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
35 #include "libavutil/crc.h"
36 #include "libavutil/random.h"
38 #include "ac3_parser.h"
39 #include "bitstream.h"
42 /** Maximum possible frame size when the specification limit is ignored */
43 #define AC3_MAX_FRAME_SIZE 21695
46 * Table of bin locations for rematrixing bands
47 * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions
49 static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 };
51 /** table for grouping exponents */
52 static uint8_t exp_ungroup_tab[128][3];
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];
63 * Quantization table: levels for symmetric. bits for asymmetric.
64 * reference: Table 7.18 Mapping of bap to Quantizer
66 static const uint8_t quantization_tab[16] = {
68 5, 6, 7, 8, 9, 10, 11, 12, 14, 16
71 /** dynamic range table. converts codes to scale factors. */
72 static float dynamic_range_tab[256];
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
82 static const float gain_levels[6] = {
86 LEVEL_MINUS_4POINT5DB,
92 * Table for default stereo downmixing coefficients
93 * reference: Section 7.8.2 Downmixing Into Two Channels
95 static const uint8_t ac3_default_coeffs[8][5][2] = {
96 { { 1, 0 }, { 0, 1 }, },
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 }, },
106 /* override ac3.h to include coupling channel */
107 #undef AC3_MAX_CHANNELS
108 #define AC3_MAX_CHANNELS 7
111 #define AC3_OUTPUT_LFEON 8
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
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
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
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
157 int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups
158 int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
159 uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
160 int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
161 int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents
162 int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values
164 int fixed_coeffs[AC3_MAX_CHANNELS][256]; ///> fixed-point transform coefficients
165 DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients
166 int downmixed; ///< indicates if coeffs are currently downmixed
169 MDCTContext imdct_512; ///< for 512 sample IMDCT
170 MDCTContext imdct_256; ///< for 256 sample IMDCT
171 DSPContext dsp; ///< for optimization
172 float add_bias; ///< offset for float_to_int16 conversion
173 float mul_bias; ///< scaling for float_to_int16 conversion
175 DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS][256]); ///< output after imdct transform and windowing
176 DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output
177 DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS][256]); ///< delay - added to the next block
178 DECLARE_ALIGNED_16(float, tmp_imdct[256]); ///< temporary storage for imdct transform
179 DECLARE_ALIGNED_16(float, tmp_output[512]); ///< temporary storage for output before windowing
180 DECLARE_ALIGNED_16(float, window[256]); ///< window coefficients
183 GetBitContext gbc; ///< bitstream reader
184 AVRandomState dith_state; ///< for dither generation
185 AVCodecContext *avctx; ///< parent context
186 uint8_t *input_buffer; ///< temp buffer to prevent overread
190 * Symmetrical Dequantization
191 * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization
192 * Tables 7.19 to 7.23
195 symmetric_dequant(int code, int levels)
197 return ((code - (levels >> 1)) << 24) / levels;
201 * Initialize tables at runtime.
203 static av_cold void ac3_tables_init(void)
207 /* generate grouped mantissa tables
208 reference: Section 7.3.5 Ungrouping of Mantissas */
209 for(i=0; i<32; i++) {
210 /* bap=1 mantissas */
211 b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3);
212 b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3);
213 b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3);
215 for(i=0; i<128; i++) {
216 /* bap=2 mantissas */
217 b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5);
218 b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5);
219 b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5);
221 /* bap=4 mantissas */
222 b4_mantissas[i][0] = symmetric_dequant(i / 11, 11);
223 b4_mantissas[i][1] = symmetric_dequant(i % 11, 11);
225 /* generate ungrouped mantissa tables
226 reference: Tables 7.21 and 7.23 */
228 /* bap=3 mantissas */
229 b3_mantissas[i] = symmetric_dequant(i, 7);
231 for(i=0; i<15; i++) {
232 /* bap=5 mantissas */
233 b5_mantissas[i] = symmetric_dequant(i, 15);
236 /* generate dynamic range table
237 reference: Section 7.7.1 Dynamic Range Control */
238 for(i=0; i<256; i++) {
239 int v = (i >> 5) - ((i >> 7) << 3) - 5;
240 dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20);
243 /* generate exponent tables
244 reference: Section 7.1.3 Exponent Decoding */
245 for(i=0; i<128; i++) {
246 exp_ungroup_tab[i][0] = i / 25;
247 exp_ungroup_tab[i][1] = (i % 25) / 5;
248 exp_ungroup_tab[i][2] = (i % 25) % 5;
254 * AVCodec initialization
256 static av_cold int ac3_decode_init(AVCodecContext *avctx)
258 AC3DecodeContext *s = avctx->priv_data;
263 ff_mdct_init(&s->imdct_256, 8, 1);
264 ff_mdct_init(&s->imdct_512, 9, 1);
265 ff_kbd_window_init(s->window, 5.0, 256);
266 dsputil_init(&s->dsp, avctx);
267 av_init_random(0, &s->dith_state);
269 /* set bias values for float to int16 conversion */
270 if(s->dsp.float_to_int16 == ff_float_to_int16_c) {
271 s->add_bias = 385.0f;
275 s->mul_bias = 32767.0f;
278 /* allow downmixing to stereo or mono */
279 if (avctx->channels > 0 && avctx->request_channels > 0 &&
280 avctx->request_channels < avctx->channels &&
281 avctx->request_channels <= 2) {
282 avctx->channels = avctx->request_channels;
286 /* allocate context input buffer */
287 if (avctx->error_resilience >= FF_ER_CAREFUL) {
288 s->input_buffer = av_mallocz(AC3_MAX_FRAME_SIZE + FF_INPUT_BUFFER_PADDING_SIZE);
289 if (!s->input_buffer)
290 return AVERROR_NOMEM;
297 * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
298 * GetBitContext within AC3DecodeContext must point to
299 * start of the synchronized ac3 bitstream.
301 static int ac3_parse_header(AC3DecodeContext *s)
304 GetBitContext *gbc = &s->gbc;
307 err = ff_ac3_parse_header(gbc, &hdr);
311 if(hdr.bitstream_id > 10)
312 return AC3_PARSE_ERROR_BSID;
314 /* get decoding parameters from header info */
315 s->bit_alloc_params.sr_code = hdr.sr_code;
316 s->channel_mode = hdr.channel_mode;
317 s->lfe_on = hdr.lfe_on;
318 s->bit_alloc_params.sr_shift = hdr.sr_shift;
319 s->sample_rate = hdr.sample_rate;
320 s->bit_rate = hdr.bit_rate;
321 s->channels = hdr.channels;
322 s->fbw_channels = s->channels - s->lfe_on;
323 s->lfe_ch = s->fbw_channels + 1;
324 s->frame_size = hdr.frame_size;
325 s->center_mix_level = hdr.center_mix_level;
326 s->surround_mix_level = hdr.surround_mix_level;
329 s->start_freq[s->lfe_ch] = 0;
330 s->end_freq[s->lfe_ch] = 7;
331 s->num_exp_groups[s->lfe_ch] = 2;
332 s->channel_in_cpl[s->lfe_ch] = 0;
335 /* read the rest of the bsi. read twice for dual mono mode. */
336 i = !(s->channel_mode);
338 skip_bits(gbc, 5); // skip dialog normalization
340 skip_bits(gbc, 8); //skip compression
342 skip_bits(gbc, 8); //skip language code
344 skip_bits(gbc, 7); //skip audio production information
347 skip_bits(gbc, 2); //skip copyright bit and original bitstream bit
349 /* skip the timecodes (or extra bitstream information for Alternate Syntax)
350 TODO: read & use the xbsi1 downmix levels */
352 skip_bits(gbc, 14); //skip timecode1 / xbsi1
354 skip_bits(gbc, 14); //skip timecode2 / xbsi2
356 /* skip additional bitstream info */
357 if (get_bits1(gbc)) {
358 i = get_bits(gbc, 6);
368 * Set stereo downmixing coefficients based on frame header info.
369 * reference: Section 7.8.2 Downmixing Into Two Channels
371 static void set_downmix_coeffs(AC3DecodeContext *s)
374 float cmix = gain_levels[s->center_mix_level];
375 float smix = gain_levels[s->surround_mix_level];
377 for(i=0; i<s->fbw_channels; i++) {
378 s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]];
379 s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]];
381 if(s->channel_mode > 1 && s->channel_mode & 1) {
382 s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix;
384 if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) {
385 int nf = s->channel_mode - 2;
386 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB;
388 if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) {
389 int nf = s->channel_mode - 4;
390 s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix;
393 /* calculate adjustment needed for each channel to avoid clipping */
394 s->downmix_coeff_adjust[0] = s->downmix_coeff_adjust[1] = 0.0f;
395 for(i=0; i<s->fbw_channels; i++) {
396 s->downmix_coeff_adjust[0] += s->downmix_coeffs[i][0];
397 s->downmix_coeff_adjust[1] += s->downmix_coeffs[i][1];
399 s->downmix_coeff_adjust[0] = 1.0f / s->downmix_coeff_adjust[0];
400 s->downmix_coeff_adjust[1] = 1.0f / s->downmix_coeff_adjust[1];
404 * Decode the grouped exponents according to exponent strategy.
405 * reference: Section 7.1.3 Exponent Decoding
407 static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps,
408 uint8_t absexp, int8_t *dexps)
410 int i, j, grp, group_size;
415 group_size = exp_strategy + (exp_strategy == EXP_D45);
416 for(grp=0,i=0; grp<ngrps; grp++) {
417 expacc = get_bits(gbc, 7);
418 dexp[i++] = exp_ungroup_tab[expacc][0];
419 dexp[i++] = exp_ungroup_tab[expacc][1];
420 dexp[i++] = exp_ungroup_tab[expacc][2];
423 /* convert to absolute exps and expand groups */
425 for(i=0; i<ngrps*3; i++) {
426 prevexp = av_clip(prevexp + dexp[i]-2, 0, 24);
427 for(j=0; j<group_size; j++) {
428 dexps[(i*group_size)+j] = prevexp;
434 * Generate transform coefficients for each coupled channel in the coupling
435 * range using the coupling coefficients and coupling coordinates.
436 * reference: Section 7.4.3 Coupling Coordinate Format
438 static void uncouple_channels(AC3DecodeContext *s)
440 int i, j, ch, bnd, subbnd;
443 i = s->start_freq[CPL_CH];
444 for(bnd=0; bnd<s->num_cpl_bands; bnd++) {
447 for(j=0; j<12; j++) {
448 for(ch=1; ch<=s->fbw_channels; ch++) {
449 if(s->channel_in_cpl[ch]) {
450 s->fixed_coeffs[ch][i] = ((int64_t)s->fixed_coeffs[CPL_CH][i] * (int64_t)s->cpl_coords[ch][bnd]) >> 23;
451 if (ch == 2 && s->phase_flags[bnd])
452 s->fixed_coeffs[ch][i] = -s->fixed_coeffs[ch][i];
457 } while(s->cpl_band_struct[subbnd]);
462 * Grouped mantissas for 3-level 5-level and 11-level quantization
474 * Get the transform coefficients for a particular channel
475 * reference: Section 7.3 Quantization and Decoding of Mantissas
477 static void get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m)
479 GetBitContext *gbc = &s->gbc;
480 int i, gcode, tbap, start, end;
485 exps = s->dexps[ch_index];
486 bap = s->bap[ch_index];
487 coeffs = s->fixed_coeffs[ch_index];
488 start = s->start_freq[ch_index];
489 end = s->end_freq[ch_index];
491 for (i = start; i < end; i++) {
495 coeffs[i] = (av_random(&s->dith_state) & 0x7FFFFF) - 4194304;
500 gcode = get_bits(gbc, 5);
501 m->b1_mant[0] = b1_mantissas[gcode][0];
502 m->b1_mant[1] = b1_mantissas[gcode][1];
503 m->b1_mant[2] = b1_mantissas[gcode][2];
506 coeffs[i] = m->b1_mant[m->b1ptr++];
511 gcode = get_bits(gbc, 7);
512 m->b2_mant[0] = b2_mantissas[gcode][0];
513 m->b2_mant[1] = b2_mantissas[gcode][1];
514 m->b2_mant[2] = b2_mantissas[gcode][2];
517 coeffs[i] = m->b2_mant[m->b2ptr++];
521 coeffs[i] = b3_mantissas[get_bits(gbc, 3)];
526 gcode = get_bits(gbc, 7);
527 m->b4_mant[0] = b4_mantissas[gcode][0];
528 m->b4_mant[1] = b4_mantissas[gcode][1];
531 coeffs[i] = m->b4_mant[m->b4ptr++];
535 coeffs[i] = b5_mantissas[get_bits(gbc, 4)];
539 /* asymmetric dequantization */
540 int qlevel = quantization_tab[tbap];
541 coeffs[i] = get_sbits(gbc, qlevel) << (24 - qlevel);
545 coeffs[i] >>= exps[i];
550 * Remove random dithering from coefficients with zero-bit mantissas
551 * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)
553 static void remove_dithering(AC3DecodeContext *s) {
559 for(ch=1; ch<=s->fbw_channels; ch++) {
560 if(!s->dither_flag[ch]) {
561 coeffs = s->fixed_coeffs[ch];
563 if(s->channel_in_cpl[ch])
564 end = s->start_freq[CPL_CH];
566 end = s->end_freq[ch];
567 for(i=0; i<end; i++) {
571 if(s->channel_in_cpl[ch]) {
572 bap = s->bap[CPL_CH];
573 for(; i<s->end_freq[CPL_CH]; i++) {
583 * Get the transform coefficients.
585 static void get_transform_coeffs(AC3DecodeContext *s)
591 m.b1ptr = m.b2ptr = m.b4ptr = 3;
593 for (ch = 1; ch <= s->channels; ch++) {
594 /* transform coefficients for full-bandwidth channel */
595 get_transform_coeffs_ch(s, ch, &m);
596 /* tranform coefficients for coupling channel come right after the
597 coefficients for the first coupled channel*/
598 if (s->channel_in_cpl[ch]) {
600 get_transform_coeffs_ch(s, CPL_CH, &m);
601 uncouple_channels(s);
604 end = s->end_freq[CPL_CH];
606 end = s->end_freq[ch];
609 s->fixed_coeffs[ch][end] = 0;
613 /* if any channel doesn't use dithering, zero appropriate coefficients */
619 * Stereo rematrixing.
620 * reference: Section 7.5.4 Rematrixing : Decoding Technique
622 static void do_rematrixing(AC3DecodeContext *s)
628 end = FFMIN(s->end_freq[1], s->end_freq[2]);
630 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) {
631 if(s->rematrixing_flags[bnd]) {
632 bndend = FFMIN(end, rematrix_band_tab[bnd+1]);
633 for(i=rematrix_band_tab[bnd]; i<bndend; i++) {
634 tmp0 = s->fixed_coeffs[1][i];
635 tmp1 = s->fixed_coeffs[2][i];
636 s->fixed_coeffs[1][i] = tmp0 + tmp1;
637 s->fixed_coeffs[2][i] = tmp0 - tmp1;
644 * Perform the 256-point IMDCT
646 static void do_imdct_256(AC3DecodeContext *s, int chindex)
649 DECLARE_ALIGNED_16(float, x[128]);
651 float *o_ptr = s->tmp_output;
654 /* de-interleave coefficients */
655 for(k=0; k<128; k++) {
656 x[k] = s->transform_coeffs[chindex][2*k+i];
659 /* run standard IMDCT */
660 s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct);
662 /* reverse the post-rotation & reordering from standard IMDCT */
663 for(k=0; k<32; k++) {
664 z[i][32+k].re = -o_ptr[128+2*k];
665 z[i][32+k].im = -o_ptr[2*k];
666 z[i][31-k].re = o_ptr[2*k+1];
667 z[i][31-k].im = o_ptr[128+2*k+1];
671 /* apply AC-3 post-rotation & reordering */
672 for(k=0; k<64; k++) {
673 o_ptr[ 2*k ] = -z[0][ k].im;
674 o_ptr[ 2*k+1] = z[0][63-k].re;
675 o_ptr[128+2*k ] = -z[0][ k].re;
676 o_ptr[128+2*k+1] = z[0][63-k].im;
677 o_ptr[256+2*k ] = -z[1][ k].re;
678 o_ptr[256+2*k+1] = z[1][63-k].im;
679 o_ptr[384+2*k ] = z[1][ k].im;
680 o_ptr[384+2*k+1] = -z[1][63-k].re;
685 * Inverse MDCT Transform.
686 * Convert frequency domain coefficients to time-domain audio samples.
687 * reference: Section 7.9.4 Transformation Equations
689 static inline void do_imdct(AC3DecodeContext *s, int channels)
693 for (ch=1; ch<=channels; ch++) {
694 if (s->block_switch[ch]) {
697 s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output,
698 s->transform_coeffs[ch], s->tmp_imdct);
700 /* For the first half of the block, apply the window, add the delay
701 from the previous block, and send to output */
702 s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output,
703 s->window, s->delay[ch-1], 0, 256, 1);
704 /* For the second half of the block, apply the window and store the
705 samples to delay, to be combined with the next block */
706 s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256,
712 * Downmix the output to mono or stereo.
714 static void ac3_downmix(AC3DecodeContext *s,
715 float samples[AC3_MAX_CHANNELS][256], int ch_offset)
720 for(i=0; i<256; i++) {
722 for(j=0; j<s->fbw_channels; j++) {
723 v0 += samples[j+ch_offset][i] * s->downmix_coeffs[j][0];
724 v1 += samples[j+ch_offset][i] * s->downmix_coeffs[j][1];
726 v0 *= s->downmix_coeff_adjust[0];
727 v1 *= s->downmix_coeff_adjust[1];
728 if(s->output_mode == AC3_CHMODE_MONO) {
729 samples[ch_offset][i] = (v0 + v1) * LEVEL_MINUS_3DB;
730 } else if(s->output_mode == AC3_CHMODE_STEREO) {
731 samples[ ch_offset][i] = v0;
732 samples[1+ch_offset][i] = v1;
738 * Upmix delay samples from stereo to original channel layout.
740 static void ac3_upmix_delay(AC3DecodeContext *s)
742 int channel_data_size = sizeof(s->delay[0]);
743 switch(s->channel_mode) {
744 case AC3_CHMODE_DUALMONO:
745 case AC3_CHMODE_STEREO:
746 /* upmix mono to stereo */
747 memcpy(s->delay[1], s->delay[0], channel_data_size);
749 case AC3_CHMODE_2F2R:
750 memset(s->delay[3], 0, channel_data_size);
751 case AC3_CHMODE_2F1R:
752 memset(s->delay[2], 0, channel_data_size);
754 case AC3_CHMODE_3F2R:
755 memset(s->delay[4], 0, channel_data_size);
756 case AC3_CHMODE_3F1R:
757 memset(s->delay[3], 0, channel_data_size);
759 memcpy(s->delay[2], s->delay[1], channel_data_size);
760 memset(s->delay[1], 0, channel_data_size);
766 * Parse an audio block from AC-3 bitstream.
768 static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
770 int fbw_channels = s->fbw_channels;
771 int channel_mode = s->channel_mode;
773 int different_transforms;
775 GetBitContext *gbc = &s->gbc;
776 uint8_t bit_alloc_stages[AC3_MAX_CHANNELS];
778 memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS);
780 /* block switch flags */
781 different_transforms = 0;
782 for (ch = 1; ch <= fbw_channels; ch++) {
783 s->block_switch[ch] = get_bits1(gbc);
784 if(ch > 1 && s->block_switch[ch] != s->block_switch[1])
785 different_transforms = 1;
788 /* dithering flags */
790 for (ch = 1; ch <= fbw_channels; ch++) {
791 s->dither_flag[ch] = get_bits1(gbc);
792 if(!s->dither_flag[ch])
797 i = !(s->channel_mode);
800 s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) *
801 s->avctx->drc_scale)+1.0;
802 } else if(blk == 0) {
803 s->dynamic_range[i] = 1.0f;
807 /* coupling strategy */
808 if (get_bits1(gbc)) {
809 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
810 s->cpl_in_use = get_bits1(gbc);
812 /* coupling in use */
813 int cpl_begin_freq, cpl_end_freq;
815 if (channel_mode < AC3_CHMODE_STEREO) {
816 av_log(s->avctx, AV_LOG_ERROR, "coupling not allowed in mono or dual-mono\n");
820 /* determine which channels are coupled */
821 for (ch = 1; ch <= fbw_channels; ch++)
822 s->channel_in_cpl[ch] = get_bits1(gbc);
824 /* phase flags in use */
825 if (channel_mode == AC3_CHMODE_STEREO)
826 s->phase_flags_in_use = get_bits1(gbc);
828 /* coupling frequency range and band structure */
829 cpl_begin_freq = get_bits(gbc, 4);
830 cpl_end_freq = get_bits(gbc, 4);
831 if (3 + cpl_end_freq - cpl_begin_freq < 0) {
832 av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq);
835 s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq;
836 s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37;
837 s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73;
838 for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) {
839 if (get_bits1(gbc)) {
840 s->cpl_band_struct[bnd] = 1;
844 s->cpl_band_struct[s->num_cpl_subbands-1] = 0;
846 /* coupling not in use */
847 for (ch = 1; ch <= fbw_channels; ch++)
848 s->channel_in_cpl[ch] = 0;
851 av_log(s->avctx, AV_LOG_ERROR, "new coupling strategy must be present in block 0\n");
855 /* coupling coordinates */
857 int cpl_coords_exist = 0;
859 for (ch = 1; ch <= fbw_channels; ch++) {
860 if (s->channel_in_cpl[ch]) {
861 if (get_bits1(gbc)) {
862 int master_cpl_coord, cpl_coord_exp, cpl_coord_mant;
863 cpl_coords_exist = 1;
864 master_cpl_coord = 3 * get_bits(gbc, 2);
865 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
866 cpl_coord_exp = get_bits(gbc, 4);
867 cpl_coord_mant = get_bits(gbc, 4);
868 if (cpl_coord_exp == 15)
869 s->cpl_coords[ch][bnd] = cpl_coord_mant << 22;
871 s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16) << 21;
872 s->cpl_coords[ch][bnd] >>= (cpl_coord_exp + master_cpl_coord);
875 av_log(s->avctx, AV_LOG_ERROR, "new coupling coordinates must be present in block 0\n");
881 if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) {
882 for (bnd = 0; bnd < s->num_cpl_bands; bnd++) {
883 s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0;
888 /* stereo rematrixing strategy and band structure */
889 if (channel_mode == AC3_CHMODE_STEREO) {
890 if (get_bits1(gbc)) {
891 s->num_rematrixing_bands = 4;
892 if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61)
893 s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37);
894 for(bnd=0; bnd<s->num_rematrixing_bands; bnd++)
895 s->rematrixing_flags[bnd] = get_bits1(gbc);
897 av_log(s->avctx, AV_LOG_ERROR, "new rematrixing strategy must be present in block 0\n");
902 /* exponent strategies for each channel */
903 s->exp_strategy[CPL_CH] = EXP_REUSE;
904 s->exp_strategy[s->lfe_ch] = EXP_REUSE;
905 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
907 s->exp_strategy[ch] = get_bits(gbc, 1);
909 s->exp_strategy[ch] = get_bits(gbc, 2);
910 if(s->exp_strategy[ch] != EXP_REUSE)
911 bit_alloc_stages[ch] = 3;
914 /* channel bandwidth */
915 for (ch = 1; ch <= fbw_channels; ch++) {
916 s->start_freq[ch] = 0;
917 if (s->exp_strategy[ch] != EXP_REUSE) {
919 int prev = s->end_freq[ch];
920 if (s->channel_in_cpl[ch])
921 s->end_freq[ch] = s->start_freq[CPL_CH];
923 int bandwidth_code = get_bits(gbc, 6);
924 if (bandwidth_code > 60) {
925 av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code);
928 s->end_freq[ch] = bandwidth_code * 3 + 73;
930 group_size = 3 << (s->exp_strategy[ch] - 1);
931 s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
932 if(blk > 0 && s->end_freq[ch] != prev)
933 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
936 if (s->cpl_in_use && s->exp_strategy[CPL_CH] != EXP_REUSE) {
937 s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
938 (3 << (s->exp_strategy[CPL_CH] - 1));
941 /* decode exponents for each channel */
942 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
943 if (s->exp_strategy[ch] != EXP_REUSE) {
944 s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
945 decode_exponents(gbc, s->exp_strategy[ch],
946 s->num_exp_groups[ch], s->dexps[ch][0],
947 &s->dexps[ch][s->start_freq[ch]+!!ch]);
948 if(ch != CPL_CH && ch != s->lfe_ch)
949 skip_bits(gbc, 2); /* skip gainrng */
953 /* bit allocation information */
954 if (get_bits1(gbc)) {
955 s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
956 s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift;
957 s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)];
958 s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)];
959 s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)];
960 for(ch=!s->cpl_in_use; ch<=s->channels; ch++)
961 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
963 av_log(s->avctx, AV_LOG_ERROR, "new bit allocation info must be present in block 0\n");
967 /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */
968 if (get_bits1(gbc)) {
970 csnr = (get_bits(gbc, 6) - 15) << 4;
971 for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */
972 s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2;
973 s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)];
975 memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
977 av_log(s->avctx, AV_LOG_ERROR, "new snr offsets must be present in block 0\n");
981 /* coupling leak information */
983 if (get_bits1(gbc)) {
984 s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3);
985 s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3);
986 bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2);
988 av_log(s->avctx, AV_LOG_ERROR, "new coupling leak info must be present in block 0\n");
993 /* delta bit allocation information */
994 if (get_bits1(gbc)) {
995 /* delta bit allocation exists (strategy) */
996 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
997 s->dba_mode[ch] = get_bits(gbc, 2);
998 if (s->dba_mode[ch] == DBA_RESERVED) {
999 av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n");
1002 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1004 /* channel delta offset, len and bit allocation */
1005 for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) {
1006 if (s->dba_mode[ch] == DBA_NEW) {
1007 s->dba_nsegs[ch] = get_bits(gbc, 3);
1008 for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) {
1009 s->dba_offsets[ch][seg] = get_bits(gbc, 5);
1010 s->dba_lengths[ch][seg] = get_bits(gbc, 4);
1011 s->dba_values[ch][seg] = get_bits(gbc, 3);
1013 /* run last 2 bit allocation stages if new dba values */
1014 bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2);
1017 } else if(blk == 0) {
1018 for(ch=0; ch<=s->channels; ch++) {
1019 s->dba_mode[ch] = DBA_NONE;
1023 /* Bit allocation */
1024 for(ch=!s->cpl_in_use; ch<=s->channels; ch++) {
1025 if(bit_alloc_stages[ch] > 2) {
1026 /* Exponent mapping into PSD and PSD integration */
1027 ff_ac3_bit_alloc_calc_psd(s->dexps[ch],
1028 s->start_freq[ch], s->end_freq[ch],
1029 s->psd[ch], s->band_psd[ch]);
1031 if(bit_alloc_stages[ch] > 1) {
1032 /* Compute excitation function, Compute masking curve, and
1033 Apply delta bit allocation */
1034 ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch],
1035 s->start_freq[ch], s->end_freq[ch],
1036 s->fast_gain[ch], (ch == s->lfe_ch),
1037 s->dba_mode[ch], s->dba_nsegs[ch],
1038 s->dba_offsets[ch], s->dba_lengths[ch],
1039 s->dba_values[ch], s->mask[ch]);
1041 if(bit_alloc_stages[ch] > 0) {
1042 /* Compute bit allocation */
1043 ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch],
1044 s->start_freq[ch], s->end_freq[ch],
1046 s->bit_alloc_params.floor,
1051 /* unused dummy data */
1052 if (get_bits1(gbc)) {
1053 int skipl = get_bits(gbc, 9);
1058 /* unpack the transform coefficients
1059 this also uncouples channels if coupling is in use. */
1060 get_transform_coeffs(s);
1062 /* recover coefficients if rematrixing is in use */
1063 if(s->channel_mode == AC3_CHMODE_STEREO)
1066 /* apply scaling to coefficients (headroom, dynrng) */
1067 for(ch=1; ch<=s->channels; ch++) {
1068 float gain = s->mul_bias / 4194304.0f;
1069 if(s->channel_mode == AC3_CHMODE_DUALMONO) {
1070 gain *= s->dynamic_range[ch-1];
1072 gain *= s->dynamic_range[0];
1074 for(i=0; i<256; i++) {
1075 s->transform_coeffs[ch][i] = s->fixed_coeffs[ch][i] * gain;
1079 /* downmix and MDCT. order depends on whether block switching is used for
1080 any channel in this block. this is because coefficients for the long
1081 and short transforms cannot be mixed. */
1082 downmix_output = s->channels != s->out_channels &&
1083 !((s->output_mode & AC3_OUTPUT_LFEON) &&
1084 s->fbw_channels == s->out_channels);
1085 if(different_transforms) {
1086 /* the delay samples have already been downmixed, so we upmix the delay
1087 samples in order to reconstruct all channels before downmixing. */
1093 do_imdct(s, s->channels);
1095 if(downmix_output) {
1096 ac3_downmix(s, s->output, 0);
1099 if(downmix_output) {
1100 ac3_downmix(s, s->transform_coeffs, 1);
1105 ac3_downmix(s, s->delay, 0);
1108 do_imdct(s, s->out_channels);
1111 /* convert float to 16-bit integer */
1112 for(ch=0; ch<s->out_channels; ch++) {
1113 for(i=0; i<256; i++) {
1114 s->output[ch][i] += s->add_bias;
1116 s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256);
1123 * Decode a single AC-3 frame.
1125 static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size,
1126 const uint8_t *buf, int buf_size)
1128 AC3DecodeContext *s = avctx->priv_data;
1129 int16_t *out_samples = (int16_t *)data;
1130 int i, blk, ch, err;
1132 /* initialize the GetBitContext with the start of valid AC-3 Frame */
1133 if (s->input_buffer) {
1134 /* copy input buffer to decoder context to avoid reading past the end
1135 of the buffer, which can be caused by a damaged input stream. */
1136 memcpy(s->input_buffer, buf, FFMIN(buf_size, AC3_MAX_FRAME_SIZE));
1137 init_get_bits(&s->gbc, s->input_buffer, buf_size * 8);
1139 init_get_bits(&s->gbc, buf, buf_size * 8);
1142 /* parse the syncinfo */
1144 err = ac3_parse_header(s);
1146 /* check that reported frame size fits in input buffer */
1147 if(s->frame_size > buf_size) {
1148 av_log(avctx, AV_LOG_ERROR, "incomplete frame\n");
1149 err = AC3_PARSE_ERROR_FRAME_SIZE;
1152 /* check for crc mismatch */
1153 if(err != AC3_PARSE_ERROR_FRAME_SIZE && avctx->error_resilience >= FF_ER_CAREFUL) {
1154 if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) {
1155 av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n");
1156 err = AC3_PARSE_ERROR_CRC;
1160 /* parse the syncinfo */
1161 if(err && err != AC3_PARSE_ERROR_CRC) {
1163 case AC3_PARSE_ERROR_SYNC:
1164 av_log(avctx, AV_LOG_ERROR, "frame sync error\n");
1166 case AC3_PARSE_ERROR_BSID:
1167 av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n");
1169 case AC3_PARSE_ERROR_SAMPLE_RATE:
1170 av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n");
1172 case AC3_PARSE_ERROR_FRAME_SIZE:
1173 av_log(avctx, AV_LOG_ERROR, "invalid frame size\n");
1175 case AC3_PARSE_ERROR_FRAME_TYPE:
1176 av_log(avctx, AV_LOG_ERROR, "invalid frame type\n");
1179 av_log(avctx, AV_LOG_ERROR, "invalid header\n");
1184 /* if frame is ok, set audio parameters */
1186 avctx->sample_rate = s->sample_rate;
1187 avctx->bit_rate = s->bit_rate;
1189 /* channel config */
1190 s->out_channels = s->channels;
1191 s->output_mode = s->channel_mode;
1193 s->output_mode |= AC3_OUTPUT_LFEON;
1194 if (avctx->request_channels > 0 && avctx->request_channels <= 2 &&
1195 avctx->request_channels < s->channels) {
1196 s->out_channels = avctx->request_channels;
1197 s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1199 avctx->channels = s->out_channels;
1201 /* set downmixing coefficients if needed */
1202 if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) &&
1203 s->fbw_channels == s->out_channels)) {
1204 set_downmix_coeffs(s);
1206 } else if (!s->out_channels) {
1207 s->out_channels = avctx->channels;
1208 if(s->out_channels < s->channels)
1209 s->output_mode = s->out_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO;
1212 /* parse the audio blocks */
1213 for (blk = 0; blk < NB_BLOCKS; blk++) {
1214 if (!err && ac3_parse_audio_block(s, blk)) {
1215 av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n");
1217 for (i = 0; i < 256; i++)
1218 for (ch = 0; ch < s->out_channels; ch++)
1219 *(out_samples++) = s->int_output[ch][i];
1221 *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t);
1222 return s->frame_size;
1226 * Uninitialize the AC-3 decoder.
1228 static av_cold int ac3_decode_end(AVCodecContext *avctx)
1230 AC3DecodeContext *s = avctx->priv_data;
1231 ff_mdct_end(&s->imdct_512);
1232 ff_mdct_end(&s->imdct_256);
1234 av_freep(&s->input_buffer);
1239 AVCodec ac3_decoder = {
1241 .type = CODEC_TYPE_AUDIO,
1243 .priv_data_size = sizeof (AC3DecodeContext),
1244 .init = ac3_decode_init,
1245 .close = ac3_decode_end,
1246 .decode = ac3_decode_frame,
1247 .long_name = "ATSC A/52 / AC-3",