Data Structures | Functions | Variables
libavcodec/ac3dec.c File Reference
#include <stdio.h>
#include <stddef.h>
#include <math.h>
#include <string.h>
#include "libavutil/crc.h"
#include "libavutil/opt.h"
#include "internal.h"
#include "aac_ac3_parser.h"
#include "ac3_parser.h"
#include "ac3dec.h"
Include dependency graph for libavcodec/ac3dec.c:

Go to the source code of this file.

Data Structures

struct  mant_groups
 Grouped mantissas for 3-level 5-level and 11-level quantization. More...
 

Functions

static int symmetric_dequant (int code, int levels)
 Symmetrical Dequantization reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization Tables 7.19 to 7.23. More...
 
static av_cold void ac3_tables_init (void)
 
static av_cold int ac3_decode_init (AVCodecContext *avctx)
 AVCodec initialization. More...
 
static int ac3_parse_header (AC3DecodeContext *s)
 Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream. More...
 
static int parse_frame_header (AC3DecodeContext *s)
 Common function to parse AC-3 or E-AC-3 frame header. More...
 
static void set_downmix_coeffs (AC3DecodeContext *s)
 Set stereo downmixing coefficients based on frame header info. More...
 
static int decode_exponents (GetBitContext *gbc, int exp_strategy, int ngrps, uint8_t absexp, int8_t *dexps)
 Decode the grouped exponents according to exponent strategy. More...
 
static void calc_transform_coeffs_cpl (AC3DecodeContext *s)
 Generate transform coefficients for each coupled channel in the coupling range using the coupling coefficients and coupling coordinates. More...
 
static void ac3_decode_transform_coeffs_ch (AC3DecodeContext *s, int ch_index, mant_groups *m)
 Decode the transform coefficients for a particular channel reference: Section 7.3 Quantization and Decoding of Mantissas. More...
 
static void remove_dithering (AC3DecodeContext *s)
 Remove random dithering from coupling range coefficients with zero-bit mantissas for coupled channels which do not use dithering. More...
 
static void decode_transform_coeffs_ch (AC3DecodeContext *s, int blk, int ch, mant_groups *m)
 
static void decode_transform_coeffs (AC3DecodeContext *s, int blk)
 Decode the transform coefficients. More...
 
static void do_rematrixing (AC3DecodeContext *s)
 Stereo rematrixing. More...
 
static void do_imdct (AC3DecodeContext *s, int channels)
 Inverse MDCT Transform. More...
 
static void ac3_upmix_delay (AC3DecodeContext *s)
 Upmix delay samples from stereo to original channel layout. More...
 
static void decode_band_structure (GetBitContext *gbc, int blk, int eac3, int ecpl, int start_subband, int end_subband, const uint8_t *default_band_struct, int *num_bands, uint8_t *band_sizes)
 Decode band structure for coupling, spectral extension, or enhanced coupling. More...
 
static int decode_audio_block (AC3DecodeContext *s, int blk)
 Decode a single audio block from the AC-3 bitstream. More...
 
static int ac3_decode_frame (AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt)
 Decode a single AC-3 frame. More...
 
static av_cold int ac3_decode_end (AVCodecContext *avctx)
 Uninitialize the AC-3 decoder. More...
 

Variables

static uint8_t ungroup_3_in_7_bits_tab [128][3]
 table for ungrouping 3 values in 7 bits. More...
 
static int b1_mantissas [32][3]
 tables for ungrouping mantissas More...
 
static int b2_mantissas [128][3]
 
static int b3_mantissas [8]
 
static int b4_mantissas [128][2]
 
static int b5_mantissas [16]
 
static const uint8_t quantization_tab [16]
 Quantization table: levels for symmetric. More...
 
static float dynamic_range_tab [256]
 dynamic range table. More...
 
static const float gain_levels [9]
 Adjustments in dB gain. More...
 
static const uint8_t ac3_default_coeffs [8][5][2]
 Table for default stereo downmixing coefficients reference: Section 7.8.2 Downmixing Into Two Channels. More...
 
static const AVOption options []
 
static const AVClass ac3_decoder_class
 
AVCodec ff_ac3_decoder
 
static const AVClass eac3_decoder_class
 
AVCodec ff_eac3_decoder
 

Function Documentation

static av_cold int ac3_decode_end ( AVCodecContext *  avctx)
static

Uninitialize the AC-3 decoder.

Definition at line 1421 of file libavcodec/ac3dec.c.

static int ac3_decode_frame ( AVCodecContext *  avctx,
void *  data,
int *  got_frame_ptr,
AVPacket *  avpkt 
)
static

Decode a single AC-3 frame.

Definition at line 1264 of file libavcodec/ac3dec.c.

static av_cold int ac3_decode_init ( AVCodecContext *  avctx)
static

AVCodec initialization.

Definition at line 160 of file libavcodec/ac3dec.c.

static void ac3_decode_transform_coeffs_ch ( AC3DecodeContext *  s,
int  ch_index,
mant_groups *  m 
)
static

Decode the transform coefficients for a particular channel reference: Section 7.3 Quantization and Decoding of Mantissas.

Definition at line 426 of file libavcodec/ac3dec.c.

Referenced by decode_transform_coeffs_ch().

static int ac3_parse_header ( AC3DecodeContext *  s)
static

Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.

GetBitContext within AC3DecodeContext must point to the start of the synchronized AC-3 bitstream.

Definition at line 201 of file libavcodec/ac3dec.c.

Referenced by parse_frame_header().

static av_cold void ac3_tables_init ( void  )
static

Definition at line 108 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_init().

static void ac3_upmix_delay ( AC3DecodeContext *  s)
static

Upmix delay samples from stereo to original channel layout.

Definition at line 625 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static void calc_transform_coeffs_cpl ( AC3DecodeContext *  s)
static

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

Definition at line 385 of file libavcodec/ac3dec.c.

Referenced by decode_transform_coeffs().

static int decode_audio_block ( AC3DecodeContext *  s,
int  blk 
)
static

Decode a single audio block from the AC-3 bitstream.

Definition at line 718 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_frame().

static void decode_band_structure ( GetBitContext *  gbc,
int  blk,
int  eac3,
int  ecpl,
int  start_subband,
int  end_subband,
const uint8_t *  default_band_struct,
int *  num_bands,
uint8_t *  band_sizes 
)
static

Decode band structure for coupling, spectral extension, or enhanced coupling.

The band structure defines how many subbands are in each band. For each subband in the range, 1 means it is combined with the previous band, and 0 means that it starts a new band.

Parameters
[in]gbcbit reader context
[in]blkblock number
[in]eac3flag to indicate E-AC-3
[in]ecplflag to indicate enhanced coupling
[in]start_subbandsubband number for start of range
[in]end_subbandsubband number for end of range
[in]default_band_structdefault band structure table
[out]num_bandsnumber of bands (optionally NULL)
[out]band_sizesarray containing the number of bins in each band (optionally NULL)

Definition at line 666 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static int decode_exponents ( GetBitContext *  gbc,
int  exp_strategy,
int  ngrps,
uint8_t  absexp,
int8_t *  dexps 
)
static

Decode the grouped exponents according to exponent strategy.

reference: Section 7.1.3 Exponent Decoding

Definition at line 348 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static void decode_transform_coeffs ( AC3DecodeContext *  s,
int  blk 
)
static

Decode the transform coefficients.

Definition at line 537 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static void decode_transform_coeffs_ch ( AC3DecodeContext *  s,
int  blk,
int  ch,
mant_groups *  m 
)
static

Definition at line 517 of file libavcodec/ac3dec.c.

Referenced by decode_transform_coeffs().

static void do_imdct ( AC3DecodeContext *  s,
int  channels 
)
inlinestatic

Inverse MDCT Transform.

Convert frequency domain coefficients to time-domain audio samples. reference: Section 7.9.4 Transformation Equations

Definition at line 597 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static void do_rematrixing ( AC3DecodeContext *  s)
static

Stereo rematrixing.

reference: Section 7.5.4 Rematrixing : Decoding Technique

Definition at line 573 of file libavcodec/ac3dec.c.

Referenced by decode_audio_block().

static int parse_frame_header ( AC3DecodeContext *  s)
static

Common function to parse AC-3 or E-AC-3 frame header.

Definition at line 241 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_frame().

static void remove_dithering ( AC3DecodeContext *  s)
static

Remove random dithering from coupling range coefficients with zero-bit mantissas for coupled channels which do not use dithering.

reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0)

Definition at line 504 of file libavcodec/ac3dec.c.

Referenced by decode_transform_coeffs().

static void set_downmix_coeffs ( AC3DecodeContext *  s)
static

Set stereo downmixing coefficients based on frame header info.

reference: Section 7.8.2 Downmixing Into Two Channels

Definition at line 301 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_frame().

static int symmetric_dequant ( int  code,
int  levels 
)
inlinestatic

Symmetrical Dequantization reference: Section 7.3.3 Expansion of Mantissas for Symmetrical Quantization Tables 7.19 to 7.23.

Definition at line 100 of file libavcodec/ac3dec.c.

Referenced by ac3_tables_init().

Variable Documentation

const AVClass ac3_decoder_class
static
Initial value:
= {
.class_name = "AC3 decoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
}
av_default_item_name
av_default_item_name
Definition: libvo-amrwbenc.c:49
options
static const AVOption options[]
Definition: libavcodec/ac3dec.c:1432
LIBAVUTIL_VERSION_INT
LIBAVUTIL_VERSION_INT
Definition: eval.c:55

Definition at line 1444 of file libavcodec/ac3dec.c.

const uint8_t ac3_default_coeffs[8][5][2]
static
Initial value:
= {
{ { 2, 7 }, { 7, 2 }, },
{ { 4, 4 }, },
{ { 2, 7 }, { 7, 2 }, },
{ { 2, 7 }, { 5, 5 }, { 7, 2 }, },
{ { 2, 7 }, { 7, 2 }, { 6, 6 }, },
{ { 2, 7 }, { 5, 5 }, { 7, 2 }, { 8, 8 }, },
{ { 2, 7 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
{ { 2, 7 }, { 5, 5 }, { 7, 2 }, { 6, 7 }, { 7, 6 }, },
}

Table for default stereo downmixing coefficients reference: Section 7.8.2 Downmixing Into Two Channels.

Definition at line 83 of file libavcodec/ac3dec.c.

Referenced by set_downmix_coeffs().

int b1_mantissas[32][3]
static

tables for ungrouping mantissas

Definition at line 48 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

int b2_mantissas[128][3]
static

Definition at line 49 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

int b3_mantissas[8]
static

Definition at line 50 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

int b4_mantissas[128][2]
static

Definition at line 51 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

int b5_mantissas[16]
static

Definition at line 52 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

float dynamic_range_tab[256]
static

dynamic range table.

converts codes to scale factors.

Definition at line 64 of file libavcodec/ac3dec.c.

Referenced by ac3_tables_init(), and decode_audio_block().

const AVClass eac3_decoder_class
static
Initial value:
= {
.class_name = "E-AC3 decoder",
.item_name = av_default_item_name,
.option = options,
.version = LIBAVUTIL_VERSION_INT,
}
av_default_item_name
av_default_item_name
Definition: libvo-amrwbenc.c:49
options
static const AVOption options[]
Definition: libavcodec/ac3dec.c:1432
LIBAVUTIL_VERSION_INT
LIBAVUTIL_VERSION_INT
Definition: eval.c:55

Definition at line 1467 of file libavcodec/ac3dec.c.

AVCodec ff_ac3_decoder
Initial value:
= {
.name = "ac3",
.type = AVMEDIA_TYPE_AUDIO,
.id = AV_CODEC_ID_AC3,
.priv_data_size = sizeof (AC3DecodeContext),
.init = ac3_decode_init,
.close = ac3_decode_end,
.decode = ac3_decode_frame,
.capabilities = CODEC_CAP_DR1,
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
AV_SAMPLE_FMT_NONE },
.priv_class = &ac3_decoder_class,
}
init
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
ac3_decode_end
static av_cold int ac3_decode_end(AVCodecContext *avctx)
Uninitialize the AC-3 decoder.
Definition: libavcodec/ac3dec.c:1421
CODEC_CAP_DR1
#define CODEC_CAP_DR1
Codec uses get_buffer() for allocating buffers and supports custom allocators.
Definition: libavcodec/avcodec.h:743
AV_SAMPLE_FMT_FLTP
float, planar
Definition: samplefmt.h:60
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: libavutil/internal.h:123
AVMEDIA_TYPE_AUDIO
Definition: avutil.h:144
ac3_decoder_class
static const AVClass ac3_decoder_class
Definition: libavcodec/ac3dec.c:1444
ac3_decode_frame
static int ac3_decode_frame(AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt)
Decode a single AC-3 frame.
Definition: libavcodec/ac3dec.c:1264
AV_CODEC_ID_AC3
Definition: libavcodec/avcodec.h:384
close
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:375
AVSampleFormat
AVSampleFormat
Audio Sample Formats.
Definition: samplefmt.h:49
decode
static int decode(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: crystalhd.c:868
ac3_decode_init
static av_cold int ac3_decode_init(AVCodecContext *avctx)
AVCodec initialization.
Definition: libavcodec/ac3dec.c:160

Definition at line 1451 of file libavcodec/ac3dec.c.

AVCodec ff_eac3_decoder
Initial value:
= {
.name = "eac3",
.type = AVMEDIA_TYPE_AUDIO,
.id = AV_CODEC_ID_EAC3,
.priv_data_size = sizeof (AC3DecodeContext),
.init = ac3_decode_init,
.close = ac3_decode_end,
.decode = ac3_decode_frame,
.capabilities = CODEC_CAP_DR1,
.long_name = NULL_IF_CONFIG_SMALL("ATSC A/52B (AC-3, E-AC-3)"),
.sample_fmts = (const enum AVSampleFormat[]) { AV_SAMPLE_FMT_FLTP,
AV_SAMPLE_FMT_NONE },
.priv_class = &eac3_decoder_class,
}
init
static av_cold int init(AVCodecContext *avctx)
Definition: avrndec.c:35
eac3_decoder_class
static const AVClass eac3_decoder_class
Definition: libavcodec/ac3dec.c:1467
ac3_decode_end
static av_cold int ac3_decode_end(AVCodecContext *avctx)
Uninitialize the AC-3 decoder.
Definition: libavcodec/ac3dec.c:1421
CODEC_CAP_DR1
#define CODEC_CAP_DR1
Codec uses get_buffer() for allocating buffers and supports custom allocators.
Definition: libavcodec/avcodec.h:743
AV_SAMPLE_FMT_FLTP
float, planar
Definition: samplefmt.h:60
NULL_IF_CONFIG_SMALL
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: libavutil/internal.h:123
AVMEDIA_TYPE_AUDIO
Definition: avutil.h:144
ac3_decode_frame
static int ac3_decode_frame(AVCodecContext *avctx, void *data, int *got_frame_ptr, AVPacket *avpkt)
Decode a single AC-3 frame.
Definition: libavcodec/ac3dec.c:1264
close
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:375
AV_CODEC_ID_EAC3
Definition: libavcodec/avcodec.h:422
AVSampleFormat
AVSampleFormat
Audio Sample Formats.
Definition: samplefmt.h:49
decode
static int decode(AVCodecContext *avctx, void *data, int *got_frame, AVPacket *avpkt)
Definition: crystalhd.c:868
ac3_decode_init
static av_cold int ac3_decode_init(AVCodecContext *avctx)
AVCodec initialization.
Definition: libavcodec/ac3dec.c:160

Definition at line 1474 of file libavcodec/ac3dec.c.

const float gain_levels[9]
static
Initial value:
= {
LEVEL_PLUS_3DB,
LEVEL_PLUS_1POINT5DB,
LEVEL_ONE,
LEVEL_MINUS_1POINT5DB,
LEVEL_MINUS_3DB,
LEVEL_MINUS_4POINT5DB,
LEVEL_MINUS_6DB,
LEVEL_ZERO,
LEVEL_MINUS_9DB
}
LEVEL_PLUS_1POINT5DB
#define LEVEL_PLUS_1POINT5DB
Definition: ac3.h:56
LEVEL_MINUS_1POINT5DB
#define LEVEL_MINUS_1POINT5DB
Definition: ac3.h:57
LEVEL_MINUS_9DB
#define LEVEL_MINUS_9DB
Definition: ac3.h:61
LEVEL_MINUS_3DB
#define LEVEL_MINUS_3DB
Definition: ac3.h:58
LEVEL_MINUS_4POINT5DB
#define LEVEL_MINUS_4POINT5DB
Definition: ac3.h:59
LEVEL_ZERO
#define LEVEL_ZERO
Definition: ac3.h:62
LEVEL_ONE
#define LEVEL_ONE
Definition: ac3.h:63
LEVEL_PLUS_3DB
#define LEVEL_PLUS_3DB
Definition: ac3.h:55
LEVEL_MINUS_6DB
#define LEVEL_MINUS_6DB
Definition: ac3.h:60

Adjustments in dB gain.

Definition at line 67 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_frame(), and set_downmix_coeffs().

const AVOption options[]
static
Initial value:
= {
{ "drc_scale", "percentage of dynamic range compression to apply", OFFSET(drc_scale), AV_OPT_TYPE_FLOAT, {.dbl = 1.0}, 0.0, 1.0, PAR },
{"dmix_mode", "Preferred Stereo Downmix Mode", OFFSET(preferred_stereo_downmix), AV_OPT_TYPE_INT, {.i64 = -1 }, -1, 2, 0, "dmix_mode"},
{"ltrt_cmixlev", "Lt/Rt Center Mix Level", OFFSET(ltrt_center_mix_level), AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
{"ltrt_surmixlev", "Lt/Rt Surround Mix Level", OFFSET(ltrt_surround_mix_level), AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
{"loro_cmixlev", "Lo/Ro Center Mix Level", OFFSET(loro_center_mix_level), AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
{"loro_surmixlev", "Lo/Ro Surround Mix Level", OFFSET(loro_surround_mix_level), AV_OPT_TYPE_FLOAT, {.dbl = -1.0 }, -1.0, 2.0, 0},
{ NULL},
}
AV_OPT_TYPE_INT
Definition: opt.h:222
AV_OPT_TYPE_FLOAT
Definition: opt.h:225
NULL
NULL
Definition: eval.c:55
PAR
Definition: af_afade.c:45
OFFSET
#define OFFSET(x)
Definition: ffmpeg_opt.c:2553

Definition at line 1432 of file libavcodec/ac3dec.c.

const uint8_t quantization_tab[16]
static
Initial value:
= {
0, 3, 5, 7, 11, 15,
5, 6, 7, 8, 9, 10, 11, 12, 14, 16
}

Quantization table: levels for symmetric.

bits for asymmetric. reference: Table 7.18 Mapping of bap to Quantizer

Definition at line 58 of file libavcodec/ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch().

uint8_t ungroup_3_in_7_bits_tab[128][3]
static

table for ungrouping 3 values in 7 bits.

used for exponents and bap=2 mantissas

Definition at line 45 of file libavcodec/ac3dec.c.

Referenced by ac3_tables_init(), and decode_exponents().

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