2 * The simplest AC-3 encoder
3 * Copyright (c) 2000 Fabrice Bellard
4 * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
5 * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
7 * This file is part of FFmpeg.
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26 * The simplest AC-3 encoder.
31 #include "libavutil/audioconvert.h"
32 #include "libavutil/crc.h"
38 #include "audioconvert.h"
41 #ifndef CONFIG_AC3ENC_FLOAT
42 #define CONFIG_AC3ENC_FLOAT 0
46 /** Maximum number of exponent groups. +1 for separate DC exponent. */
47 #define AC3_MAX_EXP_GROUPS 85
49 /* stereo rematrixing algorithms */
50 #define AC3_REMATRIXING_IS_STATIC 0x1
51 #define AC3_REMATRIXING_SUMS 0
52 #define AC3_REMATRIXING_NONE 1
53 #define AC3_REMATRIXING_ALWAYS 3
55 /** Scale a float value by 2^bits and convert to an integer. */
56 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
59 #if CONFIG_AC3ENC_FLOAT
60 #include "ac3enc_float.h"
62 #include "ac3enc_fixed.h"
67 * Data for a single audio block.
69 typedef struct AC3Block {
70 uint8_t **bap; ///< bit allocation pointers (bap)
71 CoefType **mdct_coef; ///< MDCT coefficients
72 int32_t **fixed_coef; ///< fixed-point MDCT coefficients
73 uint8_t **exp; ///< original exponents
74 uint8_t **grouped_exp; ///< grouped exponents
75 int16_t **psd; ///< psd per frequency bin
76 int16_t **band_psd; ///< psd per critical band
77 int16_t **mask; ///< masking curve
78 uint16_t **qmant; ///< quantized mantissas
79 int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values
80 uint8_t new_rematrixing_strategy; ///< send new rematrixing flags in this block
81 uint8_t rematrixing_flags[4]; ///< rematrixing flags
85 * AC-3 encoder private context.
87 typedef struct AC3EncodeContext {
88 PutBitContext pb; ///< bitstream writer context
90 AC3DSPContext ac3dsp; ///< AC-3 optimized functions
91 AC3MDCTContext mdct; ///< MDCT context
93 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
95 int bitstream_id; ///< bitstream id (bsid)
96 int bitstream_mode; ///< bitstream mode (bsmod)
98 int bit_rate; ///< target bit rate, in bits-per-second
99 int sample_rate; ///< sampling frequency, in Hz
101 int frame_size_min; ///< minimum frame size in case rounding is necessary
102 int frame_size; ///< current frame size in bytes
103 int frame_size_code; ///< frame size code (frmsizecod)
105 int bits_written; ///< bit count (used to avg. bitrate)
106 int samples_written; ///< sample count (used to avg. bitrate)
108 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
109 int channels; ///< total number of channels (nchans)
110 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
111 int lfe_channel; ///< channel index of the LFE channel
112 int channel_mode; ///< channel mode (acmod)
113 const uint8_t *channel_map; ///< channel map used to reorder channels
115 int cutoff; ///< user-specified cutoff frequency, in Hz
116 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
117 int nb_coefs[AC3_MAX_CHANNELS];
119 int rematrixing; ///< determines how rematrixing strategy is calculated
121 /* bitrate allocation control */
122 int slow_gain_code; ///< slow gain code (sgaincod)
123 int slow_decay_code; ///< slow decay code (sdcycod)
124 int fast_decay_code; ///< fast decay code (fdcycod)
125 int db_per_bit_code; ///< dB/bit code (dbpbcod)
126 int floor_code; ///< floor code (floorcod)
127 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
128 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
129 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
130 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
131 int frame_bits_fixed; ///< number of non-coefficient bits for fixed parameters
132 int frame_bits; ///< all frame bits except exponents and mantissas
133 int exponent_bits; ///< number of bits used for exponents
135 /* mantissa encoding */
136 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
137 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
139 SampleType **planar_samples;
141 uint8_t *bap1_buffer;
142 CoefType *mdct_coef_buffer;
143 int32_t *fixed_coef_buffer;
145 uint8_t *grouped_exp_buffer;
147 int16_t *band_psd_buffer;
148 int16_t *mask_buffer;
149 uint16_t *qmant_buffer;
151 uint8_t exp_strategy[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS]; ///< exponent strategies
153 DECLARE_ALIGNED(16, SampleType, windowed_samples)[AC3_WINDOW_SIZE];
157 /* prototypes for functions in ac3enc_fixed.c and ac3enc_float.c */
159 static av_cold void mdct_end(AC3MDCTContext *mdct);
161 static av_cold int mdct_init(AVCodecContext *avctx, AC3MDCTContext *mdct,
164 static void mdct512(AC3MDCTContext *mdct, CoefType *out, SampleType *in);
166 static void apply_window(DSPContext *dsp, SampleType *output, const SampleType *input,
167 const SampleType *window, int n);
169 static int normalize_samples(AC3EncodeContext *s);
171 static void scale_coefficients(AC3EncodeContext *s);
175 * LUT for number of exponent groups.
176 * exponent_group_tab[exponent strategy-1][number of coefficients]
178 static uint8_t exponent_group_tab[3][256];
182 * List of supported channel layouts.
184 static const int64_t ac3_channel_layouts[] = {
188 AV_CH_LAYOUT_SURROUND,
191 AV_CH_LAYOUT_4POINT0,
192 AV_CH_LAYOUT_5POINT0,
193 AV_CH_LAYOUT_5POINT0_BACK,
194 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
195 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
196 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
197 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
198 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
199 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
200 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
201 AV_CH_LAYOUT_5POINT1,
202 AV_CH_LAYOUT_5POINT1_BACK,
208 * Adjust the frame size to make the average bit rate match the target bit rate.
209 * This is only needed for 11025, 22050, and 44100 sample rates.
211 static void adjust_frame_size(AC3EncodeContext *s)
213 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
214 s->bits_written -= s->bit_rate;
215 s->samples_written -= s->sample_rate;
217 s->frame_size = s->frame_size_min +
218 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
219 s->bits_written += s->frame_size * 8;
220 s->samples_written += AC3_FRAME_SIZE;
225 * Deinterleave input samples.
226 * Channels are reordered from FFmpeg's default order to AC-3 order.
228 static void deinterleave_input_samples(AC3EncodeContext *s,
229 const SampleType *samples)
233 /* deinterleave and remap input samples */
234 for (ch = 0; ch < s->channels; ch++) {
235 const SampleType *sptr;
238 /* copy last 256 samples of previous frame to the start of the current frame */
239 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
240 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
244 sptr = samples + s->channel_map[ch];
245 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
246 s->planar_samples[ch][i] = *sptr;
254 * Apply the MDCT to input samples to generate frequency coefficients.
255 * This applies the KBD window and normalizes the input to reduce precision
256 * loss due to fixed-point calculations.
258 static void apply_mdct(AC3EncodeContext *s)
262 for (ch = 0; ch < s->channels; ch++) {
263 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
264 AC3Block *block = &s->blocks[blk];
265 const SampleType *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
267 apply_window(&s->dsp, s->windowed_samples, input_samples, s->mdct.window, AC3_WINDOW_SIZE);
269 block->exp_shift[ch] = normalize_samples(s);
271 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
278 * Initialize stereo rematrixing.
279 * If the strategy does not change for each frame, set the rematrixing flags.
281 static void rematrixing_init(AC3EncodeContext *s)
283 if (s->channel_mode == AC3_CHMODE_STEREO)
284 s->rematrixing = AC3_REMATRIXING_SUMS;
286 s->rematrixing = AC3_REMATRIXING_NONE;
287 /* NOTE: AC3_REMATRIXING_ALWAYS might be used in
288 the future in conjunction with channel coupling. */
290 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC) {
291 int flag = (s->rematrixing == AC3_REMATRIXING_ALWAYS);
292 s->blocks[0].new_rematrixing_strategy = 1;
293 memset(s->blocks[0].rematrixing_flags, flag,
294 sizeof(s->blocks[0].rematrixing_flags));
300 * Determine rematrixing flags for each block and band.
302 static void compute_rematrixing_strategy(AC3EncodeContext *s)
306 AC3Block *block, *block0;
308 if (s->rematrixing & AC3_REMATRIXING_IS_STATIC)
311 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
313 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
314 block = &s->blocks[blk];
315 block->new_rematrixing_strategy = !blk;
316 for (bnd = 0; bnd < 4; bnd++) {
317 /* calculate calculate sum of squared coeffs for one band in one block */
318 int start = ff_ac3_rematrix_band_tab[bnd];
319 int end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
320 CoefSumType sum[4] = {0,};
321 for (i = start; i < end; i++) {
322 CoefType lt = block->mdct_coef[0][i];
323 CoefType rt = block->mdct_coef[1][i];
324 CoefType md = lt + rt;
325 CoefType sd = lt - rt;
332 /* compare sums to determine if rematrixing will be used for this band */
333 if (FFMIN(sum[2], sum[3]) < FFMIN(sum[0], sum[1]))
334 block->rematrixing_flags[bnd] = 1;
336 block->rematrixing_flags[bnd] = 0;
338 /* determine if new rematrixing flags will be sent */
340 block->rematrixing_flags[bnd] != block0->rematrixing_flags[bnd]) {
341 block->new_rematrixing_strategy = 1;
350 * Apply stereo rematrixing to coefficients based on rematrixing flags.
352 static void apply_rematrixing(AC3EncodeContext *s)
359 if (s->rematrixing == AC3_REMATRIXING_NONE)
362 nb_coefs = FFMIN(s->nb_coefs[0], s->nb_coefs[1]);
364 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
365 AC3Block *block = &s->blocks[blk];
366 if (block->new_rematrixing_strategy)
367 flags = block->rematrixing_flags;
368 for (bnd = 0; bnd < 4; bnd++) {
370 start = ff_ac3_rematrix_band_tab[bnd];
371 end = FFMIN(nb_coefs, ff_ac3_rematrix_band_tab[bnd+1]);
372 for (i = start; i < end; i++) {
373 int32_t lt = block->fixed_coef[0][i];
374 int32_t rt = block->fixed_coef[1][i];
375 block->fixed_coef[0][i] = (lt + rt) >> 1;
376 block->fixed_coef[1][i] = (lt - rt) >> 1;
385 * Initialize exponent tables.
387 static av_cold void exponent_init(AC3EncodeContext *s)
390 for (i = 73; i < 256; i++) {
391 exponent_group_tab[0][i] = (i - 1) / 3;
392 exponent_group_tab[1][i] = (i + 2) / 6;
393 exponent_group_tab[2][i] = (i + 8) / 12;
396 exponent_group_tab[0][7] = 2;
401 * Extract exponents from the MDCT coefficients.
402 * This takes into account the normalization that was done to the input samples
403 * by adjusting the exponents by the exponent shift values.
405 static void extract_exponents(AC3EncodeContext *s)
409 for (ch = 0; ch < s->channels; ch++) {
410 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
411 AC3Block *block = &s->blocks[blk];
412 uint8_t *exp = block->exp[ch];
413 int32_t *coef = block->fixed_coef[ch];
414 int exp_shift = block->exp_shift[ch];
415 for (i = 0; i < AC3_MAX_COEFS; i++) {
417 int v = abs(coef[i]);
421 e = 23 - av_log2(v) + exp_shift;
435 * Exponent Difference Threshold.
436 * New exponents are sent if their SAD exceed this number.
438 #define EXP_DIFF_THRESHOLD 500
442 * Calculate exponent strategies for all blocks in a single channel.
444 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy,
450 /* estimate if the exponent variation & decide if they should be
451 reused in the next frame */
452 exp_strategy[0] = EXP_NEW;
453 exp += AC3_MAX_COEFS;
454 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
455 exp_diff = s->dsp.sad[0](NULL, exp, exp - AC3_MAX_COEFS, 16, 16);
456 if (exp_diff > EXP_DIFF_THRESHOLD)
457 exp_strategy[blk] = EXP_NEW;
459 exp_strategy[blk] = EXP_REUSE;
460 exp += AC3_MAX_COEFS;
463 /* now select the encoding strategy type : if exponents are often
464 recoded, we use a coarse encoding */
466 while (blk < AC3_MAX_BLOCKS) {
468 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
470 switch (blk1 - blk) {
471 case 1: exp_strategy[blk] = EXP_D45; break;
473 case 3: exp_strategy[blk] = EXP_D25; break;
474 default: exp_strategy[blk] = EXP_D15; break;
482 * Calculate exponent strategies for all channels.
483 * Array arrangement is reversed to simplify the per-channel calculation.
485 static void compute_exp_strategy(AC3EncodeContext *s)
489 for (ch = 0; ch < s->fbw_channels; ch++) {
490 compute_exp_strategy_ch(s, s->exp_strategy[ch], s->blocks[0].exp[ch]);
494 s->exp_strategy[ch][0] = EXP_D15;
495 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
496 s->exp_strategy[ch][blk] = EXP_REUSE;
502 * Update the exponents so that they are the ones the decoder will decode.
504 static void encode_exponents_blk_ch(uint8_t *exp, int nb_exps, int exp_strategy)
508 nb_groups = exponent_group_tab[exp_strategy-1][nb_exps] * 3;
510 /* for each group, compute the minimum exponent */
511 switch(exp_strategy) {
513 for (i = 1, k = 1; i <= nb_groups; i++) {
514 uint8_t exp_min = exp[k];
515 if (exp[k+1] < exp_min)
522 for (i = 1, k = 1; i <= nb_groups; i++) {
523 uint8_t exp_min = exp[k];
524 if (exp[k+1] < exp_min)
526 if (exp[k+2] < exp_min)
528 if (exp[k+3] < exp_min)
536 /* constraint for DC exponent */
540 /* decrease the delta between each groups to within 2 so that they can be
541 differentially encoded */
542 for (i = 1; i <= nb_groups; i++)
543 exp[i] = FFMIN(exp[i], exp[i-1] + 2);
546 exp[i] = FFMIN(exp[i], exp[i+1] + 2);
548 /* now we have the exponent values the decoder will see */
549 switch (exp_strategy) {
551 for (i = nb_groups, k = nb_groups * 2; i > 0; i--) {
552 uint8_t exp1 = exp[i];
558 for (i = nb_groups, k = nb_groups * 4; i > 0; i--) {
559 exp[k] = exp[k-1] = exp[k-2] = exp[k-3] = exp[i];
568 * Encode exponents from original extracted form to what the decoder will see.
569 * This copies and groups exponents based on exponent strategy and reduces
570 * deltas between adjacent exponent groups so that they can be differentially
573 static void encode_exponents(AC3EncodeContext *s)
576 uint8_t *exp, *exp1, *exp_strategy;
577 int nb_coefs, num_reuse_blocks;
579 for (ch = 0; ch < s->channels; ch++) {
580 exp = s->blocks[0].exp[ch];
581 exp_strategy = s->exp_strategy[ch];
582 nb_coefs = s->nb_coefs[ch];
585 while (blk < AC3_MAX_BLOCKS) {
588 /* count the number of EXP_REUSE blocks after the current block */
589 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
591 num_reuse_blocks = blk1 - blk - 1;
593 /* for the EXP_REUSE case we select the min of the exponents */
594 s->ac3dsp.ac3_exponent_min(exp, num_reuse_blocks, nb_coefs);
596 encode_exponents_blk_ch(exp, nb_coefs, exp_strategy[blk]);
598 /* copy encoded exponents for reuse case */
599 exp1 = exp + AC3_MAX_COEFS;
600 while (blk < blk1-1) {
601 memcpy(exp1, exp, nb_coefs * sizeof(*exp));
602 exp1 += AC3_MAX_COEFS;
614 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
615 * varies depending on exponent strategy and bandwidth.
617 static void group_exponents(AC3EncodeContext *s)
620 int group_size, nb_groups, bit_count;
622 int delta0, delta1, delta2;
626 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
627 AC3Block *block = &s->blocks[blk];
628 for (ch = 0; ch < s->channels; ch++) {
629 int exp_strategy = s->exp_strategy[ch][blk];
630 if (exp_strategy == EXP_REUSE)
632 group_size = exp_strategy + (exp_strategy == EXP_D45);
633 nb_groups = exponent_group_tab[exp_strategy-1][s->nb_coefs[ch]];
634 bit_count += 4 + (nb_groups * 7);
639 block->grouped_exp[ch][0] = exp1;
641 /* remaining exponents are delta encoded */
642 for (i = 1; i <= nb_groups; i++) {
643 /* merge three delta in one code */
647 delta0 = exp1 - exp0 + 2;
652 delta1 = exp1 - exp0 + 2;
657 delta2 = exp1 - exp0 + 2;
659 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
664 s->exponent_bits = bit_count;
669 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
670 * Extract exponents from MDCT coefficients, calculate exponent strategies,
671 * and encode final exponents.
673 static void process_exponents(AC3EncodeContext *s)
675 extract_exponents(s);
677 compute_exp_strategy(s);
688 * Count frame bits that are based solely on fixed parameters.
689 * This only has to be run once when the encoder is initialized.
691 static void count_frame_bits_fixed(AC3EncodeContext *s)
693 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
698 * no dynamic range codes
699 * no channel coupling
700 * bit allocation parameters do not change between blocks
701 * SNR offsets do not change between blocks
702 * no delta bit allocation
709 frame_bits += frame_bits_inc[s->channel_mode];
712 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
713 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
714 if (s->channel_mode == AC3_CHMODE_STEREO) {
715 frame_bits++; /* rematstr */
717 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
719 frame_bits++; /* lfeexpstr */
720 frame_bits++; /* baie */
721 frame_bits++; /* snr */
722 frame_bits += 2; /* delta / skip */
724 frame_bits++; /* cplinu for block 0 */
726 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
728 /* (fsnoffset[4] + fgaincod[4]) * c */
729 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
731 /* auxdatae, crcrsv */
737 s->frame_bits_fixed = frame_bits;
742 * Initialize bit allocation.
743 * Set default parameter codes and calculate parameter values.
745 static void bit_alloc_init(AC3EncodeContext *s)
749 /* init default parameters */
750 s->slow_decay_code = 2;
751 s->fast_decay_code = 1;
752 s->slow_gain_code = 1;
753 s->db_per_bit_code = 3;
755 for (ch = 0; ch < s->channels; ch++)
756 s->fast_gain_code[ch] = 4;
758 /* initial snr offset */
759 s->coarse_snr_offset = 40;
761 /* compute real values */
762 /* currently none of these values change during encoding, so we can just
763 set them once at initialization */
764 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
765 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
766 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
767 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
768 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
770 count_frame_bits_fixed(s);
775 * Count the bits used to encode the frame, minus exponents and mantissas.
776 * Bits based on fixed parameters have already been counted, so now we just
777 * have to add the bits based on parameters that change during encoding.
779 static void count_frame_bits(AC3EncodeContext *s)
784 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
785 /* stereo rematrixing */
786 if (s->channel_mode == AC3_CHMODE_STEREO &&
787 s->blocks[blk].new_rematrixing_strategy) {
791 for (ch = 0; ch < s->fbw_channels; ch++) {
792 if (s->exp_strategy[ch][blk] != EXP_REUSE)
793 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
796 s->frame_bits = s->frame_bits_fixed + frame_bits;
801 * Calculate the number of bits needed to encode a set of mantissas.
803 static int compute_mantissa_size(int mant_cnt[5], uint8_t *bap, int nb_coefs)
808 for (i = 0; i < nb_coefs; i++) {
811 // bap=1 to bap=4 will be counted in compute_mantissa_size_final
813 } else if (b <= 13) {
814 // bap=5 to bap=13 use (bap-1) bits
817 // bap=14 uses 14 bits and bap=15 uses 16 bits
818 bits += (b == 14) ? 14 : 16;
826 * Finalize the mantissa bit count by adding in the grouped mantissas.
828 static int compute_mantissa_size_final(int mant_cnt[5])
830 // bap=1 : 3 mantissas in 5 bits
831 int bits = (mant_cnt[1] / 3) * 5;
832 // bap=2 : 3 mantissas in 7 bits
833 // bap=4 : 2 mantissas in 7 bits
834 bits += ((mant_cnt[2] / 3) + (mant_cnt[4] >> 1)) * 7;
835 // bap=3 : each mantissa is 3 bits
836 bits += mant_cnt[3] * 3;
842 * Calculate masking curve based on the final exponents.
843 * Also calculate the power spectral densities to use in future calculations.
845 static void bit_alloc_masking(AC3EncodeContext *s)
849 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
850 AC3Block *block = &s->blocks[blk];
851 for (ch = 0; ch < s->channels; ch++) {
852 /* We only need psd and mask for calculating bap.
853 Since we currently do not calculate bap when exponent
854 strategy is EXP_REUSE we do not need to calculate psd or mask. */
855 if (s->exp_strategy[ch][blk] != EXP_REUSE) {
856 ff_ac3_bit_alloc_calc_psd(block->exp[ch], 0,
858 block->psd[ch], block->band_psd[ch]);
859 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
861 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
862 ch == s->lfe_channel,
863 DBA_NONE, 0, NULL, NULL, NULL,
872 * Ensure that bap for each block and channel point to the current bap_buffer.
873 * They may have been switched during the bit allocation search.
875 static void reset_block_bap(AC3EncodeContext *s)
878 if (s->blocks[0].bap[0] == s->bap_buffer)
880 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
881 for (ch = 0; ch < s->channels; ch++) {
882 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
889 * Run the bit allocation with a given SNR offset.
890 * This calculates the bit allocation pointers that will be used to determine
891 * the quantization of each mantissa.
892 * @return the number of bits needed for mantissas if the given SNR offset is
895 static int bit_alloc(AC3EncodeContext *s, int snr_offset)
901 snr_offset = (snr_offset - 240) << 2;
905 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
906 AC3Block *block = &s->blocks[blk];
907 // initialize grouped mantissa counts. these are set so that they are
908 // padded to the next whole group size when bits are counted in
909 // compute_mantissa_size_final
910 mant_cnt[0] = mant_cnt[3] = 0;
911 mant_cnt[1] = mant_cnt[2] = 2;
913 for (ch = 0; ch < s->channels; ch++) {
914 /* Currently the only bit allocation parameters which vary across
915 blocks within a frame are the exponent values. We can take
916 advantage of that by reusing the bit allocation pointers
917 whenever we reuse exponents. */
918 if (s->exp_strategy[ch][blk] == EXP_REUSE) {
919 memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
921 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
922 s->nb_coefs[ch], snr_offset,
923 s->bit_alloc.floor, ff_ac3_bap_tab,
926 mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
928 mantissa_bits += compute_mantissa_size_final(mant_cnt);
930 return mantissa_bits;
935 * Constant bitrate bit allocation search.
936 * Find the largest SNR offset that will allow data to fit in the frame.
938 static int cbr_bit_allocation(AC3EncodeContext *s)
942 int snr_offset, snr_incr;
944 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
946 snr_offset = s->coarse_snr_offset << 4;
948 /* if previous frame SNR offset was 1023, check if current frame can also
949 use SNR offset of 1023. if so, skip the search. */
950 if ((snr_offset | s->fine_snr_offset[0]) == 1023) {
951 if (bit_alloc(s, 1023) <= bits_left)
955 while (snr_offset >= 0 &&
956 bit_alloc(s, snr_offset) > bits_left) {
960 return AVERROR(EINVAL);
962 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
963 for (snr_incr = 64; snr_incr > 0; snr_incr >>= 2) {
964 while (snr_offset + snr_incr <= 1023 &&
965 bit_alloc(s, snr_offset + snr_incr) <= bits_left) {
966 snr_offset += snr_incr;
967 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
970 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
973 s->coarse_snr_offset = snr_offset >> 4;
974 for (ch = 0; ch < s->channels; ch++)
975 s->fine_snr_offset[ch] = snr_offset & 0xF;
982 * Downgrade exponent strategies to reduce the bits used by the exponents.
983 * This is a fallback for when bit allocation fails with the normal exponent
984 * strategies. Each time this function is run it only downgrades the
985 * strategy in 1 channel of 1 block.
986 * @return non-zero if downgrade was unsuccessful
988 static int downgrade_exponents(AC3EncodeContext *s)
992 for (ch = 0; ch < s->fbw_channels; ch++) {
993 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
994 if (s->exp_strategy[ch][blk] == EXP_D15) {
995 s->exp_strategy[ch][blk] = EXP_D25;
1000 for (ch = 0; ch < s->fbw_channels; ch++) {
1001 for (blk = AC3_MAX_BLOCKS-1; blk >= 0; blk--) {
1002 if (s->exp_strategy[ch][blk] == EXP_D25) {
1003 s->exp_strategy[ch][blk] = EXP_D45;
1008 for (ch = 0; ch < s->fbw_channels; ch++) {
1009 /* block 0 cannot reuse exponents, so only downgrade D45 to REUSE if
1010 the block number > 0 */
1011 for (blk = AC3_MAX_BLOCKS-1; blk > 0; blk--) {
1012 if (s->exp_strategy[ch][blk] > EXP_REUSE) {
1013 s->exp_strategy[ch][blk] = EXP_REUSE;
1023 * Reduce the bandwidth to reduce the number of bits used for a given SNR offset.
1024 * This is a second fallback for when bit allocation still fails after exponents
1025 * have been downgraded.
1026 * @return non-zero if bandwidth reduction was unsuccessful
1028 static int reduce_bandwidth(AC3EncodeContext *s, int min_bw_code)
1032 if (s->bandwidth_code[0] > min_bw_code) {
1033 for (ch = 0; ch < s->fbw_channels; ch++) {
1034 s->bandwidth_code[ch]--;
1035 s->nb_coefs[ch] = s->bandwidth_code[ch] * 3 + 73;
1044 * Perform bit allocation search.
1045 * Finds the SNR offset value that maximizes quality and fits in the specified
1046 * frame size. Output is the SNR offset and a set of bit allocation pointers
1047 * used to quantize the mantissas.
1049 static int compute_bit_allocation(AC3EncodeContext *s)
1053 count_frame_bits(s);
1055 bit_alloc_masking(s);
1057 ret = cbr_bit_allocation(s);
1059 /* fallback 1: downgrade exponents */
1060 if (!downgrade_exponents(s)) {
1061 extract_exponents(s);
1062 encode_exponents(s);
1064 ret = compute_bit_allocation(s);
1068 /* fallback 2: reduce bandwidth */
1069 /* only do this if the user has not specified a specific cutoff
1071 if (!s->cutoff && !reduce_bandwidth(s, 0)) {
1072 process_exponents(s);
1073 ret = compute_bit_allocation(s);
1077 /* fallbacks were not enough... */
1086 * Symmetric quantization on 'levels' levels.
1088 static inline int sym_quant(int c, int e, int levels)
1093 v = (levels * (c << e)) >> 24;
1095 v = (levels >> 1) + v;
1097 v = (levels * ((-c) << e)) >> 24;
1099 v = (levels >> 1) - v;
1101 assert(v >= 0 && v < levels);
1107 * Asymmetric quantization on 2^qbits levels.
1109 static inline int asym_quant(int c, int e, int qbits)
1113 lshift = e + qbits - 24;
1120 m = (1 << (qbits-1));
1124 return v & ((1 << qbits)-1);
1129 * Quantize a set of mantissas for a single channel in a single block.
1131 static void quantize_mantissas_blk_ch(AC3EncodeContext *s, int32_t *fixed_coef,
1132 int8_t exp_shift, uint8_t *exp,
1133 uint8_t *bap, uint16_t *qmant, int n)
1137 for (i = 0; i < n; i++) {
1139 int c = fixed_coef[i];
1140 int e = exp[i] - exp_shift;
1147 v = sym_quant(c, e, 3);
1148 switch (s->mant1_cnt) {
1150 s->qmant1_ptr = &qmant[i];
1155 *s->qmant1_ptr += 3 * v;
1160 *s->qmant1_ptr += v;
1167 v = sym_quant(c, e, 5);
1168 switch (s->mant2_cnt) {
1170 s->qmant2_ptr = &qmant[i];
1175 *s->qmant2_ptr += 5 * v;
1180 *s->qmant2_ptr += v;
1187 v = sym_quant(c, e, 7);
1190 v = sym_quant(c, e, 11);
1191 switch (s->mant4_cnt) {
1193 s->qmant4_ptr = &qmant[i];
1198 *s->qmant4_ptr += v;
1205 v = sym_quant(c, e, 15);
1208 v = asym_quant(c, e, 14);
1211 v = asym_quant(c, e, 16);
1214 v = asym_quant(c, e, b - 1);
1223 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1225 static void quantize_mantissas(AC3EncodeContext *s)
1230 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1231 AC3Block *block = &s->blocks[blk];
1232 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1233 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1235 for (ch = 0; ch < s->channels; ch++) {
1236 quantize_mantissas_blk_ch(s, block->fixed_coef[ch], block->exp_shift[ch],
1237 block->exp[ch], block->bap[ch],
1238 block->qmant[ch], s->nb_coefs[ch]);
1245 * Write the AC-3 frame header to the output bitstream.
1247 static void output_frame_header(AC3EncodeContext *s)
1249 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1250 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1251 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1252 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1253 put_bits(&s->pb, 5, s->bitstream_id);
1254 put_bits(&s->pb, 3, s->bitstream_mode);
1255 put_bits(&s->pb, 3, s->channel_mode);
1256 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1257 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1258 if (s->channel_mode & 0x04)
1259 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1260 if (s->channel_mode == AC3_CHMODE_STEREO)
1261 put_bits(&s->pb, 2, 0); /* surround not indicated */
1262 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1263 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1264 put_bits(&s->pb, 1, 0); /* no compression control word */
1265 put_bits(&s->pb, 1, 0); /* no lang code */
1266 put_bits(&s->pb, 1, 0); /* no audio production info */
1267 put_bits(&s->pb, 1, 0); /* no copyright */
1268 put_bits(&s->pb, 1, 1); /* original bitstream */
1269 put_bits(&s->pb, 1, 0); /* no time code 1 */
1270 put_bits(&s->pb, 1, 0); /* no time code 2 */
1271 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1276 * Write one audio block to the output bitstream.
1278 static void output_audio_block(AC3EncodeContext *s, int blk)
1280 int ch, i, baie, rbnd;
1281 AC3Block *block = &s->blocks[blk];
1283 /* block switching */
1284 for (ch = 0; ch < s->fbw_channels; ch++)
1285 put_bits(&s->pb, 1, 0);
1288 for (ch = 0; ch < s->fbw_channels; ch++)
1289 put_bits(&s->pb, 1, 1);
1291 /* dynamic range codes */
1292 put_bits(&s->pb, 1, 0);
1294 /* channel coupling */
1296 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1297 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1299 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1302 /* stereo rematrixing */
1303 if (s->channel_mode == AC3_CHMODE_STEREO) {
1304 put_bits(&s->pb, 1, block->new_rematrixing_strategy);
1305 if (block->new_rematrixing_strategy) {
1306 /* rematrixing flags */
1307 for (rbnd = 0; rbnd < 4; rbnd++)
1308 put_bits(&s->pb, 1, block->rematrixing_flags[rbnd]);
1312 /* exponent strategy */
1313 for (ch = 0; ch < s->fbw_channels; ch++)
1314 put_bits(&s->pb, 2, s->exp_strategy[ch][blk]);
1316 put_bits(&s->pb, 1, s->exp_strategy[s->lfe_channel][blk]);
1319 for (ch = 0; ch < s->fbw_channels; ch++) {
1320 if (s->exp_strategy[ch][blk] != EXP_REUSE)
1321 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1325 for (ch = 0; ch < s->channels; ch++) {
1328 if (s->exp_strategy[ch][blk] == EXP_REUSE)
1332 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1334 /* exponent groups */
1335 nb_groups = exponent_group_tab[s->exp_strategy[ch][blk]-1][s->nb_coefs[ch]];
1336 for (i = 1; i <= nb_groups; i++)
1337 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1339 /* gain range info */
1340 if (ch != s->lfe_channel)
1341 put_bits(&s->pb, 2, 0);
1344 /* bit allocation info */
1346 put_bits(&s->pb, 1, baie);
1348 put_bits(&s->pb, 2, s->slow_decay_code);
1349 put_bits(&s->pb, 2, s->fast_decay_code);
1350 put_bits(&s->pb, 2, s->slow_gain_code);
1351 put_bits(&s->pb, 2, s->db_per_bit_code);
1352 put_bits(&s->pb, 3, s->floor_code);
1356 put_bits(&s->pb, 1, baie);
1358 put_bits(&s->pb, 6, s->coarse_snr_offset);
1359 for (ch = 0; ch < s->channels; ch++) {
1360 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1361 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1365 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1366 put_bits(&s->pb, 1, 0); /* no data to skip */
1369 for (ch = 0; ch < s->channels; ch++) {
1371 for (i = 0; i < s->nb_coefs[ch]; i++) {
1372 q = block->qmant[ch][i];
1373 b = block->bap[ch][i];
1376 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1377 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1378 case 3: put_bits(&s->pb, 3, q); break;
1379 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1380 case 14: put_bits(&s->pb, 14, q); break;
1381 case 15: put_bits(&s->pb, 16, q); break;
1382 default: put_bits(&s->pb, b-1, q); break;
1389 /** CRC-16 Polynomial */
1390 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1393 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1410 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1416 r = mul_poly(r, a, poly);
1417 a = mul_poly(a, a, poly);
1425 * Fill the end of the frame with 0's and compute the two CRCs.
1427 static void output_frame_end(AC3EncodeContext *s)
1429 const AVCRC *crc_ctx = av_crc_get_table(AV_CRC_16_ANSI);
1430 int frame_size_58, pad_bytes, crc1, crc2_partial, crc2, crc_inv;
1433 frame_size_58 = ((s->frame_size >> 2) + (s->frame_size >> 4)) << 1;
1435 /* pad the remainder of the frame with zeros */
1436 flush_put_bits(&s->pb);
1438 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1439 assert(pad_bytes >= 0);
1441 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1444 /* this is not so easy because it is at the beginning of the data... */
1445 crc1 = av_bswap16(av_crc(crc_ctx, 0, frame + 4, frame_size_58 - 4));
1446 crc_inv = s->crc_inv[s->frame_size > s->frame_size_min];
1447 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1448 AV_WB16(frame + 2, crc1);
1451 crc2_partial = av_crc(crc_ctx, 0, frame + frame_size_58,
1452 s->frame_size - frame_size_58 - 3);
1453 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1454 /* ensure crc2 does not match sync word by flipping crcrsv bit if needed */
1455 if (crc2 == 0x770B) {
1456 frame[s->frame_size - 3] ^= 0x1;
1457 crc2 = av_crc(crc_ctx, crc2_partial, frame + s->frame_size - 3, 1);
1459 crc2 = av_bswap16(crc2);
1460 AV_WB16(frame + s->frame_size - 2, crc2);
1465 * Write the frame to the output bitstream.
1467 static void output_frame(AC3EncodeContext *s, unsigned char *frame)
1471 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1473 output_frame_header(s);
1475 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1476 output_audio_block(s, blk);
1478 output_frame_end(s);
1483 * Encode a single AC-3 frame.
1485 static int ac3_encode_frame(AVCodecContext *avctx, unsigned char *frame,
1486 int buf_size, void *data)
1488 AC3EncodeContext *s = avctx->priv_data;
1489 const SampleType *samples = data;
1492 if (s->bit_alloc.sr_code == 1)
1493 adjust_frame_size(s);
1495 deinterleave_input_samples(s, samples);
1499 compute_rematrixing_strategy(s);
1501 scale_coefficients(s);
1503 apply_rematrixing(s);
1505 process_exponents(s);
1507 ret = compute_bit_allocation(s);
1509 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1513 quantize_mantissas(s);
1515 output_frame(s, frame);
1517 return s->frame_size;
1522 * Finalize encoding and free any memory allocated by the encoder.
1524 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1527 AC3EncodeContext *s = avctx->priv_data;
1529 for (ch = 0; ch < s->channels; ch++)
1530 av_freep(&s->planar_samples[ch]);
1531 av_freep(&s->planar_samples);
1532 av_freep(&s->bap_buffer);
1533 av_freep(&s->bap1_buffer);
1534 av_freep(&s->mdct_coef_buffer);
1535 av_freep(&s->fixed_coef_buffer);
1536 av_freep(&s->exp_buffer);
1537 av_freep(&s->grouped_exp_buffer);
1538 av_freep(&s->psd_buffer);
1539 av_freep(&s->band_psd_buffer);
1540 av_freep(&s->mask_buffer);
1541 av_freep(&s->qmant_buffer);
1542 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1543 AC3Block *block = &s->blocks[blk];
1544 av_freep(&block->bap);
1545 av_freep(&block->mdct_coef);
1546 av_freep(&block->fixed_coef);
1547 av_freep(&block->exp);
1548 av_freep(&block->grouped_exp);
1549 av_freep(&block->psd);
1550 av_freep(&block->band_psd);
1551 av_freep(&block->mask);
1552 av_freep(&block->qmant);
1557 av_freep(&avctx->coded_frame);
1563 * Set channel information during initialization.
1565 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1566 int64_t *channel_layout)
1570 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1571 return AVERROR(EINVAL);
1572 if ((uint64_t)*channel_layout > 0x7FF)
1573 return AVERROR(EINVAL);
1574 ch_layout = *channel_layout;
1576 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1577 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1578 return AVERROR(EINVAL);
1580 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1581 s->channels = channels;
1582 s->fbw_channels = channels - s->lfe_on;
1583 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1585 ch_layout -= AV_CH_LOW_FREQUENCY;
1587 switch (ch_layout) {
1588 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1589 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1590 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1591 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1592 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1593 case AV_CH_LAYOUT_QUAD:
1594 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1595 case AV_CH_LAYOUT_5POINT0:
1596 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1598 return AVERROR(EINVAL);
1601 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1602 *channel_layout = ch_layout;
1604 *channel_layout |= AV_CH_LOW_FREQUENCY;
1610 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1614 /* validate channel layout */
1615 if (!avctx->channel_layout) {
1616 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1617 "encoder will guess the layout, but it "
1618 "might be incorrect.\n");
1620 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1622 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1626 /* validate sample rate */
1627 for (i = 0; i < 9; i++) {
1628 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1632 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1633 return AVERROR(EINVAL);
1635 s->sample_rate = avctx->sample_rate;
1636 s->bit_alloc.sr_shift = i % 3;
1637 s->bit_alloc.sr_code = i / 3;
1639 /* validate bit rate */
1640 for (i = 0; i < 19; i++) {
1641 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1645 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1646 return AVERROR(EINVAL);
1648 s->bit_rate = avctx->bit_rate;
1649 s->frame_size_code = i << 1;
1651 /* validate cutoff */
1652 if (avctx->cutoff < 0) {
1653 av_log(avctx, AV_LOG_ERROR, "invalid cutoff frequency\n");
1654 return AVERROR(EINVAL);
1656 s->cutoff = avctx->cutoff;
1657 if (s->cutoff > (s->sample_rate >> 1))
1658 s->cutoff = s->sample_rate >> 1;
1665 * Set bandwidth for all channels.
1666 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1667 * default value will be used.
1669 static av_cold void set_bandwidth(AC3EncodeContext *s)
1674 /* calculate bandwidth based on user-specified cutoff frequency */
1676 fbw_coeffs = s->cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1677 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1679 /* use default bandwidth setting */
1680 /* XXX: should compute the bandwidth according to the frame
1681 size, so that we avoid annoying high frequency artifacts */
1685 /* set number of coefficients for each channel */
1686 for (ch = 0; ch < s->fbw_channels; ch++) {
1687 s->bandwidth_code[ch] = bw_code;
1688 s->nb_coefs[ch] = bw_code * 3 + 73;
1691 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1695 static av_cold int allocate_buffers(AVCodecContext *avctx)
1698 AC3EncodeContext *s = avctx->priv_data;
1700 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1702 for (ch = 0; ch < s->channels; ch++) {
1703 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1704 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1707 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1708 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1709 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1710 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1711 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1712 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1713 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1714 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1715 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1716 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1717 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1718 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1719 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1720 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1721 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1722 64 * sizeof(*s->mask_buffer), alloc_fail);
1723 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1724 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1725 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1726 AC3Block *block = &s->blocks[blk];
1727 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1729 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1731 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1733 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1735 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1737 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1739 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1741 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1744 for (ch = 0; ch < s->channels; ch++) {
1745 /* arrangement: block, channel, coeff */
1746 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1747 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1748 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1749 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1750 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1751 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1752 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1754 /* arrangement: channel, block, coeff */
1755 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (AC3_MAX_BLOCKS * ch + blk)];
1759 if (CONFIG_AC3ENC_FLOAT) {
1760 FF_ALLOC_OR_GOTO(avctx, s->fixed_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1761 AC3_MAX_COEFS * sizeof(*s->fixed_coef_buffer), alloc_fail);
1762 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1763 AC3Block *block = &s->blocks[blk];
1764 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1765 sizeof(*block->fixed_coef), alloc_fail);
1766 for (ch = 0; ch < s->channels; ch++)
1767 block->fixed_coef[ch] = &s->fixed_coef_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1770 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1771 AC3Block *block = &s->blocks[blk];
1772 FF_ALLOCZ_OR_GOTO(avctx, block->fixed_coef, s->channels *
1773 sizeof(*block->fixed_coef), alloc_fail);
1774 for (ch = 0; ch < s->channels; ch++)
1775 block->fixed_coef[ch] = (int32_t *)block->mdct_coef[ch];
1781 return AVERROR(ENOMEM);
1786 * Initialize the encoder.
1788 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1790 AC3EncodeContext *s = avctx->priv_data;
1791 int ret, frame_size_58;
1793 avctx->frame_size = AC3_FRAME_SIZE;
1795 ff_ac3_common_init();
1797 ret = validate_options(avctx, s);
1801 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1802 s->bitstream_mode = 0; /* complete main audio service */
1804 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1805 s->bits_written = 0;
1806 s->samples_written = 0;
1807 s->frame_size = s->frame_size_min;
1809 /* calculate crc_inv for both possible frame sizes */
1810 frame_size_58 = (( s->frame_size >> 2) + ( s->frame_size >> 4)) << 1;
1811 s->crc_inv[0] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1812 if (s->bit_alloc.sr_code == 1) {
1813 frame_size_58 = (((s->frame_size+2) >> 2) + ((s->frame_size+2) >> 4)) << 1;
1814 s->crc_inv[1] = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1819 rematrixing_init(s);
1825 ret = mdct_init(avctx, &s->mdct, 9);
1829 ret = allocate_buffers(avctx);
1833 avctx->coded_frame= avcodec_alloc_frame();
1835 dsputil_init(&s->dsp, avctx);
1836 ff_ac3dsp_init(&s->ac3dsp);
1840 ac3_encode_close(avctx);