3 * This code was developed as part of Google Summer of Code 2006.
4 * E-AC-3 support was added as part of Google Summer of Code 2007.
6 * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com)
7 * Copyright (c) 2007-2008 Bartlomiej Wolowiec <bartek.wolowiec@gmail.com>
8 * Copyright (c) 2007 Justin Ruggles <justin.ruggles@gmail.com>
10 * This file is part of Libav.
12 * Libav is free software; you can redistribute it and/or
13 * modify it under the terms of the GNU Lesser General Public
14 * License as published by the Free Software Foundation; either
15 * version 2.1 of the License, or (at your option) any later version.
17 * Libav is distributed in the hope that it will be useful,
18 * but WITHOUT ANY WARRANTY; without even the implied warranty of
19 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
20 * Lesser General Public License for more details.
22 * You should have received a copy of the GNU Lesser General Public
23 * License along with Libav; if not, write to the Free Software
24 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
32 #include "libavutil/crc.h"
33 #include "libavutil/opt.h"
35 #include "aac_ac3_parser.h"
36 #include "ac3_parser.h"
38 #include "ac3dec_data.h"
42 * table for ungrouping 3 values in 7 bits.
43 * used for exponents and bap=2 mantissas
45 static uint8_t ungroup_3_in_7_bits_tab
[128][3];
47 /** tables for ungrouping mantissas */
48 static int b1_mantissas
[32][3];
49 static int b2_mantissas
[128][3];
50 static int b3_mantissas
[8];
51 static int b4_mantissas
[128][2];
52 static int b5_mantissas
[16];
55 * Quantization table: levels for symmetric. bits for asymmetric.
56 * reference: Table 7.18 Mapping of bap to Quantizer
58 static const uint8_t quantization_tab
[16] = {
60 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
63 /** dynamic range table. converts codes to scale factors. */
64 static float dynamic_range_tab
[256];
66 /** Adjustments in dB gain */
67 static const float gain_levels
[9] = {
71 LEVEL_MINUS_1POINT5DB
,
73 LEVEL_MINUS_4POINT5DB
,
80 * Table for default stereo downmixing coefficients
81 * reference: Section 7.8.2 Downmixing Into Two Channels
83 static const uint8_t ac3_default_coeffs
[8][5][2] = {
84 { { 2, 7 }, { 7, 2 }, },
86 { { 2, 7 }, { 7, 2 }, },
87 { { 2, 7 }, { 5, 5 }, { 7, 2 }, },
88 { { 2, 7 }, { 7, 2 }, { 6, 6 }, },
89 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 8, 8 }, },
90 { { 2, 7 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
91 { { 2, 7 }, { 5, 5 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
95 * Symmetrical Dequantization
96 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
100 symmetric_dequant(int code
, int levels
)
102 return ((code
- (levels
>> 1)) << 24) / levels
;
106 * Initialize tables at runtime.
108 static av_cold
void ac3_tables_init(void)
112 /* generate table for ungrouping 3 values in 7 bits
113 reference: Section 7.1.3 Exponent Decoding */
114 for (i
= 0; i
< 128; i
++) {
115 ungroup_3_in_7_bits_tab
[i
][0] = i
/ 25;
116 ungroup_3_in_7_bits_tab
[i
][1] = (i
% 25) / 5;
117 ungroup_3_in_7_bits_tab
[i
][2] = (i
% 25) % 5;
120 /* generate grouped mantissa tables
121 reference: Section 7.3.5 Ungrouping of Mantissas */
122 for (i
= 0; i
< 32; i
++) {
123 /* bap=1 mantissas */
124 b1_mantissas
[i
][0] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab
[i
][0], 3);
125 b1_mantissas
[i
][1] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab
[i
][1], 3);
126 b1_mantissas
[i
][2] = symmetric_dequant(ff_ac3_ungroup_3_in_5_bits_tab
[i
][2], 3);
128 for (i
= 0; i
< 128; i
++) {
129 /* bap=2 mantissas */
130 b2_mantissas
[i
][0] = symmetric_dequant(ungroup_3_in_7_bits_tab
[i
][0], 5);
131 b2_mantissas
[i
][1] = symmetric_dequant(ungroup_3_in_7_bits_tab
[i
][1], 5);
132 b2_mantissas
[i
][2] = symmetric_dequant(ungroup_3_in_7_bits_tab
[i
][2], 5);
134 /* bap=4 mantissas */
135 b4_mantissas
[i
][0] = symmetric_dequant(i
/ 11, 11);
136 b4_mantissas
[i
][1] = symmetric_dequant(i
% 11, 11);
138 /* generate ungrouped mantissa tables
139 reference: Tables 7.21 and 7.23 */
140 for (i
= 0; i
< 7; i
++) {
141 /* bap=3 mantissas */
142 b3_mantissas
[i
] = symmetric_dequant(i
, 7);
144 for (i
= 0; i
< 15; i
++) {
145 /* bap=5 mantissas */
146 b5_mantissas
[i
] = symmetric_dequant(i
, 15);
149 /* generate dynamic range table
150 reference: Section 7.7.1 Dynamic Range Control */
151 for (i
= 0; i
< 256; i
++) {
152 int v
= (i
>> 5) - ((i
>> 7) << 3) - 5;
153 dynamic_range_tab
[i
] = powf(2.0f
, v
) * ((i
& 0x1F) | 0x20);
158 * AVCodec initialization
160 static av_cold
int ac3_decode_init(AVCodecContext
*avctx
)
162 AC3DecodeContext
*s
= avctx
->priv_data
;
167 ff_ac3_common_init();
169 ff_mdct_init(&s
->imdct_256
, 8, 1, 1.0);
170 ff_mdct_init(&s
->imdct_512
, 9, 1, 1.0);
171 ff_kbd_window_init(s
->window
, 5.0, 256);
172 ff_dsputil_init(&s
->dsp
, avctx
);
173 avpriv_float_dsp_init(&s
->fdsp
, avctx
->flags
& CODEC_FLAG_BITEXACT
);
174 ff_ac3dsp_init(&s
->ac3dsp
, avctx
->flags
& CODEC_FLAG_BITEXACT
);
175 ff_fmt_convert_init(&s
->fmt_conv
, avctx
);
176 av_lfg_init(&s
->dith_state
, 0);
178 avctx
->sample_fmt
= AV_SAMPLE_FMT_FLTP
;
180 /* allow downmixing to stereo or mono */
181 if (avctx
->channels
> 0 && avctx
->request_channels
> 0 &&
182 avctx
->request_channels
< avctx
->channels
&&
183 avctx
->request_channels
<= 2) {
184 avctx
->channels
= avctx
->request_channels
;
188 avcodec_get_frame_defaults(&s
->frame
);
189 avctx
->coded_frame
= &s
->frame
;
191 for (i
= 0; i
< AC3_MAX_CHANNELS
; i
++) {
192 s
->xcfptr
[i
] = s
->transform_coeffs
[i
];
193 s
->dlyptr
[i
] = s
->delay
[i
];
200 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
201 * GetBitContext within AC3DecodeContext must point to
202 * the start of the synchronized AC-3 bitstream.
204 static int ac3_parse_header(AC3DecodeContext
*s
)
206 GetBitContext
*gbc
= &s
->gbc
;
209 /* read the rest of the bsi. read twice for dual mono mode. */
210 i
= !s
->channel_mode
;
212 skip_bits(gbc
, 5); // skip dialog normalization
214 skip_bits(gbc
, 8); //skip compression
216 skip_bits(gbc
, 8); //skip language code
218 skip_bits(gbc
, 7); //skip audio production information
221 skip_bits(gbc
, 2); //skip copyright bit and original bitstream bit
223 /* skip the timecodes (or extra bitstream information for Alternate Syntax)
224 TODO: read & use the xbsi1 downmix levels */
226 skip_bits(gbc
, 14); //skip timecode1 / xbsi1
228 skip_bits(gbc
, 14); //skip timecode2 / xbsi2
230 /* skip additional bitstream info */
231 if (get_bits1(gbc
)) {
232 i
= get_bits(gbc
, 6);
242 * Common function to parse AC-3 or E-AC-3 frame header
244 static int parse_frame_header(AC3DecodeContext
*s
)
249 err
= avpriv_ac3_parse_header(&s
->gbc
, &hdr
);
253 /* get decoding parameters from header info */
254 s
->bit_alloc_params
.sr_code
= hdr
.sr_code
;
255 s
->bitstream_mode
= hdr
.bitstream_mode
;
256 s
->channel_mode
= hdr
.channel_mode
;
257 s
->channel_layout
= hdr
.channel_layout
;
258 s
->lfe_on
= hdr
.lfe_on
;
259 s
->bit_alloc_params
.sr_shift
= hdr
.sr_shift
;
260 s
->sample_rate
= hdr
.sample_rate
;
261 s
->bit_rate
= hdr
.bit_rate
;
262 s
->channels
= hdr
.channels
;
263 s
->fbw_channels
= s
->channels
- s
->lfe_on
;
264 s
->lfe_ch
= s
->fbw_channels
+ 1;
265 s
->frame_size
= hdr
.frame_size
;
266 s
->center_mix_level
= hdr
.center_mix_level
;
267 s
->surround_mix_level
= hdr
.surround_mix_level
;
268 s
->num_blocks
= hdr
.num_blocks
;
269 s
->frame_type
= hdr
.frame_type
;
270 s
->substreamid
= hdr
.substreamid
;
273 s
->start_freq
[s
->lfe_ch
] = 0;
274 s
->end_freq
[s
->lfe_ch
] = 7;
275 s
->num_exp_groups
[s
->lfe_ch
] = 2;
276 s
->channel_in_cpl
[s
->lfe_ch
] = 0;
279 if (hdr
.bitstream_id
<= 10) {
281 s
->snr_offset_strategy
= 2;
282 s
->block_switch_syntax
= 1;
283 s
->dither_flag_syntax
= 1;
284 s
->bit_allocation_syntax
= 1;
285 s
->fast_gain_syntax
= 0;
286 s
->first_cpl_leak
= 0;
289 memset(s
->channel_uses_aht
, 0, sizeof(s
->channel_uses_aht
));
290 return ac3_parse_header(s
);
291 } else if (CONFIG_EAC3_DECODER
) {
293 return ff_eac3_parse_header(s
);
295 av_log(s
->avctx
, AV_LOG_ERROR
, "E-AC-3 support not compiled in\n");
301 * Set stereo downmixing coefficients based on frame header info.
302 * reference: Section 7.8.2 Downmixing Into Two Channels
304 static void set_downmix_coeffs(AC3DecodeContext
*s
)
307 float cmix
= gain_levels
[s
-> center_mix_level
];
308 float smix
= gain_levels
[s
->surround_mix_level
];
311 for (i
= 0; i
< s
->fbw_channels
; i
++) {
312 s
->downmix_coeffs
[i
][0] = gain_levels
[ac3_default_coeffs
[s
->channel_mode
][i
][0]];
313 s
->downmix_coeffs
[i
][1] = gain_levels
[ac3_default_coeffs
[s
->channel_mode
][i
][1]];
315 if (s
->channel_mode
> 1 && s
->channel_mode
& 1) {
316 s
->downmix_coeffs
[1][0] = s
->downmix_coeffs
[1][1] = cmix
;
318 if (s
->channel_mode
== AC3_CHMODE_2F1R
|| s
->channel_mode
== AC3_CHMODE_3F1R
) {
319 int nf
= s
->channel_mode
- 2;
320 s
->downmix_coeffs
[nf
][0] = s
->downmix_coeffs
[nf
][1] = smix
* LEVEL_MINUS_3DB
;
322 if (s
->channel_mode
== AC3_CHMODE_2F2R
|| s
->channel_mode
== AC3_CHMODE_3F2R
) {
323 int nf
= s
->channel_mode
- 4;
324 s
->downmix_coeffs
[nf
][0] = s
->downmix_coeffs
[nf
+1][1] = smix
;
329 for (i
= 0; i
< s
->fbw_channels
; i
++) {
330 norm0
+= s
->downmix_coeffs
[i
][0];
331 norm1
+= s
->downmix_coeffs
[i
][1];
333 norm0
= 1.0f
/ norm0
;
334 norm1
= 1.0f
/ norm1
;
335 for (i
= 0; i
< s
->fbw_channels
; i
++) {
336 s
->downmix_coeffs
[i
][0] *= norm0
;
337 s
->downmix_coeffs
[i
][1] *= norm1
;
340 if (s
->output_mode
== AC3_CHMODE_MONO
) {
341 for (i
= 0; i
< s
->fbw_channels
; i
++)
342 s
->downmix_coeffs
[i
][0] = (s
->downmix_coeffs
[i
][0] +
343 s
->downmix_coeffs
[i
][1]) * LEVEL_MINUS_3DB
;
348 * Decode the grouped exponents according to exponent strategy.
349 * reference: Section 7.1.3 Exponent Decoding
351 static int decode_exponents(GetBitContext
*gbc
, int exp_strategy
, int ngrps
,
352 uint8_t absexp
, int8_t *dexps
)
354 int i
, j
, grp
, group_size
;
359 group_size
= exp_strategy
+ (exp_strategy
== EXP_D45
);
360 for (grp
= 0, i
= 0; grp
< ngrps
; grp
++) {
361 expacc
= get_bits(gbc
, 7);
362 dexp
[i
++] = ungroup_3_in_7_bits_tab
[expacc
][0];
363 dexp
[i
++] = ungroup_3_in_7_bits_tab
[expacc
][1];
364 dexp
[i
++] = ungroup_3_in_7_bits_tab
[expacc
][2];
367 /* convert to absolute exps and expand groups */
369 for (i
= 0, j
= 0; i
< ngrps
* 3; i
++) {
370 prevexp
+= dexp
[i
] - 2;
373 switch (group_size
) {
374 case 4: dexps
[j
++] = prevexp
;
375 dexps
[j
++] = prevexp
;
376 case 2: dexps
[j
++] = prevexp
;
377 case 1: dexps
[j
++] = prevexp
;
384 * Generate transform coefficients for each coupled channel in the coupling
385 * range using the coupling coefficients and coupling coordinates.
386 * reference: Section 7.4.3 Coupling Coordinate Format
388 static void calc_transform_coeffs_cpl(AC3DecodeContext
*s
)
392 bin
= s
->start_freq
[CPL_CH
];
393 for (band
= 0; band
< s
->num_cpl_bands
; band
++) {
394 int band_start
= bin
;
395 int band_end
= bin
+ s
->cpl_band_sizes
[band
];
396 for (ch
= 1; ch
<= s
->fbw_channels
; ch
++) {
397 if (s
->channel_in_cpl
[ch
]) {
398 int cpl_coord
= s
->cpl_coords
[ch
][band
] << 5;
399 for (bin
= band_start
; bin
< band_end
; bin
++) {
400 s
->fixed_coeffs
[ch
][bin
] =
401 MULH(s
->fixed_coeffs
[CPL_CH
][bin
] << 4, cpl_coord
);
403 if (ch
== 2 && s
->phase_flags
[band
]) {
404 for (bin
= band_start
; bin
< band_end
; bin
++)
405 s
->fixed_coeffs
[2][bin
] = -s
->fixed_coeffs
[2][bin
];
414 * Grouped mantissas for 3-level 5-level and 11-level quantization
426 * Decode the transform coefficients for a particular channel
427 * reference: Section 7.3 Quantization and Decoding of Mantissas
429 static void ac3_decode_transform_coeffs_ch(AC3DecodeContext
*s
, int ch_index
, mant_groups
*m
)
431 int start_freq
= s
->start_freq
[ch_index
];
432 int end_freq
= s
->end_freq
[ch_index
];
433 uint8_t *baps
= s
->bap
[ch_index
];
434 int8_t *exps
= s
->dexps
[ch_index
];
435 int *coeffs
= s
->fixed_coeffs
[ch_index
];
436 int dither
= (ch_index
== CPL_CH
) || s
->dither_flag
[ch_index
];
437 GetBitContext
*gbc
= &s
->gbc
;
440 for (freq
= start_freq
; freq
< end_freq
; freq
++) {
441 int bap
= baps
[freq
];
445 /* random noise with approximate range of -0.707 to 0.707 */
447 mantissa
= (av_lfg_get(&s
->dith_state
) / 362) - 5932275;
454 mantissa
= m
->b1_mant
[m
->b1
];
456 int bits
= get_bits(gbc
, 5);
457 mantissa
= b1_mantissas
[bits
][0];
458 m
->b1_mant
[1] = b1_mantissas
[bits
][1];
459 m
->b1_mant
[0] = b1_mantissas
[bits
][2];
466 mantissa
= m
->b2_mant
[m
->b2
];
468 int bits
= get_bits(gbc
, 7);
469 mantissa
= b2_mantissas
[bits
][0];
470 m
->b2_mant
[1] = b2_mantissas
[bits
][1];
471 m
->b2_mant
[0] = b2_mantissas
[bits
][2];
476 mantissa
= b3_mantissas
[get_bits(gbc
, 3)];
481 mantissa
= m
->b4_mant
;
483 int bits
= get_bits(gbc
, 7);
484 mantissa
= b4_mantissas
[bits
][0];
485 m
->b4_mant
= b4_mantissas
[bits
][1];
490 mantissa
= b5_mantissas
[get_bits(gbc
, 4)];
492 default: /* 6 to 15 */
493 /* Shift mantissa and sign-extend it. */
494 mantissa
= get_sbits(gbc
, quantization_tab
[bap
]);
495 mantissa
<<= 24 - quantization_tab
[bap
];
498 coeffs
[freq
] = mantissa
>> exps
[freq
];
503 * Remove random dithering from coupling range coefficients with zero-bit
504 * mantissas for coupled channels which do not use dithering.
505 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
507 static void remove_dithering(AC3DecodeContext
*s
) {
510 for (ch
= 1; ch
<= s
->fbw_channels
; ch
++) {
511 if (!s
->dither_flag
[ch
] && s
->channel_in_cpl
[ch
]) {
512 for (i
= s
->start_freq
[CPL_CH
]; i
< s
->end_freq
[CPL_CH
]; i
++) {
513 if (!s
->bap
[CPL_CH
][i
])
514 s
->fixed_coeffs
[ch
][i
] = 0;
520 static void decode_transform_coeffs_ch(AC3DecodeContext
*s
, int blk
, int ch
,
523 if (!s
->channel_uses_aht
[ch
]) {
524 ac3_decode_transform_coeffs_ch(s
, ch
, m
);
526 /* if AHT is used, mantissas for all blocks are encoded in the first
527 block of the frame. */
529 if (!blk
&& CONFIG_EAC3_DECODER
)
530 ff_eac3_decode_transform_coeffs_aht_ch(s
, ch
);
531 for (bin
= s
->start_freq
[ch
]; bin
< s
->end_freq
[ch
]; bin
++) {
532 s
->fixed_coeffs
[ch
][bin
] = s
->pre_mantissa
[ch
][bin
][blk
] >> s
->dexps
[ch
][bin
];
538 * Decode the transform coefficients.
540 static void decode_transform_coeffs(AC3DecodeContext
*s
, int blk
)
546 m
.b1
= m
.b2
= m
.b4
= 0;
548 for (ch
= 1; ch
<= s
->channels
; ch
++) {
549 /* transform coefficients for full-bandwidth channel */
550 decode_transform_coeffs_ch(s
, blk
, ch
, &m
);
551 /* transform coefficients for coupling channel come right after the
552 coefficients for the first coupled channel*/
553 if (s
->channel_in_cpl
[ch
]) {
555 decode_transform_coeffs_ch(s
, blk
, CPL_CH
, &m
);
556 calc_transform_coeffs_cpl(s
);
559 end
= s
->end_freq
[CPL_CH
];
561 end
= s
->end_freq
[ch
];
564 s
->fixed_coeffs
[ch
][end
] = 0;
568 /* zero the dithered coefficients for appropriate channels */
573 * Stereo rematrixing.
574 * reference: Section 7.5.4 Rematrixing : Decoding Technique
576 static void do_rematrixing(AC3DecodeContext
*s
)
581 end
= FFMIN(s
->end_freq
[1], s
->end_freq
[2]);
583 for (bnd
= 0; bnd
< s
->num_rematrixing_bands
; bnd
++) {
584 if (s
->rematrixing_flags
[bnd
]) {
585 bndend
= FFMIN(end
, ff_ac3_rematrix_band_tab
[bnd
+ 1]);
586 for (i
= ff_ac3_rematrix_band_tab
[bnd
]; i
< bndend
; i
++) {
587 int tmp0
= s
->fixed_coeffs
[1][i
];
588 s
->fixed_coeffs
[1][i
] += s
->fixed_coeffs
[2][i
];
589 s
->fixed_coeffs
[2][i
] = tmp0
- s
->fixed_coeffs
[2][i
];
596 * Inverse MDCT Transform.
597 * Convert frequency domain coefficients to time-domain audio samples.
598 * reference: Section 7.9.4 Transformation Equations
600 static inline void do_imdct(AC3DecodeContext
*s
, int channels
)
604 for (ch
= 1; ch
<= channels
; ch
++) {
605 if (s
->block_switch
[ch
]) {
607 float *x
= s
->tmp_output
+ 128;
608 for (i
= 0; i
< 128; i
++)
609 x
[i
] = s
->transform_coeffs
[ch
][2 * i
];
610 s
->imdct_256
.imdct_half(&s
->imdct_256
, s
->tmp_output
, x
);
611 s
->fdsp
.vector_fmul_window(s
->outptr
[ch
- 1], s
->delay
[ch
- 1],
612 s
->tmp_output
, s
->window
, 128);
613 for (i
= 0; i
< 128; i
++)
614 x
[i
] = s
->transform_coeffs
[ch
][2 * i
+ 1];
615 s
->imdct_256
.imdct_half(&s
->imdct_256
, s
->delay
[ch
- 1], x
);
617 s
->imdct_512
.imdct_half(&s
->imdct_512
, s
->tmp_output
, s
->transform_coeffs
[ch
]);
618 s
->fdsp
.vector_fmul_window(s
->outptr
[ch
- 1], s
->delay
[ch
- 1],
619 s
->tmp_output
, s
->window
, 128);
620 memcpy(s
->delay
[ch
- 1], s
->tmp_output
+ 128, 128 * sizeof(float));
626 * Upmix delay samples from stereo to original channel layout.
628 static void ac3_upmix_delay(AC3DecodeContext
*s
)
630 int channel_data_size
= sizeof(s
->delay
[0]);
631 switch (s
->channel_mode
) {
632 case AC3_CHMODE_DUALMONO
:
633 case AC3_CHMODE_STEREO
:
634 /* upmix mono to stereo */
635 memcpy(s
->delay
[1], s
->delay
[0], channel_data_size
);
637 case AC3_CHMODE_2F2R
:
638 memset(s
->delay
[3], 0, channel_data_size
);
639 case AC3_CHMODE_2F1R
:
640 memset(s
->delay
[2], 0, channel_data_size
);
642 case AC3_CHMODE_3F2R
:
643 memset(s
->delay
[4], 0, channel_data_size
);
644 case AC3_CHMODE_3F1R
:
645 memset(s
->delay
[3], 0, channel_data_size
);
647 memcpy(s
->delay
[2], s
->delay
[1], channel_data_size
);
648 memset(s
->delay
[1], 0, channel_data_size
);
654 * Decode band structure for coupling, spectral extension, or enhanced coupling.
655 * The band structure defines how many subbands are in each band. For each
656 * subband in the range, 1 means it is combined with the previous band, and 0
657 * means that it starts a new band.
659 * @param[in] gbc bit reader context
660 * @param[in] blk block number
661 * @param[in] eac3 flag to indicate E-AC-3
662 * @param[in] ecpl flag to indicate enhanced coupling
663 * @param[in] start_subband subband number for start of range
664 * @param[in] end_subband subband number for end of range
665 * @param[in] default_band_struct default band structure table
666 * @param[out] num_bands number of bands (optionally NULL)
667 * @param[out] band_sizes array containing the number of bins in each band (optionally NULL)
669 static void decode_band_structure(GetBitContext
*gbc
, int blk
, int eac3
,
670 int ecpl
, int start_subband
, int end_subband
,
671 const uint8_t *default_band_struct
,
672 int *num_bands
, uint8_t *band_sizes
)
674 int subbnd
, bnd
, n_subbands
, n_bands
=0;
676 uint8_t coded_band_struct
[22];
677 const uint8_t *band_struct
;
679 n_subbands
= end_subband
- start_subband
;
681 /* decode band structure from bitstream or use default */
682 if (!eac3
|| get_bits1(gbc
)) {
683 for (subbnd
= 0; subbnd
< n_subbands
- 1; subbnd
++) {
684 coded_band_struct
[subbnd
] = get_bits1(gbc
);
686 band_struct
= coded_band_struct
;
688 band_struct
= &default_band_struct
[start_subband
+1];
690 /* no change in band structure */
694 /* calculate number of bands and band sizes based on band structure.
695 note that the first 4 subbands in enhanced coupling span only 6 bins
697 if (num_bands
|| band_sizes
) {
698 n_bands
= n_subbands
;
699 bnd_sz
[0] = ecpl
? 6 : 12;
700 for (bnd
= 0, subbnd
= 1; subbnd
< n_subbands
; subbnd
++) {
701 int subbnd_size
= (ecpl
&& subbnd
< 4) ? 6 : 12;
702 if (band_struct
[subbnd
- 1]) {
704 bnd_sz
[bnd
] += subbnd_size
;
706 bnd_sz
[++bnd
] = subbnd_size
;
711 /* set optional output params */
713 *num_bands
= n_bands
;
715 memcpy(band_sizes
, bnd_sz
, n_bands
);
719 * Decode a single audio block from the AC-3 bitstream.
721 static int decode_audio_block(AC3DecodeContext
*s
, int blk
)
723 int fbw_channels
= s
->fbw_channels
;
724 int channel_mode
= s
->channel_mode
;
726 int different_transforms
;
729 GetBitContext
*gbc
= &s
->gbc
;
730 uint8_t bit_alloc_stages
[AC3_MAX_CHANNELS
] = { 0 };
732 /* block switch flags */
733 different_transforms
= 0;
734 if (s
->block_switch_syntax
) {
735 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
736 s
->block_switch
[ch
] = get_bits1(gbc
);
737 if (ch
> 1 && s
->block_switch
[ch
] != s
->block_switch
[1])
738 different_transforms
= 1;
742 /* dithering flags */
743 if (s
->dither_flag_syntax
) {
744 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
745 s
->dither_flag
[ch
] = get_bits1(gbc
);
750 i
= !s
->channel_mode
;
752 if (get_bits1(gbc
)) {
753 s
->dynamic_range
[i
] = ((dynamic_range_tab
[get_bits(gbc
, 8)] - 1.0) *
755 } else if (blk
== 0) {
756 s
->dynamic_range
[i
] = 1.0f
;
760 /* spectral extension strategy */
761 if (s
->eac3
&& (!blk
|| get_bits1(gbc
))) {
762 s
->spx_in_use
= get_bits1(gbc
);
764 int dst_start_freq
, dst_end_freq
, src_start_freq
,
765 start_subband
, end_subband
;
767 /* determine which channels use spx */
768 if (s
->channel_mode
== AC3_CHMODE_MONO
) {
769 s
->channel_uses_spx
[1] = 1;
771 for (ch
= 1; ch
<= fbw_channels
; ch
++)
772 s
->channel_uses_spx
[ch
] = get_bits1(gbc
);
775 /* get the frequency bins of the spx copy region and the spx start
777 dst_start_freq
= get_bits(gbc
, 2);
778 start_subband
= get_bits(gbc
, 3) + 2;
779 if (start_subband
> 7)
780 start_subband
+= start_subband
- 7;
781 end_subband
= get_bits(gbc
, 3) + 5;
783 end_subband
+= end_subband
- 7;
784 dst_start_freq
= dst_start_freq
* 12 + 25;
785 src_start_freq
= start_subband
* 12 + 25;
786 dst_end_freq
= end_subband
* 12 + 25;
788 /* check validity of spx ranges */
789 if (start_subband
>= end_subband
) {
790 av_log(s
->avctx
, AV_LOG_ERROR
, "invalid spectral extension "
791 "range (%d >= %d)\n", start_subband
, end_subband
);
794 if (dst_start_freq
>= src_start_freq
) {
795 av_log(s
->avctx
, AV_LOG_ERROR
, "invalid spectral extension "
796 "copy start bin (%d >= %d)\n", dst_start_freq
, src_start_freq
);
800 s
->spx_dst_start_freq
= dst_start_freq
;
801 s
->spx_src_start_freq
= src_start_freq
;
802 s
->spx_dst_end_freq
= dst_end_freq
;
804 decode_band_structure(gbc
, blk
, s
->eac3
, 0,
805 start_subband
, end_subband
,
806 ff_eac3_default_spx_band_struct
,
810 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
811 s
->channel_uses_spx
[ch
] = 0;
812 s
->first_spx_coords
[ch
] = 1;
817 /* spectral extension coordinates */
819 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
820 if (s
->channel_uses_spx
[ch
]) {
821 if (s
->first_spx_coords
[ch
] || get_bits1(gbc
)) {
823 int bin
, master_spx_coord
;
825 s
->first_spx_coords
[ch
] = 0;
826 spx_blend
= get_bits(gbc
, 5) * (1.0f
/32);
827 master_spx_coord
= get_bits(gbc
, 2) * 3;
829 bin
= s
->spx_src_start_freq
;
830 for (bnd
= 0; bnd
< s
->num_spx_bands
; bnd
++) {
832 int spx_coord_exp
, spx_coord_mant
;
833 float nratio
, sblend
, nblend
, spx_coord
;
835 /* calculate blending factors */
836 bandsize
= s
->spx_band_sizes
[bnd
];
837 nratio
= ((float)((bin
+ (bandsize
>> 1))) / s
->spx_dst_end_freq
) - spx_blend
;
838 nratio
= av_clipf(nratio
, 0.0f
, 1.0f
);
839 nblend
= sqrtf(3.0f
* nratio
); // noise is scaled by sqrt(3)
840 // to give unity variance
841 sblend
= sqrtf(1.0f
- nratio
);
844 /* decode spx coordinates */
845 spx_coord_exp
= get_bits(gbc
, 4);
846 spx_coord_mant
= get_bits(gbc
, 2);
847 if (spx_coord_exp
== 15) spx_coord_mant
<<= 1;
848 else spx_coord_mant
+= 4;
849 spx_coord_mant
<<= (25 - spx_coord_exp
- master_spx_coord
);
850 spx_coord
= spx_coord_mant
* (1.0f
/ (1 << 23));
852 /* multiply noise and signal blending factors by spx coordinate */
853 s
->spx_noise_blend
[ch
][bnd
] = nblend
* spx_coord
;
854 s
->spx_signal_blend
[ch
][bnd
] = sblend
* spx_coord
;
858 s
->first_spx_coords
[ch
] = 1;
863 /* coupling strategy */
864 if (s
->eac3
? s
->cpl_strategy_exists
[blk
] : get_bits1(gbc
)) {
865 memset(bit_alloc_stages
, 3, AC3_MAX_CHANNELS
);
867 s
->cpl_in_use
[blk
] = get_bits1(gbc
);
868 if (s
->cpl_in_use
[blk
]) {
869 /* coupling in use */
870 int cpl_start_subband
, cpl_end_subband
;
872 if (channel_mode
< AC3_CHMODE_STEREO
) {
873 av_log(s
->avctx
, AV_LOG_ERROR
, "coupling not allowed in mono or dual-mono\n");
877 /* check for enhanced coupling */
878 if (s
->eac3
&& get_bits1(gbc
)) {
879 /* TODO: parse enhanced coupling strategy info */
880 av_log_missing_feature(s
->avctx
, "Enhanced coupling", 1);
881 return AVERROR_PATCHWELCOME
;
884 /* determine which channels are coupled */
885 if (s
->eac3
&& s
->channel_mode
== AC3_CHMODE_STEREO
) {
886 s
->channel_in_cpl
[1] = 1;
887 s
->channel_in_cpl
[2] = 1;
889 for (ch
= 1; ch
<= fbw_channels
; ch
++)
890 s
->channel_in_cpl
[ch
] = get_bits1(gbc
);
893 /* phase flags in use */
894 if (channel_mode
== AC3_CHMODE_STEREO
)
895 s
->phase_flags_in_use
= get_bits1(gbc
);
897 /* coupling frequency range */
898 cpl_start_subband
= get_bits(gbc
, 4);
899 cpl_end_subband
= s
->spx_in_use
? (s
->spx_src_start_freq
- 37) / 12 :
900 get_bits(gbc
, 4) + 3;
901 if (cpl_start_subband
>= cpl_end_subband
) {
902 av_log(s
->avctx
, AV_LOG_ERROR
, "invalid coupling range (%d >= %d)\n",
903 cpl_start_subband
, cpl_end_subband
);
906 s
->start_freq
[CPL_CH
] = cpl_start_subband
* 12 + 37;
907 s
->end_freq
[CPL_CH
] = cpl_end_subband
* 12 + 37;
909 decode_band_structure(gbc
, blk
, s
->eac3
, 0, cpl_start_subband
,
911 ff_eac3_default_cpl_band_struct
,
912 &s
->num_cpl_bands
, s
->cpl_band_sizes
);
914 /* coupling not in use */
915 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
916 s
->channel_in_cpl
[ch
] = 0;
917 s
->first_cpl_coords
[ch
] = 1;
919 s
->first_cpl_leak
= s
->eac3
;
920 s
->phase_flags_in_use
= 0;
922 } else if (!s
->eac3
) {
924 av_log(s
->avctx
, AV_LOG_ERROR
, "new coupling strategy must "
925 "be present in block 0\n");
928 s
->cpl_in_use
[blk
] = s
->cpl_in_use
[blk
-1];
931 cpl_in_use
= s
->cpl_in_use
[blk
];
933 /* coupling coordinates */
935 int cpl_coords_exist
= 0;
937 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
938 if (s
->channel_in_cpl
[ch
]) {
939 if ((s
->eac3
&& s
->first_cpl_coords
[ch
]) || get_bits1(gbc
)) {
940 int master_cpl_coord
, cpl_coord_exp
, cpl_coord_mant
;
941 s
->first_cpl_coords
[ch
] = 0;
942 cpl_coords_exist
= 1;
943 master_cpl_coord
= 3 * get_bits(gbc
, 2);
944 for (bnd
= 0; bnd
< s
->num_cpl_bands
; bnd
++) {
945 cpl_coord_exp
= get_bits(gbc
, 4);
946 cpl_coord_mant
= get_bits(gbc
, 4);
947 if (cpl_coord_exp
== 15)
948 s
->cpl_coords
[ch
][bnd
] = cpl_coord_mant
<< 22;
950 s
->cpl_coords
[ch
][bnd
] = (cpl_coord_mant
+ 16) << 21;
951 s
->cpl_coords
[ch
][bnd
] >>= (cpl_coord_exp
+ master_cpl_coord
);
954 av_log(s
->avctx
, AV_LOG_ERROR
, "new coupling coordinates must "
955 "be present in block 0\n");
959 /* channel not in coupling */
960 s
->first_cpl_coords
[ch
] = 1;
964 if (channel_mode
== AC3_CHMODE_STEREO
&& cpl_coords_exist
) {
965 for (bnd
= 0; bnd
< s
->num_cpl_bands
; bnd
++) {
966 s
->phase_flags
[bnd
] = s
->phase_flags_in_use
? get_bits1(gbc
) : 0;
971 /* stereo rematrixing strategy and band structure */
972 if (channel_mode
== AC3_CHMODE_STEREO
) {
973 if ((s
->eac3
&& !blk
) || get_bits1(gbc
)) {
974 s
->num_rematrixing_bands
= 4;
975 if (cpl_in_use
&& s
->start_freq
[CPL_CH
] <= 61) {
976 s
->num_rematrixing_bands
-= 1 + (s
->start_freq
[CPL_CH
] == 37);
977 } else if (s
->spx_in_use
&& s
->spx_src_start_freq
<= 61) {
978 s
->num_rematrixing_bands
--;
980 for (bnd
= 0; bnd
< s
->num_rematrixing_bands
; bnd
++)
981 s
->rematrixing_flags
[bnd
] = get_bits1(gbc
);
983 av_log(s
->avctx
, AV_LOG_WARNING
, "Warning: "
984 "new rematrixing strategy not present in block 0\n");
985 s
->num_rematrixing_bands
= 0;
989 /* exponent strategies for each channel */
990 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++) {
992 s
->exp_strategy
[blk
][ch
] = get_bits(gbc
, 2 - (ch
== s
->lfe_ch
));
993 if (s
->exp_strategy
[blk
][ch
] != EXP_REUSE
)
994 bit_alloc_stages
[ch
] = 3;
997 /* channel bandwidth */
998 for (ch
= 1; ch
<= fbw_channels
; ch
++) {
999 s
->start_freq
[ch
] = 0;
1000 if (s
->exp_strategy
[blk
][ch
] != EXP_REUSE
) {
1002 int prev
= s
->end_freq
[ch
];
1003 if (s
->channel_in_cpl
[ch
])
1004 s
->end_freq
[ch
] = s
->start_freq
[CPL_CH
];
1005 else if (s
->channel_uses_spx
[ch
])
1006 s
->end_freq
[ch
] = s
->spx_src_start_freq
;
1008 int bandwidth_code
= get_bits(gbc
, 6);
1009 if (bandwidth_code
> 60) {
1010 av_log(s
->avctx
, AV_LOG_ERROR
, "bandwidth code = %d > 60\n", bandwidth_code
);
1013 s
->end_freq
[ch
] = bandwidth_code
* 3 + 73;
1015 group_size
= 3 << (s
->exp_strategy
[blk
][ch
] - 1);
1016 s
->num_exp_groups
[ch
] = (s
->end_freq
[ch
] + group_size
-4) / group_size
;
1017 if (blk
> 0 && s
->end_freq
[ch
] != prev
)
1018 memset(bit_alloc_stages
, 3, AC3_MAX_CHANNELS
);
1021 if (cpl_in_use
&& s
->exp_strategy
[blk
][CPL_CH
] != EXP_REUSE
) {
1022 s
->num_exp_groups
[CPL_CH
] = (s
->end_freq
[CPL_CH
] - s
->start_freq
[CPL_CH
]) /
1023 (3 << (s
->exp_strategy
[blk
][CPL_CH
] - 1));
1026 /* decode exponents for each channel */
1027 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++) {
1028 if (s
->exp_strategy
[blk
][ch
] != EXP_REUSE
) {
1029 s
->dexps
[ch
][0] = get_bits(gbc
, 4) << !ch
;
1030 if (decode_exponents(gbc
, s
->exp_strategy
[blk
][ch
],
1031 s
->num_exp_groups
[ch
], s
->dexps
[ch
][0],
1032 &s
->dexps
[ch
][s
->start_freq
[ch
]+!!ch
])) {
1033 av_log(s
->avctx
, AV_LOG_ERROR
, "exponent out-of-range\n");
1036 if (ch
!= CPL_CH
&& ch
!= s
->lfe_ch
)
1037 skip_bits(gbc
, 2); /* skip gainrng */
1041 /* bit allocation information */
1042 if (s
->bit_allocation_syntax
) {
1043 if (get_bits1(gbc
)) {
1044 s
->bit_alloc_params
.slow_decay
= ff_ac3_slow_decay_tab
[get_bits(gbc
, 2)] >> s
->bit_alloc_params
.sr_shift
;
1045 s
->bit_alloc_params
.fast_decay
= ff_ac3_fast_decay_tab
[get_bits(gbc
, 2)] >> s
->bit_alloc_params
.sr_shift
;
1046 s
->bit_alloc_params
.slow_gain
= ff_ac3_slow_gain_tab
[get_bits(gbc
, 2)];
1047 s
->bit_alloc_params
.db_per_bit
= ff_ac3_db_per_bit_tab
[get_bits(gbc
, 2)];
1048 s
->bit_alloc_params
.floor
= ff_ac3_floor_tab
[get_bits(gbc
, 3)];
1049 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++)
1050 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 2);
1052 av_log(s
->avctx
, AV_LOG_ERROR
, "new bit allocation info must "
1053 "be present in block 0\n");
1058 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
1059 if (!s
->eac3
|| !blk
) {
1060 if (s
->snr_offset_strategy
&& get_bits1(gbc
)) {
1063 csnr
= (get_bits(gbc
, 6) - 15) << 4;
1064 for (i
= ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++) {
1066 if (ch
== i
|| s
->snr_offset_strategy
== 2)
1067 snr
= (csnr
+ get_bits(gbc
, 4)) << 2;
1068 /* run at least last bit allocation stage if snr offset changes */
1069 if (blk
&& s
->snr_offset
[ch
] != snr
) {
1070 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 1);
1072 s
->snr_offset
[ch
] = snr
;
1074 /* fast gain (normal AC-3 only) */
1076 int prev
= s
->fast_gain
[ch
];
1077 s
->fast_gain
[ch
] = ff_ac3_fast_gain_tab
[get_bits(gbc
, 3)];
1078 /* run last 2 bit allocation stages if fast gain changes */
1079 if (blk
&& prev
!= s
->fast_gain
[ch
])
1080 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 2);
1083 } else if (!s
->eac3
&& !blk
) {
1084 av_log(s
->avctx
, AV_LOG_ERROR
, "new snr offsets must be present in block 0\n");
1089 /* fast gain (E-AC-3 only) */
1090 if (s
->fast_gain_syntax
&& get_bits1(gbc
)) {
1091 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++) {
1092 int prev
= s
->fast_gain
[ch
];
1093 s
->fast_gain
[ch
] = ff_ac3_fast_gain_tab
[get_bits(gbc
, 3)];
1094 /* run last 2 bit allocation stages if fast gain changes */
1095 if (blk
&& prev
!= s
->fast_gain
[ch
])
1096 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 2);
1098 } else if (s
->eac3
&& !blk
) {
1099 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++)
1100 s
->fast_gain
[ch
] = ff_ac3_fast_gain_tab
[4];
1103 /* E-AC-3 to AC-3 converter SNR offset */
1104 if (s
->frame_type
== EAC3_FRAME_TYPE_INDEPENDENT
&& get_bits1(gbc
)) {
1105 skip_bits(gbc
, 10); // skip converter snr offset
1108 /* coupling leak information */
1110 if (s
->first_cpl_leak
|| get_bits1(gbc
)) {
1111 int fl
= get_bits(gbc
, 3);
1112 int sl
= get_bits(gbc
, 3);
1113 /* run last 2 bit allocation stages for coupling channel if
1114 coupling leak changes */
1115 if (blk
&& (fl
!= s
->bit_alloc_params
.cpl_fast_leak
||
1116 sl
!= s
->bit_alloc_params
.cpl_slow_leak
)) {
1117 bit_alloc_stages
[CPL_CH
] = FFMAX(bit_alloc_stages
[CPL_CH
], 2);
1119 s
->bit_alloc_params
.cpl_fast_leak
= fl
;
1120 s
->bit_alloc_params
.cpl_slow_leak
= sl
;
1121 } else if (!s
->eac3
&& !blk
) {
1122 av_log(s
->avctx
, AV_LOG_ERROR
, "new coupling leak info must "
1123 "be present in block 0\n");
1126 s
->first_cpl_leak
= 0;
1129 /* delta bit allocation information */
1130 if (s
->dba_syntax
&& get_bits1(gbc
)) {
1131 /* delta bit allocation exists (strategy) */
1132 for (ch
= !cpl_in_use
; ch
<= fbw_channels
; ch
++) {
1133 s
->dba_mode
[ch
] = get_bits(gbc
, 2);
1134 if (s
->dba_mode
[ch
] == DBA_RESERVED
) {
1135 av_log(s
->avctx
, AV_LOG_ERROR
, "delta bit allocation strategy reserved\n");
1138 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 2);
1140 /* channel delta offset, len and bit allocation */
1141 for (ch
= !cpl_in_use
; ch
<= fbw_channels
; ch
++) {
1142 if (s
->dba_mode
[ch
] == DBA_NEW
) {
1143 s
->dba_nsegs
[ch
] = get_bits(gbc
, 3) + 1;
1144 for (seg
= 0; seg
< s
->dba_nsegs
[ch
]; seg
++) {
1145 s
->dba_offsets
[ch
][seg
] = get_bits(gbc
, 5);
1146 s
->dba_lengths
[ch
][seg
] = get_bits(gbc
, 4);
1147 s
->dba_values
[ch
][seg
] = get_bits(gbc
, 3);
1149 /* run last 2 bit allocation stages if new dba values */
1150 bit_alloc_stages
[ch
] = FFMAX(bit_alloc_stages
[ch
], 2);
1153 } else if (blk
== 0) {
1154 for (ch
= 0; ch
<= s
->channels
; ch
++) {
1155 s
->dba_mode
[ch
] = DBA_NONE
;
1159 /* Bit allocation */
1160 for (ch
= !cpl_in_use
; ch
<= s
->channels
; ch
++) {
1161 if (bit_alloc_stages
[ch
] > 2) {
1162 /* Exponent mapping into PSD and PSD integration */
1163 ff_ac3_bit_alloc_calc_psd(s
->dexps
[ch
],
1164 s
->start_freq
[ch
], s
->end_freq
[ch
],
1165 s
->psd
[ch
], s
->band_psd
[ch
]);
1167 if (bit_alloc_stages
[ch
] > 1) {
1168 /* Compute excitation function, Compute masking curve, and
1169 Apply delta bit allocation */
1170 if (ff_ac3_bit_alloc_calc_mask(&s
->bit_alloc_params
, s
->band_psd
[ch
],
1171 s
->start_freq
[ch
], s
->end_freq
[ch
],
1172 s
->fast_gain
[ch
], (ch
== s
->lfe_ch
),
1173 s
->dba_mode
[ch
], s
->dba_nsegs
[ch
],
1174 s
->dba_offsets
[ch
], s
->dba_lengths
[ch
],
1175 s
->dba_values
[ch
], s
->mask
[ch
])) {
1176 av_log(s
->avctx
, AV_LOG_ERROR
, "error in bit allocation\n");
1180 if (bit_alloc_stages
[ch
] > 0) {
1181 /* Compute bit allocation */
1182 const uint8_t *bap_tab
= s
->channel_uses_aht
[ch
] ?
1183 ff_eac3_hebap_tab
: ff_ac3_bap_tab
;
1184 s
->ac3dsp
.bit_alloc_calc_bap(s
->mask
[ch
], s
->psd
[ch
],
1185 s
->start_freq
[ch
], s
->end_freq
[ch
],
1187 s
->bit_alloc_params
.floor
,
1188 bap_tab
, s
->bap
[ch
]);
1192 /* unused dummy data */
1193 if (s
->skip_syntax
&& get_bits1(gbc
)) {
1194 int skipl
= get_bits(gbc
, 9);
1199 /* unpack the transform coefficients
1200 this also uncouples channels if coupling is in use. */
1201 decode_transform_coeffs(s
, blk
);
1203 /* TODO: generate enhanced coupling coordinates and uncouple */
1205 /* recover coefficients if rematrixing is in use */
1206 if (s
->channel_mode
== AC3_CHMODE_STEREO
)
1209 /* apply scaling to coefficients (headroom, dynrng) */
1210 for (ch
= 1; ch
<= s
->channels
; ch
++) {
1211 float gain
= 1.0 / 4194304.0f
;
1212 if (s
->channel_mode
== AC3_CHMODE_DUALMONO
) {
1213 gain
*= s
->dynamic_range
[2 - ch
];
1215 gain
*= s
->dynamic_range
[0];
1217 s
->fmt_conv
.int32_to_float_fmul_scalar(s
->transform_coeffs
[ch
],
1218 s
->fixed_coeffs
[ch
], gain
, 256);
1221 /* apply spectral extension to high frequency bins */
1222 if (s
->spx_in_use
&& CONFIG_EAC3_DECODER
) {
1223 ff_eac3_apply_spectral_extension(s
);
1226 /* downmix and MDCT. order depends on whether block switching is used for
1227 any channel in this block. this is because coefficients for the long
1228 and short transforms cannot be mixed. */
1229 downmix_output
= s
->channels
!= s
->out_channels
&&
1230 !((s
->output_mode
& AC3_OUTPUT_LFEON
) &&
1231 s
->fbw_channels
== s
->out_channels
);
1232 if (different_transforms
) {
1233 /* the delay samples have already been downmixed, so we upmix the delay
1234 samples in order to reconstruct all channels before downmixing. */
1240 do_imdct(s
, s
->channels
);
1242 if (downmix_output
) {
1243 s
->ac3dsp
.downmix(s
->outptr
, s
->downmix_coeffs
,
1244 s
->out_channels
, s
->fbw_channels
, 256);
1247 if (downmix_output
) {
1248 s
->ac3dsp
.downmix(s
->xcfptr
+ 1, s
->downmix_coeffs
,
1249 s
->out_channels
, s
->fbw_channels
, 256);
1252 if (downmix_output
&& !s
->downmixed
) {
1254 s
->ac3dsp
.downmix(s
->dlyptr
, s
->downmix_coeffs
, s
->out_channels
,
1255 s
->fbw_channels
, 128);
1258 do_imdct(s
, s
->out_channels
);
1265 * Decode a single AC-3 frame.
1267 static int ac3_decode_frame(AVCodecContext
* avctx
, void *data
,
1268 int *got_frame_ptr
, AVPacket
*avpkt
)
1270 const uint8_t *buf
= avpkt
->data
;
1271 int buf_size
= avpkt
->size
;
1272 AC3DecodeContext
*s
= avctx
->priv_data
;
1273 int blk
, ch
, err
, ret
;
1274 const uint8_t *channel_map
;
1275 const float *output
[AC3_MAX_CHANNELS
];
1277 /* copy input buffer to decoder context to avoid reading past the end
1278 of the buffer, which can be caused by a damaged input stream. */
1279 if (buf_size
>= 2 && AV_RB16(buf
) == 0x770B) {
1280 // seems to be byte-swapped AC-3
1281 int cnt
= FFMIN(buf_size
, AC3_FRAME_BUFFER_SIZE
) >> 1;
1282 s
->dsp
.bswap16_buf((uint16_t *)s
->input_buffer
, (const uint16_t *)buf
, cnt
);
1284 memcpy(s
->input_buffer
, buf
, FFMIN(buf_size
, AC3_FRAME_BUFFER_SIZE
));
1285 buf
= s
->input_buffer
;
1286 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1287 init_get_bits(&s
->gbc
, buf
, buf_size
* 8);
1289 /* parse the syncinfo */
1290 err
= parse_frame_header(s
);
1294 case AAC_AC3_PARSE_ERROR_SYNC
:
1295 av_log(avctx
, AV_LOG_ERROR
, "frame sync error\n");
1297 case AAC_AC3_PARSE_ERROR_BSID
:
1298 av_log(avctx
, AV_LOG_ERROR
, "invalid bitstream id\n");
1300 case AAC_AC3_PARSE_ERROR_SAMPLE_RATE
:
1301 av_log(avctx
, AV_LOG_ERROR
, "invalid sample rate\n");
1303 case AAC_AC3_PARSE_ERROR_FRAME_SIZE
:
1304 av_log(avctx
, AV_LOG_ERROR
, "invalid frame size\n");
1306 case AAC_AC3_PARSE_ERROR_FRAME_TYPE
:
1307 /* skip frame if CRC is ok. otherwise use error concealment. */
1308 /* TODO: add support for substreams and dependent frames */
1309 if (s
->frame_type
== EAC3_FRAME_TYPE_DEPENDENT
|| s
->substreamid
) {
1310 av_log(avctx
, AV_LOG_ERROR
, "unsupported frame type : "
1311 "skipping frame\n");
1313 return s
->frame_size
;
1315 av_log(avctx
, AV_LOG_ERROR
, "invalid frame type\n");
1319 av_log(avctx
, AV_LOG_ERROR
, "invalid header\n");
1323 /* check that reported frame size fits in input buffer */
1324 if (s
->frame_size
> buf_size
) {
1325 av_log(avctx
, AV_LOG_ERROR
, "incomplete frame\n");
1326 err
= AAC_AC3_PARSE_ERROR_FRAME_SIZE
;
1327 } else if (avctx
->err_recognition
& AV_EF_CRCCHECK
) {
1328 /* check for crc mismatch */
1329 if (av_crc(av_crc_get_table(AV_CRC_16_ANSI
), 0, &buf
[2],
1330 s
->frame_size
- 2)) {
1331 av_log(avctx
, AV_LOG_ERROR
, "frame CRC mismatch\n");
1332 err
= AAC_AC3_PARSE_ERROR_CRC
;
1337 /* if frame is ok, set audio parameters */
1339 avctx
->sample_rate
= s
->sample_rate
;
1340 avctx
->bit_rate
= s
->bit_rate
;
1342 /* channel config */
1343 s
->out_channels
= s
->channels
;
1344 s
->output_mode
= s
->channel_mode
;
1346 s
->output_mode
|= AC3_OUTPUT_LFEON
;
1347 if (avctx
->request_channels
> 0 && avctx
->request_channels
<= 2 &&
1348 avctx
->request_channels
< s
->channels
) {
1349 s
->out_channels
= avctx
->request_channels
;
1350 s
->output_mode
= avctx
->request_channels
== 1 ? AC3_CHMODE_MONO
: AC3_CHMODE_STEREO
;
1351 s
->channel_layout
= avpriv_ac3_channel_layout_tab
[s
->output_mode
];
1353 avctx
->channels
= s
->out_channels
;
1354 avctx
->channel_layout
= s
->channel_layout
;
1356 /* set downmixing coefficients if needed */
1357 if (s
->channels
!= s
->out_channels
&& !((s
->output_mode
& AC3_OUTPUT_LFEON
) &&
1358 s
->fbw_channels
== s
->out_channels
)) {
1359 set_downmix_coeffs(s
);
1361 } else if (!s
->out_channels
) {
1362 s
->out_channels
= avctx
->channels
;
1363 if (s
->out_channels
< s
->channels
)
1364 s
->output_mode
= s
->out_channels
== 1 ? AC3_CHMODE_MONO
: AC3_CHMODE_STEREO
;
1366 /* set audio service type based on bitstream mode for AC-3 */
1367 avctx
->audio_service_type
= s
->bitstream_mode
;
1368 if (s
->bitstream_mode
== 0x7 && s
->channels
> 1)
1369 avctx
->audio_service_type
= AV_AUDIO_SERVICE_TYPE_KARAOKE
;
1371 /* get output buffer */
1372 avctx
->channels
= s
->out_channels
;
1373 s
->frame
.nb_samples
= s
->num_blocks
* 256;
1374 if ((ret
= ff_get_buffer(avctx
, &s
->frame
)) < 0) {
1375 av_log(avctx
, AV_LOG_ERROR
, "get_buffer() failed\n");
1379 /* decode the audio blocks */
1380 channel_map
= ff_ac3_dec_channel_map
[s
->output_mode
& ~AC3_OUTPUT_LFEON
][s
->lfe_on
];
1381 for (ch
= 0; ch
< s
->channels
; ch
++) {
1382 if (ch
< s
->out_channels
)
1383 s
->outptr
[channel_map
[ch
]] = (float *)s
->frame
.data
[ch
];
1385 s
->outptr
[ch
] = s
->output
[ch
];
1386 output
[ch
] = s
->output
[ch
];
1388 for (blk
= 0; blk
< s
->num_blocks
; blk
++) {
1389 if (!err
&& decode_audio_block(s
, blk
)) {
1390 av_log(avctx
, AV_LOG_ERROR
, "error decoding the audio block\n");
1394 for (ch
= 0; ch
< s
->out_channels
; ch
++)
1395 memcpy(s
->outptr
[channel_map
[ch
]], output
[ch
], 1024);
1396 for (ch
= 0; ch
< s
->out_channels
; ch
++) {
1397 output
[ch
] = s
->outptr
[channel_map
[ch
]];
1398 s
->outptr
[channel_map
[ch
]] += AC3_BLOCK_SIZE
;
1402 /* keep last block for error concealment in next frame */
1403 for (ch
= 0; ch
< s
->out_channels
; ch
++)
1404 memcpy(s
->output
[ch
], output
[ch
], 1024);
1407 *(AVFrame
*)data
= s
->frame
;
1409 return FFMIN(buf_size
, s
->frame_size
);
1413 * Uninitialize the AC-3 decoder.
1415 static av_cold
int ac3_decode_end(AVCodecContext
*avctx
)
1417 AC3DecodeContext
*s
= avctx
->priv_data
;
1418 ff_mdct_end(&s
->imdct_512
);
1419 ff_mdct_end(&s
->imdct_256
);
1424 #define OFFSET(x) offsetof(AC3DecodeContext, x)
1425 #define PAR (AV_OPT_FLAG_DECODING_PARAM | AV_OPT_FLAG_AUDIO_PARAM)
1426 static const AVOption options
[] = {
1427 { "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale
), AV_OPT_TYPE_FLOAT
, {.dbl
= 1.0}, 0.0, 1.0, PAR
},
1431 static const AVClass ac3_decoder_class
= {
1432 .class_name
= "AC3 decoder",
1433 .item_name
= av_default_item_name
,
1435 .version
= LIBAVUTIL_VERSION_INT
,
1438 AVCodec ff_ac3_decoder
= {
1440 .type
= AVMEDIA_TYPE_AUDIO
,
1441 .id
= AV_CODEC_ID_AC3
,
1442 .priv_data_size
= sizeof (AC3DecodeContext
),
1443 .init
= ac3_decode_init
,
1444 .close
= ac3_decode_end
,
1445 .decode
= ac3_decode_frame
,
1446 .capabilities
= CODEC_CAP_DR1
,
1447 .long_name
= NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
1448 .sample_fmts
= (const enum AVSampleFormat
[]) { AV_SAMPLE_FMT_FLTP
,
1449 AV_SAMPLE_FMT_NONE
},
1450 .priv_class
= &ac3_decoder_class
,
1453 #if CONFIG_EAC3_DECODER
1454 static const AVClass eac3_decoder_class
= {
1455 .class_name
= "E-AC3 decoder",
1456 .item_name
= av_default_item_name
,
1458 .version
= LIBAVUTIL_VERSION_INT
,
1461 AVCodec ff_eac3_decoder
= {
1463 .type
= AVMEDIA_TYPE_AUDIO
,
1464 .id
= AV_CODEC_ID_EAC3
,
1465 .priv_data_size
= sizeof (AC3DecodeContext
),
1466 .init
= ac3_decode_init
,
1467 .close
= ac3_decode_end
,
1468 .decode
= ac3_decode_frame
,
1469 .capabilities
= CODEC_CAP_DR1
,
1470 .long_name
= NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),
1471 .sample_fmts
= (const enum AVSampleFormat
[]) { AV_SAMPLE_FMT_FLTP
,
1472 AV_SAMPLE_FMT_NONE
},
1473 .priv_class
= &eac3_decoder_class
,