1 /*
2 * AC-3 Audio Decoder
3 * This code is developed as part of Google Summer of Code 2006 Program.
4 *
5 * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com).
6 * Copyright (c) 2007 Justin Ruggles
7 *
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>
12 *
13 * This file is part of FFmpeg.
14 *
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.
19 *
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.
24 *
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
28 */
29
30 #include <stdio.h>
31 #include <stddef.h>
32 #include <math.h>
33 #include <string.h>
34
35 #include "avcodec.h"
36 #include "ac3_parser.h"
37 #include "bitstream.h"
38 #include "crc.h"
39 #include "dsputil.h"
40 #include "random.h"
41
42 /** Maximum possible frame size when the specification limit is ignored */
43 #define AC3_MAX_FRAME_SIZE 21695
44
45 /**
46 * Table of bin locations for rematrixing bands
47 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
48 */
49 static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
50
51 /** table for grouping exponents */
52 static uint8_t exp_ungroup_tab[128][3];
53
54
55 /** tables for ungrouping mantissas */
56 static int b1_mantissas[32][3];
57 static int b2_mantissas[128][3];
58 static int b3_mantissas[8];
59 static int b4_mantissas[128][2];
60 static int b5_mantissas[16];
61
62 /**
63 * Quantization table: levels for symmetric. bits for asymmetric.
64 * reference: Table 7.18 Mapping of bap to Quantizer
65 */
66 static const uint8_t quantization_tab[16] = {
67 0, 3, 5, 7, 11, 15,
68 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
69 };
70
71 /** dynamic range table. converts codes to scale factors. */
72 static float dynamic_range_tab[256];
73
74 /** Adjustments in dB gain */
75 #define LEVEL_MINUS_3DB 0.7071067811865476
76 #define LEVEL_MINUS_4POINT5DB 0.5946035575013605
77 #define LEVEL_MINUS_6DB 0.5000000000000000
78 #define LEVEL_MINUS_9DB 0.3535533905932738
79 #define LEVEL_ZERO 0.0000000000000000
80 #define LEVEL_ONE 1.0000000000000000
81
82 static const float gain_levels[6] = {
83 LEVEL_ZERO,
84 LEVEL_ONE,
85 LEVEL_MINUS_3DB,
86 LEVEL_MINUS_4POINT5DB,
87 LEVEL_MINUS_6DB,
88 LEVEL_MINUS_9DB
89 };
90
91 /**
92 * Table for default stereo downmixing coefficients
93 * reference: Section 7.8.2 Downmixing Into Two Channels
94 */
95 static const uint8_t ac3_default_coeffs[8][5][2] = {
96 { { 1, 0 }, { 0, 1 }, },
97 { { 2, 2 }, },
98 { { 1, 0 }, { 0, 1 }, },
99 { { 1, 0 }, { 3, 3 }, { 0, 1 }, },
100 { { 1, 0 }, { 0, 1 }, { 4, 4 }, },
101 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, },
102 { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
103 { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
104 };
105
106 /* override ac3.h to include coupling channel */
107 #undef AC3_MAX_CHANNELS
108 #define AC3_MAX_CHANNELS 7
109 #define CPL_CH 0
110
111 #define AC3_OUTPUT_LFEON 8
112
113 typedef struct {
114 int channel_mode; ///< channel mode (acmod)
115 int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags
116 int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags
117 int dither_all; ///< true if all channels are dithered
118 int cpl_in_use; ///< coupling in use
119 int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling
120 int phase_flags_in_use; ///< phase flags in use
121 int phase_flags[18]; ///< phase flags
122 int cpl_band_struct[18]; ///< coupling band structure
123 int num_rematrixing_bands; ///< number of rematrixing bands
124 int rematrixing_flags[4]; ///< rematrixing flags
125 int exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies
126 int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets
127 int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values (signal-to-mask ratio)
128 int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode
129 int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments
130 uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets
131 uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths
132 uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment
133
134 int sample_rate; ///< sample frequency, in Hz
135 int bit_rate; ///< stream bit rate, in bits-per-second
136 int frame_size; ///< current frame size, in bytes
137
138 int channels; ///< number of total channels
139 int fbw_channels; ///< number of full-bandwidth channels
140 int lfe_on; ///< lfe channel in use
141 int lfe_ch; ///< index of LFE channel
142 int output_mode; ///< output channel configuration
143 int out_channels; ///< number of output channels
144
145 int center_mix_level; ///< Center mix level index
146 int surround_mix_level; ///< Surround mix level index
147 float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients
148 float downmix_coeff_adjust[2]; ///< adjustment needed for each output channel when downmixing
149 float dynamic_range[2]; ///< dynamic range
150 int cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates
151 int num_cpl_bands; ///< number of coupling bands
152 int num_cpl_subbands; ///< number of coupling sub bands
153 int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin
154 int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin
155 AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
156
157 int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
158 uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
159 int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
160 int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
161 int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
162
163 int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
164 DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
165 int downmixed; ///< indicates if coeffs are currently downmixed
166
167 /* For IMDCT. */
168 MDCTContext imdct_512; ///< for 512 sample IMDCT
169 MDCTContext imdct_256; ///< for 256 sample IMDCT
170 DSPContext dsp; ///< for optimization
171 float add_bias; ///< offset for float_to_int16 conversion
172 float mul_bias; ///< scaling for float_to_int16 conversion
173
174 DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]); ///< output after imdct transform and windowing
175 DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
176 DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]); ///< delay - added to the next block
177 DECLARE_ALIGNED_16(float, tmp_imdct[256]); ///< temporary storage for imdct transform
178 DECLARE_ALIGNED_16(float, tmp_output[512]); ///< temporary storage for output before windowing
179 DECLARE_ALIGNED_16(float, window[256]); ///< window coefficients
180
181 /* Miscellaneous. */
182 GetBitContext gbc; ///< bitstream reader
183 AVRandomState dith_state; ///< for dither generation
184 AVCodecContext *avctx; ///< parent context
185 uint8_t *input_buffer; ///< temp buffer to prevent overread
186 } AC3DecodeContext;
187
188 /**
189 * Symmetrical Dequantization
190 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
191 * Tables 7.19 to 7.23
192 */
193 static inline int
symmetric_dequant(int code,int levels)194 symmetric_dequant(int code, int levels)
195 {
196 return ((code - (levels >> 1)) << 24) / levels;
197 }
198
199 /*
200 * Initialize tables at runtime.
201 */
ac3_tables_init(void)202 static av_cold void ac3_tables_init(void)
203 {
204 int i;
205
206 /* generate grouped mantissa tables
207 reference: Section 7.3.5 Ungrouping of Mantissas */
208 for(i=0; i<32; i++) {
209 /* bap=1 mantissas */
210 b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3);
211 b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
212 b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
213 }
214 for(i=0; i<128; i++) {
215 /* bap=2 mantissas */
216 b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
217 b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
218 b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
219
220 /* bap=4 mantissas */
221 b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
222 b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
223 }
224 /* generate ungrouped mantissa tables
225 reference: Tables 7.21 and 7.23 */
226 for(i=0; i<7; i++) {
227 /* bap=3 mantissas */
228 b3_mantissas[i] = symmetric_dequant(i, 7);
229 }
230 for(i=0; i<15; i++) {
231 /* bap=5 mantissas */
232 b5_mantissas[i] = symmetric_dequant(i, 15);
233 }
234
235 /* generate dynamic range table
236 reference: Section 7.7.1 Dynamic Range Control */
237 for(i=0; i<256; i++) {
238 int v = (i >> 5) - ((i >> 7) << 3) - 5;
239 dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
240 }
241
242 /* generate exponent tables
243 reference: Section 7.1.3 Exponent Decoding */
244 for(i=0; i<128; i++) {
245 exp_ungroup_tab[i][0] = i / 25;
246 exp_ungroup_tab[i][1] = (i % 25) / 5;
247 exp_ungroup_tab[i][2] = (i % 25) % 5;
248 }
249 }
250
251
252 /**
253 * AVCodec initialization
254 */
ac3_decode_init(AVCodecContext * avctx)255 static av_cold int ac3_decode_init(AVCodecContext *avctx)
256 {
257 AC3DecodeContext *s = avctx->priv_data;
258 s->avctx = avctx;
259
260 ac3_common_init();
261 ac3_tables_init();
262 ff_mdct_init(&s->imdct_256, 8, 1);
263 ff_mdct_init(&s->imdct_512, 9, 1);
264 ff_kbd_window_init(s->window, 5.0, 256);
265 dsputil_init(&s->dsp, avctx);
266 av_init_random(0, &s->dith_state);
267
268 /* set bias values for float to int16 conversion */
269 if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
270 s->add_bias = 385.0f;
271 s->mul_bias = 1.0f;
272 } else {
273 s->add_bias = 0.0f;
274 s->mul_bias = 32767.0f;
275 }
276
277 /* allow downmixing to stereo or mono */
278 if (avctx->channels > 0 && avctx->request_channels > 0 &&
279 avctx->request_channels < avctx->channels &&
280 avctx->request_channels <= 2) {
281 avctx->channels = avctx->request_channels;
282 }
283 s->downmixed = 1;
284
285 /* allocate context input buffer */
286 if (avctx->error_resilience >= FF_ER_CAREFUL) {
287 s->input_buffer = av_mallocz(AC3_MAX_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
288 if (!s->input_buffer)
289 return AVERROR_NOMEM;
290 }
291
292 return 0;
293 }
294
295 /**
296 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
297 * GetBitContext within AC3DecodeContext must point to
298 * start of the synchronized ac3 bitstream.
299 */
ac3_parse_header(AC3DecodeContext * s)300 static int ac3_parse_header(AC3DecodeContext *s)
301 {
302 AC3HeaderInfo hdr;
303 GetBitContext *gbc = &s->gbc;
304 int err, i;
305
306 err = ff_ac3_parse_header(gbc, &hdr);
307 if(err)
308 return err;
309
310 if(hdr.bitstream_id > 10)
311 return AC3_PARSE_ERROR_BSID;
312
313 /* get decoding parameters from header info */
314 s->bit_alloc_params.sr_code = hdr.sr_code;
315 s->channel_mode = hdr.channel_mode;
316 s->lfe_on = hdr.lfe_on;
317 s->bit_alloc_params.sr_shift = hdr.sr_shift;
318 s->sample_rate = hdr.sample_rate;
319 s->bit_rate = hdr.bit_rate;
320 s->channels = hdr.channels;
321 s->fbw_channels = s->channels - s->lfe_on;
322 s->lfe_ch = s->fbw_channels + 1;
323 s->frame_size = hdr.frame_size;
324 s->center_mix_level = hdr.center_mix_level;
325 s->surround_mix_level = hdr.surround_mix_level;
326
327 /* set default output to all source channels */
328 s->out_channels = s->channels;
329 s->output_mode = s->channel_mode;
330 if(s->lfe_on)
331 s->output_mode |= AC3_OUTPUT_LFEON;
332
333 /* read the rest of the bsi. read twice for dual mono mode. */
334 i = !(s->channel_mode);
335 do {
336 skip_bits(gbc, 5); // skip dialog normalization
337 if (get_bits1(gbc))
338 skip_bits(gbc, 8); //skip compression
339 if (get_bits1(gbc))
340 skip_bits(gbc, 8); //skip language code
341 if (get_bits1(gbc))
342 skip_bits(gbc, 7); //skip audio production information
343 } while (i--);
344
345 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
346
347 /* skip the timecodes (or extra bitstream information for Alternate Syntax)
348 TODO: read & use the xbsi1 downmix levels */
349 if (get_bits1(gbc))
350 skip_bits(gbc, 14); //skip timecode1 / xbsi1
351 if (get_bits1(gbc))
352 skip_bits(gbc, 14); //skip timecode2 / xbsi2
353
354 /* skip additional bitstream info */
355 if (get_bits1(gbc)) {
356 i = get_bits(gbc, 6);
357 do {
358 skip_bits(gbc, 8);
359 } while(i--);
360 }
361
362 return 0;
363 }
364
365 /**
366 * Set stereo downmixing coefficients based on frame header info.
367 * reference: Section 7.8.2 Downmixing Into Two Channels
368 */
set_downmix_coeffs(AC3DecodeContext * s)369 static void set_downmix_coeffs(AC3DecodeContext *s)
370 {
371 int i;
372 float cmix = gain_levels[s->center_mix_level];
373 float smix = gain_levels[s->surround_mix_level];
374
375 for(i=0; i<s->fbw_channels; i++) {
376 s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
377 s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
378 }
379 if(s->channel_mode > 1 && s->channel_mode & 1) {
380 s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
381 }
382 if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
383 int nf = s->channel_mode - 2;
384 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
385 }
386 if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
387 int nf = s->channel_mode - 4;
388 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
389 }
390
391 /* calculate adjustment needed for each channel to avoid clipping */
392 s->downmix_coeff_adjust[0] = s->downmix_coeff_adjust[1] = 0.0f;
393 for(i=0; i<s->fbw_channels; i++) {
394 s->downmix_coeff_adjust[0] += s->downmix_coeffs[i][0];
395 s->downmix_coeff_adjust[1] += s->downmix_coeffs[i][1];
396 }
397 s->downmix_coeff_adjust[0] = 1.0f / s->downmix_coeff_adjust[0];
398 s->downmix_coeff_adjust[1] = 1.0f / s->downmix_coeff_adjust[1];
399 }
400
401 /**
402 * Decode the grouped exponents according to exponent strategy.
403 * reference: Section 7.1.3 Exponent Decoding
404 */
decode_exponents(GetBitContext * gbc,int exp_strategy,int ngrps,uint8_t absexp,int8_t * dexps)405 static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
406 uint8_t absexp, int8_t *dexps)
407 {
408 int i, j, grp, group_size;
409 int dexp[256];
410 int expacc, prevexp;
411
412 /* unpack groups */
413 group_size = exp_strategy + (exp_strategy == EXP_D45);
414 for(grp=0,i=0; grp<ngrps; grp++) {
415 expacc = get_bits(gbc, 7);
416 dexp[i++] = exp_ungroup_tab[expacc][0];
417 dexp[i++] = exp_ungroup_tab[expacc][1];
418 dexp[i++] = exp_ungroup_tab[expacc][2];
419 }
420
421 /* convert to absolute exps and expand groups */
422 prevexp = absexp;
423 for(i=0; i<ngrps*3; i++) {
424 prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
425 for(j=0; j<group_size; j++) {
426 dexps[(i*group_size)+j] = prevexp;
427 }
428 }
429 }
430
431 /**
432 * Generate transform coefficients for each coupled channel in the coupling
433 * range using the coupling coefficients and coupling coordinates.
434 * reference: Section 7.4.3 Coupling Coordinate Format
435 */
uncouple_channels(AC3DecodeContext * s)436 static void uncouple_channels(AC3DecodeContext *s)
437 {
438 int i, j, ch, bnd, subbnd;
439
440 subbnd = -1;
441 i = s->start_freq[CPL_CH];
442 for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
443 do {
444 subbnd++;
445 for(j=0; j<12; j++) {
446 for(ch=1; ch<=s->fbw_channels; ch++) {
447 if(s->channel_in_cpl[ch]) {
448 s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
449 if (ch == 2 && s->phase_flags[bnd])
450 s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
451 }
452 }
453 i++;
454 }
455 } while(s->cpl_band_struct[subbnd]);
456 }
457 }
458
459 /**
460 * Grouped mantissas for 3-level 5-level and 11-level quantization
461 */
462 typedef struct {
463 int b1_mant[3];
464 int b2_mant[3];
465 int b4_mant[2];
466 int b1ptr;
467 int b2ptr;
468 int b4ptr;
469 } mant_groups;
470
471 /**
472 * Get the transform coefficients for a particular channel
473 * reference: Section 7.3 Quantization and Decoding of Mantissas
474 */
get_transform_coeffs_ch(AC3DecodeContext * s,int ch_index,mant_groups * m)475 static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
476 {
477 GetBitContext *gbc = &s->gbc;
478 int i, gcode, tbap, start, end;
479 uint8_t *exps;
480 uint8_t *bap;
481 int *coeffs;
482
483 exps = s->dexps[ch_index];
484 bap = s->bap[ch_index];
485 coeffs = s->fixed_coeffs[ch_index];
486 start = s->start_freq[ch_index];
487 end = s->end_freq[ch_index];
488
489 for (i = start; i < end; i++) {
490 tbap = bap[i];
491 switch (tbap) {
492 case 0:
493 coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
494 break;
495
496 case 1:
497 if(m->b1ptr > 2) {
498 gcode = get_bits(gbc, 5);
499 m->b1_mant[0] = b1_mantissas[gcode][0];
500 m->b1_mant[1] = b1_mantissas[gcode][1];
501 m->b1_mant[2] = b1_mantissas[gcode][2];
502 m->b1ptr = 0;
503 }
504 coeffs[i] = m->b1_mant[m->b1ptr++];
505 break;
506
507 case 2:
508 if(m->b2ptr > 2) {
509 gcode = get_bits(gbc, 7);
510 m->b2_mant[0] = b2_mantissas[gcode][0];
511 m->b2_mant[1] = b2_mantissas[gcode][1];
512 m->b2_mant[2] = b2_mantissas[gcode][2];
513 m->b2ptr = 0;
514 }
515 coeffs[i] = m->b2_mant[m->b2ptr++];
516 break;
517
518 case 3:
519 coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
520 break;
521
522 case 4:
523 if(m->b4ptr > 1) {
524 gcode = get_bits(gbc, 7);
525 m->b4_mant[0] = b4_mantissas[gcode][0];
526 m->b4_mant[1] = b4_mantissas[gcode][1];
527 m->b4ptr = 0;
528 }
529 coeffs[i] = m->b4_mant[m->b4ptr++];
530 break;
531
532 case 5:
533 coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
534 break;
535
536 default: {
537 /* asymmetric dequantization */
538 int qlevel = quantization_tab[tbap];
539 coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
540 break;
541 }
542 }
543 coeffs[i] >>= exps[i];
544 }
545
546 return 0;
547 }
548
549 /**
550 * Remove random dithering from coefficients with zero-bit mantissas
551 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
552 */
remove_dithering(AC3DecodeContext * s)553 static void remove_dithering(AC3DecodeContext *s) {
554 int ch, i;
555 int end=0;
556 int *coeffs;
557 uint8_t *bap;
558
559 for(ch=1; ch<=s->fbw_channels; ch++) {
560 if(!s->dither_flag[ch]) {
561 coeffs = s->fixed_coeffs[ch];
562 bap = s->bap[ch];
563 if(s->channel_in_cpl[ch])
564 end = s->start_freq[CPL_CH];
565 else
566 end = s->end_freq[ch];
567 for(i=0; i<end; i++) {
568 if(!bap[i])
569 coeffs[i] = 0;
570 }
571 if(s->channel_in_cpl[ch]) {
572 bap = s->bap[CPL_CH];
573 for(; i<s->end_freq[CPL_CH]; i++) {
574 if(!bap[i])
575 coeffs[i] = 0;
576 }
577 }
578 }
579 }
580 }
581
582 /**
583 * Get the transform coefficients.
584 */
get_transform_coeffs(AC3DecodeContext * s)585 static int get_transform_coeffs(AC3DecodeContext *s)
586 {
587 int ch, end;
588 int got_cplchan = 0;
589 mant_groups m;
590
591 m.b1ptr = m.b2ptr = m.b4ptr = 3;
592
593 for (ch = 1; ch <= s->channels; ch++) {
594 /* transform coefficients for full-bandwidth channel */
595 if (get_transform_coeffs_ch(s, ch, &m))
596 return -1;
597 /* tranform coefficients for coupling channel come right after the
598 coefficients for the first coupled channel*/
599 if (s->channel_in_cpl[ch]) {
600 if (!got_cplchan) {
601 if (get_transform_coeffs_ch(s, CPL_CH, &m)) {
602 av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n");
603 return -1;
604 }
605 uncouple_channels(s);
606 got_cplchan = 1;
607 }
608 end = s->end_freq[CPL_CH];
609 } else {
610 end = s->end_freq[ch];
611 }
612 do
613 s->transform_coeffs[ch][end] = 0;
614 while(++end < 256);
615 }
616
617 /* if any channel doesn't use dithering, zero appropriate coefficients */
618 if(!s->dither_all)
619 remove_dithering(s);
620
621 return 0;
622 }
623
624 /**
625 * Stereo rematrixing.
626 * reference: Section 7.5.4 Rematrixing : Decoding Technique
627 */
do_rematrixing(AC3DecodeContext * s)628 static void do_rematrixing(AC3DecodeContext *s)
629 {
630 int bnd, i;
631 int end, bndend;
632 int tmp0, tmp1;
633
634 end = FFMIN(s->end_freq[1], s->end_freq[2]);
635
636 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
637 if(s->rematrixing_flags[bnd]) {
638 bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
639 for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
640 tmp0 = s->fixed_coeffs[1][i];
641 tmp1 = s->fixed_coeffs[2][i];
642 s->fixed_coeffs[1][i] = tmp0 + tmp1;
643 s->fixed_coeffs[2][i] = tmp0 - tmp1;
644 }
645 }
646 }
647 }
648
649 /**
650 * Perform the 256-point IMDCT
651 */
do_imdct_256(AC3DecodeContext * s,int chindex)652 static void do_imdct_256(AC3DecodeContext *s, int chindex)
653 {
654 int i, k;
655 DECLARE_ALIGNED_16(float, x[128]);
656 FFTComplex z[2][64];
657 float *o_ptr = s->tmp_output;
658
659 for(i=0; i<2; i++) {
660 /* de-interleave coefficients */
661 for(k=0; k<128; k++) {
662 x[k] = s->transform_coeffs[chindex][2*k+i];
663 }
664
665 /* run standard IMDCT */
666 s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
667
668 /* reverse the post-rotation & reordering from standard IMDCT */
669 for(k=0; k<32; k++) {
670 z[i][32+k].re = -o_ptr[128+2*k];
671 z[i][32+k].im = -o_ptr[2*k];
672 z[i][31-k].re = o_ptr[2*k+1];
673 z[i][31-k].im = o_ptr[128+2*k+1];
674 }
675 }
676
677 /* apply AC-3 post-rotation & reordering */
678 for(k=0; k<64; k++) {
679 o_ptr[ 2*k ] = -z[0][ k].im;
680 o_ptr[ 2*k+1] = z[0][63-k].re;
681 o_ptr[128+2*k ] = -z[0][ k].re;
682 o_ptr[128+2*k+1] = z[0][63-k].im;
683 o_ptr[256+2*k ] = -z[1][ k].re;
684 o_ptr[256+2*k+1] = z[1][63-k].im;
685 o_ptr[384+2*k ] = z[1][ k].im;
686 o_ptr[384+2*k+1] = -z[1][63-k].re;
687 }
688 }
689
690 /**
691 * Inverse MDCT Transform.
692 * Convert frequency domain coefficients to time-domain audio samples.
693 * reference: Section 7.9.4 Transformation Equations
694 */
do_imdct(AC3DecodeContext * s,int channels)695 static inline void do_imdct(AC3DecodeContext *s, int channels)
696 {
697 int ch;
698
699 for (ch=1; ch<=channels; ch++) {
700 if (s->block_switch[ch]) {
701 do_imdct_256(s, ch);
702 } else {
703 s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
704 s->transform_coeffs[ch], s->tmp_imdct);
705 }
706 /* For the first half of the block, apply the window, add the delay
707 from the previous block, and send to output */
708 s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
709 s->window, s->delay[ch-1], 0, 256, 1);
710 /* For the second half of the block, apply the window and store the
711 samples to delay, to be combined with the next block */
712 s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
713 s->window, 256);
714 }
715 }
716
717 /**
718 * Downmix the output to mono or stereo.
719 */
ac3_downmix(AC3DecodeContext * s,float samples[AC3_MAX_CHANNELS][256],int ch_offset)720 static void ac3_downmix(AC3DecodeContext *s,
721 float samples[AC3_MAX_CHANNELS][256], int ch_offset)
722 {
723 int i, j;
724 float v0, v1;
725
726 for(i=0; i<256; i++) {
727 v0 = v1 = 0.0f;
728 for(j=0; j<s->fbw_channels; j++) {
729 v0 += samples[j+ch_offset][i] * s->downmix_coeffs[j][0];
730 v1 += samples[j+ch_offset][i] * s->downmix_coeffs[j][1];
731 }
732 v0 *= s->downmix_coeff_adjust[0];
733 v1 *= s->downmix_coeff_adjust[1];
734 if(s->output_mode == AC3_CHMODE_MONO) {
735 samples[ch_offset][i] = (v0 + v1) * LEVEL_MINUS_3DB;
736 } else if(s->output_mode == AC3_CHMODE_STEREO) {
737 samples[ ch_offset][i] = v0;
738 samples[1+ch_offset][i] = v1;
739 }
740 }
741 }
742
743 /**
744 * Upmix delay samples from stereo to original channel layout.
745 */
ac3_upmix_delay(AC3DecodeContext * s)746 static void ac3_upmix_delay(AC3DecodeContext *s)
747 {
748 int channel_data_size = sizeof(s->delay[0]);
749 switch(s->channel_mode) {
750 case AC3_CHMODE_DUALMONO:
751 case AC3_CHMODE_STEREO:
752 /* upmix mono to stereo */
753 memcpy(s->delay[1], s->delay[0], channel_data_size);
754 break;
755 case AC3_CHMODE_2F2R:
756 memset(s->delay[3], 0, channel_data_size);
757 case AC3_CHMODE_2F1R:
758 memset(s->delay[2], 0, channel_data_size);
759 break;
760 case AC3_CHMODE_3F2R:
761 memset(s->delay[4], 0, channel_data_size);
762 case AC3_CHMODE_3F1R:
763 memset(s->delay[3], 0, channel_data_size);
764 case AC3_CHMODE_3F:
765 memcpy(s->delay[2], s->delay[1], channel_data_size);
766 memset(s->delay[1], 0, channel_data_size);
767 break;
768 }
769 }
770
771 /**
772 * Parse an audio block from AC-3 bitstream.
773 */
ac3_parse_audio_block(AC3DecodeContext * s,int blk)774 static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
775 {
776 int fbw_channels = s->fbw_channels;
777 int channel_mode = s->channel_mode;
778 int i, bnd, seg, ch;
779 int different_transforms;
780 int downmix_output;
781 GetBitContext *gbc = &s->gbc;
782 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
783
784 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
785
786 /* block switch flags */
787 different_transforms = 0;
788 for (ch = 1; ch <= fbw_channels; ch++) {
789 s->block_switch[ch] = get_bits1(gbc);
790 if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
791 different_transforms = 1;
792 }
793
794 /* dithering flags */
795 s->dither_all = 1;
796 for (ch = 1; ch <= fbw_channels; ch++) {
797 s->dither_flag[ch] = get_bits1(gbc);
798 if(!s->dither_flag[ch])
799 s->dither_all = 0;
800 }
801
802 /* dynamic range */
803 i = !(s->channel_mode);
804 do {
805 if(get_bits1(gbc)) {
806 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
807 s->avctx->drc_scale)+1.0;
808 } else if(blk == 0) {
809 s->dynamic_range[i] = 1.0f;
810 }
811 } while(i--);
812
813 /* coupling strategy */
814 if (get_bits1(gbc)) {
815 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
816 s->cpl_in_use = get_bits1(gbc);
817 if (s->cpl_in_use) {
818 /* coupling in use */
819 int cpl_begin_freq, cpl_end_freq;
820
821 /* determine which channels are coupled */
822 for (ch = 1; ch <= fbw_channels; ch++)
823 s->channel_in_cpl[ch] = get_bits1(gbc);
824
825 /* phase flags in use */
826 if (channel_mode == AC3_CHMODE_STEREO)
827 s->phase_flags_in_use = get_bits1(gbc);
828
829 /* coupling frequency range and band structure */
830 cpl_begin_freq = get_bits(gbc, 4);
831 cpl_end_freq = get_bits(gbc, 4);
832 if (3 + cpl_end_freq - cpl_begin_freq < 0) {
833 av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
834 return -1;
835 }
836 s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
837 s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
838 s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
839 for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
840 if (get_bits1(gbc)) {
841 s->cpl_band_struct[bnd] = 1;
842 s->num_cpl_bands--;
843 }
844 }
845 s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
846 } else {
847 /* coupling not in use */
848 for (ch = 1; ch <= fbw_channels; ch++)
849 s->channel_in_cpl[ch] = 0;
850 }
851 }
852
853 /* coupling coordinates */
854 if (s->cpl_in_use) {
855 int cpl_coords_exist = 0;
856
857 for (ch = 1; ch <= fbw_channels; ch++) {
858 if (s->channel_in_cpl[ch]) {
859 if (get_bits1(gbc)) {
860 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
861 cpl_coords_exist = 1;
862 master_cpl_coord = 3 * get_bits(gbc, 2);
863 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
864 cpl_coord_exp = get_bits(gbc, 4);
865 cpl_coord_mant = get_bits(gbc, 4);
866 if (cpl_coord_exp == 15)
867 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
868 else
869 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
870 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
871 }
872 }
873 }
874 }
875 /* phase flags */
876 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
877 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
878 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
879 }
880 }
881 }
882
883 /* stereo rematrixing strategy and band structure */
884 if (channel_mode == AC3_CHMODE_STEREO) {
885 if (get_bits1(gbc)) {
886 s->num_rematrixing_bands = 4;
887 if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
888 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
889 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
890 s->rematrixing_flags[bnd] = get_bits1(gbc);
891 }
892 }
893
894 /* exponent strategies for each channel */
895 s->exp_strategy[CPL_CH] = EXP_REUSE;
896 s->exp_strategy[s->lfe_ch] = EXP_REUSE;
897 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
898 if(ch == s->lfe_ch)
899 s->exp_strategy[ch] = get_bits(gbc, 1);
900 else
901 s->exp_strategy[ch] = get_bits(gbc, 2);
902 if(s->exp_strategy[ch] != EXP_REUSE)
903 bit_alloc_stages[ch] = 3;
904 }
905
906 /* channel bandwidth */
907 for (ch = 1; ch <= fbw_channels; ch++) {
908 s->start_freq[ch] = 0;
909 if (s->exp_strategy[ch] != EXP_REUSE) {
910 int prev = s->end_freq[ch];
911 if (s->channel_in_cpl[ch])
912 s->end_freq[ch] = s->start_freq[CPL_CH];
913 else {
914 int bandwidth_code = get_bits(gbc, 6);
915 if (bandwidth_code > 60) {
916 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
917 return -1;
918 }
919 s->end_freq[ch] = bandwidth_code * 3 + 73;
920 }
921 if(blk > 0 && s->end_freq[ch] != prev)
922 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
923 }
924 }
925 s->start_freq[s->lfe_ch] = 0;
926 s->end_freq[s->lfe_ch] = 7;
927
928 /* decode exponents for each channel */
929 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
930 if (s->exp_strategy[ch] != EXP_REUSE) {
931 int group_size, num_groups;
932 group_size = 3 << (s->exp_strategy[ch] - 1);
933 if(ch == CPL_CH)
934 num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
935 else if(ch == s->lfe_ch)
936 num_groups = 2;
937 else
938 num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
939 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
940 decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
941 &s->dexps[ch][s->start_freq[ch]+!!ch]);
942 if(ch != CPL_CH && ch != s->lfe_ch)
943 skip_bits(gbc, 2); /* skip gainrng */
944 }
945 }
946
947 /* bit allocation information */
948 if (get_bits1(gbc)) {
949 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
950 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
951 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
952 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
953 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
954 for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
955 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
956 }
957 }
958
959 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
960 if (get_bits1(gbc)) {
961 int csnr;
962 csnr = (get_bits(gbc, 6) - 15) << 4;
963 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
964 s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
965 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
966 }
967 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
968 }
969
970 /* coupling leak information */
971 if (s->cpl_in_use && get_bits1(gbc)) {
972 s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
973 s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
974 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
975 }
976
977 /* delta bit allocation information */
978 if (get_bits1(gbc)) {
979 /* delta bit allocation exists (strategy) */
980 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
981 s->dba_mode[ch] = get_bits(gbc, 2);
982 if (s->dba_mode[ch] == DBA_RESERVED) {
983 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
984 return -1;
985 }
986 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
987 }
988 /* channel delta offset, len and bit allocation */
989 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
990 if (s->dba_mode[ch] == DBA_NEW) {
991 s->dba_nsegs[ch] = get_bits(gbc, 3);
992 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
993 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
994 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
995 s->dba_values[ch][seg] = get_bits(gbc, 3);
996 }
997 }
998 }
999 } else if(blk == 0) {
1000 for(ch=0; ch<=s->channels; ch++) {
1001 s->dba_mode[ch] = DBA_NONE;
1002 }
1003 }
1004
1005 /* Bit allocation */
1006 for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
1007 if(bit_alloc_stages[ch] > 2) {
1008 /* Exponent mapping into PSD and PSD integration */
1009 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1010 s->start_freq[ch], s->end_freq[ch],
1011 s->psd[ch], s->band_psd[ch]);
1012 }
1013 if(bit_alloc_stages[ch] > 1) {
1014 /* Compute excitation function, Compute masking curve, and
1015 Apply delta bit allocation */
1016 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1017 s->start_freq[ch], s->end_freq[ch],
1018 s->fast_gain[ch], (ch == s->lfe_ch),
1019 s->dba_mode[ch], s->dba_nsegs[ch],
1020 s->dba_offsets[ch], s->dba_lengths[ch],
1021 s->dba_values[ch], s->mask[ch]);
1022 }
1023 if(bit_alloc_stages[ch] > 0) {
1024 /* Compute bit allocation */
1025 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1026 s->start_freq[ch], s->end_freq[ch],
1027 s->snr_offset[ch],
1028 s->bit_alloc_params.floor,
1029 s->bap[ch]);
1030 }
1031 }
1032
1033 /* unused dummy data */
1034 if (get_bits1(gbc)) {
1035 int skipl = get_bits(gbc, 9);
1036 while(skipl--)
1037 skip_bits(gbc, 8);
1038 }
1039
1040 /* unpack the transform coefficients
1041 this also uncouples channels if coupling is in use. */
1042 if (get_transform_coeffs(s)) {
1043 av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n");
1044 return -1;
1045 }
1046
1047 /* recover coefficients if rematrixing is in use */
1048 if(s->channel_mode == AC3_CHMODE_STEREO)
1049 do_rematrixing(s);
1050
1051 /* apply scaling to coefficients (headroom, dynrng) */
1052 for(ch=1; ch<=s->channels; ch++) {
1053 float gain = s->mul_bias / 4194304.0f;
1054 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1055 gain *= s->dynamic_range[ch-1];
1056 } else {
1057 gain *= s->dynamic_range[0];
1058 }
1059 for(i=0; i<256; i++) {
1060 s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
1061 }
1062 }
1063
1064 /* downmix and MDCT. order depends on whether block switching is used for
1065 any channel in this block. this is because coefficients for the long
1066 and short transforms cannot be mixed. */
1067 downmix_output = s->channels != s->out_channels &&
1068 !((s->output_mode & AC3_OUTPUT_LFEON) &&
1069 s->fbw_channels == s->out_channels);
1070 if(different_transforms) {
1071 /* the delay samples have already been downmixed, so we upmix the delay
1072 samples in order to reconstruct all channels before downmixing. */
1073 if(s->downmixed) {
1074 s->downmixed = 0;
1075 ac3_upmix_delay(s);
1076 }
1077
1078 do_imdct(s, s->channels);
1079
1080 if(downmix_output) {
1081 ac3_downmix(s, s->output, 0);
1082 }
1083 } else {
1084 if(downmix_output) {
1085 ac3_downmix(s, s->transform_coeffs, 1);
1086 }
1087
1088 if(!s->downmixed) {
1089 s->downmixed = 1;
1090 ac3_downmix(s, s->delay, 0);
1091 }
1092
1093 do_imdct(s, s->out_channels);
1094 }
1095
1096 /* convert float to 16-bit integer */
1097 for(ch=0; ch<s->out_channels; ch++) {
1098 for(i=0; i<256; i++) {
1099 s->output[ch][i] += s->add_bias;
1100 }
1101 s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1102 }
1103
1104 return 0;
1105 }
1106
1107 /**
1108 * Decode a single AC-3 frame.
1109 */
ac3_decode_frame(AVCodecContext * avctx,void * data,int * data_size,const uint8_t * buf,int buf_size)1110 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1111 const uint8_t *buf, int buf_size)
1112 {
1113 AC3DecodeContext *s = avctx->priv_data;
1114 int16_t *out_samples = (int16_t *)data;
1115 int i, blk, ch, err;
1116
1117 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1118 if (s->input_buffer) {
1119 /* copy input buffer to decoder context to avoid reading past the end
1120 of the buffer, which can be caused by a damaged input stream. */
1121 memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_MAX_FRAME_SIZE));
1122 init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1123 } else {
1124 init_get_bits(&s->gbc, buf, buf_size * 8);
1125 }
1126
1127 /* parse the syncinfo */
1128 err = ac3_parse_header(s);
1129 if(err) {
1130 switch(err) {
1131 case AC3_PARSE_ERROR_SYNC:
1132 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1133 break;
1134 case AC3_PARSE_ERROR_BSID:
1135 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1136 break;
1137 case AC3_PARSE_ERROR_SAMPLE_RATE:
1138 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1139 break;
1140 case AC3_PARSE_ERROR_FRAME_SIZE:
1141 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1142 break;
1143 case AC3_PARSE_ERROR_FRAME_TYPE:
1144 av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1145 break;
1146 default:
1147 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1148 break;
1149 }
1150 return -1;
1151 }
1152
1153 /* check that reported frame size fits in input buffer */
1154 if(s->frame_size > buf_size) {
1155 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1156 return -1;
1157 }
1158
1159 /* check for crc mismatch */
1160 if(avctx->error_resilience >= FF_ER_CAREFUL) {
1161 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1162 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1163 return -1;
1164 }
1165 /* TODO: error concealment */
1166 }
1167
1168 avctx->sample_rate = s->sample_rate;
1169 avctx->bit_rate = s->bit_rate;
1170
1171 /* channel config */
1172 s->out_channels = s->channels;
1173 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1174 avctx->request_channels < s->channels) {
1175 s->out_channels = avctx->request_channels;
1176 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1177 }
1178 avctx->channels = s->out_channels;
1179
1180 /* set downmixing coefficients if needed */
1181 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1182 s->fbw_channels == s->out_channels)) {
1183 set_downmix_coeffs(s);
1184 }
1185
1186 /* parse the audio blocks */
1187 for (blk = 0; blk < NB_BLOCKS; blk++) {
1188 if (ac3_parse_audio_block(s, blk)) {
1189 av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1190 *data_size = 0;
1191 return s->frame_size;
1192 }
1193 for (i = 0; i < 256; i++)
1194 for (ch = 0; ch < s->out_channels; ch++)
1195 *(out_samples++) = s->int_output[ch][i];
1196 }
1197 *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1198 return s->frame_size;
1199 }
1200
1201 /**
1202 * Uninitialize the AC-3 decoder.
1203 */
ac3_decode_end(AVCodecContext * avctx)1204 static av_cold int ac3_decode_end(AVCodecContext *avctx)
1205 {
1206 AC3DecodeContext *s = avctx->priv_data;
1207 ff_mdct_end(&s->imdct_512);
1208 ff_mdct_end(&s->imdct_256);
1209
1210 av_freep(&s->input_buffer);
1211
1212 return 0;
1213 }
1214
1215 AVCodec ac3_decoder = {
1216 .name = "ac3",
1217 .type = CODEC_TYPE_AUDIO,
1218 .id = CODEC_ID_AC3,
1219 .priv_data_size = sizeof (AC3DecodeContext),
1220 .init = ac3_decode_init,
1221 .close = ac3_decode_end,
1222 .decode = ac3_decode_frame,
1223 .long_name = "ATSC A/52 / AC-3",
1224 };
1225