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Diffstat (limited to 'contrib/ffmpeg/libavcodec/ac3dec.c')
| -rw-r--r-- | contrib/ffmpeg/libavcodec/ac3dec.c | 1173 |
1 files changed, 1173 insertions, 0 deletions
diff --git a/contrib/ffmpeg/libavcodec/ac3dec.c b/contrib/ffmpeg/libavcodec/ac3dec.c new file mode 100644 index 000000000..0ce75e769 --- /dev/null +++ b/contrib/ffmpeg/libavcodec/ac3dec.c @@ -0,0 +1,1173 @@ +/* + * AC-3 Audio Decoder + * This code is developed as part of Google Summer of Code 2006 Program. + * + * Copyright (c) 2006 Kartikey Mahendra BHATT (bhattkm at gmail dot com). + * Copyright (c) 2007 Justin Ruggles + * + * Portions of this code are derived from liba52 + * http://liba52.sourceforge.net + * Copyright (C) 2000-2003 Michel Lespinasse <walken@zoy.org> + * Copyright (C) 1999-2000 Aaron Holtzman <aholtzma@ess.engr.uvic.ca> + * + * This file is part of FFmpeg. + * + * FFmpeg is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + * + * FFmpeg is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public + * License along with FFmpeg; if not, write to the Free Software + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA + */ + +#include <stdio.h> +#include <stddef.h> +#include <math.h> +#include <string.h> + +#include "avcodec.h" +#include "ac3_parser.h" +#include "bitstream.h" +#include "crc.h" +#include "dsputil.h" +#include "random.h" + +/** + * Table of bin locations for rematrixing bands + * reference: Section 7.5.2 Rematrixing : Frequency Band Definitions + */ +static const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 }; + +/** + * table for exponent to scale_factor mapping + * scale_factors[i] = 2 ^ -i + */ +static float scale_factors[25]; + +/** table for grouping exponents */ +static uint8_t exp_ungroup_tab[128][3]; + + +/** tables for ungrouping mantissas */ +static float b1_mantissas[32][3]; +static float b2_mantissas[128][3]; +static float b3_mantissas[8]; +static float b4_mantissas[128][2]; +static float b5_mantissas[16]; + +/** + * Quantization table: levels for symmetric. bits for asymmetric. + * reference: Table 7.18 Mapping of bap to Quantizer + */ +static const uint8_t quantization_tab[16] = { + 0, 3, 5, 7, 11, 15, + 5, 6, 7, 8, 9, 10, 11, 12, 14, 16 +}; + +/** dynamic range table. converts codes to scale factors. */ +static float dynamic_range_tab[256]; + +/** Adjustments in dB gain */ +#define LEVEL_MINUS_3DB 0.7071067811865476 +#define LEVEL_MINUS_4POINT5DB 0.5946035575013605 +#define LEVEL_MINUS_6DB 0.5000000000000000 +#define LEVEL_MINUS_9DB 0.3535533905932738 +#define LEVEL_ZERO 0.0000000000000000 +#define LEVEL_ONE 1.0000000000000000 + +static const float gain_levels[6] = { + LEVEL_ZERO, + LEVEL_ONE, + LEVEL_MINUS_3DB, + LEVEL_MINUS_4POINT5DB, + LEVEL_MINUS_6DB, + LEVEL_MINUS_9DB +}; + +/** + * Table for center mix levels + * reference: Section 5.4.2.4 cmixlev + */ +static const uint8_t center_levels[4] = { 2, 3, 4, 3 }; + +/** + * Table for surround mix levels + * reference: Section 5.4.2.5 surmixlev + */ +static const uint8_t surround_levels[4] = { 2, 4, 0, 4 }; + +/** + * Table for default stereo downmixing coefficients + * reference: Section 7.8.2 Downmixing Into Two Channels + */ +static const uint8_t ac3_default_coeffs[8][5][2] = { + { { 1, 0 }, { 0, 1 }, }, + { { 2, 2 }, }, + { { 1, 0 }, { 0, 1 }, }, + { { 1, 0 }, { 3, 3 }, { 0, 1 }, }, + { { 1, 0 }, { 0, 1 }, { 4, 4 }, }, + { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 }, }, + { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, }, + { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, }, +}; + +/* override ac3.h to include coupling channel */ +#undef AC3_MAX_CHANNELS +#define AC3_MAX_CHANNELS 7 +#define CPL_CH 0 + +#define AC3_OUTPUT_LFEON 8 + +typedef struct { + int channel_mode; ///< channel mode (acmod) + int block_switch[AC3_MAX_CHANNELS]; ///< block switch flags + int dither_flag[AC3_MAX_CHANNELS]; ///< dither flags + int dither_all; ///< true if all channels are dithered + int cpl_in_use; ///< coupling in use + int channel_in_cpl[AC3_MAX_CHANNELS]; ///< channel in coupling + int phase_flags_in_use; ///< phase flags in use + int phase_flags[18]; ///< phase flags + int cpl_band_struct[18]; ///< coupling band structure + int num_rematrixing_bands; ///< number of rematrixing bands + int rematrixing_flags[4]; ///< rematrixing flags + int exp_strategy[AC3_MAX_CHANNELS]; ///< exponent strategies + int snr_offset[AC3_MAX_CHANNELS]; ///< signal-to-noise ratio offsets + int fast_gain[AC3_MAX_CHANNELS]; ///< fast gain values (signal-to-mask ratio) + int dba_mode[AC3_MAX_CHANNELS]; ///< delta bit allocation mode + int dba_nsegs[AC3_MAX_CHANNELS]; ///< number of delta segments + uint8_t dba_offsets[AC3_MAX_CHANNELS][8]; ///< delta segment offsets + uint8_t dba_lengths[AC3_MAX_CHANNELS][8]; ///< delta segment lengths + uint8_t dba_values[AC3_MAX_CHANNELS][8]; ///< delta values for each segment + + int sample_rate; ///< sample frequency, in Hz + int bit_rate; ///< stream bit rate, in bits-per-second + int frame_size; ///< current frame size, in bytes + + int channels; ///< number of total channels + int fbw_channels; ///< number of full-bandwidth channels + int lfe_on; ///< lfe channel in use + int lfe_ch; ///< index of LFE channel + int output_mode; ///< output channel configuration + int out_channels; ///< number of output channels + + int center_mix_level; ///< Center mix level index + int surround_mix_level; ///< Surround mix level index + float downmix_coeffs[AC3_MAX_CHANNELS][2]; ///< stereo downmix coefficients + float dynamic_range[2]; ///< dynamic range + float cpl_coords[AC3_MAX_CHANNELS][18]; ///< coupling coordinates + int num_cpl_bands; ///< number of coupling bands + int num_cpl_subbands; ///< number of coupling sub bands + int start_freq[AC3_MAX_CHANNELS]; ///< start frequency bin + int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin + AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters + + int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents + uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers + int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents + int16_t band_psd[AC3_MAX_CHANNELS][50]; ///< interpolated exponents + int16_t mask[AC3_MAX_CHANNELS][50]; ///< masking curve values + + DECLARE_ALIGNED_16(float, transform_coeffs[AC3_MAX_CHANNELS][256]); ///< transform coefficients + + /* For IMDCT. */ + MDCTContext imdct_512; ///< for 512 sample IMDCT + MDCTContext imdct_256; ///< for 256 sample IMDCT + DSPContext dsp; ///< for optimization + float add_bias; ///< offset for float_to_int16 conversion + float mul_bias; ///< scaling for float_to_int16 conversion + + DECLARE_ALIGNED_16(float, output[AC3_MAX_CHANNELS-1][256]); ///< output after imdct transform and windowing + DECLARE_ALIGNED_16(short, int_output[AC3_MAX_CHANNELS-1][256]); ///< final 16-bit integer output + DECLARE_ALIGNED_16(float, delay[AC3_MAX_CHANNELS-1][256]); ///< delay - added to the next block + DECLARE_ALIGNED_16(float, tmp_imdct[256]); ///< temporary storage for imdct transform + DECLARE_ALIGNED_16(float, tmp_output[512]); ///< temporary storage for output before windowing + DECLARE_ALIGNED_16(float, window[256]); ///< window coefficients + + /* Miscellaneous. */ + GetBitContext gbc; ///< bitstream reader + AVRandomState dith_state; ///< for dither generation + AVCodecContext *avctx; ///< parent context +} AC3DecodeContext; + +/** + * Symmetrical Dequantization + * reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization + * Tables 7.19 to 7.23 + */ +static inline float +symmetric_dequant(int code, int levels) +{ + return (code - (levels >> 1)) * (2.0f / levels); +} + +/* + * Initialize tables at runtime. + */ +static void ac3_tables_init(void) +{ + int i; + + /* generate grouped mantissa tables + reference: Section 7.3.5 Ungrouping of Mantissas */ + for(i=0; i<32; i++) { + /* bap=1 mantissas */ + b1_mantissas[i][0] = symmetric_dequant( i / 9 , 3); + b1_mantissas[i][1] = symmetric_dequant((i % 9) / 3, 3); + b1_mantissas[i][2] = symmetric_dequant((i % 9) % 3, 3); + } + for(i=0; i<128; i++) { + /* bap=2 mantissas */ + b2_mantissas[i][0] = symmetric_dequant( i / 25 , 5); + b2_mantissas[i][1] = symmetric_dequant((i % 25) / 5, 5); + b2_mantissas[i][2] = symmetric_dequant((i % 25) % 5, 5); + + /* bap=4 mantissas */ + b4_mantissas[i][0] = symmetric_dequant(i / 11, 11); + b4_mantissas[i][1] = symmetric_dequant(i % 11, 11); + } + /* generate ungrouped mantissa tables + reference: Tables 7.21 and 7.23 */ + for(i=0; i<7; i++) { + /* bap=3 mantissas */ + b3_mantissas[i] = symmetric_dequant(i, 7); + } + for(i=0; i<15; i++) { + /* bap=5 mantissas */ + b5_mantissas[i] = symmetric_dequant(i, 15); + } + + /* generate dynamic range table + reference: Section 7.7.1 Dynamic Range Control */ + for(i=0; i<256; i++) { + int v = (i >> 5) - ((i >> 7) << 3) - 5; + dynamic_range_tab[i] = powf(2.0f, v) * ((i & 0x1F) | 0x20); + } + + /* generate scale factors for exponents and asymmetrical dequantization + reference: Section 7.3.2 Expansion of Mantissas for Asymmetric Quantization */ + for (i = 0; i < 25; i++) + scale_factors[i] = pow(2.0, -i); + + /* generate exponent tables + reference: Section 7.1.3 Exponent Decoding */ + for(i=0; i<128; i++) { + exp_ungroup_tab[i][0] = i / 25; + exp_ungroup_tab[i][1] = (i % 25) / 5; + exp_ungroup_tab[i][2] = (i % 25) % 5; + } +} + + +/** + * AVCodec initialization + */ +static int ac3_decode_init(AVCodecContext *avctx) +{ + AC3DecodeContext *s = avctx->priv_data; + s->avctx = avctx; + + ac3_common_init(); + ac3_tables_init(); + ff_mdct_init(&s->imdct_256, 8, 1); + ff_mdct_init(&s->imdct_512, 9, 1); + ff_kbd_window_init(s->window, 5.0, 256); + dsputil_init(&s->dsp, avctx); + av_init_random(0, &s->dith_state); + + /* set bias values for float to int16 conversion */ + if(s->dsp.float_to_int16 == ff_float_to_int16_c) { + s->add_bias = 385.0f; + s->mul_bias = 1.0f; + } else { + s->add_bias = 0.0f; + s->mul_bias = 32767.0f; + } + + /* allow downmixing to stereo or mono */ + if (avctx->channels > 0 && avctx->request_channels > 0 && + avctx->request_channels < avctx->channels && + avctx->request_channels <= 2) { + avctx->channels = avctx->request_channels; + } + + return 0; +} + +/** + * Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream. + * GetBitContext within AC3DecodeContext must point to + * start of the synchronized ac3 bitstream. + */ +static int ac3_parse_header(AC3DecodeContext *s) +{ + AC3HeaderInfo hdr; + GetBitContext *gbc = &s->gbc; + int err, i; + + err = ff_ac3_parse_header(gbc->buffer, &hdr); + if(err) + return err; + + if(hdr.bitstream_id > 10) + return AC3_PARSE_ERROR_BSID; + + /* get decoding parameters from header info */ + s->bit_alloc_params.sr_code = hdr.sr_code; + s->channel_mode = hdr.channel_mode; + s->lfe_on = hdr.lfe_on; + s->bit_alloc_params.sr_shift = hdr.sr_shift; + s->sample_rate = hdr.sample_rate; + s->bit_rate = hdr.bit_rate; + s->channels = hdr.channels; + s->fbw_channels = s->channels - s->lfe_on; + s->lfe_ch = s->fbw_channels + 1; + s->frame_size = hdr.frame_size; + + /* set default output to all source channels */ + s->out_channels = s->channels; + s->output_mode = s->channel_mode; + if(s->lfe_on) + s->output_mode |= AC3_OUTPUT_LFEON; + + /* set default mix levels */ + s->center_mix_level = 3; // -4.5dB + s->surround_mix_level = 4; // -6.0dB + + /* skip over portion of header which has already been read */ + skip_bits(gbc, 16); // skip the sync_word + skip_bits(gbc, 16); // skip crc1 + skip_bits(gbc, 8); // skip fscod and frmsizecod + skip_bits(gbc, 11); // skip bsid, bsmod, and acmod + if(s->channel_mode == AC3_CHMODE_STEREO) { + skip_bits(gbc, 2); // skip dsurmod + } else { + if((s->channel_mode & 1) && s->channel_mode != AC3_CHMODE_MONO) + s->center_mix_level = center_levels[get_bits(gbc, 2)]; + if(s->channel_mode & 4) + s->surround_mix_level = surround_levels[get_bits(gbc, 2)]; + } + skip_bits1(gbc); // skip lfeon + + /* read the rest of the bsi. read twice for dual mono mode. */ + i = !(s->channel_mode); + do { + skip_bits(gbc, 5); // skip dialog normalization + if (get_bits1(gbc)) + skip_bits(gbc, 8); //skip compression + if (get_bits1(gbc)) + skip_bits(gbc, 8); //skip language code + if (get_bits1(gbc)) + skip_bits(gbc, 7); //skip audio production information + } while (i--); + + skip_bits(gbc, 2); //skip copyright bit and original bitstream bit + + /* skip the timecodes (or extra bitstream information for Alternate Syntax) + TODO: read & use the xbsi1 downmix levels */ + if (get_bits1(gbc)) + skip_bits(gbc, 14); //skip timecode1 / xbsi1 + if (get_bits1(gbc)) + skip_bits(gbc, 14); //skip timecode2 / xbsi2 + + /* skip additional bitstream info */ + if (get_bits1(gbc)) { + i = get_bits(gbc, 6); + do { + skip_bits(gbc, 8); + } while(i--); + } + + return 0; +} + +/** + * Set stereo downmixing coefficients based on frame header info. + * reference: Section 7.8.2 Downmixing Into Two Channels + */ +static void set_downmix_coeffs(AC3DecodeContext *s) +{ + int i; + float cmix = gain_levels[s->center_mix_level]; + float smix = gain_levels[s->surround_mix_level]; + + for(i=0; i<s->fbw_channels; i++) { + s->downmix_coeffs[i][0] = gain_levels[ac3_default_coeffs[s->channel_mode][i][0]]; + s->downmix_coeffs[i][1] = gain_levels[ac3_default_coeffs[s->channel_mode][i][1]]; + } + if(s->channel_mode > 1 && s->channel_mode & 1) { + s->downmix_coeffs[1][0] = s->downmix_coeffs[1][1] = cmix; + } + if(s->channel_mode == AC3_CHMODE_2F1R || s->channel_mode == AC3_CHMODE_3F1R) { + int nf = s->channel_mode - 2; + s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf][1] = smix * LEVEL_MINUS_3DB; + } + if(s->channel_mode == AC3_CHMODE_2F2R || s->channel_mode == AC3_CHMODE_3F2R) { + int nf = s->channel_mode - 4; + s->downmix_coeffs[nf][0] = s->downmix_coeffs[nf+1][1] = smix; + } +} + +/** + * Decode the grouped exponents according to exponent strategy. + * reference: Section 7.1.3 Exponent Decoding + */ +static void decode_exponents(GetBitContext *gbc, int exp_strategy, int ngrps, + uint8_t absexp, int8_t *dexps) +{ + int i, j, grp, group_size; + int dexp[256]; + int expacc, prevexp; + + /* unpack groups */ + group_size = exp_strategy + (exp_strategy == EXP_D45); + for(grp=0,i=0; grp<ngrps; grp++) { + expacc = get_bits(gbc, 7); + dexp[i++] = exp_ungroup_tab[expacc][0]; + dexp[i++] = exp_ungroup_tab[expacc][1]; + dexp[i++] = exp_ungroup_tab[expacc][2]; + } + + /* convert to absolute exps and expand groups */ + prevexp = absexp; + for(i=0; i<ngrps*3; i++) { + prevexp = av_clip(prevexp + dexp[i]-2, 0, 24); + for(j=0; j<group_size; j++) { + dexps[(i*group_size)+j] = prevexp; + } + } +} + +/** + * Generate transform coefficients for each coupled channel in the coupling + * range using the coupling coefficients and coupling coordinates. + * reference: Section 7.4.3 Coupling Coordinate Format + */ +static void uncouple_channels(AC3DecodeContext *s) +{ + int i, j, ch, bnd, subbnd; + + subbnd = -1; + i = s->start_freq[CPL_CH]; + for(bnd=0; bnd<s->num_cpl_bands; bnd++) { + do { + subbnd++; + for(j=0; j<12; j++) { + for(ch=1; ch<=s->fbw_channels; ch++) { + if(s->channel_in_cpl[ch]) { + s->transform_coeffs[ch][i] = s->transform_coeffs[CPL_CH][i] * s->cpl_coords[ch][bnd] * 8.0f; + if (ch == 2 && s->phase_flags[bnd]) + s->transform_coeffs[ch][i] = -s->transform_coeffs[ch][i]; + } + } + i++; + } + } while(s->cpl_band_struct[subbnd]); + } +} + +/** + * Grouped mantissas for 3-level 5-level and 11-level quantization + */ +typedef struct { + float b1_mant[3]; + float b2_mant[3]; + float b4_mant[2]; + int b1ptr; + int b2ptr; + int b4ptr; +} mant_groups; + +/** + * Get the transform coefficients for a particular channel + * reference: Section 7.3 Quantization and Decoding of Mantissas + */ +static int get_transform_coeffs_ch(AC3DecodeContext *s, int ch_index, mant_groups *m) +{ + GetBitContext *gbc = &s->gbc; + int i, gcode, tbap, start, end; + uint8_t *exps; + uint8_t *bap; + float *coeffs; + + exps = s->dexps[ch_index]; + bap = s->bap[ch_index]; + coeffs = s->transform_coeffs[ch_index]; + start = s->start_freq[ch_index]; + end = s->end_freq[ch_index]; + + for (i = start; i < end; i++) { + tbap = bap[i]; + switch (tbap) { + case 0: + coeffs[i] = ((av_random(&s->dith_state) & 0xFFFF) / 65535.0f) - 0.5f; + break; + + case 1: + if(m->b1ptr > 2) { + gcode = get_bits(gbc, 5); + m->b1_mant[0] = b1_mantissas[gcode][0]; + m->b1_mant[1] = b1_mantissas[gcode][1]; + m->b1_mant[2] = b1_mantissas[gcode][2]; + m->b1ptr = 0; + } + coeffs[i] = m->b1_mant[m->b1ptr++]; + break; + + case 2: + if(m->b2ptr > 2) { + gcode = get_bits(gbc, 7); + m->b2_mant[0] = b2_mantissas[gcode][0]; + m->b2_mant[1] = b2_mantissas[gcode][1]; + m->b2_mant[2] = b2_mantissas[gcode][2]; + m->b2ptr = 0; + } + coeffs[i] = m->b2_mant[m->b2ptr++]; + break; + + case 3: + coeffs[i] = b3_mantissas[get_bits(gbc, 3)]; + break; + + case 4: + if(m->b4ptr > 1) { + gcode = get_bits(gbc, 7); + m->b4_mant[0] = b4_mantissas[gcode][0]; + m->b4_mant[1] = b4_mantissas[gcode][1]; + m->b4ptr = 0; + } + coeffs[i] = m->b4_mant[m->b4ptr++]; + break; + + case 5: + coeffs[i] = b5_mantissas[get_bits(gbc, 4)]; + break; + + default: + /* asymmetric dequantization */ + coeffs[i] = get_sbits(gbc, quantization_tab[tbap]) * scale_factors[quantization_tab[tbap]-1]; + break; + } + coeffs[i] *= scale_factors[exps[i]]; + } + + return 0; +} + +/** + * Remove random dithering from coefficients with zero-bit mantissas + * reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0) + */ +static void remove_dithering(AC3DecodeContext *s) { + int ch, i; + int end=0; + float *coeffs; + uint8_t *bap; + + for(ch=1; ch<=s->fbw_channels; ch++) { + if(!s->dither_flag[ch]) { + coeffs = s->transform_coeffs[ch]; + bap = s->bap[ch]; + if(s->channel_in_cpl[ch]) + end = s->start_freq[CPL_CH]; + else + end = s->end_freq[ch]; + for(i=0; i<end; i++) { + if(!bap[i]) + coeffs[i] = 0.0f; + } + if(s->channel_in_cpl[ch]) { + bap = s->bap[CPL_CH]; + for(; i<s->end_freq[CPL_CH]; i++) { + if(!bap[i]) + coeffs[i] = 0.0f; + } + } + } + } +} + +/** + * Get the transform coefficients. + */ +static int get_transform_coeffs(AC3DecodeContext *s) +{ + int ch, end; + int got_cplchan = 0; + mant_groups m; + + m.b1ptr = m.b2ptr = m.b4ptr = 3; + + for (ch = 1; ch <= s->channels; ch++) { + /* transform coefficients for full-bandwidth channel */ + if (get_transform_coeffs_ch(s, ch, &m)) + return -1; + /* tranform coefficients for coupling channel come right after the + coefficients for the first coupled channel*/ + if (s->channel_in_cpl[ch]) { + if (!got_cplchan) { + if (get_transform_coeffs_ch(s, CPL_CH, &m)) { + av_log(s->avctx, AV_LOG_ERROR, "error in decoupling channels\n"); + return -1; + } + uncouple_channels(s); + got_cplchan = 1; + } + end = s->end_freq[CPL_CH]; + } else { + end = s->end_freq[ch]; + } + do + s->transform_coeffs[ch][end] = 0; + while(++end < 256); + } + + /* if any channel doesn't use dithering, zero appropriate coefficients */ + if(!s->dither_all) + remove_dithering(s); + + return 0; +} + +/** + * Stereo rematrixing. + * reference: Section 7.5.4 Rematrixing : Decoding Technique + */ +static void do_rematrixing(AC3DecodeContext *s) +{ + int bnd, i; + int end, bndend; + float tmp0, tmp1; + + end = FFMIN(s->end_freq[1], s->end_freq[2]); + + for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) { + if(s->rematrixing_flags[bnd]) { + bndend = FFMIN(end, rematrix_band_tab[bnd+1]); + for(i=rematrix_band_tab[bnd]; i<bndend; i++) { + tmp0 = s->transform_coeffs[1][i]; + tmp1 = s->transform_coeffs[2][i]; + s->transform_coeffs[1][i] = tmp0 + tmp1; + s->transform_coeffs[2][i] = tmp0 - tmp1; + } + } + } +} + +/** + * Perform the 256-point IMDCT + */ +static void do_imdct_256(AC3DecodeContext *s, int chindex) +{ + int i, k; + DECLARE_ALIGNED_16(float, x[128]); + FFTComplex z[2][64]; + float *o_ptr = s->tmp_output; + + for(i=0; i<2; i++) { + /* de-interleave coefficients */ + for(k=0; k<128; k++) { + x[k] = s->transform_coeffs[chindex][2*k+i]; + } + + /* run standard IMDCT */ + s->imdct_256.fft.imdct_calc(&s->imdct_256, o_ptr, x, s->tmp_imdct); + + /* reverse the post-rotation & reordering from standard IMDCT */ + for(k=0; k<32; k++) { + z[i][32+k].re = -o_ptr[128+2*k]; + z[i][32+k].im = -o_ptr[2*k]; + z[i][31-k].re = o_ptr[2*k+1]; + z[i][31-k].im = o_ptr[128+2*k+1]; + } + } + + /* apply AC-3 post-rotation & reordering */ + for(k=0; k<64; k++) { + o_ptr[ 2*k ] = -z[0][ k].im; + o_ptr[ 2*k+1] = z[0][63-k].re; + o_ptr[128+2*k ] = -z[0][ k].re; + o_ptr[128+2*k+1] = z[0][63-k].im; + o_ptr[256+2*k ] = -z[1][ k].re; + o_ptr[256+2*k+1] = z[1][63-k].im; + o_ptr[384+2*k ] = z[1][ k].im; + o_ptr[384+2*k+1] = -z[1][63-k].re; + } +} + +/** + * Inverse MDCT Transform. + * Convert frequency domain coefficients to time-domain audio samples. + * reference: Section 7.9.4 Transformation Equations + */ +static inline void do_imdct(AC3DecodeContext *s) +{ + int ch; + int channels; + + /* Don't perform the IMDCT on the LFE channel unless it's used in the output */ + channels = s->fbw_channels; + if(s->output_mode & AC3_OUTPUT_LFEON) + channels++; + + for (ch=1; ch<=channels; ch++) { + if (s->block_switch[ch]) { + do_imdct_256(s, ch); + } else { + s->imdct_512.fft.imdct_calc(&s->imdct_512, s->tmp_output, + s->transform_coeffs[ch], s->tmp_imdct); + } + /* For the first half of the block, apply the window, add the delay + from the previous block, and send to output */ + s->dsp.vector_fmul_add_add(s->output[ch-1], s->tmp_output, + s->window, s->delay[ch-1], 0, 256, 1); + /* For the second half of the block, apply the window and store the + samples to delay, to be combined with the next block */ + s->dsp.vector_fmul_reverse(s->delay[ch-1], s->tmp_output+256, + s->window, 256); + } +} + +/** + * Downmix the output to mono or stereo. + */ +static void ac3_downmix(AC3DecodeContext *s) +{ + int i, j; + float v0, v1, s0, s1; + + for(i=0; i<256; i++) { + v0 = v1 = s0 = s1 = 0.0f; + for(j=0; j<s->fbw_channels; j++) { + v0 += s->output[j][i] * s->downmix_coeffs[j][0]; + v1 += s->output[j][i] * s->downmix_coeffs[j][1]; + s0 += s->downmix_coeffs[j][0]; + s1 += s->downmix_coeffs[j][1]; + } + v0 /= s0; + v1 /= s1; + if(s->output_mode == AC3_CHMODE_MONO) { + s->output[0][i] = (v0 + v1) * LEVEL_MINUS_3DB; + } else if(s->output_mode == AC3_CHMODE_STEREO) { + s->output[0][i] = v0; + s->output[1][i] = v1; + } + } +} + +/** + * Parse an audio block from AC-3 bitstream. + */ +static int ac3_parse_audio_block(AC3DecodeContext *s, int blk) +{ + int fbw_channels = s->fbw_channels; + int channel_mode = s->channel_mode; + int i, bnd, seg, ch; + GetBitContext *gbc = &s->gbc; + uint8_t bit_alloc_stages[AC3_MAX_CHANNELS]; + + memset(bit_alloc_stages, 0, AC3_MAX_CHANNELS); + + /* block switch flags */ + for (ch = 1; ch <= fbw_channels; ch++) + s->block_switch[ch] = get_bits1(gbc); + + /* dithering flags */ + s->dither_all = 1; + for (ch = 1; ch <= fbw_channels; ch++) { + s->dither_flag[ch] = get_bits1(gbc); + if(!s->dither_flag[ch]) + s->dither_all = 0; + } + + /* dynamic range */ + i = !(s->channel_mode); + do { + if(get_bits1(gbc)) { + s->dynamic_range[i] = ((dynamic_range_tab[get_bits(gbc, 8)]-1.0) * + s->avctx->drc_scale)+1.0; + } else if(blk == 0) { + s->dynamic_range[i] = 1.0f; + } + } while(i--); + + /* coupling strategy */ + if (get_bits1(gbc)) { + memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS); + s->cpl_in_use = get_bits1(gbc); + if (s->cpl_in_use) { + /* coupling in use */ + int cpl_begin_freq, cpl_end_freq; + + /* determine which channels are coupled */ + for (ch = 1; ch <= fbw_channels; ch++) + s->channel_in_cpl[ch] = get_bits1(gbc); + + /* phase flags in use */ + if (channel_mode == AC3_CHMODE_STEREO) + s->phase_flags_in_use = get_bits1(gbc); + + /* coupling frequency range and band structure */ + cpl_begin_freq = get_bits(gbc, 4); + cpl_end_freq = get_bits(gbc, 4); + if (3 + cpl_end_freq - cpl_begin_freq < 0) { + av_log(s->avctx, AV_LOG_ERROR, "3+cplendf = %d < cplbegf = %d\n", 3+cpl_end_freq, cpl_begin_freq); + return -1; + } + s->num_cpl_bands = s->num_cpl_subbands = 3 + cpl_end_freq - cpl_begin_freq; + s->start_freq[CPL_CH] = cpl_begin_freq * 12 + 37; + s->end_freq[CPL_CH] = cpl_end_freq * 12 + 73; + for (bnd = 0; bnd < s->num_cpl_subbands - 1; bnd++) { + if (get_bits1(gbc)) { + s->cpl_band_struct[bnd] = 1; + s->num_cpl_bands--; + } + } + s->cpl_band_struct[s->num_cpl_subbands-1] = 0; + } else { + /* coupling not in use */ + for (ch = 1; ch <= fbw_channels; ch++) + s->channel_in_cpl[ch] = 0; + } + } + + /* coupling coordinates */ + if (s->cpl_in_use) { + int cpl_coords_exist = 0; + + for (ch = 1; ch <= fbw_channels; ch++) { + if (s->channel_in_cpl[ch]) { + if (get_bits1(gbc)) { + int master_cpl_coord, cpl_coord_exp, cpl_coord_mant; + cpl_coords_exist = 1; + master_cpl_coord = 3 * get_bits(gbc, 2); + for (bnd = 0; bnd < s->num_cpl_bands; bnd++) { + cpl_coord_exp = get_bits(gbc, 4); + cpl_coord_mant = get_bits(gbc, 4); + if (cpl_coord_exp == 15) + s->cpl_coords[ch][bnd] = cpl_coord_mant / 16.0f; + else + s->cpl_coords[ch][bnd] = (cpl_coord_mant + 16.0f) / 32.0f; + s->cpl_coords[ch][bnd] *= scale_factors[cpl_coord_exp + master_cpl_coord]; + } + } + } + } + /* phase flags */ + if (channel_mode == AC3_CHMODE_STEREO && cpl_coords_exist) { + for (bnd = 0; bnd < s->num_cpl_bands; bnd++) { + s->phase_flags[bnd] = s->phase_flags_in_use? get_bits1(gbc) : 0; + } + } + } + + /* stereo rematrixing strategy and band structure */ + if (channel_mode == AC3_CHMODE_STEREO) { + if (get_bits1(gbc)) { + s->num_rematrixing_bands = 4; + if(s->cpl_in_use && s->start_freq[CPL_CH] <= 61) + s->num_rematrixing_bands -= 1 + (s->start_freq[CPL_CH] == 37); + for(bnd=0; bnd<s->num_rematrixing_bands; bnd++) + s->rematrixing_flags[bnd] = get_bits1(gbc); + } + } + + /* exponent strategies for each channel */ + s->exp_strategy[CPL_CH] = EXP_REUSE; + s->exp_strategy[s->lfe_ch] = EXP_REUSE; + for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { + if(ch == s->lfe_ch) + s->exp_strategy[ch] = get_bits(gbc, 1); + else + s->exp_strategy[ch] = get_bits(gbc, 2); + if(s->exp_strategy[ch] != EXP_REUSE) + bit_alloc_stages[ch] = 3; + } + + /* channel bandwidth */ + for (ch = 1; ch <= fbw_channels; ch++) { + s->start_freq[ch] = 0; + if (s->exp_strategy[ch] != EXP_REUSE) { + int prev = s->end_freq[ch]; + if (s->channel_in_cpl[ch]) + s->end_freq[ch] = s->start_freq[CPL_CH]; + else { + int bandwidth_code = get_bits(gbc, 6); + if (bandwidth_code > 60) { + av_log(s->avctx, AV_LOG_ERROR, "bandwidth code = %d > 60", bandwidth_code); + return -1; + } + s->end_freq[ch] = bandwidth_code * 3 + 73; + } + if(blk > 0 && s->end_freq[ch] != prev) + memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS); + } + } + s->start_freq[s->lfe_ch] = 0; + s->end_freq[s->lfe_ch] = 7; + + /* decode exponents for each channel */ + for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { + if (s->exp_strategy[ch] != EXP_REUSE) { + int group_size, num_groups; + group_size = 3 << (s->exp_strategy[ch] - 1); + if(ch == CPL_CH) + num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size; + else if(ch == s->lfe_ch) + num_groups = 2; + else + num_groups = (s->end_freq[ch] + group_size - 4) / group_size; + s->dexps[ch][0] = get_bits(gbc, 4) << !ch; + decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0], + &s->dexps[ch][s->start_freq[ch]+!!ch]); + if(ch != CPL_CH && ch != s->lfe_ch) + skip_bits(gbc, 2); /* skip gainrng */ + } + } + + /* bit allocation information */ + if (get_bits1(gbc)) { + s->bit_alloc_params.slow_decay = ff_ac3_slow_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift; + s->bit_alloc_params.fast_decay = ff_ac3_fast_decay_tab[get_bits(gbc, 2)] >> s->bit_alloc_params.sr_shift; + s->bit_alloc_params.slow_gain = ff_ac3_slow_gain_tab[get_bits(gbc, 2)]; + s->bit_alloc_params.db_per_bit = ff_ac3_db_per_bit_tab[get_bits(gbc, 2)]; + s->bit_alloc_params.floor = ff_ac3_floor_tab[get_bits(gbc, 3)]; + for(ch=!s->cpl_in_use; ch<=s->channels; ch++) { + bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2); + } + } + + /* signal-to-noise ratio offsets and fast gains (signal-to-mask ratios) */ + if (get_bits1(gbc)) { + int csnr; + csnr = (get_bits(gbc, 6) - 15) << 4; + for (ch = !s->cpl_in_use; ch <= s->channels; ch++) { /* snr offset and fast gain */ + s->snr_offset[ch] = (csnr + get_bits(gbc, 4)) << 2; + s->fast_gain[ch] = ff_ac3_fast_gain_tab[get_bits(gbc, 3)]; + } + memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS); + } + + /* coupling leak information */ + if (s->cpl_in_use && get_bits1(gbc)) { + s->bit_alloc_params.cpl_fast_leak = get_bits(gbc, 3); + s->bit_alloc_params.cpl_slow_leak = get_bits(gbc, 3); + bit_alloc_stages[CPL_CH] = FFMAX(bit_alloc_stages[CPL_CH], 2); + } + + /* delta bit allocation information */ + if (get_bits1(gbc)) { + /* delta bit allocation exists (strategy) */ + for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) { + s->dba_mode[ch] = get_bits(gbc, 2); + if (s->dba_mode[ch] == DBA_RESERVED) { + av_log(s->avctx, AV_LOG_ERROR, "delta bit allocation strategy reserved\n"); + return -1; + } + bit_alloc_stages[ch] = FFMAX(bit_alloc_stages[ch], 2); + } + /* channel delta offset, len and bit allocation */ + for (ch = !s->cpl_in_use; ch <= fbw_channels; ch++) { + if (s->dba_mode[ch] == DBA_NEW) { + s->dba_nsegs[ch] = get_bits(gbc, 3); + for (seg = 0; seg <= s->dba_nsegs[ch]; seg++) { + s->dba_offsets[ch][seg] = get_bits(gbc, 5); + s->dba_lengths[ch][seg] = get_bits(gbc, 4); + s->dba_values[ch][seg] = get_bits(gbc, 3); + } + } + } + } else if(blk == 0) { + for(ch=0; ch<=s->channels; ch++) { + s->dba_mode[ch] = DBA_NONE; + } + } + + /* Bit allocation */ + for(ch=!s->cpl_in_use; ch<=s->channels; ch++) { + if(bit_alloc_stages[ch] > 2) { + /* Exponent mapping into PSD and PSD integration */ + ff_ac3_bit_alloc_calc_psd(s->dexps[ch], + s->start_freq[ch], s->end_freq[ch], + s->psd[ch], s->band_psd[ch]); + } + if(bit_alloc_stages[ch] > 1) { + /* Compute excitation function, Compute masking curve, and + Apply delta bit allocation */ + ff_ac3_bit_alloc_calc_mask(&s->bit_alloc_params, s->band_psd[ch], + s->start_freq[ch], s->end_freq[ch], + s->fast_gain[ch], (ch == s->lfe_ch), + s->dba_mode[ch], s->dba_nsegs[ch], + s->dba_offsets[ch], s->dba_lengths[ch], + s->dba_values[ch], s->mask[ch]); + } + if(bit_alloc_stages[ch] > 0) { + /* Compute bit allocation */ + ff_ac3_bit_alloc_calc_bap(s->mask[ch], s->psd[ch], + s->start_freq[ch], s->end_freq[ch], + s->snr_offset[ch], + s->bit_alloc_params.floor, + s->bap[ch]); + } + } + + /* unused dummy data */ + if (get_bits1(gbc)) { + int skipl = get_bits(gbc, 9); + while(skipl--) + skip_bits(gbc, 8); + } + + /* unpack the transform coefficients + this also uncouples channels if coupling is in use. */ + if (get_transform_coeffs(s)) { + av_log(s->avctx, AV_LOG_ERROR, "Error in routine get_transform_coeffs\n"); + return -1; + } + + /* recover coefficients if rematrixing is in use */ + if(s->channel_mode == AC3_CHMODE_STEREO) + do_rematrixing(s); + + /* apply scaling to coefficients (headroom, dynrng) */ + for(ch=1; ch<=s->channels; ch++) { + float gain = 2.0f * s->mul_bias; + if(s->channel_mode == AC3_CHMODE_DUALMONO) { + gain *= s->dynamic_range[ch-1]; + } else { + gain *= s->dynamic_range[0]; + } + for(i=0; i<s->end_freq[ch]; i++) { + s->transform_coeffs[ch][i] *= gain; + } + } + + do_imdct(s); + + /* downmix output if needed */ + if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) && + s->fbw_channels == s->out_channels)) { + ac3_downmix(s); + } + + /* convert float to 16-bit integer */ + for(ch=0; ch<s->out_channels; ch++) { + for(i=0; i<256; i++) { + s->output[ch][i] += s->add_bias; + } + s->dsp.float_to_int16(s->int_output[ch], s->output[ch], 256); + } + + return 0; +} + +/** + * Decode a single AC-3 frame. + */ +static int ac3_decode_frame(AVCodecContext * avctx, void *data, int *data_size, uint8_t *buf, int buf_size) +{ + AC3DecodeContext *s = avctx->priv_data; + int16_t *out_samples = (int16_t *)data; + int i, blk, ch, err; + + /* initialize the GetBitContext with the start of valid AC-3 Frame */ + init_get_bits(&s->gbc, buf, buf_size * 8); + + /* parse the syncinfo */ + err = ac3_parse_header(s); + if(err) { + switch(err) { + case AC3_PARSE_ERROR_SYNC: + av_log(avctx, AV_LOG_ERROR, "frame sync error\n"); + break; + case AC3_PARSE_ERROR_BSID: + av_log(avctx, AV_LOG_ERROR, "invalid bitstream id\n"); + break; + case AC3_PARSE_ERROR_SAMPLE_RATE: + av_log(avctx, AV_LOG_ERROR, "invalid sample rate\n"); + break; + case AC3_PARSE_ERROR_FRAME_SIZE: + av_log(avctx, AV_LOG_ERROR, "invalid frame size\n"); + break; + default: + av_log(avctx, AV_LOG_ERROR, "invalid header\n"); + break; + } + return -1; + } + + /* check that reported frame size fits in input buffer */ + if(s->frame_size > buf_size) { + av_log(avctx, AV_LOG_ERROR, "incomplete frame\n"); + return -1; + } + + /* check for crc mismatch */ + if(avctx->error_resilience >= FF_ER_CAREFUL) { + if(av_crc(av_crc_get_table(AV_CRC_16_ANSI), 0, &buf[2], s->frame_size-2)) { + av_log(avctx, AV_LOG_ERROR, "frame CRC mismatch\n"); + return -1; + } + /* TODO: error concealment */ + } + + avctx->sample_rate = s->sample_rate; + avctx->bit_rate = s->bit_rate; + + /* channel config */ + s->out_channels = s->channels; + if (avctx->request_channels > 0 && avctx->request_channels <= 2 && + avctx->request_channels < s->channels) { + s->out_channels = avctx->request_channels; + s->output_mode = avctx->request_channels == 1 ? AC3_CHMODE_MONO : AC3_CHMODE_STEREO; + } + avctx->channels = s->out_channels; + + /* set downmixing coefficients if needed */ + if(s->channels != s->out_channels && !((s->output_mode & AC3_OUTPUT_LFEON) && + s->fbw_channels == s->out_channels)) { + set_downmix_coeffs(s); + } + + /* parse the audio blocks */ + for (blk = 0; blk < NB_BLOCKS; blk++) { + if (ac3_parse_audio_block(s, blk)) { + av_log(avctx, AV_LOG_ERROR, "error parsing the audio block\n"); + *data_size = 0; + return s->frame_size; + } + for (i = 0; i < 256; i++) + for (ch = 0; ch < s->out_channels; ch++) + *(out_samples++) = s->int_output[ch][i]; + } + *data_size = NB_BLOCKS * 256 * avctx->channels * sizeof (int16_t); + return s->frame_size; +} + +/** + * Uninitialize the AC-3 decoder. + */ +static int ac3_decode_end(AVCodecContext *avctx) +{ + AC3DecodeContext *s = avctx->priv_data; + ff_mdct_end(&s->imdct_512); + ff_mdct_end(&s->imdct_256); + + return 0; +} + +AVCodec ac3_decoder = { + .name = "ac3", + .type = CODEC_TYPE_AUDIO, + .id = CODEC_ID_AC3, + .priv_data_size = sizeof (AC3DecodeContext), + .init = ac3_decode_init, + .close = ac3_decode_end, + .decode = ac3_decode_frame, +}; |