decay_code = 2;
759 s->fast_decay_code = 1;
760 s->slow_gain_code = 1;
761 s->db_per_bit_code = 3;
763 for (ch = 0; ch < s->channels; ch++)
764 s->fast_gain_code[ch] = 4;
766 /* initial snr offset */
767 s->coarse_snr_offset = 40;
769 /* compute real values */
770 /* currently none of these values change during encoding, so we can just
771 set them once at initialization */
772 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
773 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
774 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
775 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
776 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
778 count_frame_bits_fixed(s);
783 * Count the bits used to encode the frame, minus exponents and mantissas.
784 * Bits based on fixed parameters have already been counted, so now we just
785 * have to add the bits based on parameters that change during encoding.
787 static void count_frame_bits(AC3EncodeContext *s)
792 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
793 /* stereo rematrixing */
794 if (s->channel_mode == AC3_CHMODE_STEREO &&
795 s->blocks[blk].new_rematrixing_strategy) {
796 frame_bits += s->num_rematrixing_bands;
799 for (ch = 0; ch < s->fbw_channels; ch++) {
800 if (s->exp_strategy[ch][blk] != EXP_REUSE)
801 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
804 s->frame_bits = s->frame_bits_fixed + frame_bits;
809 * Calculate the number of bits needed to encode a set of mantissas.
811 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
816 for (i = 0; i < nb_coefs; i++) {
819 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
821 } else if (b <= 13) {
822 // bap=5 to bap=13 use (bap-1) bits
825 // bap=14 uses 14 bits and bap=15 uses 16 bits
826 bits += (b == 14) ? 14 : 16;
834 * Finalize the mantissa bit count by adding in the grouped mantissas.
836 static int compute_mantissa_size_final(int mant_cnt[5])
838 // bap=1 : 3 mantissas in 5 bits
839 int bits = (mant_cnt[1] / 3) * 5;
840 // bap=2 : 3 mantissas in 7 bits
841 // bap=4 : 2 mantissas in 7 bits
842 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
843 // bap=3 : each mantissa is 3 bits
844 bits += mant_cnt[3] * 3;
850 * Calculate masking curve based on the final exponents.
851 * Also calculate the power spectral densities to use in future calculations.
853 static void bit_alloc_masking(AC3EncodeContext *s)
857 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
858 AC3Block *block = &s->blocks[blk];
859 for (ch = 0; ch < s->channels; ch++) {
860 /* We only need psd and mask for calculating bap.
861 Since we currently do not calculate bap when exponent
862 strategy is EXP_REUSE we do not need to calculate psd or mask. */
863 if (s->exp_strategy[ch][blk] != EXP_REUSE) {
864 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
866 block->psd[ch], block->band_psd[ch]);
867 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
869 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
870 ch == s->lfe_channel,
871 DBA_NONE, 0, NULL, NULL, NULL,
880 * Ensure that bap for each block and channel point to the current bap_buffer.
881 * They may have been switched during the bit allocation search.
883 static void reset_block_bap(AC3EncodeContext *s)
886 if (s->blocks[0].bap[0] == s->bap_buffer)
888 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
889 for (ch = 0; ch < s->channels; ch++) {
890 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
897 * Run the bit allocation with a given SNR offset.
898 * This calculates the bit allocation pointers that will be used to determine
899 * the quantization of each mantissa.
900 * @return the number of bits needed for mantissas if the given SNR offset is
903 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
909 snr_offset = (snr_offset - 240) << 2;
913 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
914 AC3Block *block = &s->blocks[blk];
915 // initialize grouped mantissa counts. these are set so that they are
916 // padded to the next whole group size when bits are counted in
917 // compute_mantissa_size_final
918 mant_cnt[0] = mant_cnt[3] = 0;
919 mant_cnt[1] = mant_cnt[2] = 2;
921 for (ch = 0; ch < s->channels; ch++) {
922 /* Currently the only bit allocation parameters which vary across
923 blocks within a frame are the exponent values. We can take
924 advantage of that by reusing the bit allocation pointers
925 whenever we reuse exponents. */
926 if (s->exp_strategy[ch][blk] == EXP_REUSE) {
927 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
929 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
930 s->nb_coefs[ch], snr_offset,
931 s->bit_alloc.floor, ff_ac3_bap_tab,
934 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
936 mantissa_bits += compute_mantissa_size_final(mant_cnt);
938 return mantissa_bits;
943 * Constant bitrate bit allocation search.
944 * Find the largest SNR offset that will allow data to fit in the frame.
946 static int cbr_bit_allocation(AC3EncodeContext *s)
950 int snr_offset, snr_incr;
952 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
953 av_assert2(bits_left >= 0);
955 snr_offset = s->coarse_snr_offset << 4;
957 /* if previous frame SNR offset was 1023, check if current frame can also
958 use SNR offset of 1023. if so, skip the search. */
959 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
960 if (bit_alloc(s, 1023) <= bits_left)
964 while (snr_offset >= 0 &&
965 bit_alloc(s, snr_offset) > bits_left) {
969 return AVERROR(EINVAL);
971 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
972 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
973 while (snr_offset + snr_incr <= 1023 &&
974 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
975 snr_offset += snr_incr;
976 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
979 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
982 s->coarse_snr_offset = snr_offset >> 4;
983 for (ch = 0; ch < s->channels; ch++)
984 s->fine_snr_offset[ch] = snr_offset & 0xF;
991 * Downgrade exponent strategies to reduce the bits used by the exponents.
992 * This is a fallback for when bit allocation fails with the normal exponent
993 * strategies. Each time this function is run it only downgrades the
994 * strategy in 1 channel of 1 block.
995 * @return non-zero if downgrade was unsuccessful
997 static int downgrade_exponents(AC3EncodeContext *s)
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_D15) {
1004 s->exp_strategy[ch][blk] = EXP_D25;
1009 for (ch = 0; ch < s->fbw_channels; ch++) {
1010 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1011 if (s->exp_strategy[ch][blk] == EXP_D25) {
1012 s->exp_strategy[ch][blk] = EXP_D45;
1017 for (ch = 0; ch < s->fbw_channels; ch++) {
1018 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1019 the block number > 0 */
1020 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1021 if (s->exp_strategy[ch][blk] > EXP_REUSE) {
1022 s->exp_strategy[ch][blk] = EXP_REUSE;
1032 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1033 * This is a second fallback for when bit allocation still fails after exponents
1034 * have been downgraded.
1035 * @return non-zero if bandwidth reduction was unsuccessful
1037 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1041 if (s->bandwidth_code[0] > min_bw_code) {
1042 for (ch = 0; ch < s->fbw_channels; ch++) {
1043 s->bandwidth_code[ch]--;
1044 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1053 * Perform bit allocation search.
1054 * Finds the SNR offset value that maximizes quality and fits in the specified
1055 * frame size. Output is the SNR offset and a set of bit allocation pointers
1056 * used to quantize the mantissas.
1058 static int compute_bit_allocation(AC3EncodeContext *s)
1062 count_frame_bits(s);
1064 bit_alloc_masking(s);
1066 ret = cbr_bit_allocation(s);
1068 /* fallback 1: downgrade exponents */
1069 if (!downgrade_exponents(s)) {
1070 extract_exponents(s);
1071 encode_exponents(s);
1073 ret = compute_bit_allocation(s);
1077 /* fallback 2: reduce bandwidth */
1078 /* only do this if the user has not specified a specific cutoff
1080 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1081 process_exponents(s);
1082 ret = compute_bit_allocation(s);
1086 /* fallbacks were not enough... */
1095 * Symmetric quantization on 'levels' levels.
1097 static inline int sym_quant(int c, int e, int levels)
1102 v = (levels * (c << e)) >> 24;
1104 v = (levels >> 1) + v;
1106 v = (levels * ((-c) << e)) >> 24;
1108 v = (levels >> 1) - v;
1110 av_assert2(v >= 0 && v < levels);
1116 * Asymmetric quantization on 2^qbits levels.
1118 static inline int asym_quant(int c, int e, int qbits)
1122 lshift = e + qbits - 24;
1129 m = (1 << (qbits-1));
1132 av_assert2(v >= -m);
1133 return v & ((1 << qbits)-1);
1138 * Quantize a set of mantissas for a single channel in a single block.
1140 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1142 uint8_t *bap, uint16_t *qmant, int n)
1146 for (i = 0; i < n; i++) {
1148 int c = fixed_coef[i];
1156 v = sym_quant(c, e, 3);
1157 switch (s->mant1_cnt) {
1159 s->qmant1_ptr = &qmant[i];
1164 *s->qmant1_ptr += 3 * v;
1169 *s->qmant1_ptr += v;
1176 v = sym_quant(c, e, 5);
1177 switch (s->mant2_cnt) {
1179 s->qmant2_ptr = &qmant[i];
1184 *s->qmant2_ptr += 5 * v;
1189 *s->qmant2_ptr += v;
1196 v = sym_quant(c, e, 7);
1199 v = sym_quant(c, e, 11);
1200 switch (s->mant4_cnt) {
1202 s->qmant4_ptr = &qmant[i];
1207 *s->qmant4_ptr += v;
1214 v = sym_quant(c, e, 15);
1217 v = asym_quant(c, e, 14);
1220 v = asym_quant(c, e, 16);
1223 v = asym_quant(c, e, b - 1);
1232 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1234 static void quantize_mantissas(AC3EncodeContext *s)
1239 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1240 AC3Block *block = &s->blocks[blk];
1241 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1242 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1244 for (ch = 0; ch < s->channels; ch++) {
1245 quantize_mantissas_blk_ch(s, block->fixed_coef[ch],
1246 block->exp[ch], block->bap[ch],
1247 block->qmant[ch], s->nb_coefs[ch]);
1254 * Write the AC-3 frame header to the output bitstream.
1256 static void output_frame_header(AC3EncodeContext *s)
1258 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1259 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1260 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1261 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1262 put_bits(&s->pb, 5, s->bitstream_id);
1263 put_bits(&s->pb, 3, s->bitstream_mode);
1264 put_bits(&s->pb, 3, s->channel_mode);
1265 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1266 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1267 if (s->channel_mode & 0x04)
1268 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1269 if (s->channel_mode == AC3_CHMODE_STEREO)
1270 put_bits(&s->pb, 2, 0); /* surround not indicated */
1271 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1272 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1273 put_bits(&s->pb, 1, 0); /* no compression control word */
1274 put_bits(&s->pb, 1, 0); /* no lang code */
1275 put_bits(&s->pb, 1, 0); /* no audio production info */
1276 put_bits(&s->pb, 1, 0); /* no copyright */
1277 put_bits(&s->pb, 1, 1); /* original bitstream */
1278 put_bits(&s->pb, 1, 0); /* no time code 1 */
1279 put_bits(&s->pb, 1, 0); /* no time code 2 */
1280 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1285 * Write one audio block to the output bitstream.
1287 static void output_audio_block(AC3EncodeContext *s, int blk)
1289 int ch, i, baie, rbnd;
1290 AC3Block *block = &s->blocks[blk];
1292 /* block switching */
1293 for (ch = 0; ch < s->fbw_channels; ch++)
1294 put_bits(&s->pb, 1, 0);
1297 for (ch = 0; ch < s->fbw_channels; ch++)
1298 put_bits(&s->pb, 1, 1);
1300 /* dynamic range codes */
1301 put_bits(&s->pb, 1, 0);
1303 /* channel coupling */
1305 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1306 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1308 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1311 /* stereo rematrixing */
1312 if (s->channel_mode == AC3_CHMODE_STEREO) {
1313 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1314 if (block->new_rematrixing_strategy) {
1315 /* rematrixing flags */
1316 for (rbnd = 0; rbnd < s->num_rematrixing_bands; rbnd++)
1317 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1321 /* exponent strategy */
1322 for (ch = 0; ch < s->fbw_channels; ch++)
1323 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
1325 put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
1328 for (ch = 0; ch < s->fbw_channels; ch++) {
1329 if (s->exp_strategy[ch][blk] != EXP_REUSE)
1330 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1334 for (ch = 0; ch < s->channels; ch++) {
1337 if (s->exp_strategy[ch][blk] == EXP_REUSE)
1341 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1343 /* exponent groups */
1344 nb_groups = exponent_group_tab[s->exp_strategy[ch][blk]-1][s->nb_coefs[ch]];
1345 for (i = 1; i <= nb_groups; i++)
1346 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1348 /* gain range info */
1349 if (ch != s->lfe_channel)
1350 put_bits(&s->pb, 2, 0);
1353 /* bit allocation info */
1355 put_bits(&s->pb, 1, baie);
1357 put_bits(&s->pb, 2, s->slow_decay_code);
1358 put_bits(&s->pb, 2, s->fast_decay_code);
1359 put_bits(&s->pb, 2, s->slow_gain_code);
1360 put_bits(&s->pb, 2, s->db_per_bit_code);
1361 put_bits(&s->pb, 3, s->floor_code);
1365 put_bits(&s->pb, 1, baie);
1367 put_bits(&s->pb, 6, s->coarse_snr_offset);
1368 for (ch = 0; ch < s->channels; ch++) {
1369 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1370 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1374 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1375 put_bits(&s->pb, 1, 0); /* no data to skip */
1378 for (ch = 0; ch < s->channels; ch++) {
1380 for (i = 0; i < s->nb_coefs[ch]; i++) {
1381 q = block->qmant[ch][i];
1382 b = block->bap[ch][i];
1385 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1386 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1387 case 3: put_bits(&s->pb, 3, q); break;
1388 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1389 case 14: put_bits(&s->pb, 14, q); break;
1390 case 15: put_bits(&s->pb, 16, q); break;
1391 default: put_bits(&s->pb, b-1, q); break;
1398 /** CRC-16 Polynomial */
1399 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1402 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1419 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1425 r = mul_poly(r, a, poly);
1426 a = mul_poly(a, a, poly);
1434 * Fill the end of the frame with 0's and compute the two CRCs.
1436 static void output_frame_end(AC3EncodeContext *s)
1438 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1439 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1442 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1444 /* pad the remainder of the frame with zeros */
1445 av_assert2(s->frame_size * 8 - put_bits_count(&s->pb) >= 18);
1446 flush_put_bits(&s->pb);
1448 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1449 av_assert2(pad_bytes >= 0);
1451 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1454 /* this is not so easy because it is at the beginning of the data... */
1455 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1456 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1457 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1458 AV_WB16(frame + 2, crc1);
1461 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1462 s->frame_size - frame_size_58 - 3);
1463 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1464 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1465 if (crc2 == 0x770B) {
1466 frame[s->frame_size - 3] ^= 0x1;
1467 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1469 crc2 = av_bswap16(crc2);
1470 AV_WB16(frame + s->frame_size - 2, crc2);
1475 * Write the frame to the output bitstream.
1477 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1481 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1483 output_frame_header(s);
1485 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1486 output_audio_block(s, blk);
1488 output_frame_end(s);
1493 * Encode a single AC-3 frame.
1495 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1496 int buf_size, void *data)
1498 AC3EncodeContext *s = avctx->priv_data;
1499 const SampleType *samples = data;
1502 if (s->bit_alloc.sr_code == 1)
1503 adjust_frame_size(s);
1505 deinterleave_input_samples(s, samples);
1509 scale_coefficients(s);
1511 compute_rematrixing_strategy(s);
1513 apply_rematrixing(s);
1515 process_exponents(s);
1517 ret = compute_bit_allocation(s);
1519 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1523 quantize_mantissas(s);
1525 output_frame(s, frame);
1527 return s->frame_size;
1532 * Finalize encoding and free any memory allocated by the encoder.
1534 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1537 AC3EncodeContext *s = avctx->priv_data;
1539 for (ch = 0; ch < s->channels; ch++)
1540 av_freep(&s->planar_samples[ch]);
1541 av_freep(&s->planar_samples);
1542 av_freep(&s->bap_buffer);
1543 av_freep(&s->bap1_buffer);
1544 av_freep(&s->mdct_coef_buffer);
1545 av_freep(&s->fixed_coef_buffer);
1546 av_freep(&s->exp_buffer);
1547 av_freep(&s->grouped_exp_buffer);
1548 av_freep(&s->psd_buffer);
1549 av_freep(&s->band_psd_buffer);
1550 av_freep(&s->mask_buffer);
1551 av_freep(&s->qmant_buffer);
1552 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1553 AC3Block *block = &s->blocks[blk];
1554 av_freep(&block->bap);
1555 av_freep(&block->mdct_coef);
1556 av_freep(&block->fixed_coef);
1557 av_freep(&block->exp);
1558 av_freep(&block->grouped_exp);
1559 av_freep(&block->psd);
1560 av_freep(&block->band_psd);
1561 av_freep(&block->mask);
1562 av_freep(&block->qmant);
1567 av_freep(&avctx->coded_frame);
1573 * Set channel information during initialization.
1575 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1576 int64_t *channel_layout)
1580 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1581 return AVERROR(EINVAL);
1582 if ((uint64_t)*channel_layout > 0x7FF)
1583 return AVERROR(EINVAL);
1584 ch_layout = *channel_layout;
1586 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1587 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1588 return AVERROR(EINVAL);
1590 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1591 s->channels = channels;
1592 s->fbw_channels = channels - s->lfe_on;
1593 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1595 ch_layout -= AV_CH_LOW_FREQUENCY;
1597 switch (ch_layout) {
1598 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1599 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1600 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1601 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1602 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1603 case AV_CH_LAYOUT_QUAD:
1604 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1605 case AV_CH_LAYOUT_5POINT0:
1606 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1608 return AVERROR(EINVAL);
1611 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1612 *channel_layout = ch_layout;
1614 *channel_layout |= AV_CH_LOW_FREQUENCY;
1620 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1624 /* validate channel layout */
1625 if (!avctx->channel_layout) {
1626 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1627 "encoder will guess the layout, but it "
1628 "might be incorrect.\n");
1630 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1632 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1636 /* validate sample rate */
1637 for (i = 0; i < 9; i++) {
1638 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1642 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1643 return AVERROR(EINVAL);
1645 s->sample_rate = avctx->sample_rate;
1646 s->bit_alloc.sr_shift = i % 3;
1647 s->bit_alloc.sr_code = i / 3;
1649 /* validate bit rate */
1650 for (i = 0; i < 19; i++) {
1651 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1655 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1656 return AVERROR(EINVAL);
1658 s->bit_rate = avctx->bit_rate;
1659 s->frame_size_code = i << 1;
1661 /* validate cutoff */
1662 if (avctx->cutoff < 0) {
1663 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1664 return AVERROR(EINVAL);
1666 s->cutoff = avctx->cutoff;
1667 if (s->cutoff > (s->sample_rate >> 1))
1668 s->cutoff = s->sample_rate >> 1;
1675 * Set bandwidth for all channels.
1676 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1677 * default value will be used.
1679 static av_cold void set_bandwidth(AC3EncodeContext *s)
1684 /* calculate bandwidth based on user-specified cutoff frequency */
1686 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1687 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1689 /* use default bandwidth setting */
1690 /* XXX: should compute the bandwidth according to the frame
1691 size, so that we avoid annoying high frequency artifacts */
1695 /* set number of coefficients for each channel */
1696 for (ch = 0; ch < s->fbw_channels; ch++) {
1697 s->bandwidth_code[ch] = bw_code;
1698 s->nb_coefs[ch] = bw_code * 3 + 73;
1701 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1705 static av_cold int allocate_buffers(AVCodecContext *avctx)
1708 AC3EncodeContext *s = avctx->priv_data;
1710 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1712 for (ch = 0; ch < s->channels; ch++) {
1713 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1714 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1717 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1718 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1719 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1720 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1721 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1722 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1723 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1724 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1725 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1726 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1727 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1728 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1729 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1730 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1731 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1732 64 * sizeof(*s->mask_buffer), alloc_fail);
1733 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1734 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1735 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1736 AC3Block *block = &s->blocks[blk];
1737 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1739 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1741 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1743 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1745 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1747 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1749 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1751 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1754 for (ch = 0; ch < s->channels; ch++) {
1755 /* arrangement: block, channel, coeff */
1756 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1757 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1758 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1759 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1760 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1761 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1762 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1764 /* arrangement: channel, block, coeff */
1765 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)];
1769 if (CONFIG_AC3ENC_FLOAT) {
1770 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1771 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1772 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1773 AC3Block *block = &s->blocks[blk];
1774 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1775 sizeof(*block->fixed_coef), alloc_fail);
1776 for (ch = 0; ch < s->channels; ch++)
1777 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1780 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1781 AC3Block *block = &s->blocks[blk];
1782 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1783 sizeof(*block->fixed_coef), alloc_fail);
1784 for (ch = 0; ch < s->channels; ch++)
1785 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1791 return AVERROR(ENOMEM);
1796 * Initialize the encoder.
1798 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1800 AC3EncodeContext *s = avctx->priv_data;
1801 int ret, frame_size_58;
1803 avctx->frame_size = AC3_FRAME_SIZE;
1805 ff_ac3_common_init();
1807 ret = validate_options(avctx, s);
1811 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1812 s->bitstream_mode = 0; /* complete main audio service */
1814 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1815 s->bits_written = 0;
1816 s->samples_written = 0;
1817 s->frame_size = s->frame_size_min;
1819 /* calculate crc_inv for both possible frame sizes */
1820 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1821 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1822 if (s->bit_alloc.sr_code == 1) {
1823 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1824 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1829 rematrixing_init(s);
1835 ret = mdct_init(avctx, &s->mdct, 9);
1839 ret = allocate_buffers(avctx);
1843 avctx->coded_frame= avcodec_alloc_frame();
1845 dsputil_init(&s->dsp, avctx);
1846 ff_ac3dsp_init(&s->ac3dsp, avctx->flags & CODEC_FLAG_BITEXACT);
1850 ac3_encode_close(avctx);