3 * This code is developed as part of Google Summer of Code 2006 Program.
5 * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
6 * Copyright (c) 2007 Justin Ruggles
8 * Portions of this code are derived from liba52
9 * http://liba52.sourceforge.net
10 * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org>
11 * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca>
13 * This file is part of FFmpeg.
15 * FFmpeg is free software; you can redistribute it and/or
16 * modify it under the terms of the GNU General Public
17 * License as published by the Free Software Foundation; either
18 * version 2 of the License, or (at your option) any later version.
20 * FFmpeg is distributed in the hope that it will be useful,
21 * but WITHOUT ANY WARRANTY; without even the implied warranty of
22 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
23 * General Public License for more details.
25 * You should have received a copy of the GNU General Public
26 * License along with FFmpeg; if not, write to the Free Software
27 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
36 #include "ac3_parser.h"
37 #include "bitstream.h"
42 * Table of bin locations for rematrixing bands
43 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
45 static const uint8_t rematrix_band_tbl[5] = { 13, 25, 37, 61, 253 };
47 /* table for exponent to scale_factor mapping
48 * scale_factor[i] = 2 ^ -(i + 15)
50 static float scale_factors[25];
52 /** table for grouping exponents */
53 static uint8_t exp_ungroup_tbl[128][3];
55 static int16_t l3_quantizers_1[32];
56 static int16_t l3_quantizers_2[32];
57 static int16_t l3_quantizers_3[32];
59 static int16_t l5_quantizers_1[128];
60 static int16_t l5_quantizers_2[128];
61 static int16_t l5_quantizers_3[128];
63 static int16_t l7_quantizers[7];
65 static int16_t l11_quantizers_1[128];
66 static int16_t l11_quantizers_2[128];
68 static int16_t l15_quantizers[15];
70 static const uint8_t qntztab[16] = { 0, 5, 7, 3, 7, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 };
72 /* Adjustmens in dB gain */
73 #define LEVEL_MINUS_3DB 0.7071067811865476
74 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
75 #define LEVEL_MINUS_6DB 0.5000000000000000
76 #define LEVEL_PLUS_3DB 1.4142135623730951
77 #define LEVEL_PLUS_6DB 2.0000000000000000
78 #define LEVEL_ZERO 0.0000000000000000
80 static const float clevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_4POINT5DB,
81 LEVEL_MINUS_6DB, LEVEL_MINUS_4POINT5DB };
83 static const float slevs[4] = { LEVEL_MINUS_3DB, LEVEL_MINUS_6DB, LEVEL_ZERO, LEVEL_MINUS_6DB };
85 #define AC3_OUTPUT_LFEON 8
93 int blksw[AC3_MAX_CHANNELS];
94 int dithflag[AC3_MAX_CHANNELS];
96 int chincpl[AC3_MAX_CHANNELS];
102 int rematflg[AC3_MAX_CHANNELS];
115 uint8_t cpldeltoffst[8];
116 uint8_t cpldeltlen[8];
117 uint8_t cpldeltba[8];
119 uint8_t deltoffst[5][8];
120 uint8_t deltlen[5][8];
121 uint8_t deltba[5][8];
123 /* Derived Attributes. */
128 int nchans; //number of total channels
129 int nfchans; //number of full-bandwidth channels
130 int lfeon; //lfe channel in use
131 int output_mode; ///< output channel configuration
132 int out_channels; ///< number of output channels
134 float dynrng; //dynamic range gain
135 float dynrng2; //dynamic range gain for 1+1 mode
136 float cplco[5][18]; //coupling coordinates
137 int ncplbnd; //number of coupling bands
138 int ncplsubnd; //number of coupling sub bands
139 int cplstrtmant; //coupling start mantissa
140 int cplendmant; //coupling end mantissa
141 int endmant[5]; //channel end mantissas
142 AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
144 int8_t dcplexps[256]; //decoded coupling exponents
145 int8_t dexps[5][256]; //decoded fbw channel exponents
146 int8_t dlfeexps[256]; //decoded lfe channel exponents
147 uint8_t cplbap[256]; //coupling bit allocation pointers
148 uint8_t bap[5][256]; //fbw channel bit allocation pointers
149 uint8_t lfebap[256]; //lfe channel bit allocation pointers
151 DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); //transform coefficients
154 MDCTContext imdct_512; //for 512 sample imdct transform
155 MDCTContext imdct_256; //for 256 sample imdct transform
156 DSPContext dsp; //for optimization
158 DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]); //output after imdct transform and windowing
159 DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]); //delay - added to the next block
160 DECLARE_ALIGNED_16(float, tmp_imdct[256]); //temporary storage for imdct transform
161 DECLARE_ALIGNED_16(float, tmp_output[512]); //temporary storage for output before windowing
162 DECLARE_ALIGNED_16(float, window[256]); //window coefficients
166 AVRandomState dith_state; //for dither generation
169 /*********** BEGIN INIT HELPER FUNCTIONS ***********/
171 * Generate a Kaiser-Bessel Derived Window.
173 static void ac3_window_init(float *window)
176 double sum = 0.0, bessel, tmp;
177 double local_window[256];
178 double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
180 for (i = 0; i < 256; i++) {
181 tmp = i * (256 - i) * alpha2;
183 for (j = 100; j > 0; j--) /* defaul to 100 iterations */
184 bessel = bessel * tmp / (j * j) + 1;
186 local_window[i] = sum;
190 for (i = 0; i < 256; i++)
191 window[i] = sqrt(local_window[i] / sum);
195 * Generate quantizer tables.
197 static void generate_quantizers_table(int16_t quantizers[], int level, int length)
201 for (i = 0; i < length; i++)
202 quantizers[i] = ((2 * i - level + 1) << 15) / level;
205 static void generate_quantizers_table_1(int16_t quantizers[], int level, int length1, int length2, int size)
210 for (i = 0; i < length1; i++) {
211 v = ((2 * i - level + 1) << 15) / level;
212 for (j = 0; j < length2; j++)
213 quantizers[i * length2 + j] = v;
216 for (i = length1 * length2; i < size; i++)
220 static void generate_quantizers_table_2(int16_t quantizers[], int level, int length1, int length2, int size)
225 for (i = 0; i < length1; i++) {
226 v = ((2 * (i % level) - level + 1) << 15) / level;
227 for (j = 0; j < length2; j++)
228 quantizers[i * length2 + j] = v;
231 for (i = length1 * length2; i < size; i++)
236 static void generate_quantizers_table_3(int16_t quantizers[], int level, int length1, int length2, int size)
240 for (i = 0; i < length1; i++)
241 for (j = 0; j < length2; j++)
242 quantizers[i * length2 + j] = ((2 * (j % level) - level + 1) << 15) / level;
244 for (i = length1 * length2; i < size; i++)
249 * Initialize tables at runtime.
251 static void ac3_tables_init(void)
255 /* Quantizer ungrouping tables. */
256 // for level-3 quantizers
257 generate_quantizers_table_1(l3_quantizers_1, 3, 3, 9, 32);
258 generate_quantizers_table_2(l3_quantizers_2, 3, 9, 3, 32);
259 generate_quantizers_table_3(l3_quantizers_3, 3, 9, 3, 32);
261 //for level-5 quantizers
262 generate_quantizers_table_1(l5_quantizers_1, 5, 5, 25, 128);
263 generate_quantizers_table_2(l5_quantizers_2, 5, 25, 5, 128);
264 generate_quantizers_table_3(l5_quantizers_3, 5, 25, 5, 128);
266 //for level-7 quantizers
267 generate_quantizers_table(l7_quantizers, 7, 7);
269 //for level-4 quantizers
270 generate_quantizers_table_2(l11_quantizers_1, 11, 11, 11, 128);
271 generate_quantizers_table_3(l11_quantizers_2, 11, 11, 11, 128);
273 //for level-15 quantizers
274 generate_quantizers_table(l15_quantizers, 15, 15);
275 /* End Quantizer ungrouping tables. */
277 //generate scale factors
278 for (i = 0; i < 25; i++)
279 scale_factors[i] = pow(2.0, -(i + 15));
281 /* generate exponent tables
282 reference: Section 7.1.3 Exponent Decoding */
283 for(i=0; i<128; i++) {
284 exp_ungroup_tbl[i][0] = i / 25;
285 exp_ungroup_tbl[i][1] = (i % 25) / 5;
286 exp_ungroup_tbl[i][2] = (i % 25) % 5;
291 static int ac3_decode_init(AVCodecContext *avctx)
293 AC3DecodeContext *ctx = avctx->priv_data;
297 ff_mdct_init(&ctx->imdct_256, 8, 1);
298 ff_mdct_init(&ctx->imdct_512, 9, 1);
299 ac3_window_init(ctx->window);
300 dsputil_init(&ctx->dsp, avctx);
301 av_init_random(0, &ctx->dith_state);
305 /*********** END INIT FUNCTIONS ***********/
308 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
309 * GetBitContext within AC3DecodeContext must point to
310 * start of the synchronized ac3 bitstream.
312 static int ac3_parse_header(AC3DecodeContext *ctx)
315 GetBitContext *gb = &ctx->gb;
318 err = ff_ac3_parse_header(gb->buffer, &hdr);
322 /* get decoding parameters from header info */
323 ctx->bit_alloc_params.fscod = hdr.fscod;
324 ctx->acmod = hdr.acmod;
325 ctx->cmixlev = hdr.cmixlev;
326 ctx->surmixlev = hdr.surmixlev;
327 ctx->dsurmod = hdr.dsurmod;
328 ctx->lfeon = hdr.lfeon;
329 ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
330 ctx->sampling_rate = hdr.sample_rate;
331 ctx->bit_rate = hdr.bit_rate;
332 ctx->nchans = hdr.channels;
333 ctx->nfchans = ctx->nchans - ctx->lfeon;
334 ctx->frame_size = hdr.frame_size;
336 /* set default output to all source channels */
337 ctx->out_channels = ctx->nchans;
338 ctx->output_mode = ctx->acmod;
340 ctx->output_mode |= AC3_OUTPUT_LFEON;
342 /* skip over portion of header which has already been read */
343 skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
344 skip_bits(gb, 16); // skip crc1
345 skip_bits(gb, 8); // skip fscod and frmsizecod
346 skip_bits(gb, 11); // skip bsid, bsmod, and acmod
347 if(ctx->acmod == AC3_ACMOD_STEREO) {
348 skip_bits(gb, 2); // skip dsurmod
350 if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
351 skip_bits(gb, 2); // skip cmixlev
353 skip_bits(gb, 2); // skip surmixlev
355 skip_bits1(gb); // skip lfeon
357 /* read the rest of the bsi. read twice for dual mono mode. */
360 skip_bits(gb, 5); //skip dialog normalization
362 skip_bits(gb, 8); //skip compression
364 skip_bits(gb, 8); //skip language code
366 skip_bits(gb, 7); //skip audio production information
369 skip_bits(gb, 2); //skip copyright bit and original bitstream bit
371 /* FIXME: read & use the xbsi1 downmix levels */
373 skip_bits(gb, 14); //skip timecode1
375 skip_bits(gb, 14); //skip timecode2
378 i = get_bits(gb, 6); //additional bsi length
388 * Decodes the grouped exponents.
389 * This function decodes the coded exponents according to exponent strategy
390 * and stores them in the decoded exponents buffer.
392 * @param[in] gb GetBitContext which points to start of coded exponents
393 * @param[in] expstr Exponent coding strategy
394 * @param[in] ngrps Number of grouped exponents
395 * @param[in] absexp Absolute exponent or DC exponent
396 * @param[out] dexps Decoded exponents are stored in dexps
398 static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
399 uint8_t absexp, int8_t *dexps)
401 int i, j, grp, grpsize;
406 grpsize = expstr + (expstr == EXP_D45);
407 for(grp=0,i=0; grp<ngrps; grp++) {
408 expacc = get_bits(gb, 7);
409 dexp[i++] = exp_ungroup_tbl[expacc][0];
410 dexp[i++] = exp_ungroup_tbl[expacc][1];
411 dexp[i++] = exp_ungroup_tbl[expacc][2];
414 /* convert to absolute exps and expand groups */
416 for(i=0; i<ngrps*3; i++) {
417 prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
418 for(j=0; j<grpsize; j++) {
419 dexps[(i*grpsize)+j] = prevexp;
424 typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
425 int16_t l3_quantizers[3];
426 int16_t l5_quantizers[3];
427 int16_t l11_quantizers[2];
433 /* Get the transform coefficients for coupling channel and uncouple channels.
434 * The coupling transform coefficients starts at the the cplstrtmant, which is
435 * equal to endmant[ch] for fbw channels. Hence we can uncouple channels before
436 * getting transform coefficients for the channel.
438 static int get_transform_coeffs_cpling(AC3DecodeContext *ctx, mant_groups *m)
440 GetBitContext *gb = &ctx->gb;
441 int ch, start, end, cplbndstrc, bnd, gcode, tbap;
442 float cplcos[5], cplcoeff;
443 uint8_t *exps = ctx->dcplexps;
444 uint8_t *bap = ctx->cplbap;
446 cplbndstrc = ctx->cplbndstrc;
447 start = ctx->cplstrtmant;
450 while (start < ctx->cplendmant) {
452 while (cplbndstrc & 1) {
457 for (ch = 0; ch < ctx->nfchans; ch++)
458 cplcos[ch] = ctx->cplco[ch][bnd];
461 while (start < end) {
465 for (ch = 0; ch < ctx->nfchans; ch++)
466 if (ctx->chincpl[ch]) {
467 if (ctx->dithflag[ch]) {
468 cplcoeff = (av_random(&ctx->dith_state) & 0xFFFF) * scale_factors[exps[start]];
469 ctx->transform_coeffs[ch + 1][start] = cplcoeff * cplcos[ch] * LEVEL_MINUS_3DB;
471 ctx->transform_coeffs[ch + 1][start] = 0;
477 gcode = get_bits(gb, 5);
478 m->l3_quantizers[0] = l3_quantizers_1[gcode];
479 m->l3_quantizers[1] = l3_quantizers_2[gcode];
480 m->l3_quantizers[2] = l3_quantizers_3[gcode];
483 cplcoeff = m->l3_quantizers[m->l3ptr++] * scale_factors[exps[start]];
488 gcode = get_bits(gb, 7);
489 m->l5_quantizers[0] = l5_quantizers_1[gcode];
490 m->l5_quantizers[1] = l5_quantizers_2[gcode];
491 m->l5_quantizers[2] = l5_quantizers_3[gcode];
494 cplcoeff = m->l5_quantizers[m->l5ptr++] * scale_factors[exps[start]];
498 cplcoeff = l7_quantizers[get_bits(gb, 3)] * scale_factors[exps[start]];
503 gcode = get_bits(gb, 7);
504 m->l11_quantizers[0] = l11_quantizers_1[gcode];
505 m->l11_quantizers[1] = l11_quantizers_2[gcode];
508 cplcoeff = m->l11_quantizers[m->l11ptr++] * scale_factors[exps[start]];
512 cplcoeff = l15_quantizers[get_bits(gb, 4)] * scale_factors[exps[start]];
516 cplcoeff = (get_sbits(gb, qntztab[tbap]) << (16 - qntztab[tbap])) * scale_factors[exps[start]];
518 for (ch = 0; ch < ctx->nfchans; ch++)
519 if (ctx->chincpl[ch])
520 ctx->transform_coeffs[ch + 1][start] = cplcoeff * cplcos[ch];
528 /* Get the transform coefficients for particular channel */
529 static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
531 GetBitContext *gb = &ctx->gb;
532 int i, gcode, tbap, dithflag, end;
537 if (ch_index != -1) { /* fbw channels */
538 dithflag = ctx->dithflag[ch_index];
539 exps = ctx->dexps[ch_index];
540 bap = ctx->bap[ch_index];
541 coeffs = ctx->transform_coeffs[ch_index + 1];
542 end = ctx->endmant[ch_index];
543 } else if (ch_index == -1) {
545 exps = ctx->dlfeexps;
547 coeffs = ctx->transform_coeffs[0];
552 for (i = 0; i < end; i++) {
561 coeffs[i] = (av_random(&ctx->dith_state) & 0xFFFF) * scale_factors[exps[i]];
562 coeffs[i] *= LEVEL_MINUS_3DB;
568 gcode = get_bits(gb, 5);
569 m->l3_quantizers[0] = l3_quantizers_1[gcode];
570 m->l3_quantizers[1] = l3_quantizers_2[gcode];
571 m->l3_quantizers[2] = l3_quantizers_3[gcode];
574 coeffs[i] = m->l3_quantizers[m->l3ptr++] * scale_factors[exps[i]];
579 gcode = get_bits(gb, 7);
580 m->l5_quantizers[0] = l5_quantizers_1[gcode];
581 m->l5_quantizers[1] = l5_quantizers_2[gcode];
582 m->l5_quantizers[2] = l5_quantizers_3[gcode];
585 coeffs[i] = m->l5_quantizers[m->l5ptr++] * scale_factors[exps[i]];
589 coeffs[i] = l7_quantizers[get_bits(gb, 3)] * scale_factors[exps[i]];
594 gcode = get_bits(gb, 7);
595 m->l11_quantizers[0] = l11_quantizers_1[gcode];
596 m->l11_quantizers[1] = l11_quantizers_2[gcode];
599 coeffs[i] = m->l11_quantizers[m->l11ptr++] * scale_factors[exps[i]];
603 coeffs[i] = l15_quantizers[get_bits(gb, 4)] * scale_factors[exps[i]];
607 coeffs[i] = (get_sbits(gb, qntztab[tbap]) << (16 - qntztab[tbap])) * scale_factors[exps[i]];
615 /* Get the transform coefficients.
616 * This function extracts the tranform coefficients form the ac3 bitstream.
617 * This function is called after bit allocation is performed.
619 static int get_transform_coeffs(AC3DecodeContext * ctx)
625 m.l3ptr = m.l5ptr = m.l11ptr = 3;
627 for (i = 0; i < ctx->nfchans; i++) {
628 /* transform coefficients for individual channel */
629 if (get_transform_coeffs_ch(ctx, i, &m))
631 /* tranform coefficients for coupling channels */
632 if (ctx->chincpl[i]) {
634 if (get_transform_coeffs_cpling(ctx, &m)) {
635 av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
640 end = ctx->cplendmant;
642 end = ctx->endmant[i];
644 ctx->transform_coeffs[i + 1][end] = 0;
648 if (get_transform_coeffs_ch(ctx, -1, &m))
650 for (i = 7; i < 256; i++) {
651 ctx->transform_coeffs[0][i] = 0;
659 * Performs stereo rematrixing.
660 * reference: Section 7.5.4 Rematrixing : Decoding Technique
662 static void do_rematrixing(AC3DecodeContext *ctx)
668 end = FFMIN(ctx->endmant[0], ctx->endmant[1]);
670 for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
671 if(ctx->rematflg[bnd]) {
672 bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
673 for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
674 tmp0 = ctx->transform_coeffs[1][i];
675 tmp1 = ctx->transform_coeffs[2][i];
676 ctx->transform_coeffs[1][i] = tmp0 + tmp1;
677 ctx->transform_coeffs[2][i] = tmp0 - tmp1;
683 /* This function performs the imdct on 256 sample transform
686 static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
691 float *o_ptr = ctx->tmp_output;
694 /* de-interleave coefficients */
695 for(k=0; k<128; k++) {
696 x[k] = ctx->transform_coeffs[chindex][2*k+i];
699 /* run standard IMDCT */
700 ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
702 /* reverse the post-rotation & reordering from standard IMDCT */
703 for(k=0; k<32; k++) {
704 z[i][32+k].re = -o_ptr[128+2*k];
705 z[i][32+k].im = -o_ptr[2*k];
706 z[i][31-k].re = o_ptr[2*k+1];
707 z[i][31-k].im = o_ptr[128+2*k+1];
711 /* apply AC-3 post-rotation & reordering */
712 for(k=0; k<64; k++) {
713 o_ptr[ 2*k ] = -z[0][ k].im;
714 o_ptr[ 2*k+1] = z[0][63-k].re;
715 o_ptr[128+2*k ] = -z[0][ k].re;
716 o_ptr[128+2*k+1] = z[0][63-k].im;
717 o_ptr[256+2*k ] = -z[1][ k].re;
718 o_ptr[256+2*k+1] = z[1][63-k].im;
719 o_ptr[384+2*k ] = z[1][ k].im;
720 o_ptr[384+2*k+1] = -z[1][63-k].re;
724 /* IMDCT Transform. */
725 static inline void do_imdct(AC3DecodeContext *ctx)
729 if (ctx->output_mode & AC3_OUTPUT_LFEON) {
730 ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
731 ctx->transform_coeffs[0], ctx->tmp_imdct);
732 ctx->dsp.vector_fmul_add_add(ctx->output[0], ctx->tmp_output,
733 ctx->window, ctx->delay[0], 384, 256, 1);
734 ctx->dsp.vector_fmul_reverse(ctx->delay[0], ctx->tmp_output+256,
737 for (ch=1; ch<=ctx->nfchans; ch++) {
738 if (ctx->blksw[ch-1])
739 do_imdct_256(ctx, ch);
741 ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
742 ctx->transform_coeffs[ch],
745 ctx->dsp.vector_fmul_add_add(ctx->output[ch], ctx->tmp_output,
746 ctx->window, ctx->delay[ch], 384, 256, 1);
747 ctx->dsp.vector_fmul_reverse(ctx->delay[ch], ctx->tmp_output+256,
752 /* Parse the audio block from ac3 bitstream.
753 * This function extract the audio block from the ac3 bitstream
754 * and produces the output for the block. This function must
755 * be called for each of the six audio block in the ac3 bitstream.
757 static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
759 int nfchans = ctx->nfchans;
760 int acmod = ctx->acmod;
761 int i, bnd, seg, grpsize, ch;
762 GetBitContext *gb = &ctx->gb;
763 int bit_alloc_flags = 0;
765 int mstrcplco, cplcoexp, cplcomant;
766 int dynrng, chbwcod, ngrps, cplabsexp, skipl;
768 for (i = 0; i < nfchans; i++) /*block switch flag */
769 ctx->blksw[i] = get_bits1(gb);
771 for (i = 0; i < nfchans; i++) /* dithering flag */
772 ctx->dithflag[i] = get_bits1(gb);
774 if (get_bits1(gb)) { /* dynamic range */
775 dynrng = get_sbits(gb, 8);
776 ctx->dynrng = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
777 } else if(blk == 0) {
781 if(acmod == AC3_ACMOD_DUALMONO) { /* dynamic range 1+1 mode */
783 dynrng = get_sbits(gb, 8);
784 ctx->dynrng2 = ((((dynrng & 0x1f) | 0x20) << 13) * scale_factors[3 - (dynrng >> 5)]);
785 } else if(blk == 0) {
790 if (get_bits1(gb)) { /* coupling strategy */
791 ctx->cplinu = get_bits1(gb);
793 if (ctx->cplinu) { /* coupling in use */
794 int cplbegf, cplendf;
796 for (i = 0; i < nfchans; i++)
797 ctx->chincpl[i] = get_bits1(gb);
799 if (acmod == AC3_ACMOD_STEREO)
800 ctx->phsflginu = get_bits1(gb); //phase flag in use
802 cplbegf = get_bits(gb, 4);
803 cplendf = get_bits(gb, 4);
805 if (3 + cplendf - cplbegf < 0) {
806 av_log(NULL, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
810 ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
811 ctx->cplstrtmant = cplbegf * 12 + 37;
812 ctx->cplendmant = cplendf * 12 + 73;
813 for (i = 0; i < ctx->ncplsubnd - 1; i++) /* coupling band structure */
815 ctx->cplbndstrc |= 1 << i;
819 for (i = 0; i < nfchans; i++)
827 for (i = 0; i < nfchans; i++)
829 if (get_bits1(gb)) { /* coupling co-ordinates */
830 ctx->cplcoe |= 1 << i;
831 mstrcplco = 3 * get_bits(gb, 2);
832 for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
833 cplcoexp = get_bits(gb, 4);
834 cplcomant = get_bits(gb, 4);
838 cplcomant = (cplcomant | 0x10) << 13;
839 ctx->cplco[i][bnd] = cplcomant * scale_factors[cplcoexp + mstrcplco];
843 if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && (ctx->cplcoe & 1 || ctx->cplcoe & 2))
844 for (bnd = 0; bnd < ctx->ncplbnd; bnd++)
846 ctx->cplco[1][bnd] = -ctx->cplco[1][bnd];
849 if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
850 ctx->rematstr = get_bits1(gb);
853 if(ctx->cplinu && ctx->cplstrtmant <= 61)
854 ctx->nrematbnd -= 1 + (ctx->cplstrtmant == 37);
855 for(bnd=0; bnd<ctx->nrematbnd; bnd++)
856 ctx->rematflg[bnd] = get_bits1(gb);
860 ctx->cplexpstr = EXP_REUSE;
861 ctx->lfeexpstr = EXP_REUSE;
862 if (ctx->cplinu) /* coupling exponent strategy */
863 ctx->cplexpstr = get_bits(gb, 2);
864 for (i = 0; i < nfchans; i++) /* channel exponent strategy */
865 ctx->chexpstr[i] = get_bits(gb, 2);
866 if (ctx->lfeon) /* lfe exponent strategy */
867 ctx->lfeexpstr = get_bits1(gb);
869 for (i = 0; i < nfchans; i++) /* channel bandwidth code */
870 if (ctx->chexpstr[i] != EXP_REUSE) {
872 ctx->endmant[i] = ctx->cplstrtmant;
874 chbwcod = get_bits(gb, 6);
876 av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
879 ctx->endmant[i] = chbwcod * 3 + 73;
883 if (ctx->cplexpstr != EXP_REUSE) {/* coupling exponents */
884 bit_alloc_flags = 64;
885 cplabsexp = get_bits(gb, 4) << 1;
886 ngrps = (ctx->cplendmant - ctx->cplstrtmant) / (3 << (ctx->cplexpstr - 1));
887 decode_exponents(gb, ctx->cplexpstr, ngrps, cplabsexp, ctx->dcplexps + ctx->cplstrtmant);
890 for (i = 0; i < nfchans; i++) /* fbw channel exponents */
891 if (ctx->chexpstr[i] != EXP_REUSE) {
892 bit_alloc_flags |= 1 << i;
893 grpsize = 3 << (ctx->chexpstr[i] - 1);
894 ngrps = (ctx->endmant[i] + grpsize - 4) / grpsize;
895 dexps = ctx->dexps[i];
896 dexps[0] = get_bits(gb, 4);
897 decode_exponents(gb, ctx->chexpstr[i], ngrps, dexps[0], dexps + 1);
898 skip_bits(gb, 2); /* skip gainrng */
901 if (ctx->lfeexpstr != EXP_REUSE) { /* lfe exponents */
902 bit_alloc_flags |= 32;
903 ctx->dlfeexps[0] = get_bits(gb, 4);
904 decode_exponents(gb, ctx->lfeexpstr, 2, ctx->dlfeexps[0], ctx->dlfeexps + 1);
907 if (get_bits1(gb)) { /* bit allocation information */
908 bit_alloc_flags = 127;
909 ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
910 ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
911 ctx->bit_alloc_params.sgain = ff_sgaintab[get_bits(gb, 2)];
912 ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
913 ctx->bit_alloc_params.floor = ff_floortab[get_bits(gb, 3)];
916 if (get_bits1(gb)) { /* snroffset */
918 bit_alloc_flags = 127;
919 csnr = (get_bits(gb, 6) - 15) << 4;
920 if (ctx->cplinu) { /* coupling fine snr offset and fast gain code */
921 ctx->cplsnroffst = (csnr + get_bits(gb, 4)) << 2;
922 ctx->cplfgain = ff_fgaintab[get_bits(gb, 3)];
924 for (i = 0; i < nfchans; i++) { /* channel fine snr offset and fast gain code */
925 ctx->snroffst[i] = (csnr + get_bits(gb, 4)) << 2;
926 ctx->fgain[i] = ff_fgaintab[get_bits(gb, 3)];
928 if (ctx->lfeon) { /* lfe fine snr offset and fast gain code */
929 ctx->lfesnroffst = (csnr + get_bits(gb, 4)) << 2;
930 ctx->lfefgain = ff_fgaintab[get_bits(gb, 3)];
934 if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
935 bit_alloc_flags |= 64;
936 ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
937 ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
940 if (get_bits1(gb)) { /* delta bit allocation information */
941 bit_alloc_flags = 127;
944 ctx->cpldeltbae = get_bits(gb, 2);
945 if (ctx->cpldeltbae == DBA_RESERVED) {
946 av_log(NULL, AV_LOG_ERROR, "coupling delta bit allocation strategy reserved\n");
951 for (i = 0; i < nfchans; i++) {
952 ctx->deltbae[i] = get_bits(gb, 2);
953 if (ctx->deltbae[i] == DBA_RESERVED) {
954 av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
960 if (ctx->cpldeltbae == DBA_NEW) { /*coupling delta offset, len and bit allocation */
961 ctx->cpldeltnseg = get_bits(gb, 3);
962 for (seg = 0; seg <= ctx->cpldeltnseg; seg++) {
963 ctx->cpldeltoffst[seg] = get_bits(gb, 5);
964 ctx->cpldeltlen[seg] = get_bits(gb, 4);
965 ctx->cpldeltba[seg] = get_bits(gb, 3);
969 for (i = 0; i < nfchans; i++)
970 if (ctx->deltbae[i] == DBA_NEW) {/*channel delta offset, len and bit allocation */
971 ctx->deltnseg[i] = get_bits(gb, 3);
972 for (seg = 0; seg <= ctx->deltnseg[i]; seg++) {
973 ctx->deltoffst[i][seg] = get_bits(gb, 5);
974 ctx->deltlen[i][seg] = get_bits(gb, 4);
975 ctx->deltba[i][seg] = get_bits(gb, 3);
978 } else if(blk == 0) {
980 ctx->cpldeltbae = DBA_NONE;
981 for(i=0; i<nfchans; i++) {
982 ctx->deltbae[i] = DBA_NONE;
986 if (bit_alloc_flags) {
987 if (ctx->cplinu && (bit_alloc_flags & 64))
988 ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->cplbap,
989 ctx->dcplexps, ctx->cplstrtmant,
990 ctx->cplendmant, ctx->cplsnroffst,
992 ctx->cpldeltbae, ctx->cpldeltnseg,
993 ctx->cpldeltoffst, ctx->cpldeltlen,
995 for (i = 0; i < nfchans; i++)
996 if ((bit_alloc_flags >> i) & 1)
997 ac3_parametric_bit_allocation(&ctx->bit_alloc_params,
998 ctx->bap[i], ctx->dexps[i], 0,
999 ctx->endmant[i], ctx->snroffst[i],
1000 ctx->fgain[i], 0, ctx->deltbae[i],
1001 ctx->deltnseg[i], ctx->deltoffst[i],
1002 ctx->deltlen[i], ctx->deltba[i]);
1003 if (ctx->lfeon && (bit_alloc_flags & 32))
1004 ac3_parametric_bit_allocation(&ctx->bit_alloc_params, ctx->lfebap,
1005 ctx->dlfeexps, 0, 7, ctx->lfesnroffst,
1007 DBA_NONE, 0, NULL, NULL, NULL);
1010 if (get_bits1(gb)) { /* unused dummy data */
1011 skipl = get_bits(gb, 9);
1015 /* unpack the transform coefficients
1016 * * this also uncouples channels if coupling is in use.
1018 if (get_transform_coeffs(ctx)) {
1019 av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1023 /* recover coefficients if rematrixing is in use */
1024 if(ctx->acmod == AC3_ACMOD_STEREO)
1025 do_rematrixing(ctx);
1027 /* apply scaling to coefficients (headroom, dynrng) */
1029 for(i=0; i<7; i++) {
1030 ctx->transform_coeffs[0][i] *= 2.0f * ctx->dynrng;
1033 for(ch=1; ch<=ctx->nfchans; ch++) {
1035 if(ctx->acmod == AC3_ACMOD_DUALMONO && ch == 2) {
1036 gain *= ctx->dynrng2;
1038 gain *= ctx->dynrng;
1040 for(i=0; i<ctx->endmant[ch-1]; i++) {
1041 ctx->transform_coeffs[ch][i] *= gain;
1050 static inline int16_t convert(int32_t i)
1054 else if (i <= 0x43bf8000)
1057 return (i - 0x43c00000);
1060 /* Decode ac3 frame.
1062 * @param avctx Pointer to AVCodecContext
1063 * @param data Pointer to pcm smaples
1064 * @param data_size Set to number of pcm samples produced by decoding
1065 * @param buf Data to be decoded
1066 * @param buf_size Size of the buffer
1068 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1070 AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1071 int16_t *out_samples = (int16_t *)data;
1073 int32_t *int_ptr[6];
1075 for (i = 0; i < 6; i++)
1076 int_ptr[i] = (int32_t *)(&ctx->output[i]);
1078 //Initialize the GetBitContext with the start of valid AC3 Frame.
1079 init_get_bits(&ctx->gb, buf, buf_size * 8);
1081 //Parse the syncinfo.
1082 if (ac3_parse_header(ctx)) {
1083 av_log(avctx, AV_LOG_ERROR, "\n");
1088 avctx->sample_rate = ctx->sampling_rate;
1089 avctx->bit_rate = ctx->bit_rate;
1091 /* channel config */
1092 if (avctx->channels == 0) {
1093 avctx->channels = ctx->out_channels;
1095 if(avctx->channels != ctx->out_channels) {
1096 av_log(avctx, AV_LOG_ERROR, "Cannot mix AC3 to %d channels.\n",
1101 //av_log(avctx, AV_LOG_INFO, "channels = %d \t bit rate = %d \t sampling rate = %d \n", avctx->channels, avctx->bit_rate * 1000, avctx->sample_rate);
1103 //Parse the Audio Blocks.
1104 for (i = 0; i < NB_BLOCKS; i++) {
1105 if (ac3_parse_audio_block(ctx, i)) {
1106 av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1108 return ctx->frame_size;
1110 start = (ctx->output_mode & AC3_OUTPUT_LFEON) ? 0 : 1;
1111 for (k = 0; k < 256; k++)
1112 for (j = start; j <= ctx->nfchans; j++)
1113 *(out_samples++) = convert(int_ptr[j][k]);
1115 *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1116 return ctx->frame_size;
1119 /* Uninitialize ac3 decoder.
1121 static int ac3_decode_end(AVCodecContext *avctx)
1123 AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1124 ff_mdct_end(&ctx->imdct_512);
1125 ff_mdct_end(&ctx->imdct_256);
1130 AVCodec ac3_decoder = {
1132 .type = CODEC_TYPE_AUDIO,
1134 .priv_data_size = sizeof (AC3DecodeContext),
1135 .init = ac3_decode_init,
1136 .close = ac3_decode_end,
1137 .decode = ac3_decode_frame,