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 int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent 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->exp_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;
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 int exp_shift = block->exp_shift[ch];
420 for (i = 0; i < AC3_MAX_COEFS; i++) {
422 int v = abs(coef[i]);
426 e = 23 - av_log2(v) + exp_shift;
441 * Exponent Difference Threshold.
442 * New exponents are sent if their SAD exceed this number.
444 #define EXP_DIFF_THRESHOLD 500
448 * Calculate exponent strategies for all blocks in a single channel.
450 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
456 /* estimate if the exponent variation & decide if they should be
457 reused in the next frame */
458 exp_strategy[0] = EXP_NEW;
459 exp += AC3_MAX_COEFS;
460 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
461 exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
462 if (exp_diff > EXP_DIFF_THRESHOLD)
463 exp_strategy[blk] = EXP_NEW;
465 exp_strategy[blk] = EXP_REUSE;
466 exp += AC3_MAX_COEFS;
469 /* now select the encoding strategy type : if exponents are often
470 recoded, we use a coarse encoding */
472 while (blk < AC3_MAX_BLOCKS) {
474 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
476 switch (blk1 - blk) {
477 case 1: exp_strategy[blk] = EXP_D45; break;
479 case 3: exp_strategy[blk] = EXP_D25; break;
480 default: exp_strategy[blk] = EXP_D15; break;
488 * Calculate exponent strategies for all channels.
489 * Array arrangement is reversed to simplify the per-channel calculation.
491 static void compute_exp_strategy(AC3EncodeContext *s)
495 for (ch = 0; ch < s->fbw_channels; ch++) {
496 compute_exp_strategy_ch(s, s->exp_strategy[ch], s->blocks[0].exp[ch]);
500 s->exp_strategy[ch][0] = EXP_D15;
501 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
502 s->exp_strategy[ch][blk] = EXP_REUSE;
508 * Update the exponents so that they are the ones the decoder will decode.
510 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
514 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
516 /* for each group, compute the minimum exponent */
517 switch(exp_strategy) {
519 for (i = 1, k = 1; i <= nb_groups; i++) {
520 uint8_t exp_min = exp[k];
521 if (exp[k+1] < exp_min)
528 for (i = 1, k = 1; i <= nb_groups; i++) {
529 uint8_t exp_min = exp[k];
530 if (exp[k+1] < exp_min)
532 if (exp[k+2] < exp_min)
534 if (exp[k+3] < exp_min)
542 /* constraint for DC exponent */
546 /* decrease the delta between each groups to within 2 so that they can be
547 differentially encoded */
548 for (i = 1; i <= nb_groups; i++)
549 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
552 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
554 /* now we have the exponent values the decoder will see */
555 switch (exp_strategy) {
557 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
558 uint8_t exp1 = exp[i];
564 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
565 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
574 * Encode exponents from original extracted form to what the decoder will see.
575 * This copies and groups exponents based on exponent strategy and reduces
576 * deltas between adjacent exponent groups so that they can be differentially
579 static void encode_exponents(AC3EncodeContext *s)
582 uint8_t *exp, *exp1, *exp_strategy;
583 int nb_coefs, num_reuse_blocks;
585 for (ch = 0; ch < s->channels; ch++) {
586 exp = s->blocks[0].exp[ch];
587 exp_strategy = s->exp_strategy[ch];
588 nb_coefs = s->nb_coefs[ch];
591 while (blk < AC3_MAX_BLOCKS) {
594 /* count the number of EXP_REUSE blocks after the current block */
595 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
597 num_reuse_blocks = blk1 - blk - 1;
599 /* for the EXP_REUSE case we select the min of the exponents */
600 s->ac3dsp.ac3_exponent_min(exp, num_reuse_blocks, nb_coefs);
602 encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]);
604 /* copy encoded exponents for reuse case */
605 exp1 = exp + AC3_MAX_COEFS;
606 while (blk < blk1-1) {
607 memcpy(exp1, exp, nb_coefs * sizeof(*exp));
608 exp1 += AC3_MAX_COEFS;
620 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
621 * varies depending on exponent strategy and bandwidth.
623 static void group_exponents(AC3EncodeContext *s)
626 int group_size, nb_groups, bit_count;
628 int delta0, delta1, delta2;
632 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
633 AC3Block *block = &s->blocks[blk];
634 for (ch = 0; ch < s->channels; ch++) {
635 int exp_strategy = s->exp_strategy[ch][blk];
636 if (exp_strategy == EXP_REUSE)
638 group_size = exp_strategy + (exp_strategy == EXP_D45);
639 nb_groups = exponent_group_tab[exp_strategy-1][s->nb_coefs[ch]];
640 bit_count += 4 + (nb_groups * 7);
645 block->grouped_exp[ch][0] = exp1;
647 /* remaining exponents are delta encoded */
648 for (i = 1; i <= nb_groups; i++) {
649 /* merge three delta in one code */
653 delta0 = exp1 - exp0 + 2;
654 av_assert2(delta0 >= 0 && delta0 <= 4);
659 delta1 = exp1 - exp0 + 2;
660 av_assert2(delta1 >= 0 && delta1 <= 4);
665 delta2 = exp1 - exp0 + 2;
666 av_assert2(delta2 >= 0 && delta2 <= 4);
668 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
673 s->exponent_bits = bit_count;
678 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
679 * Extract exponents from MDCT coefficients, calculate exponent strategies,
680 * and encode final exponents.
682 static void process_exponents(AC3EncodeContext *s)
684 extract_exponents(s);
686 compute_exp_strategy(s);
697 * Count frame bits that are based solely on fixed parameters.
698 * This only has to be run once when the encoder is initialized.
700 static void count_frame_bits_fixed(AC3EncodeContext *s)
702 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
707 * no dynamic range codes
708 * no channel coupling
709 * bit allocation parameters do not change between blocks
710 * SNR offsets do not change between blocks
711 * no delta bit allocation
718 frame_bits += frame_bits_inc[s->channel_mode];
721 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
722 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
723 if (s->channel_mode == AC3_CHMODE_STEREO) {
724 frame_bits++; /* rematstr */
726 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
728 frame_bits++; /* lfeexpstr */
729 frame_bits++; /* baie */
730 frame_bits++; /* snr */
731 frame_bits += 2; /* delta / skip */
733 frame_bits++; /* cplinu for block 0 */
735 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
737 /* (fsnoffset[4] + fgaincod[4]) * c */
738 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
740 /* auxdatae, crcrsv */
746 s->frame_bits_fixed = frame_bits;
751 * Initialize bit allocation.
752 * Set default parameter codes and calculate parameter values.
754 static void bit_alloc_init(AC3EncodeContext *s)
758 /* init default parameters */
759 s->slow_decay_code = 2;
760 s->fast_decay_code = 1;
761 s->slow_gain_code = 1;
762 s->db_per_bit_code = 3;
764 for (ch = 0; ch < s->channels; ch++)
765 s->fast_gain_code[ch] = 4;
767 /* initial snr offset */
768 s->coarse_snr_offset = 40;
770 /* compute real values */
771 /* currently none of these values change during encoding, so we can just
772 set them once at initialization */
773 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
774 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
775 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
776 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
777 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
779 count_frame_bits_fixed(s);
784 * Count the bits used to encode the frame, minus exponents and mantissas.
785 * Bits based on fixed parameters have already been counted, so now we just
786 * have to add the bits based on parameters that change during encoding.
788 static void count_frame_bits(AC3EncodeContext *s)
793 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
794 /* stereo rematrixing */
795 if (s->channel_mode == AC3_CHMODE_STEREO &&
796 s->blocks[blk].new_rematrixing_strategy) {
797 frame_bits += s->num_rematrixing_bands;
800 for (ch = 0; ch < s->fbw_channels; ch++) {
801 if (s->exp_strategy[ch][blk] != EXP_REUSE)
802 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
805 s->frame_bits = s->frame_bits_fixed + frame_bits;
810 * Calculate the number of bits needed to encode a set of mantissas.
812 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
817 for (i = 0; i < nb_coefs; i++) {
820 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
822 } else if (b <= 13) {
823 // bap=5 to bap=13 use (bap-1) bits
826 // bap=14 uses 14 bits and bap=15 uses 16 bits
827 bits += (b == 14) ? 14 : 16;
835 * Finalize the mantissa bit count by adding in the grouped mantissas.
837 static int compute_mantissa_size_final(int mant_cnt[5])
839 // bap=1 : 3 mantissas in 5 bits
840 int bits = (mant_cnt[1] / 3) * 5;
841 // bap=2 : 3 mantissas in 7 bits
842 // bap=4 : 2 mantissas in 7 bits
843 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
844 // bap=3 : each mantissa is 3 bits
845 bits += mant_cnt[3] * 3;
851 * Calculate masking curve based on the final exponents.
852 * Also calculate the power spectral densities to use in future calculations.
854 static void bit_alloc_masking(AC3EncodeContext *s)
858 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
859 AC3Block *block = &s->blocks[blk];
860 for (ch = 0; ch < s->channels; ch++) {
861 /* We only need psd and mask for calculating bap.
862 Since we currently do not calculate bap when exponent
863 strategy is EXP_REUSE we do not need to calculate psd or mask. */
864 if (s->exp_strategy[ch][blk] != EXP_REUSE) {
865 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
867 block->psd[ch], block->band_psd[ch]);
868 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
870 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
871 ch == s->lfe_channel,
872 DBA_NONE, 0, NULL, NULL, NULL,
881 * Ensure that bap for each block and channel point to the current bap_buffer.
882 * They may have been switched during the bit allocation search.
884 static void reset_block_bap(AC3EncodeContext *s)
887 if (s->blocks[0].bap[0] == s->bap_buffer)
889 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
890 for (ch = 0; ch < s->channels; ch++) {
891 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
898 * Run the bit allocation with a given SNR offset.
899 * This calculates the bit allocation pointers that will be used to determine
900 * the quantization of each mantissa.
901 * @return the number of bits needed for mantissas if the given SNR offset is
904 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
910 snr_offset = (snr_offset - 240) << 2;
914 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
915 AC3Block *block = &s->blocks[blk];
916 // initialize grouped mantissa counts. these are set so that they are
917 // padded to the next whole group size when bits are counted in
918 // compute_mantissa_size_final
919 mant_cnt[0] = mant_cnt[3] = 0;
920 mant_cnt[1] = mant_cnt[2] = 2;
922 for (ch = 0; ch < s->channels; ch++) {
923 /* Currently the only bit allocation parameters which vary across
924 blocks within a frame are the exponent values. We can take
925 advantage of that by reusing the bit allocation pointers
926 whenever we reuse exponents. */
927 if (s->exp_strategy[ch][blk] == EXP_REUSE) {
928 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
930 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
931 s->nb_coefs[ch], snr_offset,
932 s->bit_alloc.floor, ff_ac3_bap_tab,
935 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
937 mantissa_bits += compute_mantissa_size_final(mant_cnt);
939 return mantissa_bits;
944 * Constant bitrate bit allocation search.
945 * Find the largest SNR offset that will allow data to fit in the frame.
947 static int cbr_bit_allocation(AC3EncodeContext *s)
951 int snr_offset, snr_incr;
953 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
954 av_assert2(bits_left >= 0);
956 snr_offset = s->coarse_snr_offset << 4;
958 /* if previous frame SNR offset was 1023, check if current frame can also
959 use SNR offset of 1023. if so, skip the search. */
960 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
961 if (bit_alloc(s, 1023) <= bits_left)
965 while (snr_offset >= 0 &&
966 bit_alloc(s, snr_offset) > bits_left) {
970 return AVERROR(EINVAL);
972 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
973 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
974 while (snr_offset + snr_incr <= 1023 &&
975 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
976 snr_offset += snr_incr;
977 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
980 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
983 s->coarse_snr_offset = snr_offset >> 4;
984 for (ch = 0; ch < s->channels; ch++)
985 s->fine_snr_offset[ch] = snr_offset & 0xF;
992 * Downgrade exponent strategies to reduce the bits used by the exponents.
993 * This is a fallback for when bit allocation fails with the normal exponent
994 * strategies. Each time this function is run it only downgrades the
995 * strategy in 1 channel of 1 block.
996 * @return non-zero if downgrade was unsuccessful
998 static int downgrade_exponents(AC3EncodeContext *s)
1002 for (ch = 0; ch < s->fbw_channels; ch++) {
1003 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1004 if (s->exp_strategy[ch][blk] == EXP_D15) {
1005 s->exp_strategy[ch][blk] = EXP_D25;
1010 for (ch = 0; ch < s->fbw_channels; ch++) {
1011 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1012 if (s->exp_strategy[ch][blk] == EXP_D25) {
1013 s->exp_strategy[ch][blk] = EXP_D45;
1018 for (ch = 0; ch < s->fbw_channels; ch++) {
1019 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1020 the block number > 0 */
1021 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1022 if (s->exp_strategy[ch][blk] > EXP_REUSE) {
1023 s->exp_strategy[ch][blk] = EXP_REUSE;
1033 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1034 * This is a second fallback for when bit allocation still fails after exponents
1035 * have been downgraded.
1036 * @return non-zero if bandwidth reduction was unsuccessful
1038 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1042 if (s->bandwidth_code[0] > min_bw_code) {
1043 for (ch = 0; ch < s->fbw_channels; ch++) {
1044 s->bandwidth_code[ch]--;
1045 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1054 * Perform bit allocation search.
1055 * Finds the SNR offset value that maximizes quality and fits in the specified
1056 * frame size. Output is the SNR offset and a set of bit allocation pointers
1057 * used to quantize the mantissas.
1059 static int compute_bit_allocation(AC3EncodeContext *s)
1063 count_frame_bits(s);
1065 bit_alloc_masking(s);
1067 ret = cbr_bit_allocation(s);
1069 /* fallback 1: downgrade exponents */
1070 if (!downgrade_exponents(s)) {
1071 extract_exponents(s);
1072 encode_exponents(s);
1074 ret = compute_bit_allocation(s);
1078 /* fallback 2: reduce bandwidth */
1079 /* only do this if the user has not specified a specific cutoff
1081 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1082 process_exponents(s);
1083 ret = compute_bit_allocation(s);
1087 /* fallbacks were not enough... */
1096 * Symmetric quantization on 'levels' levels.
1098 static inline int sym_quant(int c, int e, int levels)
1103 v = (levels * (c << e)) >> 24;
1105 v = (levels >> 1) + v;
1107 v = (levels * ((-c) << e)) >> 24;
1109 v = (levels >> 1) - v;
1111 av_assert2(v >= 0 && v < levels);
1117 * Asymmetric quantization on 2^qbits levels.
1119 static inline int asym_quant(int c, int e, int qbits)
1123 lshift = e + qbits - 24;
1130 m = (1 << (qbits-1));
1133 av_assert2(v >= -m);
1134 return v & ((1 << qbits)-1);
1139 * Quantize a set of mantissas for a single channel in a single block.
1141 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1142 int8_t exp_shift, uint8_t *exp,
1143 uint8_t *bap, uint16_t *qmant, int n)
1147 for (i = 0; i < n; i++) {
1149 int c = fixed_coef[i];
1150 int e = exp[i] - exp_shift;
1157 v = sym_quant(c, e, 3);
1158 switch (s->mant1_cnt) {
1160 s->qmant1_ptr = &qmant[i];
1165 *s->qmant1_ptr += 3 * v;
1170 *s->qmant1_ptr += v;
1177 v = sym_quant(c, e, 5);
1178 switch (s->mant2_cnt) {
1180 s->qmant2_ptr = &qmant[i];
1185 *s->qmant2_ptr += 5 * v;
1190 *s->qmant2_ptr += v;
1197 v = sym_quant(c, e, 7);
1200 v = sym_quant(c, e, 11);
1201 switch (s->mant4_cnt) {
1203 s->qmant4_ptr = &qmant[i];
1208 *s->qmant4_ptr += v;
1215 v = sym_quant(c, e, 15);
1218 v = asym_quant(c, e, 14);
1221 v = asym_quant(c, e, 16);
1224 v = asym_quant(c, e, b - 1);
1233 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1235 static void quantize_mantissas(AC3EncodeContext *s)
1240 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1241 AC3Block *block = &s->blocks[blk];
1242 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1243 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1245 for (ch = 0; ch < s->channels; ch++) {
1246 quantize_mantissas_blk_ch(s, block->fixed_coef[ch], block->exp_shift[ch],
1247 block->exp[ch], block->bap[ch],
1248 block->qmant[ch], s->nb_coefs[ch]);
1255 * Write the AC-3 frame header to the output bitstream.
1257 static void output_frame_header(AC3EncodeContext *s)
1259 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1260 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1261 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1262 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1263 put_bits(&s->pb, 5, s->bitstream_id);
1264 put_bits(&s->pb, 3, s->bitstream_mode);
1265 put_bits(&s->pb, 3, s->channel_mode);
1266 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1267 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1268 if (s->channel_mode & 0x04)
1269 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1270 if (s->channel_mode == AC3_CHMODE_STEREO)
1271 put_bits(&s->pb, 2, 0); /* surround not indicated */
1272 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1273 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1274 put_bits(&s->pb, 1, 0); /* no compression control word */
1275 put_bits(&s->pb, 1, 0); /* no lang code */
1276 put_bits(&s->pb, 1, 0); /* no audio production info */
1277 put_bits(&s->pb, 1, 0); /* no copyright */
1278 put_bits(&s->pb, 1, 1); /* original bitstream */
1279 put_bits(&s->pb, 1, 0); /* no time code 1 */
1280 put_bits(&s->pb, 1, 0); /* no time code 2 */
1281 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1286 * Write one audio block to the output bitstream.
1288 static void output_audio_block(AC3EncodeContext *s, int blk)
1290 int ch, i, baie, rbnd;
1291 AC3Block *block = &s->blocks[blk];
1293 /* block switching */
1294 for (ch = 0; ch < s->fbw_channels; ch++)
1295 put_bits(&s->pb, 1, 0);
1298 for (ch = 0; ch < s->fbw_channels; ch++)
1299 put_bits(&s->pb, 1, 1);
1301 /* dynamic range codes */
1302 put_bits(&s->pb, 1, 0);
1304 /* channel coupling */
1306 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1307 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1309 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1312 /* stereo rematrixing */
1313 if (s->channel_mode == AC3_CHMODE_STEREO) {
1314 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1315 if (block->new_rematrixing_strategy) {
1316 /* rematrixing flags */
1317 for (rbnd = 0; rbnd < s->num_rematrixing_bands; rbnd++)
1318 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1322 /* exponent strategy */
1323 for (ch = 0; ch < s->fbw_channels; ch++)
1324 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
1326 put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
1329 for (ch = 0; ch < s->fbw_channels; ch++) {
1330 if (s->exp_strategy[ch][blk] != EXP_REUSE)
1331 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1335 for (ch = 0; ch < s->channels; ch++) {
1338 if (s->exp_strategy[ch][blk] == EXP_REUSE)
1342 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1344 /* exponent groups */
1345 nb_groups = exponent_group_tab[s->exp_strategy[ch][blk]-1][s->nb_coefs[ch]];
1346 for (i = 1; i <= nb_groups; i++)
1347 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1349 /* gain range info */
1350 if (ch != s->lfe_channel)
1351 put_bits(&s->pb, 2, 0);
1354 /* bit allocation info */
1356 put_bits(&s->pb, 1, baie);
1358 put_bits(&s->pb, 2, s->slow_decay_code);
1359 put_bits(&s->pb, 2, s->fast_decay_code);
1360 put_bits(&s->pb, 2, s->slow_gain_code);
1361 put_bits(&s->pb, 2, s->db_per_bit_code);
1362 put_bits(&s->pb, 3, s->floor_code);
1366 put_bits(&s->pb, 1, baie);
1368 put_bits(&s->pb, 6, s->coarse_snr_offset);
1369 for (ch = 0; ch < s->channels; ch++) {
1370 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1371 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1375 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1376 put_bits(&s->pb, 1, 0); /* no data to skip */
1379 for (ch = 0; ch < s->channels; ch++) {
1381 for (i = 0; i < s->nb_coefs[ch]; i++) {
1382 q = block->qmant[ch][i];
1383 b = block->bap[ch][i];
1386 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1387 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1388 case 3: put_bits(&s->pb, 3, q); break;
1389 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1390 case 14: put_bits(&s->pb, 14, q); break;
1391 case 15: put_bits(&s->pb, 16, q); break;
1392 default: put_bits(&s->pb, b-1, q); break;
1399 /** CRC-16 Polynomial */
1400 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1403 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1420 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1426 r = mul_poly(r, a, poly);
1427 a = mul_poly(a, a, poly);
1435 * Fill the end of the frame with 0's and compute the two CRCs.
1437 static void output_frame_end(AC3EncodeContext *s)
1439 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1440 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1443 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1445 /* pad the remainder of the frame with zeros */
1446 av_assert2(s->frame_size * 8 - put_bits_count(&s->pb) >= 18);
1447 flush_put_bits(&s->pb);
1449 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1450 av_assert2(pad_bytes >= 0);
1452 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1455 /* this is not so easy because it is at the beginning of the data... */
1456 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1457 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1458 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1459 AV_WB16(frame + 2, crc1);
1462 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1463 s->frame_size - frame_size_58 - 3);
1464 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1465 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1466 if (crc2 == 0x770B) {
1467 frame[s->frame_size - 3] ^= 0x1;
1468 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1470 crc2 = av_bswap16(crc2);
1471 AV_WB16(frame + s->frame_size - 2, crc2);
1476 * Write the frame to the output bitstream.
1478 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1482 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1484 output_frame_header(s);
1486 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1487 output_audio_block(s, blk);
1489 output_frame_end(s);
1494 * Encode a single AC-3 frame.
1496 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1497 int buf_size, void *data)
1499 AC3EncodeContext *s = avctx->priv_data;
1500 const SampleType *samples = data;
1503 if (s->bit_alloc.sr_code == 1)
1504 adjust_frame_size(s);
1506 deinterleave_input_samples(s, samples);
1510 compute_rematrixing_strategy(s);
1512 scale_coefficients(s);
1514 apply_rematrixing(s);
1516 process_exponents(s);
1518 ret = compute_bit_allocation(s);
1520 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1524 quantize_mantissas(s);
1526 output_frame(s, frame);
1528 return s->frame_size;
1533 * Finalize encoding and free any memory allocated by the encoder.
1535 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1538 AC3EncodeContext *s = avctx->priv_data;
1540 for (ch = 0; ch < s->channels; ch++)
1541 av_freep(&s->planar_samples[ch]);
1542 av_freep(&s->planar_samples);
1543 av_freep(&s->bap_buffer);
1544 av_freep(&s->bap1_buffer);
1545 av_freep(&s->mdct_coef_buffer);
1546 av_freep(&s->fixed_coef_buffer);
1547 av_freep(&s->exp_buffer);
1548 av_freep(&s->grouped_exp_buffer);
1549 av_freep(&s->psd_buffer);
1550 av_freep(&s->band_psd_buffer);
1551 av_freep(&s->mask_buffer);
1552 av_freep(&s->qmant_buffer);
1553 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1554 AC3Block *block = &s->blocks[blk];
1555 av_freep(&block->bap);
1556 av_freep(&block->mdct_coef);
1557 av_freep(&block->fixed_coef);
1558 av_freep(&block->exp);
1559 av_freep(&block->grouped_exp);
1560 av_freep(&block->psd);
1561 av_freep(&block->band_psd);
1562 av_freep(&block->mask);
1563 av_freep(&block->qmant);
1568 av_freep(&avctx->coded_frame);
1574 * Set channel information during initialization.
1576 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1577 int64_t *channel_layout)
1581 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1582 return AVERROR(EINVAL);
1583 if ((uint64_t)*channel_layout > 0x7FF)
1584 return AVERROR(EINVAL);
1585 ch_layout = *channel_layout;
1587 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1588 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1589 return AVERROR(EINVAL);
1591 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1592 s->channels = channels;
1593 s->fbw_channels = channels - s->lfe_on;
1594 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1596 ch_layout -= AV_CH_LOW_FREQUENCY;
1598 switch (ch_layout) {
1599 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1600 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1601 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1602 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1603 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1604 case AV_CH_LAYOUT_QUAD:
1605 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1606 case AV_CH_LAYOUT_5POINT0:
1607 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1609 return AVERROR(EINVAL);
1612 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1613 *channel_layout = ch_layout;
1615 *channel_layout |= AV_CH_LOW_FREQUENCY;
1621 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1625 /* validate channel layout */
1626 if (!avctx->channel_layout) {
1627 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1628 "encoder will guess the layout, but it "
1629 "might be incorrect.\n");
1631 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1633 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1637 /* validate sample rate */
1638 for (i = 0; i < 9; i++) {
1639 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1643 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1644 return AVERROR(EINVAL);
1646 s->sample_rate = avctx->sample_rate;
1647 s->bit_alloc.sr_shift = i % 3;
1648 s->bit_alloc.sr_code = i / 3;
1650 /* validate bit rate */
1651 for (i = 0; i < 19; i++) {
1652 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1656 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1657 return AVERROR(EINVAL);
1659 s->bit_rate = avctx->bit_rate;
1660 s->frame_size_code = i << 1;
1662 /* validate cutoff */
1663 if (avctx->cutoff < 0) {
1664 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1665 return AVERROR(EINVAL);
1667 s->cutoff = avctx->cutoff;
1668 if (s->cutoff > (s->sample_rate >> 1))
1669 s->cutoff = s->sample_rate >> 1;
1676 * Set bandwidth for all channels.
1677 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1678 * default value will be used.
1680 static av_cold void set_bandwidth(AC3EncodeContext *s)
1685 /* calculate bandwidth based on user-specified cutoff frequency */
1687 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1688 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1690 /* use default bandwidth setting */
1691 /* XXX: should compute the bandwidth according to the frame
1692 size, so that we avoid annoying high frequency artifacts */
1696 /* set number of coefficients for each channel */
1697 for (ch = 0; ch < s->fbw_channels; ch++) {
1698 s->bandwidth_code[ch] = bw_code;
1699 s->nb_coefs[ch] = bw_code * 3 + 73;
1702 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1706 static av_cold int allocate_buffers(AVCodecContext *avctx)
1709 AC3EncodeContext *s = avctx->priv_data;
1711 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1713 for (ch = 0; ch < s->channels; ch++) {
1714 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1715 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1718 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1719 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1720 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1721 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1722 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1723 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1724 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1725 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1726 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1727 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1728 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1729 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1730 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1731 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1732 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1733 64 * sizeof(*s->mask_buffer), alloc_fail);
1734 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1735 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1736 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1737 AC3Block *block = &s->blocks[blk];
1738 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1740 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1742 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1744 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1746 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1748 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1750 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1752 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1755 for (ch = 0; ch < s->channels; ch++) {
1756 /* arrangement: block, channel, coeff */
1757 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1758 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1759 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1760 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1761 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1762 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1763 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1765 /* arrangement: channel, block, coeff */
1766 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)];
1770 if (CONFIG_AC3ENC_FLOAT) {
1771 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1772 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1773 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1774 AC3Block *block = &s->blocks[blk];
1775 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1776 sizeof(*block->fixed_coef), alloc_fail);
1777 for (ch = 0; ch < s->channels; ch++)
1778 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1781 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1782 AC3Block *block = &s->blocks[blk];
1783 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1784 sizeof(*block->fixed_coef), alloc_fail);
1785 for (ch = 0; ch < s->channels; ch++)
1786 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1792 return AVERROR(ENOMEM);
1797 * Initialize the encoder.
1799 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1801 AC3EncodeContext *s = avctx->priv_data;
1802 int ret, frame_size_58;
1804 avctx->frame_size = AC3_FRAME_SIZE;
1806 ff_ac3_common_init();
1808 ret = validate_options(avctx, s);
1812 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1813 s->bitstream_mode = 0; /* complete main audio service */
1815 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1816 s->bits_written = 0;
1817 s->samples_written = 0;
1818 s->frame_size = s->frame_size_min;
1820 /* calculate crc_inv for both possible frame sizes */
1821 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1822 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1823 if (s->bit_alloc.sr_code == 1) {
1824 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1825 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1830 rematrixing_init(s);
1836 ret = mdct_init(avctx, &s->mdct, 9);
1840 ret = allocate_buffers(avctx);
1844 avctx->coded_frame= avcodec_alloc_frame();
1846 dsputil_init(&s->dsp, avctx);
1847 ff_ac3dsp_init(&s->ac3dsp);
1851 ac3_encode_close(avctx);