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"
43 * Table of bin locations for rematrixing bands
44 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
46 static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
48 /** table for grouping exponents */
49 static uint8_t exp_ungroup_tab[128][3];
52 /** tables for ungrouping mantissas */
53 static int b1_mantissas[32][3];
54 static int b2_mantissas[128][3];
55 static int b3_mantissas[8];
56 static int b4_mantissas[128][2];
57 static int b5_mantissas[16];
60 * Quantization table: levels for symmetric. bits for asymmetric.
61 * reference: Table 7.18 Mapping of bap to Quantizer
63 static const uint8_t quantization_tab[16] = {
65 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
68 /** dynamic range table. converts codes to scale factors. */
69 static float dynamic_range_tab[256];
71 /** Adjustments in dB gain */
72 #define LEVEL_MINUS_3DB 0.7071067811865476
73 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
74 #define LEVEL_MINUS_6DB 0.5000000000000000
75 #define LEVEL_MINUS_9DB 0.3535533905932738
76 #define LEVEL_ZERO 0.0000000000000000
77 #define LEVEL_ONE 1.0000000000000000
79 static const float gain_levels[6] = {
83 LEVEL_MINUS_4POINT5DB,
89 * Table for center mix levels
90 * reference: Section 5.4.2.4 cmixlev
92 static const uint8_t center_levels[4] = { 2, 3, 4, 3 };
95 * Table for surround mix levels
96 * reference: Section 5.4.2.5 surmixlev
98 static const uint8_t surround_levels[4] = { 2, 4, 0, 4 };
101 * Table for default stereo downmixing coefficients
102 * reference: Section 7.8.2 Downmixing Into Two Channels
104 static const uint8_t ac3_default_coeffs[8][5][2] = {
105 { { 1, 0 }, { 0, 1 }, },
107 { { 1, 0 }, { 0, 1 }, },
108 { { 1, 0 }, { 3, 3 }, { 0, 1 }, },
109 { { 1, 0 }, { 0, 1 }, { 4, 4 }, },
110 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, },
111 { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
112 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
115 /* override ac3.h to include coupling channel */
116 #undef AC3_MAX_CHANNELS
117 #define AC3_MAX_CHANNELS 7
120 #define AC3_OUTPUT_LFEON 8
123 int channel_mode; ///< channel mode (acmod)
124 int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags
125 int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags
126 int dither_all; ///< true if all channels are dithered
127 int cpl_in_use; ///< coupling in use
128 int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling
129 int phase_flags_in_use; ///< phase flags in use
130 int phase_flags[18]; ///< phase flags
131 int cpl_band_struct[18]; ///< coupling band structure
132 int num_rematrixing_bands; ///< number of rematrixing bands
133 int rematrixing_flags[4]; ///< rematrixing flags
134 int exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
135 int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets
136 int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values (signal-to-mask ratio)
137 int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
138 int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
139 uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
140 uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
141 uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
143 int sample_rate; ///< sample frequency, in Hz
144 int bit_rate; ///< stream bit rate, in bits-per-second
145 int frame_size; ///< current frame size, in bytes
147 int channels; ///< number of total channels
148 int fbw_channels; ///< number of full-bandwidth channels
149 int lfe_on; ///< lfe channel in use
150 int lfe_ch; ///< index of LFE channel
151 int output_mode; ///< output channel configuration
152 int out_channels; ///< number of output channels
154 int center_mix_level; ///< Center mix level index
155 int surround_mix_level; ///< Surround mix level index
156 float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
157 float dynamic_range[2]; ///< dynamic range
158 int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
159 int num_cpl_bands; ///< number of coupling bands
160 int num_cpl_subbands; ///< number of coupling sub bands
161 int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin
162 int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin
163 AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
165 int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
166 uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
167 int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
168 int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
169 int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
171 int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
172 DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
175 MDCTContext imdct_512; ///< for 512 sample IMDCT
176 MDCTContext imdct_256; ///< for 256 sample IMDCT
177 DSPContext dsp; ///< for optimization
178 float add_bias; ///< offset for float_to_int16 conversion
179 float mul_bias; ///< scaling for float_to_int16 conversion
181 DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]); ///< output after imdct transform and windowing
182 DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
183 DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]); ///< delay - added to the next block
184 DECLARE_ALIGNED_16(float, tmp_imdct[256]); ///< temporary storage for imdct transform
185 DECLARE_ALIGNED_16(float, tmp_output[512]); ///< temporary storage for output before windowing
186 DECLARE_ALIGNED_16(float, window[256]); ///< window coefficients
189 GetBitContext gbc; ///< bitstream reader
190 AVRandomState dith_state; ///< for dither generation
191 AVCodecContext *avctx; ///< parent context
195 * Symmetrical Dequantization
196 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
197 * Tables 7.19 to 7.23
200 symmetric_dequant(int code, int levels)
202 return ((code - (levels >> 1)) << 24) / levels;
206 * Initialize tables at runtime.
208 static void ac3_tables_init(void)
212 /* generate grouped mantissa tables
213 reference: Section 7.3.5 Ungrouping of Mantissas */
214 for(i=0; i<32; i++) {
215 /* bap=1 mantissas */
216 b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3);
217 b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
218 b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
220 for(i=0; i<128; i++) {
221 /* bap=2 mantissas */
222 b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
223 b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
224 b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
226 /* bap=4 mantissas */
227 b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
228 b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
230 /* generate ungrouped mantissa tables
231 reference: Tables 7.21 and 7.23 */
233 /* bap=3 mantissas */
234 b3_mantissas[i] = symmetric_dequant(i, 7);
236 for(i=0; i<15; i++) {
237 /* bap=5 mantissas */
238 b5_mantissas[i] = symmetric_dequant(i, 15);
241 /* generate dynamic range table
242 reference: Section 7.7.1 Dynamic Range Control */
243 for(i=0; i<256; i++) {
244 int v = (i >> 5) - ((i >> 7) << 3) - 5;
245 dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
248 /* generate exponent tables
249 reference: Section 7.1.3 Exponent Decoding */
250 for(i=0; i<128; i++) {
251 exp_ungroup_tab[i][0] = i / 25;
252 exp_ungroup_tab[i][1] = (i % 25) / 5;
253 exp_ungroup_tab[i][2] = (i % 25) % 5;
259 * AVCodec initialization
261 static int ac3_decode_init(AVCodecContext *avctx)
263 AC3DecodeContext *s = avctx->priv_data;
268 ff_mdct_init(&s->imdct_256, 8, 1);
269 ff_mdct_init(&s->imdct_512, 9, 1);
270 ff_kbd_window_init(s->window, 5.0, 256);
271 dsputil_init(&s->dsp, avctx);
272 av_init_random(0, &s->dith_state);
274 /* set bias values for float to int16 conversion */
275 if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
276 s->add_bias = 385.0f;
280 s->mul_bias = 32767.0f;
283 /* allow downmixing to stereo or mono */
284 if (avctx->channels > 0 && avctx->request_channels > 0 &&
285 avctx->request_channels < avctx->channels &&
286 avctx->request_channels <= 2) {
287 avctx->channels = avctx->request_channels;
294 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
295 * GetBitContext within AC3DecodeContext must point to
296 * start of the synchronized ac3 bitstream.
298 static int ac3_parse_header(AC3DecodeContext *s)
301 GetBitContext *gbc = &s->gbc;
304 err = ff_ac3_parse_header(gbc->buffer, &hdr);
308 if(hdr.bitstream_id > 10)
309 return AC3_PARSE_ERROR_BSID;
311 /* get decoding parameters from header info */
312 s->bit_alloc_params.sr_code = hdr.sr_code;
313 s->channel_mode = hdr.channel_mode;
314 s->lfe_on = hdr.lfe_on;
315 s->bit_alloc_params.sr_shift = hdr.sr_shift;
316 s->sample_rate = hdr.sample_rate;
317 s->bit_rate = hdr.bit_rate;
318 s->channels = hdr.channels;
319 s->fbw_channels = s->channels - s->lfe_on;
320 s->lfe_ch = s->fbw_channels + 1;
321 s->frame_size = hdr.frame_size;
323 /* set default output to all source channels */
324 s->out_channels = s->channels;
325 s->output_mode = s->channel_mode;
327 s->output_mode |= AC3_OUTPUT_LFEON;
329 /* set default mix levels */
330 s->center_mix_level = 3; // -4.5dB
331 s->surround_mix_level = 4; // -6.0dB
333 /* skip over portion of header which has already been read */
334 skip_bits(gbc, 16); // skip the sync_word
335 skip_bits(gbc, 16); // skip crc1
336 skip_bits(gbc, 8); // skip fscod and frmsizecod
337 skip_bits(gbc, 11); // skip bsid, bsmod, and acmod
338 if(s->channel_mode == AC3_CHMODE_STEREO) {
339 skip_bits(gbc, 2); // skip dsurmod
341 if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO)
342 s->center_mix_level = center_levels[get_bits(gbc, 2)];
343 if(s->channel_mode & 4)
344 s->surround_mix_level = surround_levels[get_bits(gbc, 2)];
346 skip_bits1(gbc); // skip lfeon
348 /* read the rest of the bsi. read twice for dual mono mode. */
349 i = !(s->channel_mode);
351 skip_bits(gbc, 5); // skip dialog normalization
353 skip_bits(gbc, 8); //skip compression
355 skip_bits(gbc, 8); //skip language code
357 skip_bits(gbc, 7); //skip audio production information
360 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
362 /* skip the timecodes (or extra bitstream information for Alternate Syntax)
363 TODO: read & use the xbsi1 downmix levels */
365 skip_bits(gbc, 14); //skip timecode1 / xbsi1
367 skip_bits(gbc, 14); //skip timecode2 / xbsi2
369 /* skip additional bitstream info */
370 if (get_bits1(gbc)) {
371 i = get_bits(gbc, 6);
381 * Set stereo downmixing coefficients based on frame header info.
382 * reference: Section 7.8.2 Downmixing Into Two Channels
384 static void set_downmix_coeffs(AC3DecodeContext *s)
387 float cmix = gain_levels[s->center_mix_level];
388 float smix = gain_levels[s->surround_mix_level];
390 for(i=0; i<s->fbw_channels; i++) {
391 s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
392 s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
394 if(s->channel_mode > 1 && s->channel_mode & 1) {
395 s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
397 if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
398 int nf = s->channel_mode - 2;
399 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
401 if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
402 int nf = s->channel_mode - 4;
403 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
408 * Decode the grouped exponents according to exponent strategy.
409 * reference: Section 7.1.3 Exponent Decoding
411 static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
412 uint8_t absexp, int8_t *dexps)
414 int i, j, grp, group_size;
419 group_size = exp_strategy + (exp_strategy == EXP_D45);
420 for(grp=0,i=0; grp<ngrps; grp++) {
421 expacc = get_bits(gbc, 7);
422 dexp[i++] = exp_ungroup_tab[expacc][0];
423 dexp[i++] = exp_ungroup_tab[expacc][1];
424 dexp[i++] = exp_ungroup_tab[expacc][2];
427 /* convert to absolute exps and expand groups */
429 for(i=0; i<ngrps*3; i++) {
430 prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
431 for(j=0; j<group_size; j++) {
432 dexps[(i*group_size)+j] = prevexp;
438 * Generate transform coefficients for each coupled channel in the coupling
439 * range using the coupling coefficients and coupling coordinates.
440 * reference: Section 7.4.3 Coupling Coordinate Format
442 static void uncouple_channels(AC3DecodeContext *s)
444 int i, j, ch, bnd, subbnd;
447 i = s->start_freq[CPL_CH];
448 for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
451 for(j=0; j<12; j++) {
452 for(ch=1; ch<=s->fbw_channels; ch++) {
453 if(s->channel_in_cpl[ch]) {
454 s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
455 if (ch == 2 && s->phase_flags[bnd])
456 s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
461 } while(s->cpl_band_struct[subbnd]);
466 * Grouped mantissas for 3-level 5-level and 11-level quantization
478 * Get the transform coefficients for a particular channel
479 * reference: Section 7.3 Quantization and Decoding of Mantissas
481 static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
483 GetBitContext *gbc = &s->gbc;
484 int i, gcode, tbap, start, end;
489 exps = s->dexps[ch_index];
490 bap = s->bap[ch_index];
491 coeffs = s->fixed_coeffs[ch_index];
492 start = s->start_freq[ch_index];
493 end = s->end_freq[ch_index];
495 for (i = start; i < end; i++) {
499 coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
504 gcode = get_bits(gbc, 5);
505 m->b1_mant[0] = b1_mantissas[gcode][0];
506 m->b1_mant[1] = b1_mantissas[gcode][1];
507 m->b1_mant[2] = b1_mantissas[gcode][2];
510 coeffs[i] = m->b1_mant[m->b1ptr++];
515 gcode = get_bits(gbc, 7);
516 m->b2_mant[0] = b2_mantissas[gcode][0];
517 m->b2_mant[1] = b2_mantissas[gcode][1];
518 m->b2_mant[2] = b2_mantissas[gcode][2];
521 coeffs[i] = m->b2_mant[m->b2ptr++];
525 coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
530 gcode = get_bits(gbc, 7);
531 m->b4_mant[0] = b4_mantissas[gcode][0];
532 m->b4_mant[1] = b4_mantissas[gcode][1];
535 coeffs[i] = m->b4_mant[m->b4ptr++];
539 coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
543 /* asymmetric dequantization */
544 int qlevel = quantization_tab[tbap];
545 coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
549 coeffs[i] >>= exps[i];
556 * Remove random dithering from coefficients with zero-bit mantissas
557 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
559 static void remove_dithering(AC3DecodeContext *s) {
565 for(ch=1; ch<=s->fbw_channels; ch++) {
566 if(!s->dither_flag[ch]) {
567 coeffs = s->fixed_coeffs[ch];
569 if(s->channel_in_cpl[ch])
570 end = s->start_freq[CPL_CH];
572 end = s->end_freq[ch];
573 for(i=0; i<end; i++) {
577 if(s->channel_in_cpl[ch]) {
578 bap = s->bap[CPL_CH];
579 for(; i<s->end_freq[CPL_CH]; i++) {
589 * Get the transform coefficients.
591 static int get_transform_coeffs(AC3DecodeContext *s)
597 m.b1ptr = m.b2ptr = m.b4ptr = 3;
599 for (ch = 1; ch <= s->channels; ch++) {
600 /* transform coefficients for full-bandwidth channel */
601 if (get_transform_coeffs_ch(s, ch, &m))
603 /* tranform coefficients for coupling channel come right after the
604 coefficients for the first coupled channel*/
605 if (s->channel_in_cpl[ch]) {
607 if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
608 av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
611 uncouple_channels(s);
614 end = s->end_freq[CPL_CH];
616 end = s->end_freq[ch];
619 s->transform_coeffs[ch][end] = 0;
623 /* if any channel doesn't use dithering, zero appropriate coefficients */
631 * Stereo rematrixing.
632 * reference: Section 7.5.4 Rematrixing : Decoding Technique
634 static void do_rematrixing(AC3DecodeContext *s)
640 end = FFMIN(s->end_freq[1], s->end_freq[2]);
642 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
643 if(s->rematrixing_flags[bnd]) {
644 bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
645 for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
646 tmp0 = s->fixed_coeffs[1][i];
647 tmp1 = s->fixed_coeffs[2][i];
648 s->fixed_coeffs[1][i] = tmp0 + tmp1;
649 s->fixed_coeffs[2][i] = tmp0 - tmp1;
656 * Perform the 256-point IMDCT
658 static void do_imdct_256(AC3DecodeContext *s, int chindex)
661 DECLARE_ALIGNED_16(float, x[128]);
663 float *o_ptr = s->tmp_output;
666 /* de-interleave coefficients */
667 for(k=0; k<128; k++) {
668 x[k] = s->transform_coeffs[chindex][2*k+i];
671 /* run standard IMDCT */
672 s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
674 /* reverse the post-rotation & reordering from standard IMDCT */
675 for(k=0; k<32; k++) {
676 z[i][32+k].re = -o_ptr[128+2*k];
677 z[i][32+k].im = -o_ptr[2*k];
678 z[i][31-k].re = o_ptr[2*k+1];
679 z[i][31-k].im = o_ptr[128+2*k+1];
683 /* apply AC-3 post-rotation & reordering */
684 for(k=0; k<64; k++) {
685 o_ptr[ 2*k ] = -z[0][ k].im;
686 o_ptr[ 2*k+1] = z[0][63-k].re;
687 o_ptr[128+2*k ] = -z[0][ k].re;
688 o_ptr[128+2*k+1] = z[0][63-k].im;
689 o_ptr[256+2*k ] = -z[1][ k].re;
690 o_ptr[256+2*k+1] = z[1][63-k].im;
691 o_ptr[384+2*k ] = z[1][ k].im;
692 o_ptr[384+2*k+1] = -z[1][63-k].re;
697 * Inverse MDCT Transform.
698 * Convert frequency domain coefficients to time-domain audio samples.
699 * reference: Section 7.9.4 Transformation Equations
701 static inline void do_imdct(AC3DecodeContext *s)
706 /* Don't perform the IMDCT on the LFE channel unless it's used in the output */
707 channels = s->fbw_channels;
708 if(s->output_mode & AC3_OUTPUT_LFEON)
711 for (ch=1; ch<=channels; ch++) {
712 if (s->block_switch[ch]) {
715 s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
716 s->transform_coeffs[ch], s->tmp_imdct);
718 /* For the first half of the block, apply the window, add the delay
719 from the previous block, and send to output */
720 s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
721 s->window, s->delay[ch-1], 0, 256, 1);
722 /* For the second half of the block, apply the window and store the
723 samples to delay, to be combined with the next block */
724 s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
730 * Downmix the output to mono or stereo.
732 static void ac3_downmix(AC3DecodeContext *s)
735 float v0, v1, s0, s1;
737 for(i=0; i<256; i++) {
738 v0 = v1 = s0 = s1 = 0.0f;
739 for(j=0; j<s->fbw_channels; j++) {
740 v0 += s->output[j][i] * s->downmix_coeffs[j][0];
741 v1 += s->output[j][i] * s->downmix_coeffs[j][1];
742 s0 += s->downmix_coeffs[j][0];
743 s1 += s->downmix_coeffs[j][1];
747 if(s->output_mode == AC3_CHMODE_MONO) {
748 s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB;
749 } else if(s->output_mode == AC3_CHMODE_STEREO) {
750 s->output[0][i] = v0;
751 s->output[1][i] = v1;
757 * Parse an audio block from AC-3 bitstream.
759 static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
761 int fbw_channels = s->fbw_channels;
762 int channel_mode = s->channel_mode;
764 GetBitContext *gbc = &s->gbc;
765 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
767 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
769 /* block switch flags */
770 for (ch = 1; ch <= fbw_channels; ch++)
771 s->block_switch[ch] = get_bits1(gbc);
773 /* dithering flags */
775 for (ch = 1; ch <= fbw_channels; ch++) {
776 s->dither_flag[ch] = get_bits1(gbc);
777 if(!s->dither_flag[ch])
782 i = !(s->channel_mode);
785 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
786 s->avctx->drc_scale)+1.0;
787 } else if(blk == 0) {
788 s->dynamic_range[i] = 1.0f;
792 /* coupling strategy */
793 if (get_bits1(gbc)) {
794 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
795 s->cpl_in_use = get_bits1(gbc);
797 /* coupling in use */
798 int cpl_begin_freq, cpl_end_freq;
800 /* determine which channels are coupled */
801 for (ch = 1; ch <= fbw_channels; ch++)
802 s->channel_in_cpl[ch] = get_bits1(gbc);
804 /* phase flags in use */
805 if (channel_mode == AC3_CHMODE_STEREO)
806 s->phase_flags_in_use = get_bits1(gbc);
808 /* coupling frequency range and band structure */
809 cpl_begin_freq = get_bits(gbc, 4);
810 cpl_end_freq = get_bits(gbc, 4);
811 if (3 + cpl_end_freq - cpl_begin_freq < 0) {
812 av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
815 s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
816 s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
817 s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
818 for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
819 if (get_bits1(gbc)) {
820 s->cpl_band_struct[bnd] = 1;
824 s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
826 /* coupling not in use */
827 for (ch = 1; ch <= fbw_channels; ch++)
828 s->channel_in_cpl[ch] = 0;
832 /* coupling coordinates */
834 int cpl_coords_exist = 0;
836 for (ch = 1; ch <= fbw_channels; ch++) {
837 if (s->channel_in_cpl[ch]) {
838 if (get_bits1(gbc)) {
839 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
840 cpl_coords_exist = 1;
841 master_cpl_coord = 3 * get_bits(gbc, 2);
842 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
843 cpl_coord_exp = get_bits(gbc, 4);
844 cpl_coord_mant = get_bits(gbc, 4);
845 if (cpl_coord_exp == 15)
846 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
848 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
849 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
855 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
856 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
857 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
862 /* stereo rematrixing strategy and band structure */
863 if (channel_mode == AC3_CHMODE_STEREO) {
864 if (get_bits1(gbc)) {
865 s->num_rematrixing_bands = 4;
866 if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
867 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
868 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
869 s->rematrixing_flags[bnd] = get_bits1(gbc);
873 /* exponent strategies for each channel */
874 s->exp_strategy[CPL_CH] = EXP_REUSE;
875 s->exp_strategy[s->lfe_ch] = EXP_REUSE;
876 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
878 s->exp_strategy[ch] = get_bits(gbc, 1);
880 s->exp_strategy[ch] = get_bits(gbc, 2);
881 if(s->exp_strategy[ch] != EXP_REUSE)
882 bit_alloc_stages[ch] = 3;
885 /* channel bandwidth */
886 for (ch = 1; ch <= fbw_channels; ch++) {
887 s->start_freq[ch] = 0;
888 if (s->exp_strategy[ch] != EXP_REUSE) {
889 int prev = s->end_freq[ch];
890 if (s->channel_in_cpl[ch])
891 s->end_freq[ch] = s->start_freq[CPL_CH];
893 int bandwidth_code = get_bits(gbc, 6);
894 if (bandwidth_code > 60) {
895 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
898 s->end_freq[ch] = bandwidth_code * 3 + 73;
900 if(blk > 0 && s->end_freq[ch] != prev)
901 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
904 s->start_freq[s->lfe_ch] = 0;
905 s->end_freq[s->lfe_ch] = 7;
907 /* decode exponents for each channel */
908 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
909 if (s->exp_strategy[ch] != EXP_REUSE) {
910 int group_size, num_groups;
911 group_size = 3 << (s->exp_strategy[ch] - 1);
913 num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
914 else if(ch == s->lfe_ch)
917 num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
918 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
919 decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
920 &s->dexps[ch][s->start_freq[ch]+!!ch]);
921 if(ch != CPL_CH && ch != s->lfe_ch)
922 skip_bits(gbc, 2); /* skip gainrng */
926 /* bit allocation information */
927 if (get_bits1(gbc)) {
928 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
929 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
930 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
931 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
932 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
933 for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
934 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
938 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
939 if (get_bits1(gbc)) {
941 csnr = (get_bits(gbc, 6) - 15) << 4;
942 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
943 s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
944 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
946 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
949 /* coupling leak information */
950 if (s->cpl_in_use && get_bits1(gbc)) {
951 s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
952 s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
953 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
956 /* delta bit allocation information */
957 if (get_bits1(gbc)) {
958 /* delta bit allocation exists (strategy) */
959 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
960 s->dba_mode[ch] = get_bits(gbc, 2);
961 if (s->dba_mode[ch] == DBA_RESERVED) {
962 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
965 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
967 /* channel delta offset, len and bit allocation */
968 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
969 if (s->dba_mode[ch] == DBA_NEW) {
970 s->dba_nsegs[ch] = get_bits(gbc, 3);
971 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
972 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
973 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
974 s->dba_values[ch][seg] = get_bits(gbc, 3);
978 } else if(blk == 0) {
979 for(ch=0; ch<=s->channels; ch++) {
980 s->dba_mode[ch] = DBA_NONE;
985 for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
986 if(bit_alloc_stages[ch] > 2) {
987 /* Exponent mapping into PSD and PSD integration */
988 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
989 s->start_freq[ch], s->end_freq[ch],
990 s->psd[ch], s->band_psd[ch]);
992 if(bit_alloc_stages[ch] > 1) {
993 /* Compute excitation function, Compute masking curve, and
994 Apply delta bit allocation */
995 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
996 s->start_freq[ch], s->end_freq[ch],
997 s->fast_gain[ch], (ch == s->lfe_ch),
998 s->dba_mode[ch], s->dba_nsegs[ch],
999 s->dba_offsets[ch], s->dba_lengths[ch],
1000 s->dba_values[ch], s->mask[ch]);
1002 if(bit_alloc_stages[ch] > 0) {
1003 /* Compute bit allocation */
1004 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1005 s->start_freq[ch], s->end_freq[ch],
1007 s->bit_alloc_params.floor,
1012 /* unused dummy data */
1013 if (get_bits1(gbc)) {
1014 int skipl = get_bits(gbc, 9);
1019 /* unpack the transform coefficients
1020 this also uncouples channels if coupling is in use. */
1021 if (get_transform_coeffs(s)) {
1022 av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1026 /* recover coefficients if rematrixing is in use */
1027 if(s->channel_mode == AC3_CHMODE_STEREO)
1030 /* apply scaling to coefficients (headroom, dynrng) */
1031 for(ch=1; ch<=s->channels; ch++) {
1032 float gain = s->mul_bias / 4194304.0f;
1033 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1034 gain *= s->dynamic_range[ch-1];
1036 gain *= s->dynamic_range[0];
1038 for(i=0; i<256; i++) {
1039 s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
1045 /* downmix output if needed */
1046 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1047 s->fbw_channels == s->out_channels)) {
1051 /* convert float to 16-bit integer */
1052 for(ch=0; ch<s->out_channels; ch++) {
1053 for(i=0; i<256; i++) {
1054 s->output[ch][i] += s->add_bias;
1056 s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1063 * Decode a single AC-3 frame.
1065 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size)
1067 AC3DecodeContext *s = avctx->priv_data;
1068 int16_t *out_samples = (int16_t *)data;
1069 int i, blk, ch, err;
1071 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1072 init_get_bits(&s->gbc, buf, buf_size * 8);
1074 /* parse the syncinfo */
1075 err = ac3_parse_header(s);
1078 case AC3_PARSE_ERROR_SYNC:
1079 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1081 case AC3_PARSE_ERROR_BSID:
1082 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1084 case AC3_PARSE_ERROR_SAMPLE_RATE:
1085 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1087 case AC3_PARSE_ERROR_FRAME_SIZE:
1088 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1091 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1097 /* check that reported frame size fits in input buffer */
1098 if(s->frame_size > buf_size) {
1099 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1103 /* check for crc mismatch */
1104 if(avctx->error_resilience >= FF_ER_CAREFUL) {
1105 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1106 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1109 /* TODO: error concealment */
1112 avctx->sample_rate = s->sample_rate;
1113 avctx->bit_rate = s->bit_rate;
1115 /* channel config */
1116 s->out_channels = s->channels;
1117 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1118 avctx->request_channels < s->channels) {
1119 s->out_channels = avctx->request_channels;
1120 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1122 avctx->channels = s->out_channels;
1124 /* set downmixing coefficients if needed */
1125 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1126 s->fbw_channels == s->out_channels)) {
1127 set_downmix_coeffs(s);
1130 /* parse the audio blocks */
1131 for (blk = 0; blk < NB_BLOCKS; blk++) {
1132 if (ac3_parse_audio_block(s, blk)) {
1133 av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1135 return s->frame_size;
1137 for (i = 0; i < 256; i++)
1138 for (ch = 0; ch < s->out_channels; ch++)
1139 *(out_samples++) = s->int_output[ch][i];
1141 *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1142 return s->frame_size;
1146 * Uninitialize the AC-3 decoder.
1148 static int ac3_decode_end(AVCodecContext *avctx)
1150 AC3DecodeContext *s = avctx->priv_data;
1151 ff_mdct_end(&s->imdct_512);
1152 ff_mdct_end(&s->imdct_256);
1157 AVCodec ac3_decoder = {
1159 .type = CODEC_TYPE_AUDIO,
1161 .priv_data_size = sizeof (AC3DecodeContext),
1162 .init = ac3_decode_init,
1163 .close = ac3_decode_end,
1164 .decode = ac3_decode_frame,