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];
56 /** tables for ungrouping mantissas */
57 static float b1_mantissas[32][3];
58 static float b2_mantissas[128][3];
59 static float b3_mantissas[8];
60 static float b4_mantissas[128][2];
61 static float b5_mantissas[16];
64 * Quantization table: levels for symmetric. bits for asymmetric.
65 * reference: Table 7.18 Mapping of bap to Quantizer
67 static const uint8_t qntztab[16] = {
69 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
72 /** dynamic range table. converts codes to scale factors. */
73 static float dynrng_tbl[256];
75 /** dialogue normalization table */
76 static float dialnorm_tbl[32];
78 /* Adjustmens in dB gain */
79 #define LEVEL_MINUS_3DB 0.7071067811865476
80 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
81 #define LEVEL_MINUS_6DB 0.5000000000000000
82 #define LEVEL_MINUS_9DB 0.3535533905932738
83 #define LEVEL_ZERO 0.0000000000000000
84 #define LEVEL_ONE 1.0000000000000000
86 static const float gain_levels[6] = {
90 LEVEL_MINUS_4POINT5DB,
96 * Table for center mix levels
97 * reference: Section 5.4.2.4 cmixlev
99 static const uint8_t clevs[4] = { 2, 3, 4, 3 };
102 * Table for surround mix levels
103 * reference: Section 5.4.2.5 surmixlev
105 static const uint8_t slevs[4] = { 2, 4, 0, 4 };
108 * Table for default stereo downmixing coefficients
109 * reference: Section 7.8.2 Downmixing Into Two Channels
111 static const uint8_t ac3_default_coeffs[8][5][2] = {
112 { { 1, 0 }, { 0, 1 }, },
114 { { 1, 0 }, { 0, 1 }, },
115 { { 1, 0 }, { 3, 3 }, { 0, 1 }, },
116 { { 1, 0 }, { 0, 1 }, { 4, 4 }, },
117 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, },
118 { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
119 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
122 /* override ac3.h to include coupling channel */
123 #undef AC3_MAX_CHANNELS
124 #define AC3_MAX_CHANNELS 7
127 #define AC3_OUTPUT_LFEON 8
133 int blksw[AC3_MAX_CHANNELS];
134 int dithflag[AC3_MAX_CHANNELS];
137 int chincpl[AC3_MAX_CHANNELS];
143 int expstr[AC3_MAX_CHANNELS];
144 int snroffst[AC3_MAX_CHANNELS];
145 int fgain[AC3_MAX_CHANNELS];
146 int deltbae[AC3_MAX_CHANNELS];
147 int deltnseg[AC3_MAX_CHANNELS];
148 uint8_t deltoffst[AC3_MAX_CHANNELS][8];
149 uint8_t deltlen[AC3_MAX_CHANNELS][8];
150 uint8_t deltba[AC3_MAX_CHANNELS][8];
152 /* Derived Attributes. */
157 int nchans; //number of total channels
158 int nfchans; //number of full-bandwidth channels
159 int lfeon; //lfe channel in use
160 int lfe_ch; ///< index of LFE channel
161 int output_mode; ///< output channel configuration
162 int out_channels; ///< number of output channels
164 float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
165 float dialnorm[2]; ///< dialogue normalization
166 float dynrng[2]; ///< dynamic range
167 float cplco[AC3_MAX_CHANNELS][18]; //coupling coordinates
168 int ncplbnd; //number of coupling bands
169 int ncplsubnd; //number of coupling sub bands
170 int startmant[AC3_MAX_CHANNELS]; ///< start frequency bin
171 int endmant[AC3_MAX_CHANNELS]; //channel end mantissas
172 AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
174 int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
175 uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
176 int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
177 int16_t bndpsd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
178 int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
180 DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); //transform coefficients
183 MDCTContext imdct_512; //for 512 sample imdct transform
184 MDCTContext imdct_256; //for 256 sample imdct transform
185 DSPContext dsp; //for optimization
186 float add_bias; ///< offset for float_to_int16 conversion
187 float mul_bias; ///< scaling for float_to_int16 conversion
189 DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]); //output after imdct transform and windowing
190 DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
191 DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]); //delay - added to the next block
192 DECLARE_ALIGNED_16(float, tmp_imdct[256]); //temporary storage for imdct transform
193 DECLARE_ALIGNED_16(float, tmp_output[512]); //temporary storage for output before windowing
194 DECLARE_ALIGNED_16(float, window[256]); //window coefficients
198 AVRandomState dith_state; //for dither generation
201 /*********** BEGIN INIT HELPER FUNCTIONS ***********/
203 * Generate a Kaiser-Bessel Derived Window.
205 static void ac3_window_init(float *window)
208 double sum = 0.0, bessel, tmp;
209 double local_window[256];
210 double alpha2 = (5.0 * M_PI / 256.0) * (5.0 * M_PI / 256.0);
212 for (i = 0; i < 256; i++) {
213 tmp = i * (256 - i) * alpha2;
215 for (j = 100; j > 0; j--) /* defaul to 100 iterations */
216 bessel = bessel * tmp / (j * j) + 1;
218 local_window[i] = sum;
222 for (i = 0; i < 256; i++)
223 window[i] = sqrt(local_window[i] / sum);
227 symmetric_dequant(int code, int levels)
229 return (code - (levels >> 1)) * (2.0f / levels);
233 * Initialize tables at runtime.
235 static void ac3_tables_init(void)
239 /* generate grouped mantissa tables
240 reference: Section 7.3.5 Ungrouping of Mantissas */
241 for(i=0; i<32; i++) {
242 /* bap=1 mantissas */
243 b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3);
244 b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
245 b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
247 for(i=0; i<128; i++) {
248 /* bap=2 mantissas */
249 b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
250 b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
251 b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
253 /* bap=4 mantissas */
254 b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
255 b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
257 /* generate ungrouped mantissa tables
258 reference: Tables 7.21 and 7.23 */
260 /* bap=3 mantissas */
261 b3_mantissas[i] = symmetric_dequant(i, 7);
263 for(i=0; i<15; i++) {
264 /* bap=5 mantissas */
265 b5_mantissas[i] = symmetric_dequant(i, 15);
268 /* generate dynamic range table
269 reference: Section 7.7.1 Dynamic Range Control */
270 for(i=0; i<256; i++) {
271 int v = (i >> 5) - ((i >> 7) << 3) - 5;
272 dynrng_tbl[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
275 /* generate dialogue normalization table
276 references: Section 5.4.2.8 dialnorm
277 Section 7.6 Dialogue Normalization */
278 for(i=1; i<32; i++) {
279 dialnorm_tbl[i] = expf((i-31) * M_LN10 / 20.0f);
281 dialnorm_tbl[0] = dialnorm_tbl[31];
283 //generate scale factors
284 for (i = 0; i < 25; i++)
285 scale_factors[i] = pow(2.0, -i);
287 /* generate exponent tables
288 reference: Section 7.1.3 Exponent Decoding */
289 for(i=0; i<128; i++) {
290 exp_ungroup_tbl[i][0] = i / 25;
291 exp_ungroup_tbl[i][1] = (i % 25) / 5;
292 exp_ungroup_tbl[i][2] = (i % 25) % 5;
297 static int ac3_decode_init(AVCodecContext *avctx)
299 AC3DecodeContext *ctx = avctx->priv_data;
303 ff_mdct_init(&ctx->imdct_256, 8, 1);
304 ff_mdct_init(&ctx->imdct_512, 9, 1);
305 ac3_window_init(ctx->window);
306 dsputil_init(&ctx->dsp, avctx);
307 av_init_random(0, &ctx->dith_state);
309 if(ctx->dsp.float_to_int16 == ff_float_to_int16_c) {
310 ctx->add_bias = 385.0f;
311 ctx->mul_bias = 1.0f;
313 ctx->add_bias = 0.0f;
314 ctx->mul_bias = 32767.0f;
319 /*********** END INIT FUNCTIONS ***********/
322 * Parses the 'sync info' and 'bit stream info' from the AC-3 bitstream.
323 * GetBitContext within AC3DecodeContext must point to
324 * start of the synchronized ac3 bitstream.
326 static int ac3_parse_header(AC3DecodeContext *ctx)
329 GetBitContext *gb = &ctx->gb;
330 float cmixlev, surmixlev;
333 err = ff_ac3_parse_header(gb->buffer, &hdr);
337 /* get decoding parameters from header info */
338 ctx->bit_alloc_params.fscod = hdr.fscod;
339 ctx->acmod = hdr.acmod;
340 cmixlev = gain_levels[clevs[hdr.cmixlev]];
341 surmixlev = gain_levels[slevs[hdr.surmixlev]];
342 ctx->dsurmod = hdr.dsurmod;
343 ctx->lfeon = hdr.lfeon;
344 ctx->bit_alloc_params.halfratecod = hdr.halfratecod;
345 ctx->sampling_rate = hdr.sample_rate;
346 ctx->bit_rate = hdr.bit_rate;
347 ctx->nchans = hdr.channels;
348 ctx->nfchans = ctx->nchans - ctx->lfeon;
349 ctx->lfe_ch = ctx->nfchans + 1;
350 ctx->frame_size = hdr.frame_size;
352 /* set default output to all source channels */
353 ctx->out_channels = ctx->nchans;
354 ctx->output_mode = ctx->acmod;
356 ctx->output_mode |= AC3_OUTPUT_LFEON;
358 /* skip over portion of header which has already been read */
359 skip_bits(gb, 16); //skip the sync_word, sync_info->sync_word = get_bits(gb, 16);
360 skip_bits(gb, 16); // skip crc1
361 skip_bits(gb, 8); // skip fscod and frmsizecod
362 skip_bits(gb, 11); // skip bsid, bsmod, and acmod
363 if(ctx->acmod == AC3_ACMOD_STEREO) {
364 skip_bits(gb, 2); // skip dsurmod
366 if((ctx->acmod & 1) && ctx->acmod != AC3_ACMOD_MONO)
367 skip_bits(gb, 2); // skip cmixlev
369 skip_bits(gb, 2); // skip surmixlev
371 skip_bits1(gb); // skip lfeon
373 /* read the rest of the bsi. read twice for dual mono mode. */
376 ctx->dialnorm[i] = dialnorm_tbl[get_bits(gb, 5)]; // dialogue normalization
378 skip_bits(gb, 8); //skip compression
380 skip_bits(gb, 8); //skip language code
382 skip_bits(gb, 7); //skip audio production information
385 skip_bits(gb, 2); //skip copyright bit and original bitstream bit
387 /* FIXME: read & use the xbsi1 downmix levels */
389 skip_bits(gb, 14); //skip timecode1
391 skip_bits(gb, 14); //skip timecode2
394 i = get_bits(gb, 6); //additional bsi length
400 /* set stereo downmixing coefficients
401 reference: Section 7.8.2 Downmixing Into Two Channels */
402 for(i=0; i<ctx->nfchans; i++) {
403 ctx->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[ctx->acmod][i][0]];
404 ctx->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[ctx->acmod][i][1]];
406 if(ctx->acmod > 1 && ctx->acmod & 1) {
407 ctx->downmix_coeffs[1][0] = ctx->downmix_coeffs[1][1] = cmixlev;
409 if(ctx->acmod == AC3_ACMOD_2F1R || ctx->acmod == AC3_ACMOD_3F1R) {
410 int nf = ctx->acmod - 2;
411 ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf][1] = surmixlev * LEVEL_MINUS_3DB;
413 if(ctx->acmod == AC3_ACMOD_2F2R || ctx->acmod == AC3_ACMOD_3F2R) {
414 int nf = ctx->acmod - 4;
415 ctx->downmix_coeffs[nf][0] = ctx->downmix_coeffs[nf+1][1] = surmixlev;
422 * Decodes the grouped exponents.
423 * This function decodes the coded exponents according to exponent strategy
424 * and stores them in the decoded exponents buffer.
426 * @param[in] gb GetBitContext which points to start of coded exponents
427 * @param[in] expstr Exponent coding strategy
428 * @param[in] ngrps Number of grouped exponents
429 * @param[in] absexp Absolute exponent or DC exponent
430 * @param[out] dexps Decoded exponents are stored in dexps
432 static void decode_exponents(GetBitContext *gb, int expstr, int ngrps,
433 uint8_t absexp, int8_t *dexps)
435 int i, j, grp, grpsize;
440 grpsize = expstr + (expstr == EXP_D45);
441 for(grp=0,i=0; grp<ngrps; grp++) {
442 expacc = get_bits(gb, 7);
443 dexp[i++] = exp_ungroup_tbl[expacc][0];
444 dexp[i++] = exp_ungroup_tbl[expacc][1];
445 dexp[i++] = exp_ungroup_tbl[expacc][2];
448 /* convert to absolute exps and expand groups */
450 for(i=0; i<ngrps*3; i++) {
451 prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
452 for(j=0; j<grpsize; j++) {
453 dexps[(i*grpsize)+j] = prevexp;
459 * Generates transform coefficients for each coupled channel in the coupling
460 * range using the coupling coefficients and coupling coordinates.
461 * reference: Section 7.4.3 Coupling Coordinate Format
463 static void uncouple_channels(AC3DecodeContext *ctx)
465 int i, j, ch, bnd, subbnd;
468 i = ctx->startmant[CPL_CH];
469 for(bnd=0; bnd<ctx->ncplbnd; bnd++) {
472 for(j=0; j<12; j++) {
473 for(ch=1; ch<=ctx->nfchans; ch++) {
475 ctx->transform_coeffs[ch][i] = ctx->transform_coeffs[CPL_CH][i] * ctx->cplco[ch][bnd] * 8.0f;
479 } while(ctx->cplbndstrc[subbnd]);
483 typedef struct { /* grouped mantissas for 3-level 5-leve and 11-level quantization */
492 /* Get the transform coefficients for particular channel */
493 static int get_transform_coeffs_ch(AC3DecodeContext *ctx, int ch_index, mant_groups *m)
495 GetBitContext *gb = &ctx->gb;
496 int i, gcode, tbap, start, end;
501 exps = ctx->dexps[ch_index];
502 bap = ctx->bap[ch_index];
503 coeffs = ctx->transform_coeffs[ch_index];
504 start = ctx->startmant[ch_index];
505 end = ctx->endmant[ch_index];
508 for (i = start; i < end; i++) {
512 coeffs[i] = ((av_random(&ctx->dith_state) & 0xFFFF) * LEVEL_MINUS_3DB) / 32768.0f;
517 gcode = get_bits(gb, 5);
518 m->b1_mant[0] = b1_mantissas[gcode][0];
519 m->b1_mant[1] = b1_mantissas[gcode][1];
520 m->b1_mant[2] = b1_mantissas[gcode][2];
523 coeffs[i] = m->b1_mant[m->b1ptr++];
528 gcode = get_bits(gb, 7);
529 m->b2_mant[0] = b2_mantissas[gcode][0];
530 m->b2_mant[1] = b2_mantissas[gcode][1];
531 m->b2_mant[2] = b2_mantissas[gcode][2];
534 coeffs[i] = m->b2_mant[m->b2ptr++];
538 coeffs[i] = b3_mantissas[get_bits(gb, 3)];
543 gcode = get_bits(gb, 7);
544 m->b4_mant[0] = b4_mantissas[gcode][0];
545 m->b4_mant[1] = b4_mantissas[gcode][1];
548 coeffs[i] = m->b4_mant[m->b4ptr++];
552 coeffs[i] = b5_mantissas[get_bits(gb, 4)];
556 coeffs[i] = get_sbits(gb, qntztab[tbap]) * scale_factors[qntztab[tbap]-1];
559 coeffs[i] *= scale_factors[exps[i]];
566 * Removes random dithering from coefficients with zero-bit mantissas
567 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
569 static void remove_dithering(AC3DecodeContext *ctx) {
575 for(ch=1; ch<=ctx->nfchans; ch++) {
576 if(!ctx->dithflag[ch]) {
577 coeffs = ctx->transform_coeffs[ch];
580 end = ctx->startmant[CPL_CH];
582 end = ctx->endmant[ch];
583 for(i=0; i<end; i++) {
587 if(ctx->chincpl[ch]) {
588 bap = ctx->bap[CPL_CH];
589 for(; i<ctx->endmant[CPL_CH]; i++) {
598 /* Get the transform coefficients.
599 * This function extracts the tranform coefficients form the ac3 bitstream.
600 * This function is called after bit allocation is performed.
602 static int get_transform_coeffs(AC3DecodeContext * ctx)
608 m.b1ptr = m.b2ptr = m.b4ptr = 3;
610 for (ch = 1; ch <= ctx->nchans; ch++) {
611 /* transform coefficients for individual channel */
612 if (get_transform_coeffs_ch(ctx, ch, &m))
614 /* tranform coefficients for coupling channels */
615 if (ctx->chincpl[ch]) {
617 if (get_transform_coeffs_ch(ctx, CPL_CH, &m)) {
618 av_log(NULL, AV_LOG_ERROR, "error in decoupling channels\n");
621 uncouple_channels(ctx);
624 end = ctx->endmant[CPL_CH];
626 end = ctx->endmant[ch];
629 ctx->transform_coeffs[ch][end] = 0;
633 /* if any channel doesn't use dithering, zero appropriate coefficients */
635 remove_dithering(ctx);
641 * Performs stereo rematrixing.
642 * reference: Section 7.5.4 Rematrixing : Decoding Technique
644 static void do_rematrixing(AC3DecodeContext *ctx)
650 end = FFMIN(ctx->endmant[1], ctx->endmant[2]);
652 for(bnd=0; bnd<ctx->nrematbnd; bnd++) {
653 if(ctx->rematflg[bnd]) {
654 bndend = FFMIN(end, rematrix_band_tbl[bnd+1]);
655 for(i=rematrix_band_tbl[bnd]; i<bndend; i++) {
656 tmp0 = ctx->transform_coeffs[1][i];
657 tmp1 = ctx->transform_coeffs[2][i];
658 ctx->transform_coeffs[1][i] = tmp0 + tmp1;
659 ctx->transform_coeffs[2][i] = tmp0 - tmp1;
665 /* This function performs the imdct on 256 sample transform
668 static void do_imdct_256(AC3DecodeContext *ctx, int chindex)
671 DECLARE_ALIGNED_16(float, x[128]);
673 float *o_ptr = ctx->tmp_output;
676 /* de-interleave coefficients */
677 for(k=0; k<128; k++) {
678 x[k] = ctx->transform_coeffs[chindex][2*k+i];
681 /* run standard IMDCT */
682 ctx->imdct_256.fft.imdct_calc(&ctx->imdct_256, o_ptr, x, ctx->tmp_imdct);
684 /* reverse the post-rotation & reordering from standard IMDCT */
685 for(k=0; k<32; k++) {
686 z[i][32+k].re = -o_ptr[128+2*k];
687 z[i][32+k].im = -o_ptr[2*k];
688 z[i][31-k].re = o_ptr[2*k+1];
689 z[i][31-k].im = o_ptr[128+2*k+1];
693 /* apply AC-3 post-rotation & reordering */
694 for(k=0; k<64; k++) {
695 o_ptr[ 2*k ] = -z[0][ k].im;
696 o_ptr[ 2*k+1] = z[0][63-k].re;
697 o_ptr[128+2*k ] = -z[0][ k].re;
698 o_ptr[128+2*k+1] = z[0][63-k].im;
699 o_ptr[256+2*k ] = -z[1][ k].re;
700 o_ptr[256+2*k+1] = z[1][63-k].im;
701 o_ptr[384+2*k ] = z[1][ k].im;
702 o_ptr[384+2*k+1] = -z[1][63-k].re;
706 /* IMDCT Transform. */
707 static inline void do_imdct(AC3DecodeContext *ctx)
712 nchans = ctx->nfchans;
713 if(ctx->output_mode & AC3_OUTPUT_LFEON)
716 for (ch=1; ch<=nchans; ch++) {
717 if (ctx->blksw[ch]) {
718 do_imdct_256(ctx, ch);
720 ctx->imdct_512.fft.imdct_calc(&ctx->imdct_512, ctx->tmp_output,
721 ctx->transform_coeffs[ch],
724 ctx->dsp.vector_fmul_add_add(ctx->output[ch-1], ctx->tmp_output,
725 ctx->window, ctx->delay[ch-1], 0, 256, 1);
726 ctx->dsp.vector_fmul_reverse(ctx->delay[ch-1], ctx->tmp_output+256,
732 * Downmixes the output to stereo.
734 static void ac3_downmix(float samples[AC3_MAX_CHANNELS][256], int nfchans,
735 int output_mode, float coef[AC3_MAX_CHANNELS][2])
738 float v0, v1, s0, s1;
740 for(i=0; i<256; i++) {
741 v0 = v1 = s0 = s1 = 0.0f;
742 for(j=0; j<nfchans; j++) {
743 v0 += samples[j][i] * coef[j][0];
744 v1 += samples[j][i] * coef[j][1];
750 if(output_mode == AC3_ACMOD_MONO) {
751 samples[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
752 } else if(output_mode == AC3_ACMOD_STEREO) {
759 /* Parse the audio block from ac3 bitstream.
760 * This function extract the audio block from the ac3 bitstream
761 * and produces the output for the block. This function must
762 * be called for each of the six audio block in the ac3 bitstream.
764 static int ac3_parse_audio_block(AC3DecodeContext *ctx, int blk)
766 int nfchans = ctx->nfchans;
767 int acmod = ctx->acmod;
769 GetBitContext *gb = &ctx->gb;
770 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
772 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
774 for (ch = 1; ch <= nfchans; ch++) /*block switch flag */
775 ctx->blksw[ch] = get_bits1(gb);
778 for (ch = 1; ch <= nfchans; ch++) { /* dithering flag */
779 ctx->dithflag[ch] = get_bits1(gb);
780 if(!ctx->dithflag[ch])
788 ctx->dynrng[i] = dynrng_tbl[get_bits(gb, 8)];
789 } else if(blk == 0) {
790 ctx->dynrng[i] = 1.0f;
794 if (get_bits1(gb)) { /* coupling strategy */
795 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
796 ctx->cplinu = get_bits1(gb);
797 if (ctx->cplinu) { /* coupling in use */
798 int cplbegf, cplendf;
800 for (ch = 1; ch <= nfchans; ch++)
801 ctx->chincpl[ch] = get_bits1(gb);
803 if (acmod == AC3_ACMOD_STEREO)
804 ctx->phsflginu = get_bits1(gb); //phase flag in use
806 cplbegf = get_bits(gb, 4);
807 cplendf = get_bits(gb, 4);
809 if (3 + cplendf - cplbegf < 0) {
810 av_log(NULL, AV_LOG_ERROR, "cplendf = %d < cplbegf = %d\n", cplendf, cplbegf);
814 ctx->ncplbnd = ctx->ncplsubnd = 3 + cplendf - cplbegf;
815 ctx->startmant[CPL_CH] = cplbegf * 12 + 37;
816 ctx->endmant[CPL_CH] = cplendf * 12 + 73;
817 for (bnd = 0; bnd < ctx->ncplsubnd - 1; bnd++) { /* coupling band structure */
819 ctx->cplbndstrc[bnd] = 1;
824 for (ch = 1; ch <= nfchans; ch++)
825 ctx->chincpl[ch] = 0;
832 for (ch = 1; ch <= nfchans; ch++) {
833 if (ctx->chincpl[ch]) {
834 if (get_bits1(gb)) { /* coupling co-ordinates */
835 int mstrcplco, cplcoexp, cplcomant;
837 mstrcplco = 3 * get_bits(gb, 2);
838 for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
839 cplcoexp = get_bits(gb, 4);
840 cplcomant = get_bits(gb, 4);
842 ctx->cplco[ch][bnd] = cplcomant / 16.0f;
844 ctx->cplco[ch][bnd] = (cplcomant + 16.0f) / 32.0f;
845 ctx->cplco[ch][bnd] *= scale_factors[cplcoexp + mstrcplco];
851 if (acmod == AC3_ACMOD_STEREO && ctx->phsflginu && cplcoe) {
852 for (bnd = 0; bnd < ctx->ncplbnd; bnd++) {
854 ctx->cplco[2][bnd] = -ctx->cplco[2][bnd];
859 if (acmod == AC3_ACMOD_STEREO) {/* rematrixing */
860 ctx->rematstr = get_bits1(gb);
863 if(ctx->cplinu && ctx->startmant[CPL_CH] <= 61)
864 ctx->nrematbnd -= 1 + (ctx->startmant[CPL_CH] == 37);
865 for(bnd=0; bnd<ctx->nrematbnd; bnd++)
866 ctx->rematflg[bnd] = get_bits1(gb);
870 ctx->expstr[CPL_CH] = EXP_REUSE;
871 ctx->expstr[ctx->lfe_ch] = EXP_REUSE;
872 for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
873 if(ch == ctx->lfe_ch)
874 ctx->expstr[ch] = get_bits(gb, 1);
876 ctx->expstr[ch] = get_bits(gb, 2);
877 if(ctx->expstr[ch] != EXP_REUSE)
878 bit_alloc_stages[ch] = 3;
881 for (ch = 1; ch <= nfchans; ch++) { /* channel bandwidth code */
882 ctx->startmant[ch] = 0;
883 if (ctx->expstr[ch] != EXP_REUSE) {
884 int prev = ctx->endmant[ch];
885 if (ctx->chincpl[ch])
886 ctx->endmant[ch] = ctx->startmant[CPL_CH];
888 int chbwcod = get_bits(gb, 6);
890 av_log(NULL, AV_LOG_ERROR, "chbwcod = %d > 60", chbwcod);
893 ctx->endmant[ch] = chbwcod * 3 + 73;
895 if(blk > 0 && ctx->endmant[ch] != prev)
896 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
899 ctx->startmant[ctx->lfe_ch] = 0;
900 ctx->endmant[ctx->lfe_ch] = 7;
902 for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) {
903 if (ctx->expstr[ch] != EXP_REUSE) {
905 grpsize = 3 << (ctx->expstr[ch] - 1);
907 ngrps = (ctx->endmant[ch] - ctx->startmant[ch]) / grpsize;
908 else if(ch == ctx->lfe_ch)
911 ngrps = (ctx->endmant[ch] + grpsize - 4) / grpsize;
912 ctx->dexps[ch][0] = get_bits(gb, 4) << !ch;
913 decode_exponents(gb, ctx->expstr[ch], ngrps, ctx->dexps[ch][0],
914 &ctx->dexps[ch][ctx->startmant[ch]+!!ch]);
915 if(ch != CPL_CH && ch != ctx->lfe_ch)
916 skip_bits(gb, 2); /* skip gainrng */
920 if (get_bits1(gb)) { /* bit allocation information */
921 ctx->bit_alloc_params.sdecay = ff_sdecaytab[get_bits(gb, 2)];
922 ctx->bit_alloc_params.fdecay = ff_fdecaytab[get_bits(gb, 2)];
923 ctx->bit_alloc_params.sgain = ff_sgaintab[get_bits(gb, 2)];
924 ctx->bit_alloc_params.dbknee = ff_dbkneetab[get_bits(gb, 2)];
925 ctx->bit_alloc_params.floor = ff_floortab[get_bits(gb, 3)];
926 for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
927 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
931 if (get_bits1(gb)) { /* snroffset */
933 csnr = (get_bits(gb, 6) - 15) << 4;
934 for (ch = !ctx->cplinu; ch <= ctx->nchans; ch++) { /* snr offset and fast gain */
935 ctx->snroffst[ch] = (csnr + get_bits(gb, 4)) << 2;
936 ctx->fgain[ch] = ff_fgaintab[get_bits(gb, 3)];
938 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
941 if (ctx->cplinu && get_bits1(gb)) { /* coupling leak information */
942 ctx->bit_alloc_params.cplfleak = get_bits(gb, 3);
943 ctx->bit_alloc_params.cplsleak = get_bits(gb, 3);
944 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
947 if (get_bits1(gb)) { /* delta bit allocation information */
948 for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
949 ctx->deltbae[ch] = get_bits(gb, 2);
950 if (ctx->deltbae[ch] == DBA_RESERVED) {
951 av_log(NULL, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
954 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
957 for (ch = !ctx->cplinu; ch <= nfchans; ch++) {
958 if (ctx->deltbae[ch] == DBA_NEW) {/*channel delta offset, len and bit allocation */
959 ctx->deltnseg[ch] = get_bits(gb, 3);
960 for (seg = 0; seg <= ctx->deltnseg[ch]; seg++) {
961 ctx->deltoffst[ch][seg] = get_bits(gb, 5);
962 ctx->deltlen[ch][seg] = get_bits(gb, 4);
963 ctx->deltba[ch][seg] = get_bits(gb, 3);
967 } else if(blk == 0) {
968 for(ch=0; ch<=ctx->nchans; ch++) {
969 ctx->deltbae[ch] = DBA_NONE;
973 for(ch=!ctx->cplinu; ch<=ctx->nchans; ch++) {
974 if(bit_alloc_stages[ch] > 2) {
975 /* Exponent mapping into PSD and PSD integration */
976 ff_ac3_bit_alloc_calc_psd(ctx->dexps[ch],
977 ctx->startmant[ch], ctx->endmant[ch],
978 ctx->psd[ch], ctx->bndpsd[ch]);
980 if(bit_alloc_stages[ch] > 1) {
981 /* Compute excitation function, Compute masking curve, and
982 Apply delta bit allocation */
983 ff_ac3_bit_alloc_calc_mask(&ctx->bit_alloc_params, ctx->bndpsd[ch],
984 ctx->startmant[ch], ctx->endmant[ch],
985 ctx->fgain[ch], (ch == ctx->lfe_ch),
986 ctx->deltbae[ch], ctx->deltnseg[ch],
987 ctx->deltoffst[ch], ctx->deltlen[ch],
988 ctx->deltba[ch], ctx->mask[ch]);
990 if(bit_alloc_stages[ch] > 0) {
991 /* Compute bit allocation */
992 ff_ac3_bit_alloc_calc_bap(ctx->mask[ch], ctx->psd[ch],
993 ctx->startmant[ch], ctx->endmant[ch],
995 ctx->bit_alloc_params.floor,
1000 if (get_bits1(gb)) { /* unused dummy data */
1001 int skipl = get_bits(gb, 9);
1005 /* unpack the transform coefficients
1006 * * this also uncouples channels if coupling is in use.
1008 if (get_transform_coeffs(ctx)) {
1009 av_log(NULL, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1013 /* recover coefficients if rematrixing is in use */
1014 if(ctx->acmod == AC3_ACMOD_STEREO)
1015 do_rematrixing(ctx);
1017 /* apply scaling to coefficients (headroom, dialnorm, dynrng) */
1018 for(ch=1; ch<=ctx->nchans; ch++) {
1019 float gain = 2.0f * ctx->mul_bias;
1020 if(ctx->acmod == AC3_ACMOD_DUALMONO) {
1021 gain *= ctx->dialnorm[ch-1] * ctx->dynrng[ch-1];
1023 gain *= ctx->dialnorm[0] * ctx->dynrng[0];
1025 for(i=0; i<ctx->endmant[ch]; i++) {
1026 ctx->transform_coeffs[ch][i] *= gain;
1032 /* downmix output if needed */
1033 if(ctx->nchans != ctx->out_channels && !((ctx->output_mode & AC3_OUTPUT_LFEON) &&
1034 ctx->nfchans == ctx->out_channels)) {
1035 ac3_downmix(ctx->output, ctx->nfchans, ctx->output_mode,
1036 ctx->downmix_coeffs);
1039 /* convert float to 16-bit integer */
1040 for(ch=0; ch<ctx->out_channels; ch++) {
1041 for(i=0; i<256; i++) {
1042 ctx->output[ch][i] += ctx->add_bias;
1044 ctx->dsp.float_to_int16(ctx->int_output[ch], ctx->output[ch], 256);
1050 /* Decode ac3 frame.
1052 * @param avctx Pointer to AVCodecContext
1053 * @param data Pointer to pcm smaples
1054 * @param data_size Set to number of pcm samples produced by decoding
1055 * @param buf Data to be decoded
1056 * @param buf_size Size of the buffer
1058 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1060 AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1061 int16_t *out_samples = (int16_t *)data;
1064 //Initialize the GetBitContext with the start of valid AC3 Frame.
1065 init_get_bits(&ctx->gb, buf, buf_size * 8);
1067 //Parse the syncinfo.
1068 if (ac3_parse_header(ctx)) {
1069 av_log(avctx, AV_LOG_ERROR, "\n");
1074 avctx->sample_rate = ctx->sampling_rate;
1075 avctx->bit_rate = ctx->bit_rate;
1077 /* channel config */
1078 ctx->out_channels = ctx->nchans;
1079 if (avctx->channels == 0) {
1080 avctx->channels = ctx->out_channels;
1081 } else if(ctx->out_channels < avctx->channels) {
1082 av_log(avctx, AV_LOG_ERROR, "Cannot upmix AC3 from %d to %d channels.\n",
1083 ctx->out_channels, avctx->channels);
1086 if(avctx->channels == 2) {
1087 ctx->output_mode = AC3_ACMOD_STEREO;
1088 } else if(avctx->channels == 1) {
1089 ctx->output_mode = AC3_ACMOD_MONO;
1090 } else if(avctx->channels != ctx->out_channels) {
1091 av_log(avctx, AV_LOG_ERROR, "Cannot downmix AC3 from %d to %d channels.\n",
1092 ctx->out_channels, avctx->channels);
1095 ctx->out_channels = avctx->channels;
1097 //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);
1099 //Parse the Audio Blocks.
1100 for (blk = 0; blk < NB_BLOCKS; blk++) {
1101 if (ac3_parse_audio_block(ctx, blk)) {
1102 av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1104 return ctx->frame_size;
1106 for (i = 0; i < 256; i++)
1107 for (ch = 0; ch < ctx->out_channels; ch++)
1108 *(out_samples++) = ctx->int_output[ch][i];
1110 *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1111 return ctx->frame_size;
1114 /* Uninitialize ac3 decoder.
1116 static int ac3_decode_end(AVCodecContext *avctx)
1118 AC3DecodeContext *ctx = (AC3DecodeContext *)avctx->priv_data;
1119 ff_mdct_end(&ctx->imdct_512);
1120 ff_mdct_end(&ctx->imdct_256);
1125 AVCodec ac3_decoder = {
1127 .type = CODEC_TYPE_AUDIO,
1129 .priv_data_size = sizeof (AC3DecodeContext),
1130 .init = ac3_decode_init,
1131 .close = ac3_decode_end,
1132 .decode = ac3_decode_frame,