2 * The simplest AC-3 encoder
3 * Copyright (c) 2000 Fabrice Bellard
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
10 * version 2.1 of the License, or (at your option) any later version.
12 * FFmpeg is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Lesser General Public License for more details.
17 * You should have received a copy of the GNU Lesser General Public
18 * License along with FFmpeg; if not, write to the Free Software
19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
24 * The simplest AC-3 encoder.
29 #include "libavcore/audioconvert.h"
30 #include "libavutil/crc.h"
35 #include "audioconvert.h"
39 #define MDCT_SAMPLES (1 << MDCT_NBITS)
41 /** Maximum number of exponent groups. +1 for separate DC exponent. */
42 #define AC3_MAX_EXP_GROUPS 85
44 /** Scale a float value by 2^bits and convert to an integer. */
45 #define SCALE_FLOAT(a, bits) lrintf((a) * (float)(1 << (bits)))
47 /** Scale a float value by 2^15, convert to an integer, and clip to int16_t range. */
48 #define FIX15(a) av_clip_int16(SCALE_FLOAT(a, 15))
53 * Used in fixed-point MDCT calculation.
55 typedef struct IComplex {
59 typedef struct AC3MDCTContext {
60 AVCodecContext *avctx; ///< parent context for av_log()
61 int16_t *rot_tmp; ///< temp buffer for pre-rotated samples
62 IComplex *cplx_tmp; ///< temp buffer for complex pre-rotated samples
66 * Data for a single audio block.
68 typedef struct AC3Block {
69 uint8_t **bap; ///< bit allocation pointers (bap)
70 int32_t **mdct_coef; ///< MDCT coefficients
71 uint8_t **exp; ///< original exponents
72 uint8_t **encoded_exp; ///< encoded exponents
73 uint8_t **grouped_exp; ///< grouped exponents
74 int16_t **psd; ///< psd per frequency bin
75 int16_t **band_psd; ///< psd per critical band
76 int16_t **mask; ///< masking curve
77 uint16_t **qmant; ///< quantized mantissas
78 uint8_t num_exp_groups[AC3_MAX_CHANNELS]; ///< number of exponent groups
79 uint8_t exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
80 int8_t exp_shift[AC3_MAX_CHANNELS]; ///< exponent shift values
84 * AC-3 encoder private context.
86 typedef struct AC3EncodeContext {
87 PutBitContext pb; ///< bitstream writer context
89 AC3MDCTContext mdct; ///< MDCT context
91 AC3Block blocks[AC3_MAX_BLOCKS]; ///< per-block info
93 int bitstream_id; ///< bitstream id (bsid)
94 int bitstream_mode; ///< bitstream mode (bsmod)
96 int bit_rate; ///< target bit rate, in bits-per-second
97 int sample_rate; ///< sampling frequency, in Hz
99 int frame_size_min; ///< minimum frame size in case rounding is necessary
100 int frame_size; ///< current frame size in bytes
101 int frame_size_code; ///< frame size code (frmsizecod)
102 int bits_written; ///< bit count (used to avg. bitrate)
103 int samples_written; ///< sample count (used to avg. bitrate)
105 int fbw_channels; ///< number of full-bandwidth channels (nfchans)
106 int channels; ///< total number of channels (nchans)
107 int lfe_on; ///< indicates if there is an LFE channel (lfeon)
108 int lfe_channel; ///< channel index of the LFE channel
109 int channel_mode; ///< channel mode (acmod)
110 const uint8_t *channel_map; ///< channel map used to reorder channels
112 int bandwidth_code[AC3_MAX_CHANNELS]; ///< bandwidth code (0 to 60) (chbwcod)
113 int nb_coefs[AC3_MAX_CHANNELS];
115 /* bitrate allocation control */
116 int slow_gain_code; ///< slow gain code (sgaincod)
117 int slow_decay_code; ///< slow decay code (sdcycod)
118 int fast_decay_code; ///< fast decay code (fdcycod)
119 int db_per_bit_code; ///< dB/bit code (dbpbcod)
120 int floor_code; ///< floor code (floorcod)
121 AC3BitAllocParameters bit_alloc; ///< bit allocation parameters
122 int coarse_snr_offset; ///< coarse SNR offsets (csnroffst)
123 int fast_gain_code[AC3_MAX_CHANNELS]; ///< fast gain codes (signal-to-mask ratio) (fgaincod)
124 int fine_snr_offset[AC3_MAX_CHANNELS]; ///< fine SNR offsets (fsnroffst)
125 int frame_bits; ///< all frame bits except exponents and mantissas
126 int exponent_bits; ///< number of bits used for exponents
128 /* mantissa encoding */
129 int mant1_cnt, mant2_cnt, mant4_cnt; ///< mantissa counts for bap=1,2,4
130 uint16_t *qmant1_ptr, *qmant2_ptr, *qmant4_ptr; ///< mantissa pointers for bap=1,2,4
132 int16_t **planar_samples;
134 uint8_t *bap1_buffer;
135 int32_t *mdct_coef_buffer;
137 uint8_t *encoded_exp_buffer;
138 uint8_t *grouped_exp_buffer;
140 int16_t *band_psd_buffer;
141 int16_t *mask_buffer;
142 uint16_t *qmant_buffer;
144 DECLARE_ALIGNED(16, int16_t, windowed_samples)[AC3_WINDOW_SIZE];
148 /** MDCT and FFT tables */
149 static int16_t costab[64];
150 static int16_t sintab[64];
151 static int16_t xcos1[128];
152 static int16_t xsin1[128];
156 * Adjust the frame size to make the average bit rate match the target bit rate.
157 * This is only needed for 11025, 22050, and 44100 sample rates.
159 static void adjust_frame_size(AC3EncodeContext *s)
161 while (s->bits_written >= s->bit_rate && s->samples_written >= s->sample_rate) {
162 s->bits_written -= s->bit_rate;
163 s->samples_written -= s->sample_rate;
165 s->frame_size = s->frame_size_min +
166 2 * (s->bits_written * s->sample_rate < s->samples_written * s->bit_rate);
167 s->bits_written += s->frame_size * 8;
168 s->samples_written += AC3_FRAME_SIZE;
173 * Deinterleave input samples.
174 * Channels are reordered from FFmpeg's default order to AC-3 order.
176 static void deinterleave_input_samples(AC3EncodeContext *s,
177 const int16_t *samples)
181 /* deinterleave and remap input samples */
182 for (ch = 0; ch < s->channels; ch++) {
186 /* copy last 256 samples of previous frame to the start of the current frame */
187 memcpy(&s->planar_samples[ch][0], &s->planar_samples[ch][AC3_FRAME_SIZE],
188 AC3_BLOCK_SIZE * sizeof(s->planar_samples[0][0]));
192 sptr = samples + s->channel_map[ch];
193 for (i = AC3_BLOCK_SIZE; i < AC3_FRAME_SIZE+AC3_BLOCK_SIZE; i++) {
194 s->planar_samples[ch][i] = *sptr;
202 * Finalize MDCT and free allocated memory.
204 static av_cold void mdct_end(AC3MDCTContext *mdct)
206 av_freep(&mdct->rot_tmp);
207 av_freep(&mdct->cplx_tmp);
213 * Initialize FFT tables.
214 * @param ln log2(FFT size)
216 static av_cold void fft_init(int ln)
224 for (i = 0; i < n2; i++) {
225 alpha = 2.0 * M_PI * i / n;
226 costab[i] = FIX15(cos(alpha));
227 sintab[i] = FIX15(sin(alpha));
233 * Initialize MDCT tables.
234 * @param nbits log2(MDCT size)
236 static av_cold int mdct_init(AC3MDCTContext *mdct, int nbits)
245 FF_ALLOC_OR_GOTO(mdct->avctx, mdct->rot_tmp, n * sizeof(*mdct->rot_tmp),
247 FF_ALLOC_OR_GOTO(mdct->avctx, mdct->cplx_tmp, n4 * sizeof(*mdct->cplx_tmp),
250 for (i = 0; i < n4; i++) {
251 float alpha = 2.0 * M_PI * (i + 1.0 / 8.0) / n;
252 xcos1[i] = FIX15(-cos(alpha));
253 xsin1[i] = FIX15(-sin(alpha));
258 return AVERROR(ENOMEM);
263 #define BF(pre, pim, qre, qim, pre1, pim1, qre1, qim1) \
265 int ax, ay, bx, by; \
270 pre = (bx + ax) >> 1; \
271 pim = (by + ay) >> 1; \
272 qre = (bx - ax) >> 1; \
273 qim = (by - ay) >> 1; \
277 /** Complex multiply */
278 #define CMUL(pre, pim, are, aim, bre, bim) \
280 pre = (MUL16(are, bre) - MUL16(aim, bim)) >> 15; \
281 pim = (MUL16(are, bim) + MUL16(bre, aim)) >> 15; \
286 * Calculate a 2^n point complex FFT on 2^ln points.
287 * @param z complex input/output samples
288 * @param ln log2(FFT size)
290 static void fft(IComplex *z, int ln)
294 register IComplex *p,*q;
300 for (j = 0; j < np; j++) {
301 int k = av_reverse[j] >> (8 - ln);
303 FFSWAP(IComplex, z[k], z[j]);
311 BF(p[0].re, p[0].im, p[1].re, p[1].im,
312 p[0].re, p[0].im, p[1].re, p[1].im);
321 BF(p[0].re, p[0].im, p[2].re, p[2].im,
322 p[0].re, p[0].im, p[2].re, p[2].im);
323 BF(p[1].re, p[1].im, p[3].re, p[3].im,
324 p[1].re, p[1].im, p[3].im, -p[3].re);
336 for (j = 0; j < nblocks; j++) {
337 BF(p->re, p->im, q->re, q->im,
338 p->re, p->im, q->re, q->im);
341 for(l = nblocks; l < np2; l += nblocks) {
342 CMUL(tmp_re, tmp_im, costab[l], -sintab[l], q->re, q->im);
343 BF(p->re, p->im, q->re, q->im,
344 p->re, p->im, tmp_re, tmp_im);
351 nblocks = nblocks >> 1;
352 nloops = nloops << 1;
358 * Calculate a 512-point MDCT
359 * @param out 256 output frequency coefficients
360 * @param in 512 windowed input audio samples
362 static void mdct512(AC3MDCTContext *mdct, int32_t *out, int16_t *in)
365 int16_t *rot = mdct->rot_tmp;
366 IComplex *x = mdct->cplx_tmp;
368 /* shift to simplify computations */
369 for (i = 0; i < MDCT_SAMPLES/4; i++)
370 rot[i] = -in[i + 3*MDCT_SAMPLES/4];
371 memcpy(&rot[MDCT_SAMPLES/4], &in[0], 3*MDCT_SAMPLES/4*sizeof(*in));
374 for (i = 0; i < MDCT_SAMPLES/4; i++) {
375 re = ((int)rot[ 2*i] - (int)rot[MDCT_SAMPLES -1-2*i]) >> 1;
376 im = -((int)rot[MDCT_SAMPLES/2+2*i] - (int)rot[MDCT_SAMPLES/2-1-2*i]) >> 1;
377 CMUL(x[i].re, x[i].im, re, im, -xcos1[i], xsin1[i]);
380 fft(x, MDCT_NBITS - 2);
383 for (i = 0; i < MDCT_SAMPLES/4; i++) {
386 CMUL(out[MDCT_SAMPLES/2-1-2*i], out[2*i], re, im, xsin1[i], xcos1[i]);
392 * Apply KBD window to input samples prior to MDCT.
394 static void apply_window(int16_t *output, const int16_t *input,
395 const int16_t *window, int n)
400 for (i = 0; i < n2; i++) {
401 output[i] = MUL16(input[i], window[i]) >> 15;
402 output[n-i-1] = MUL16(input[n-i-1], window[i]) >> 15;
408 * Calculate the log2() of the maximum absolute value in an array.
409 * @param tab input array
410 * @param n number of values in the array
411 * @return log2(max(abs(tab[])))
413 static int log2_tab(int16_t *tab, int n)
418 for (i = 0; i < n; i++)
426 * Left-shift each value in an array by a specified amount.
427 * @param tab input array
428 * @param n number of values in the array
429 * @param lshift left shift amount. a negative value means right shift.
431 static void lshift_tab(int16_t *tab, int n, int lshift)
436 for (i = 0; i < n; i++)
438 } else if (lshift < 0) {
440 for (i = 0; i < n; i++)
447 * Normalize the input samples to use the maximum available precision.
448 * This assumes signed 16-bit input samples. Exponents are reduced by 9 to
449 * match the 24-bit internal precision for MDCT coefficients.
451 * @return exponent shift
453 static int normalize_samples(AC3EncodeContext *s)
455 int v = 14 - log2_tab(s->windowed_samples, AC3_WINDOW_SIZE);
457 lshift_tab(s->windowed_samples, AC3_WINDOW_SIZE, v);
463 * Apply the MDCT to input samples to generate frequency coefficients.
464 * This applies the KBD window and normalizes the input to reduce precision
465 * loss due to fixed-point calculations.
467 static void apply_mdct(AC3EncodeContext *s)
471 for (ch = 0; ch < s->channels; ch++) {
472 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
473 AC3Block *block = &s->blocks[blk];
474 const int16_t *input_samples = &s->planar_samples[ch][blk * AC3_BLOCK_SIZE];
476 apply_window(s->windowed_samples, input_samples, ff_ac3_window, AC3_WINDOW_SIZE);
478 block->exp_shift[ch] = normalize_samples(s);
480 mdct512(&s->mdct, block->mdct_coef[ch], s->windowed_samples);
487 * Extract exponents from the MDCT coefficients.
488 * This takes into account the normalization that was done to the input samples
489 * by adjusting the exponents by the exponent shift values.
491 static void extract_exponents(AC3EncodeContext *s)
495 for (ch = 0; ch < s->channels; ch++) {
496 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
497 AC3Block *block = &s->blocks[blk];
498 for (i = 0; i < AC3_MAX_COEFS; i++) {
500 int v = abs(block->mdct_coef[ch][i]);
504 e = 23 - av_log2(v) + block->exp_shift[ch];
507 block->mdct_coef[ch][i] = 0;
510 block->exp[ch][i] = e;
518 * Exponent Difference Threshold.
519 * New exponents are sent if their SAD exceed this number.
521 #define EXP_DIFF_THRESHOLD 1000
525 * Calculate exponent strategies for all blocks in a single channel.
527 static void compute_exp_strategy_ch(AC3EncodeContext *s, uint8_t *exp_strategy, uint8_t **exp)
532 /* estimate if the exponent variation & decide if they should be
533 reused in the next frame */
534 exp_strategy[0] = EXP_NEW;
535 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++) {
536 exp_diff = s->dsp.sad[0](NULL, exp[blk], exp[blk-1], 16, 16);
537 if (exp_diff > EXP_DIFF_THRESHOLD)
538 exp_strategy[blk] = EXP_NEW;
540 exp_strategy[blk] = EXP_REUSE;
543 /* now select the encoding strategy type : if exponents are often
544 recoded, we use a coarse encoding */
546 while (blk < AC3_MAX_BLOCKS) {
548 while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE)
550 switch (blk1 - blk) {
551 case 1: exp_strategy[blk] = EXP_D45; break;
553 case 3: exp_strategy[blk] = EXP_D25; break;
554 default: exp_strategy[blk] = EXP_D15; break;
562 * Calculate exponent strategies for all channels.
563 * Array arrangement is reversed to simplify the per-channel calculation.
565 static void compute_exp_strategy(AC3EncodeContext *s)
567 uint8_t *exp1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
568 uint8_t exp_str1[AC3_MAX_CHANNELS][AC3_MAX_BLOCKS];
571 for (ch = 0; ch < s->fbw_channels; ch++) {
572 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
573 exp1[ch][blk] = s->blocks[blk].exp[ch];
574 exp_str1[ch][blk] = s->blocks[blk].exp_strategy[ch];
577 compute_exp_strategy_ch(s, exp_str1[ch], exp1[ch]);
579 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
580 s->blocks[blk].exp_strategy[ch] = exp_str1[ch][blk];
584 s->blocks[0].exp_strategy[ch] = EXP_D15;
585 for (blk = 1; blk < AC3_MAX_BLOCKS; blk++)
586 s->blocks[blk].exp_strategy[ch] = EXP_REUSE;
592 * Set each encoded exponent in a block to the minimum of itself and the
593 * exponent in the same frequency bin of a following block.
594 * exp[i] = min(exp[i], exp1[i]
596 static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
599 for (i = 0; i < n; i++) {
600 if (exp1[i] < exp[i])
607 * Update the exponents so that they are the ones the decoder will decode.
609 static void encode_exponents_blk_ch(uint8_t *encoded_exp, uint8_t *exp,
610 int nb_exps, int exp_strategy,
611 uint8_t *num_exp_groups)
613 int group_size, nb_groups, i, j, k, exp_min;
614 uint8_t exp1[AC3_MAX_COEFS];
616 group_size = exp_strategy + (exp_strategy == EXP_D45);
617 *num_exp_groups = (nb_exps + (group_size * 3) - 4) / (3 * group_size);
618 nb_groups = *num_exp_groups * 3;
620 /* for each group, compute the minimum exponent */
621 exp1[0] = exp[0]; /* DC exponent is handled separately */
623 for (i = 1; i <= nb_groups; i++) {
625 assert(exp_min >= 0 && exp_min <= 24);
626 for (j = 1; j < group_size; j++) {
627 if (exp[k+j] < exp_min)
634 /* constraint for DC exponent */
638 /* decrease the delta between each groups to within 2 so that they can be
639 differentially encoded */
640 for (i = 1; i <= nb_groups; i++)
641 exp1[i] = FFMIN(exp1[i], exp1[i-1] + 2);
642 for (i = nb_groups-1; i >= 0; i--)
643 exp1[i] = FFMIN(exp1[i], exp1[i+1] + 2);
645 /* now we have the exponent values the decoder will see */
646 encoded_exp[0] = exp1[0];
648 for (i = 1; i <= nb_groups; i++) {
649 for (j = 0; j < group_size; j++)
650 encoded_exp[k+j] = exp1[i];
657 * Encode exponents from original extracted form to what the decoder will see.
658 * This copies and groups exponents based on exponent strategy and reduces
659 * deltas between adjacent exponent groups so that they can be differentially
662 static void encode_exponents(AC3EncodeContext *s)
664 int blk, blk1, blk2, ch;
665 AC3Block *block, *block1, *block2;
667 for (ch = 0; ch < s->channels; ch++) {
669 block = &s->blocks[0];
670 while (blk < AC3_MAX_BLOCKS) {
673 /* for the EXP_REUSE case we select the min of the exponents */
674 while (blk1 < AC3_MAX_BLOCKS && block1->exp_strategy[ch] == EXP_REUSE) {
675 exponent_min(block->exp[ch], block1->exp[ch], s->nb_coefs[ch]);
679 encode_exponents_blk_ch(block->encoded_exp[ch],
680 block->exp[ch], s->nb_coefs[ch],
681 block->exp_strategy[ch],
682 &block->num_exp_groups[ch]);
683 /* copy encoded exponents for reuse case */
685 for (blk2 = blk+1; blk2 < blk1; blk2++, block2++) {
686 memcpy(block2->encoded_exp[ch], block->encoded_exp[ch],
687 s->nb_coefs[ch] * sizeof(uint8_t));
698 * 3 delta-encoded exponents are in each 7-bit group. The number of groups
699 * varies depending on exponent strategy and bandwidth.
701 static void group_exponents(AC3EncodeContext *s)
704 int group_size, bit_count;
706 int delta0, delta1, delta2;
710 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
711 AC3Block *block = &s->blocks[blk];
712 for (ch = 0; ch < s->channels; ch++) {
713 if (block->exp_strategy[ch] == EXP_REUSE) {
714 block->num_exp_groups[ch] = 0;
717 group_size = block->exp_strategy[ch] + (block->exp_strategy[ch] == EXP_D45);
718 bit_count += 4 + (block->num_exp_groups[ch] * 7);
719 p = block->encoded_exp[ch];
723 block->grouped_exp[ch][0] = exp1;
725 /* remaining exponents are delta encoded */
726 for (i = 1; i <= block->num_exp_groups[ch]; i++) {
727 /* merge three delta in one code */
731 delta0 = exp1 - exp0 + 2;
736 delta1 = exp1 - exp0 + 2;
741 delta2 = exp1 - exp0 + 2;
743 block->grouped_exp[ch][i] = ((delta0 * 5 + delta1) * 5) + delta2;
748 s->exponent_bits = bit_count;
753 * Calculate final exponents from the supplied MDCT coefficients and exponent shift.
754 * Extract exponents from MDCT coefficients, calculate exponent strategies,
755 * and encode final exponents.
757 static void process_exponents(AC3EncodeContext *s)
759 extract_exponents(s);
761 compute_exp_strategy(s);
770 * Initialize bit allocation.
771 * Set default parameter codes and calculate parameter values.
773 static void bit_alloc_init(AC3EncodeContext *s)
777 /* init default parameters */
778 s->slow_decay_code = 2;
779 s->fast_decay_code = 1;
780 s->slow_gain_code = 1;
781 s->db_per_bit_code = 2;
783 for (ch = 0; ch < s->channels; ch++)
784 s->fast_gain_code[ch] = 4;
786 /* initial snr offset */
787 s->coarse_snr_offset = 40;
789 /* compute real values */
790 /* currently none of these values change during encoding, so we can just
791 set them once at initialization */
792 s->bit_alloc.slow_decay = ff_ac3_slow_decay_tab[s->slow_decay_code] >> s->bit_alloc.sr_shift;
793 s->bit_alloc.fast_decay = ff_ac3_fast_decay_tab[s->fast_decay_code] >> s->bit_alloc.sr_shift;
794 s->bit_alloc.slow_gain = ff_ac3_slow_gain_tab[s->slow_gain_code];
795 s->bit_alloc.db_per_bit = ff_ac3_db_per_bit_tab[s->db_per_bit_code];
796 s->bit_alloc.floor = ff_ac3_floor_tab[s->floor_code];
801 * Count the bits used to encode the frame, minus exponents and mantissas.
803 static void count_frame_bits(AC3EncodeContext *s)
805 static const int frame_bits_inc[8] = { 0, 0, 2, 2, 2, 4, 2, 4 };
811 frame_bits += frame_bits_inc[s->channel_mode];
814 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
815 frame_bits += s->fbw_channels * 2 + 2; /* blksw * c, dithflag * c, dynrnge, cplstre */
816 if (s->channel_mode == AC3_CHMODE_STEREO) {
817 frame_bits++; /* rematstr */
821 frame_bits += 2 * s->fbw_channels; /* chexpstr[2] * c */
823 frame_bits++; /* lfeexpstr */
824 for (ch = 0; ch < s->fbw_channels; ch++) {
825 if (s->blocks[blk].exp_strategy[ch] != EXP_REUSE)
826 frame_bits += 6 + 2; /* chbwcod[6], gainrng[2] */
828 frame_bits++; /* baie */
829 frame_bits++; /* snr */
830 frame_bits += 2; /* delta / skip */
832 frame_bits++; /* cplinu for block 0 */
834 /* sdcycod[2], fdcycod[2], sgaincod[2], dbpbcod[2], floorcod[3] */
836 /* (fsnoffset[4] + fgaincod[4]) * c */
837 frame_bits += 2*4 + 3 + 6 + s->channels * (4 + 3);
839 /* auxdatae, crcrsv */
845 s->frame_bits = frame_bits;
850 * Calculate the number of bits needed to encode a set of mantissas.
852 static int compute_mantissa_size(AC3EncodeContext *s, uint8_t *bap, int nb_coefs)
857 for (i = 0; i < nb_coefs; i++) {
861 /* bap=0 mantissas are not encoded */
864 /* 3 mantissas in 5 bits */
865 if (s->mant1_cnt == 0)
867 if (++s->mant1_cnt == 3)
871 /* 3 mantissas in 7 bits */
872 if (s->mant2_cnt == 0)
874 if (++s->mant2_cnt == 3)
881 /* 2 mantissas in 7 bits */
882 if (s->mant4_cnt == 0)
884 if (++s->mant4_cnt == 2)
903 * Calculate masking curve based on the final exponents.
904 * Also calculate the power spectral densities to use in future calculations.
906 static void bit_alloc_masking(AC3EncodeContext *s)
910 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
911 AC3Block *block = &s->blocks[blk];
912 for (ch = 0; ch < s->channels; ch++) {
913 if (block->exp_strategy[ch] == EXP_REUSE) {
914 AC3Block *block1 = &s->blocks[blk-1];
915 memcpy(block->psd[ch], block1->psd[ch], AC3_MAX_COEFS*sizeof(block->psd[0][0]));
916 memcpy(block->mask[ch], block1->mask[ch], AC3_CRITICAL_BANDS*sizeof(block->mask[0][0]));
918 ff_ac3_bit_alloc_calc_psd(block->encoded_exp[ch], 0,
920 block->psd[ch], block->band_psd[ch]);
921 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc, block->band_psd[ch],
923 ff_ac3_fast_gain_tab[s->fast_gain_code[ch]],
924 ch == s->lfe_channel,
925 DBA_NONE, 0, NULL, NULL, NULL,
934 * Ensure that bap for each block and channel point to the current bap_buffer.
935 * They may have been switched during the bit allocation search.
937 static void reset_block_bap(AC3EncodeContext *s)
940 if (s->blocks[0].bap[0] == s->bap_buffer)
942 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
943 for (ch = 0; ch < s->channels; ch++) {
944 s->blocks[blk].bap[ch] = &s->bap_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
951 * Run the bit allocation with a given SNR offset.
952 * This calculates the bit allocation pointers that will be used to determine
953 * the quantization of each mantissa.
954 * @return the number of bits needed for mantissas if the given SNR offset is
957 static int bit_alloc(AC3EncodeContext *s,
963 snr_offset = (snr_offset - 240) << 2;
967 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
968 AC3Block *block = &s->blocks[blk];
972 for (ch = 0; ch < s->channels; ch++) {
973 ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
974 s->nb_coefs[ch], snr_offset,
975 s->bit_alloc.floor, ff_ac3_bap_tab,
977 mantissa_bits += compute_mantissa_size(s, block->bap[ch], s->nb_coefs[ch]);
980 return mantissa_bits;
985 * Constant bitrate bit allocation search.
986 * Find the largest SNR offset that will allow data to fit in the frame.
988 static int cbr_bit_allocation(AC3EncodeContext *s)
994 bits_left = 8 * s->frame_size - (s->frame_bits + s->exponent_bits);
996 snr_offset = s->coarse_snr_offset << 4;
998 while (snr_offset >= 0 &&
999 bit_alloc(s, snr_offset) > bits_left) {
1003 return AVERROR(EINVAL);
1005 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1006 while (snr_offset + 64 <= 1023 &&
1007 bit_alloc(s, snr_offset + 64) <= bits_left) {
1009 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1011 while (snr_offset + 16 <= 1023 &&
1012 bit_alloc(s, snr_offset + 16) <= bits_left) {
1014 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1016 while (snr_offset + 4 <= 1023 &&
1017 bit_alloc(s, snr_offset + 4) <= bits_left) {
1019 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1021 while (snr_offset + 1 <= 1023 &&
1022 bit_alloc(s, snr_offset + 1) <= bits_left) {
1024 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1026 FFSWAP(uint8_t *, s->bap_buffer, s->bap1_buffer);
1029 s->coarse_snr_offset = snr_offset >> 4;
1030 for (ch = 0; ch < s->channels; ch++)
1031 s->fine_snr_offset[ch] = snr_offset & 0xF;
1038 * Perform bit allocation search.
1039 * Finds the SNR offset value that maximizes quality and fits in the specified
1040 * frame size. Output is the SNR offset and a set of bit allocation pointers
1041 * used to quantize the mantissas.
1043 static int compute_bit_allocation(AC3EncodeContext *s)
1045 count_frame_bits(s);
1047 bit_alloc_masking(s);
1049 return cbr_bit_allocation(s);
1054 * Symmetric quantization on 'levels' levels.
1056 static inline int sym_quant(int c, int e, int levels)
1061 v = (levels * (c << e)) >> 24;
1063 v = (levels >> 1) + v;
1065 v = (levels * ((-c) << e)) >> 24;
1067 v = (levels >> 1) - v;
1069 assert(v >= 0 && v < levels);
1075 * Asymmetric quantization on 2^qbits levels.
1077 static inline int asym_quant(int c, int e, int qbits)
1081 lshift = e + qbits - 24;
1088 m = (1 << (qbits-1));
1092 return v & ((1 << qbits)-1);
1097 * Quantize a set of mantissas for a single channel in a single block.
1099 static void quantize_mantissas_blk_ch(AC3EncodeContext *s,
1100 int32_t *mdct_coef, int8_t exp_shift,
1101 uint8_t *encoded_exp, uint8_t *bap,
1102 uint16_t *qmant, int n)
1106 for (i = 0; i < n; i++) {
1108 int c = mdct_coef[i];
1109 int e = encoded_exp[i] - exp_shift;
1116 v = sym_quant(c, e, 3);
1117 switch (s->mant1_cnt) {
1119 s->qmant1_ptr = &qmant[i];
1124 *s->qmant1_ptr += 3 * v;
1129 *s->qmant1_ptr += v;
1136 v = sym_quant(c, e, 5);
1137 switch (s->mant2_cnt) {
1139 s->qmant2_ptr = &qmant[i];
1144 *s->qmant2_ptr += 5 * v;
1149 *s->qmant2_ptr += v;
1156 v = sym_quant(c, e, 7);
1159 v = sym_quant(c, e, 11);
1160 switch (s->mant4_cnt) {
1162 s->qmant4_ptr = &qmant[i];
1167 *s->qmant4_ptr += v;
1174 v = sym_quant(c, e, 15);
1177 v = asym_quant(c, e, 14);
1180 v = asym_quant(c, e, 16);
1183 v = asym_quant(c, e, b - 1);
1192 * Quantize mantissas using coefficients, exponents, and bit allocation pointers.
1194 static void quantize_mantissas(AC3EncodeContext *s)
1199 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1200 AC3Block *block = &s->blocks[blk];
1201 s->mant1_cnt = s->mant2_cnt = s->mant4_cnt = 0;
1202 s->qmant1_ptr = s->qmant2_ptr = s->qmant4_ptr = NULL;
1204 for (ch = 0; ch < s->channels; ch++) {
1205 quantize_mantissas_blk_ch(s, block->mdct_coef[ch], block->exp_shift[ch],
1206 block->encoded_exp[ch], block->bap[ch],
1207 block->qmant[ch], s->nb_coefs[ch]);
1214 * Write the AC-3 frame header to the output bitstream.
1216 static void output_frame_header(AC3EncodeContext *s)
1218 put_bits(&s->pb, 16, 0x0b77); /* frame header */
1219 put_bits(&s->pb, 16, 0); /* crc1: will be filled later */
1220 put_bits(&s->pb, 2, s->bit_alloc.sr_code);
1221 put_bits(&s->pb, 6, s->frame_size_code + (s->frame_size - s->frame_size_min) / 2);
1222 put_bits(&s->pb, 5, s->bitstream_id);
1223 put_bits(&s->pb, 3, s->bitstream_mode);
1224 put_bits(&s->pb, 3, s->channel_mode);
1225 if ((s->channel_mode & 0x01) && s->channel_mode != AC3_CHMODE_MONO)
1226 put_bits(&s->pb, 2, 1); /* XXX -4.5 dB */
1227 if (s->channel_mode & 0x04)
1228 put_bits(&s->pb, 2, 1); /* XXX -6 dB */
1229 if (s->channel_mode == AC3_CHMODE_STEREO)
1230 put_bits(&s->pb, 2, 0); /* surround not indicated */
1231 put_bits(&s->pb, 1, s->lfe_on); /* LFE */
1232 put_bits(&s->pb, 5, 31); /* dialog norm: -31 db */
1233 put_bits(&s->pb, 1, 0); /* no compression control word */
1234 put_bits(&s->pb, 1, 0); /* no lang code */
1235 put_bits(&s->pb, 1, 0); /* no audio production info */
1236 put_bits(&s->pb, 1, 0); /* no copyright */
1237 put_bits(&s->pb, 1, 1); /* original bitstream */
1238 put_bits(&s->pb, 1, 0); /* no time code 1 */
1239 put_bits(&s->pb, 1, 0); /* no time code 2 */
1240 put_bits(&s->pb, 1, 0); /* no additional bit stream info */
1245 * Write one audio block to the output bitstream.
1247 static void output_audio_block(AC3EncodeContext *s,
1250 int ch, i, baie, rbnd;
1251 AC3Block *block = &s->blocks[block_num];
1253 /* block switching */
1254 for (ch = 0; ch < s->fbw_channels; ch++)
1255 put_bits(&s->pb, 1, 0);
1258 for (ch = 0; ch < s->fbw_channels; ch++)
1259 put_bits(&s->pb, 1, 1);
1261 /* dynamic range codes */
1262 put_bits(&s->pb, 1, 0);
1264 /* channel coupling */
1266 put_bits(&s->pb, 1, 1); /* coupling strategy present */
1267 put_bits(&s->pb, 1, 0); /* no coupling strategy */
1269 put_bits(&s->pb, 1, 0); /* no new coupling strategy */
1272 /* stereo rematrixing */
1273 if (s->channel_mode == AC3_CHMODE_STEREO) {
1275 /* first block must define rematrixing (rematstr) */
1276 put_bits(&s->pb, 1, 1);
1278 /* dummy rematrixing rematflg(1:4)=0 */
1279 for (rbnd = 0; rbnd < 4; rbnd++)
1280 put_bits(&s->pb, 1, 0);
1282 /* no matrixing (but should be used in the future) */
1283 put_bits(&s->pb, 1, 0);
1287 /* exponent strategy */
1288 for (ch = 0; ch < s->fbw_channels; ch++)
1289 put_bits(&s->pb, 2, block->exp_strategy[ch]);
1291 put_bits(&s->pb, 1, block->exp_strategy[s->lfe_channel]);
1294 for (ch = 0; ch < s->fbw_channels; ch++) {
1295 if (block->exp_strategy[ch] != EXP_REUSE)
1296 put_bits(&s->pb, 6, s->bandwidth_code[ch]);
1300 for (ch = 0; ch < s->channels; ch++) {
1301 if (block->exp_strategy[ch] == EXP_REUSE)
1305 put_bits(&s->pb, 4, block->grouped_exp[ch][0]);
1307 /* exponent groups */
1308 for (i = 1; i <= block->num_exp_groups[ch]; i++)
1309 put_bits(&s->pb, 7, block->grouped_exp[ch][i]);
1311 /* gain range info */
1312 if (ch != s->lfe_channel)
1313 put_bits(&s->pb, 2, 0);
1316 /* bit allocation info */
1317 baie = (block_num == 0);
1318 put_bits(&s->pb, 1, baie);
1320 put_bits(&s->pb, 2, s->slow_decay_code);
1321 put_bits(&s->pb, 2, s->fast_decay_code);
1322 put_bits(&s->pb, 2, s->slow_gain_code);
1323 put_bits(&s->pb, 2, s->db_per_bit_code);
1324 put_bits(&s->pb, 3, s->floor_code);
1328 put_bits(&s->pb, 1, baie);
1330 put_bits(&s->pb, 6, s->coarse_snr_offset);
1331 for (ch = 0; ch < s->channels; ch++) {
1332 put_bits(&s->pb, 4, s->fine_snr_offset[ch]);
1333 put_bits(&s->pb, 3, s->fast_gain_code[ch]);
1337 put_bits(&s->pb, 1, 0); /* no delta bit allocation */
1338 put_bits(&s->pb, 1, 0); /* no data to skip */
1341 for (ch = 0; ch < s->channels; ch++) {
1343 for (i = 0; i < s->nb_coefs[ch]; i++) {
1344 q = block->qmant[ch][i];
1345 b = block->bap[ch][i];
1348 case 1: if (q != 128) put_bits(&s->pb, 5, q); break;
1349 case 2: if (q != 128) put_bits(&s->pb, 7, q); break;
1350 case 3: put_bits(&s->pb, 3, q); break;
1351 case 4: if (q != 128) put_bits(&s->pb, 7, q); break;
1352 case 14: put_bits(&s->pb, 14, q); break;
1353 case 15: put_bits(&s->pb, 16, q); break;
1354 default: put_bits(&s->pb, b-1, q); break;
1361 /** CRC-16 Polynomial */
1362 #define CRC16_POLY ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
1365 static unsigned int mul_poly(unsigned int a, unsigned int b, unsigned int poly)
1382 static unsigned int pow_poly(unsigned int a, unsigned int n, unsigned int poly)
1388 r = mul_poly(r, a, poly);
1389 a = mul_poly(a, a, poly);
1397 * Fill the end of the frame with 0's and compute the two CRCs.
1399 static void output_frame_end(AC3EncodeContext *s)
1401 int frame_size, frame_size_58, pad_bytes, crc1, crc2, crc_inv;
1404 frame_size = s->frame_size;
1405 frame_size_58 = ((frame_size >> 2) + (frame_size >> 4)) << 1;
1407 /* pad the remainder of the frame with zeros */
1408 flush_put_bits(&s->pb);
1410 pad_bytes = s->frame_size - (put_bits_ptr(&s->pb) - frame) - 2;
1411 assert(pad_bytes >= 0);
1413 memset(put_bits_ptr(&s->pb), 0, pad_bytes);
1416 /* this is not so easy because it is at the beginning of the data... */
1417 crc1 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1418 frame + 4, frame_size_58 - 4));
1419 /* XXX: could precompute crc_inv */
1420 crc_inv = pow_poly((CRC16_POLY >> 1), (8 * frame_size_58) - 16, CRC16_POLY);
1421 crc1 = mul_poly(crc_inv, crc1, CRC16_POLY);
1422 AV_WB16(frame + 2, crc1);
1425 crc2 = av_bswap16(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0,
1426 frame + frame_size_58,
1427 frame_size - frame_size_58 - 2));
1428 AV_WB16(frame + frame_size - 2, crc2);
1433 * Write the frame to the output bitstream.
1435 static void output_frame(AC3EncodeContext *s,
1436 unsigned char *frame)
1440 init_put_bits(&s->pb, frame, AC3_MAX_CODED_FRAME_SIZE);
1442 output_frame_header(s);
1444 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++)
1445 output_audio_block(s, blk);
1447 output_frame_end(s);
1452 * Encode a single AC-3 frame.
1454 static int ac3_encode_frame(AVCodecContext *avctx,
1455 unsigned char *frame, int buf_size, void *data)
1457 AC3EncodeContext *s = avctx->priv_data;
1458 const int16_t *samples = data;
1461 if (s->bit_alloc.sr_code == 1)
1462 adjust_frame_size(s);
1464 deinterleave_input_samples(s, samples);
1468 process_exponents(s);
1470 ret = compute_bit_allocation(s);
1472 av_log(avctx, AV_LOG_ERROR, "Bit allocation failed. Try increasing the bitrate.\n");
1476 quantize_mantissas(s);
1478 output_frame(s, frame);
1480 return s->frame_size;
1485 * Finalize encoding and free any memory allocated by the encoder.
1487 static av_cold int ac3_encode_close(AVCodecContext *avctx)
1490 AC3EncodeContext *s = avctx->priv_data;
1492 for (ch = 0; ch < s->channels; ch++)
1493 av_freep(&s->planar_samples[ch]);
1494 av_freep(&s->planar_samples);
1495 av_freep(&s->bap_buffer);
1496 av_freep(&s->bap1_buffer);
1497 av_freep(&s->mdct_coef_buffer);
1498 av_freep(&s->exp_buffer);
1499 av_freep(&s->encoded_exp_buffer);
1500 av_freep(&s->grouped_exp_buffer);
1501 av_freep(&s->psd_buffer);
1502 av_freep(&s->band_psd_buffer);
1503 av_freep(&s->mask_buffer);
1504 av_freep(&s->qmant_buffer);
1505 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1506 AC3Block *block = &s->blocks[blk];
1507 av_freep(&block->bap);
1508 av_freep(&block->mdct_coef);
1509 av_freep(&block->exp);
1510 av_freep(&block->encoded_exp);
1511 av_freep(&block->grouped_exp);
1512 av_freep(&block->psd);
1513 av_freep(&block->band_psd);
1514 av_freep(&block->mask);
1515 av_freep(&block->qmant);
1520 av_freep(&avctx->coded_frame);
1526 * Set channel information during initialization.
1528 static av_cold int set_channel_info(AC3EncodeContext *s, int channels,
1529 int64_t *channel_layout)
1533 if (channels < 1 || channels > AC3_MAX_CHANNELS)
1534 return AVERROR(EINVAL);
1535 if ((uint64_t)*channel_layout > 0x7FF)
1536 return AVERROR(EINVAL);
1537 ch_layout = *channel_layout;
1539 ch_layout = avcodec_guess_channel_layout(channels, CODEC_ID_AC3, NULL);
1540 if (av_get_channel_layout_nb_channels(ch_layout) != channels)
1541 return AVERROR(EINVAL);
1543 s->lfe_on = !!(ch_layout & AV_CH_LOW_FREQUENCY);
1544 s->channels = channels;
1545 s->fbw_channels = channels - s->lfe_on;
1546 s->lfe_channel = s->lfe_on ? s->fbw_channels : -1;
1548 ch_layout -= AV_CH_LOW_FREQUENCY;
1550 switch (ch_layout) {
1551 case AV_CH_LAYOUT_MONO: s->channel_mode = AC3_CHMODE_MONO; break;
1552 case AV_CH_LAYOUT_STEREO: s->channel_mode = AC3_CHMODE_STEREO; break;
1553 case AV_CH_LAYOUT_SURROUND: s->channel_mode = AC3_CHMODE_3F; break;
1554 case AV_CH_LAYOUT_2_1: s->channel_mode = AC3_CHMODE_2F1R; break;
1555 case AV_CH_LAYOUT_4POINT0: s->channel_mode = AC3_CHMODE_3F1R; break;
1556 case AV_CH_LAYOUT_QUAD:
1557 case AV_CH_LAYOUT_2_2: s->channel_mode = AC3_CHMODE_2F2R; break;
1558 case AV_CH_LAYOUT_5POINT0:
1559 case AV_CH_LAYOUT_5POINT0_BACK: s->channel_mode = AC3_CHMODE_3F2R; break;
1561 return AVERROR(EINVAL);
1564 s->channel_map = ff_ac3_enc_channel_map[s->channel_mode][s->lfe_on];
1565 *channel_layout = ch_layout;
1567 *channel_layout |= AV_CH_LOW_FREQUENCY;
1573 static av_cold int validate_options(AVCodecContext *avctx, AC3EncodeContext *s)
1577 /* validate channel layout */
1578 if (!avctx->channel_layout) {
1579 av_log(avctx, AV_LOG_WARNING, "No channel layout specified. The "
1580 "encoder will guess the layout, but it "
1581 "might be incorrect.\n");
1583 ret = set_channel_info(s, avctx->channels, &avctx->channel_layout);
1585 av_log(avctx, AV_LOG_ERROR, "invalid channel layout\n");
1589 /* validate sample rate */
1590 for (i = 0; i < 9; i++) {
1591 if ((ff_ac3_sample_rate_tab[i / 3] >> (i % 3)) == avctx->sample_rate)
1595 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1596 return AVERROR(EINVAL);
1598 s->sample_rate = avctx->sample_rate;
1599 s->bit_alloc.sr_shift = i % 3;
1600 s->bit_alloc.sr_code = i / 3;
1602 /* validate bit rate */
1603 for (i = 0; i < 19; i++) {
1604 if ((ff_ac3_bitrate_tab[i] >> s->bit_alloc.sr_shift)*1000 == avctx->bit_rate)
1608 av_log(avctx, AV_LOG_ERROR, "invalid bit rate\n");
1609 return AVERROR(EINVAL);
1611 s->bit_rate = avctx->bit_rate;
1612 s->frame_size_code = i << 1;
1619 * Set bandwidth for all channels.
1620 * The user can optionally supply a cutoff frequency. Otherwise an appropriate
1621 * default value will be used.
1623 static av_cold void set_bandwidth(AC3EncodeContext *s, int cutoff)
1628 /* calculate bandwidth based on user-specified cutoff frequency */
1630 cutoff = av_clip(cutoff, 1, s->sample_rate >> 1);
1631 fbw_coeffs = cutoff * 2 * AC3_MAX_COEFS / s->sample_rate;
1632 bw_code = av_clip((fbw_coeffs - 73) / 3, 0, 60);
1634 /* use default bandwidth setting */
1635 /* XXX: should compute the bandwidth according to the frame
1636 size, so that we avoid annoying high frequency artifacts */
1640 /* set number of coefficients for each channel */
1641 for (ch = 0; ch < s->fbw_channels; ch++) {
1642 s->bandwidth_code[ch] = bw_code;
1643 s->nb_coefs[ch] = bw_code * 3 + 73;
1646 s->nb_coefs[s->lfe_channel] = 7; /* LFE channel always has 7 coefs */
1650 static av_cold int allocate_buffers(AVCodecContext *avctx)
1653 AC3EncodeContext *s = avctx->priv_data;
1655 FF_ALLOC_OR_GOTO(avctx, s->planar_samples, s->channels * sizeof(*s->planar_samples),
1657 for (ch = 0; ch < s->channels; ch++) {
1658 FF_ALLOCZ_OR_GOTO(avctx, s->planar_samples[ch],
1659 (AC3_FRAME_SIZE+AC3_BLOCK_SIZE) * sizeof(**s->planar_samples),
1662 FF_ALLOC_OR_GOTO(avctx, s->bap_buffer, AC3_MAX_BLOCKS * s->channels *
1663 AC3_MAX_COEFS * sizeof(*s->bap_buffer), alloc_fail);
1664 FF_ALLOC_OR_GOTO(avctx, s->bap1_buffer, AC3_MAX_BLOCKS * s->channels *
1665 AC3_MAX_COEFS * sizeof(*s->bap1_buffer), alloc_fail);
1666 FF_ALLOC_OR_GOTO(avctx, s->mdct_coef_buffer, AC3_MAX_BLOCKS * s->channels *
1667 AC3_MAX_COEFS * sizeof(*s->mdct_coef_buffer), alloc_fail);
1668 FF_ALLOC_OR_GOTO(avctx, s->exp_buffer, AC3_MAX_BLOCKS * s->channels *
1669 AC3_MAX_COEFS * sizeof(*s->exp_buffer), alloc_fail);
1670 FF_ALLOC_OR_GOTO(avctx, s->encoded_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1671 AC3_MAX_COEFS * sizeof(*s->encoded_exp_buffer), alloc_fail);
1672 FF_ALLOC_OR_GOTO(avctx, s->grouped_exp_buffer, AC3_MAX_BLOCKS * s->channels *
1673 128 * sizeof(*s->grouped_exp_buffer), alloc_fail);
1674 FF_ALLOC_OR_GOTO(avctx, s->psd_buffer, AC3_MAX_BLOCKS * s->channels *
1675 AC3_MAX_COEFS * sizeof(*s->psd_buffer), alloc_fail);
1676 FF_ALLOC_OR_GOTO(avctx, s->band_psd_buffer, AC3_MAX_BLOCKS * s->channels *
1677 64 * sizeof(*s->band_psd_buffer), alloc_fail);
1678 FF_ALLOC_OR_GOTO(avctx, s->mask_buffer, AC3_MAX_BLOCKS * s->channels *
1679 64 * sizeof(*s->mask_buffer), alloc_fail);
1680 FF_ALLOC_OR_GOTO(avctx, s->qmant_buffer, AC3_MAX_BLOCKS * s->channels *
1681 AC3_MAX_COEFS * sizeof(*s->qmant_buffer), alloc_fail);
1682 for (blk = 0; blk < AC3_MAX_BLOCKS; blk++) {
1683 AC3Block *block = &s->blocks[blk];
1684 FF_ALLOC_OR_GOTO(avctx, block->bap, s->channels * sizeof(*block->bap),
1686 FF_ALLOCZ_OR_GOTO(avctx, block->mdct_coef, s->channels * sizeof(*block->mdct_coef),
1688 FF_ALLOCZ_OR_GOTO(avctx, block->exp, s->channels * sizeof(*block->exp),
1690 FF_ALLOCZ_OR_GOTO(avctx, block->encoded_exp, s->channels * sizeof(*block->encoded_exp),
1692 FF_ALLOCZ_OR_GOTO(avctx, block->grouped_exp, s->channels * sizeof(*block->grouped_exp),
1694 FF_ALLOCZ_OR_GOTO(avctx, block->psd, s->channels * sizeof(*block->psd),
1696 FF_ALLOCZ_OR_GOTO(avctx, block->band_psd, s->channels * sizeof(*block->band_psd),
1698 FF_ALLOCZ_OR_GOTO(avctx, block->mask, s->channels * sizeof(*block->mask),
1700 FF_ALLOCZ_OR_GOTO(avctx, block->qmant, s->channels * sizeof(*block->qmant),
1703 for (ch = 0; ch < s->channels; ch++) {
1704 block->bap[ch] = &s->bap_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1705 block->mdct_coef[ch] = &s->mdct_coef_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1706 block->exp[ch] = &s->exp_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1707 block->encoded_exp[ch] = &s->encoded_exp_buffer[AC3_MAX_COEFS * (blk * s->channels + ch)];
1708 block->grouped_exp[ch] = &s->grouped_exp_buffer[128 * (blk * s->channels + ch)];
1709 block->psd[ch] = &s->psd_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1710 block->band_psd[ch] = &s->band_psd_buffer [64 * (blk * s->channels + ch)];
1711 block->mask[ch] = &s->mask_buffer [64 * (blk * s->channels + ch)];
1712 block->qmant[ch] = &s->qmant_buffer [AC3_MAX_COEFS * (blk * s->channels + ch)];
1718 return AVERROR(ENOMEM);
1723 * Initialize the encoder.
1725 static av_cold int ac3_encode_init(AVCodecContext *avctx)
1727 AC3EncodeContext *s = avctx->priv_data;
1730 avctx->frame_size = AC3_FRAME_SIZE;
1734 ret = validate_options(avctx, s);
1738 s->bitstream_id = 8 + s->bit_alloc.sr_shift;
1739 s->bitstream_mode = 0; /* complete main audio service */
1741 s->frame_size_min = 2 * ff_ac3_frame_size_tab[s->frame_size_code][s->bit_alloc.sr_code];
1742 s->bits_written = 0;
1743 s->samples_written = 0;
1744 s->frame_size = s->frame_size_min;
1746 set_bandwidth(s, avctx->cutoff);
1750 s->mdct.avctx = avctx;
1751 ret = mdct_init(&s->mdct, 9);
1755 ret = allocate_buffers(avctx);
1759 avctx->coded_frame= avcodec_alloc_frame();
1761 dsputil_init(&s->dsp, avctx);
1765 ac3_encode_close(avctx);
1771 /*************************************************************************/
1774 #include "libavutil/lfg.h"
1776 #define FN (MDCT_SAMPLES/4)
1779 static void fft_test(AVLFG *lfg)
1781 IComplex in[FN], in1[FN];
1783 float sum_re, sum_im, a;
1785 for (i = 0; i < FN; i++) {
1786 in[i].re = av_lfg_get(lfg) % 65535 - 32767;
1787 in[i].im = av_lfg_get(lfg) % 65535 - 32767;
1793 for (k = 0; k < FN; k++) {
1796 for (n = 0; n < FN; n++) {
1797 a = -2 * M_PI * (n * k) / FN;
1798 sum_re += in1[n].re * cos(a) - in1[n].im * sin(a);
1799 sum_im += in1[n].re * sin(a) + in1[n].im * cos(a);
1801 av_log(NULL, AV_LOG_DEBUG, "%3d: %6d,%6d %6.0f,%6.0f\n",
1802 k, in[k].re, in[k].im, sum_re / FN, sum_im / FN);
1807 static void mdct_test(AVLFG *lfg)
1809 int16_t input[MDCT_SAMPLES];
1810 int32_t output[AC3_MAX_COEFS];
1811 float input1[MDCT_SAMPLES];
1812 float output1[AC3_MAX_COEFS];
1813 float s, a, err, e, emax;
1816 for (i = 0; i < MDCT_SAMPLES; i++) {
1817 input[i] = (av_lfg_get(lfg) % 65535 - 32767) * 9 / 10;
1818 input1[i] = input[i];
1821 mdct512(output, input);
1824 for (k = 0; k < AC3_MAX_COEFS; k++) {
1826 for (n = 0; n < MDCT_SAMPLES; n++) {
1827 a = (2*M_PI*(2*n+1+MDCT_SAMPLES/2)*(2*k+1) / (4 * MDCT_SAMPLES));
1828 s += input1[n] * cos(a);
1830 output1[k] = -2 * s / MDCT_SAMPLES;
1835 for (i = 0; i < AC3_MAX_COEFS; i++) {
1836 av_log(NULL, AV_LOG_DEBUG, "%3d: %7d %7.0f\n", i, output[i], output1[i]);
1837 e = output[i] - output1[i];
1842 av_log(NULL, AV_LOG_DEBUG, "err2=%f emax=%f\n", err / AC3_MAX_COEFS, emax);
1850 av_log_set_level(AV_LOG_DEBUG);
1861 AVCodec ac3_encoder = {
1865 sizeof(AC3EncodeContext),
1870 .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
1871 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1872 .channel_layouts = (const int64_t[]){
1874 AV_CH_LAYOUT_STEREO,
1876 AV_CH_LAYOUT_SURROUND,
1879 AV_CH_LAYOUT_4POINT0,
1880 AV_CH_LAYOUT_5POINT0,
1881 AV_CH_LAYOUT_5POINT0_BACK,
1882 (AV_CH_LAYOUT_MONO | AV_CH_LOW_FREQUENCY),
1883 (AV_CH_LAYOUT_STEREO | AV_CH_LOW_FREQUENCY),
1884 (AV_CH_LAYOUT_2_1 | AV_CH_LOW_FREQUENCY),
1885 (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
1886 (AV_CH_LAYOUT_2_2 | AV_CH_LOW_FREQUENCY),
1887 (AV_CH_LAYOUT_QUAD | AV_CH_LOW_FREQUENCY),
1888 (AV_CH_LAYOUT_4POINT0 | AV_CH_LOW_FREQUENCY),
1889 AV_CH_LAYOUT_5POINT1,
1890 AV_CH_LAYOUT_5POINT1_BACK,