#include <stdio.h>
#include <stddef.h>
#include <math.h>
#include <string.h>
#include "libavutil/channel_layout.h"
#include "libavutil/crc.h"
#include "libavutil/downmix_info.h"
#include "libavutil/opt.h"
#include "bswapdsp.h"
#include "internal.h"
#include "aac_ac3_parser.h"
#include "ac3_parser_internal.h"
#include "ac3dec.h"
#include "ac3dec_data.h"
#include "kbdwin.h"

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 int	set_downmix_coeffs (AC3DecodeContext *s)
	Set stereo downmixing coefficients based on frame header info. More...

static int	decode_exponents (AC3DecodeContext s, 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, int offset)
	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, uint8_t *band_struct, int band_struct_size)
	Decode band structure for coupling, spectral extension, or enhanced coupling. More...

static int	spx_strategy (AC3DecodeContext *s, int blk)

static void	spx_coordinates (AC3DecodeContext *s)

static int	coupling_strategy (AC3DecodeContext s, int blk, uint8_t bit_alloc_stages)

static int	coupling_coordinates (AC3DecodeContext *s, int blk)

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

float	ff_ac3_heavy_dynamic_range_tab [256]

static const float	gain_levels [9]
	Adjustments in dB gain. More...

static const float	gain_levels_lfe [32]
	Adjustments in dB gain (LFE, +10 to -21 dB) 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...

Function Documentation

◆ symmetric_dequant()

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 115 of file ac3dec.c.

Referenced by ac3_tables_init().

◆ ac3_tables_init()

static av_cold void ac3_tables_init ( void )

static

Definition at line 123 of file ac3dec.c.

Referenced by ac3_decode_init().

◆ ac3_decode_init()

static av_cold int ac3_decode_init ( AVCodecContext * avctx )

static

AVCodec initialization.

Definition at line 184 of file ac3dec.c.

◆ ac3_parse_header()

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 234 of file ac3dec.c.

Referenced by parse_frame_header().

◆ parse_frame_header()

static int parse_frame_header ( AC3DecodeContext * s )

static

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

Definition at line 298 of file ac3dec.c.

Referenced by ac3_decode_frame().

◆ set_downmix_coeffs()

static int 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 366 of file ac3dec.c.

Referenced by ac3_decode_frame().

◆ decode_exponents()

static int decode_exponents	(	AC3DecodeContext *	s,
		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 428 of file ac3dec.c.

Referenced by decode_audio_block().

◆ calc_transform_coeffs_cpl()

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 472 of file ac3dec.c.

Referenced by decode_transform_coeffs().

◆ ac3_decode_transform_coeffs_ch()

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 513 of file ac3dec.c.

Referenced by decode_transform_coeffs_ch().

◆ remove_dithering()

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 594 of file ac3dec.c.

Referenced by decode_transform_coeffs().

◆ decode_transform_coeffs_ch()

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

inlinestatic

Definition at line 607 of file ac3dec.c.

Referenced by decode_transform_coeffs().

◆ decode_transform_coeffs()

static void decode_transform_coeffs	(	AC3DecodeContext *	s,
		int	blk
	)

inlinestatic

Decode the transform coefficients.

Definition at line 627 of file ac3dec.c.

Referenced by decode_audio_block().

◆ do_rematrixing()

static void do_rematrixing ( AC3DecodeContext * s )

static

Stereo rematrixing.

reference: Section 7.5.4 Rematrixing : Decoding Technique

Definition at line 663 of file ac3dec.c.

Referenced by decode_audio_block().

◆ do_imdct()

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

inlinestatic

Inverse MDCT Transform.

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

Definition at line 687 of file ac3dec.c.

Referenced by decode_audio_block().

◆ ac3_upmix_delay()

static void ac3_upmix_delay ( AC3DecodeContext * s )

static

Upmix delay samples from stereo to original channel layout.

Definition at line 725 of file ac3dec.c.

Referenced by decode_audio_block().

◆ decode_band_structure()

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,
		uint8_t *	band_struct,
		int	band_struct_size
	)

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]	gbc	bit reader context
[in]	blk	block number
[in]	eac3	flag to indicate E-AC-3
[in]	ecpl	flag to indicate enhanced coupling
[in]	start_subband	subband number for start of range
[in]	end_subband	subband number for end of range
[in]	default_band_struct	default band structure table
[out]	num_bands	number of bands (optionally NULL)
[out]	band_sizes	array containing the number of bins in each band (optionally NULL)
[in,out]	band_struct	current band structure

Definition at line 767 of file ac3dec.c.

Referenced by coupling_strategy(), and spx_strategy().

◆ spx_strategy()

static int spx_strategy	(	AC3DecodeContext *	s,
		int	blk
	)

inlinestatic

Definition at line 816 of file ac3dec.c.

Referenced by decode_audio_block().

◆ spx_coordinates()

static void spx_coordinates ( AC3DecodeContext * s )

inlinestatic

Definition at line 873 of file ac3dec.c.

Referenced by decode_audio_block().

◆ coupling_strategy()

static int coupling_strategy	(	AC3DecodeContext *	s,
		int	blk,
		uint8_t *	bit_alloc_stages
	)

inlinestatic

Definition at line 951 of file ac3dec.c.

Referenced by decode_audio_block().

◆ coupling_coordinates()

static int coupling_coordinates	(	AC3DecodeContext *	s,
		int	blk
	)

inlinestatic

Definition at line 1021 of file ac3dec.c.

Referenced by decode_audio_block().

◆ decode_audio_block()

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

static

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

Definition at line 1067 of file ac3dec.c.

Referenced by ac3_decode_frame().

◆ ac3_decode_frame()

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 1462 of file ac3dec.c.

◆ ac3_decode_end()

static av_cold int ac3_decode_end ( AVCodecContext * avctx )

static

Uninitialize the AC-3 decoder.

Definition at line 1831 of file ac3dec.c.

Variable Documentation

◆ ungroup_3_in_7_bits_tab

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 48 of file ac3dec.c.

Referenced by ac3_tables_init(), and decode_exponents().

◆ b1_mantissas

int b1_mantissas[32][3]

static

tables for ungrouping mantissas

Definition at line 51 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

◆ b2_mantissas

int b2_mantissas[128][3]

static

Definition at line 52 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

◆ b3_mantissas

int b3_mantissas[8]

static

Definition at line 53 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

◆ b4_mantissas

int b4_mantissas[128][2]

static

Definition at line 54 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

◆ b5_mantissas

int b5_mantissas[16]

static

Definition at line 55 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch(), and ac3_tables_init().

◆ quantization_tab

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 61 of file ac3dec.c.

Referenced by ac3_decode_transform_coeffs_ch().

◆ dynamic_range_tab

float dynamic_range_tab[256]

static

dynamic range table.

converts codes to scale factors.

Definition at line 68 of file ac3dec.c.

Referenced by ac3_tables_init().

◆ ff_ac3_heavy_dynamic_range_tab

float ff_ac3_heavy_dynamic_range_tab[256]

Definition at line 69 of file ac3dec.c.

Referenced by ac3_tables_init().

◆ gain_levels

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
}

Adjustments in dB gain.

Definition at line 73 of file ac3dec.c.

Referenced by ac3_decode_frame(), and set_downmix_coeffs().

◆ gain_levels_lfe

const float gain_levels_lfe[32]

static

Initial value:

= {
162275, 2.818382, 2.511886, 2.238719, 1.995261, 1.778278, 1.584893,
412536, 1.258924, 1.122018, 1.000000, 0.891251, 0.794328, 0.707946,
630957, 0.562341, 0.501187, 0.446683, 0.398107, 0.354813, 0.316227,
281838, 0.251188, 0.223872, 0.199526, 0.177828, 0.158489, 0.141253,
125892, 0.112201, 0.100000, 0.089125
}

Adjustments in dB gain (LFE, +10 to -21 dB)

Definition at line 86 of file ac3dec.c.

Referenced by ac3_decode_frame().

◆ ac3_default_coeffs

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 98 of file ac3dec.c.

Referenced by set_downmix_coeffs().

Data Structures

Functions

Variables

Function Documentation

◆ symmetric_dequant()

◆ ac3_tables_init()

◆ ac3_decode_init()

◆ ac3_parse_header()

◆ parse_frame_header()

◆ set_downmix_coeffs()

◆ decode_exponents()

◆ calc_transform_coeffs_cpl()

◆ ac3_decode_transform_coeffs_ch()

◆ remove_dithering()

◆ decode_transform_coeffs_ch()

◆ decode_transform_coeffs()

◆ do_rematrixing()

◆ do_imdct()

◆ ac3_upmix_delay()

◆ decode_band_structure()

◆ spx_strategy()

◆ spx_coordinates()

◆ coupling_strategy()

◆ coupling_coordinates()

◆ decode_audio_block()

◆ ac3_decode_frame()

◆ ac3_decode_end()

Variable Documentation

◆ ungroup_3_in_7_bits_tab

◆ b1_mantissas

◆ b2_mantissas

◆ b3_mantissas

◆ b4_mantissas

◆ b5_mantissas

◆ quantization_tab

◆ dynamic_range_tab

◆ ff_ac3_heavy_dynamic_range_tab

◆ gain_levels

◆ gain_levels_lfe

◆ ac3_default_coeffs