ac3.h File Reference

Common code between the AC-3 encoder and decoder. More...

#include "libavutil/opt.h"
#include "avcodec.h"
#include "ac3tab.h"

Go to the source code of this file.

Data Structures
struct	AC3BitAllocParameters
struct	AC3HeaderInfo
	Coded AC-3 header values up to the lfeon element, plus derived values. More...

Macros
#define	AC3_MAX_CODED_FRAME_SIZE   3840 /* in bytes */
#define	EAC3_MAX_CHANNELS   16
	maximum number of channels in EAC3 More...
#define	AC3_MAX_CHANNELS   7
	maximum number of channels, including coupling channel More...
#define	CPL_CH   0
	coupling channel index More...
#define	AC3_MAX_COEFS   256
#define	AC3_BLOCK_SIZE   256
#define	AC3_MAX_BLOCKS   6
#define	AC3_FRAME_SIZE   (AC3_MAX_BLOCKS * 256)
#define	AC3_WINDOW_SIZE   (AC3_BLOCK_SIZE * 2)
#define	AC3_CRITICAL_BANDS   50
#define	AC3_MAX_CPL_BANDS   18
#define	EXP_REUSE   0
#define	EXP_NEW   1
#define	EXP_D15   1
#define	EXP_D25   2
#define	EXP_D45   3
#define	FIXR(x)   ((float)(x))
#define	FIXR12(x)   ((float)(x))
#define	FIXR15(x)   ((float)(x))
#define	ROUND15(x)   (x)
#define	AC3_RENAME(x)   x
#define	AC3_NORM(norm)   (1.0f/(norm))
#define	AC3_MUL(a, b)   ((a) * (b))
#define	AC3_RANGE(x)   (dynamic_range_tab[(x)])
#define	AC3_HEAVY_RANGE(x)   (ff_ac3_heavy_dynamic_range_tab[(x)])
#define	AC3_DYNAMIC_RANGE(x)   (powf(x, s->drc_scale))
#define	AC3_SPX_BLEND(x)   (x)* (1.0f/32)
#define	AC3_DYNAMIC_RANGE1   1.0f
#define	AC3_LEVEL(x)   ROUND15((x) * FIXR15(M_SQRT1_2))
#define	LEVEL_PLUS_3DB   M_SQRT2
#define	LEVEL_PLUS_1POINT5DB   1.1892071150027209
#define	LEVEL_MINUS_1POINT5DB   0.8408964152537145
#define	LEVEL_MINUS_3DB   M_SQRT1_2
#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

Typedefs
typedef float	INTFLOAT
typedef float	SHORTFLOAT

Enumerations
enum	AC3DeltaStrategy { DBA_REUSE = 0, DBA_NEW, DBA_NONE, DBA_RESERVED }
	Delta bit allocation strategy. More...
enum	AC3ChannelMode {   AC3_CHMODE_DUALMONO = 0, AC3_CHMODE_MONO, AC3_CHMODE_STEREO, AC3_CHMODE_3F,   AC3_CHMODE_2F1R, AC3_CHMODE_3F1R, AC3_CHMODE_2F2R, AC3_CHMODE_3F2R }
	Channel mode (audio coding mode) More...
enum	AC3DolbySurroundMode { AC3_DSURMOD_NOTINDICATED = 0, AC3_DSURMOD_OFF, AC3_DSURMOD_ON, AC3_DSURMOD_RESERVED }
	Dolby Surround mode. More...
enum	AC3DolbySurroundEXMode { AC3_DSUREXMOD_NOTINDICATED = 0, AC3_DSUREXMOD_OFF, AC3_DSUREXMOD_ON, AC3_DSUREXMOD_PLIIZ }
	Dolby Surround EX mode. More...
enum	AC3DolbyHeadphoneMode { AC3_DHEADPHONMOD_NOTINDICATED = 0, AC3_DHEADPHONMOD_OFF, AC3_DHEADPHONMOD_ON, AC3_DHEADPHONMOD_RESERVED }
	Dolby Headphone mode. More...
enum	AC3PreferredStereoDownmixMode { AC3_DMIXMOD_NOTINDICATED = 0, AC3_DMIXMOD_LTRT, AC3_DMIXMOD_LORO, AC3_DMIXMOD_DPLII }
	Preferred Stereo Downmix mode. More...
enum	EAC3FrameType { EAC3_FRAME_TYPE_INDEPENDENT = 0, EAC3_FRAME_TYPE_DEPENDENT, EAC3_FRAME_TYPE_AC3_CONVERT, EAC3_FRAME_TYPE_RESERVED }

Functions
void	ff_ac3_common_init (void)
void	ff_ac3_bit_alloc_calc_psd (int8_t *exp, int start, int end, int16_t *psd, int16_t *band_psd)
	Calculate the log power-spectral density of the input signal. More...
int	ff_ac3_bit_alloc_calc_mask (AC3BitAllocParameters *s, int16_t *band_psd, int start, int end, int fast_gain, int is_lfe, int dba_mode, int dba_nsegs, uint8_t *dba_offsets, uint8_t *dba_lengths, uint8_t *dba_values, int16_t *mask)
	Calculate the masking curve. More...

Detailed Description

Common code between the AC-3 encoder and decoder.

Definition in file ac3.h.

Macro Definition Documentation

#define AC3_MAX_CODED_FRAME_SIZE   3840 /* in bytes */

Definition at line 30 of file ac3.h.

Referenced by ff_ac3_output_frame().

#define EAC3_MAX_CHANNELS   16

maximum number of channels in EAC3

Definition at line 31 of file ac3.h.

Referenced by ac3_decode_frame().

#define AC3_MAX_CHANNELS   7

maximum number of channels, including coupling channel

Definition at line 32 of file ac3.h.

Referenced by ac3_decode_frame(), ac3_decode_init(), apply_channel_coupling(), coupling_strategy(), decode_audio_block(), ff_eac3_set_cpl_states(), set_channel_info(), and set_downmix_coeffs().

#define CPL_CH   0

coupling channel index

Definition at line 33 of file ac3.h.

Referenced by ac3_decode_transform_coeffs_ch(), apply_channel_coupling(), calc_transform_coeffs_cpl(), compute_exp_strategy(), compute_rematrixing_strategy(), count_exponent_bits(), count_mantissa_bits_update_ch(), coupling_strategy(), decode_audio_block(), decode_transform_coeffs(), encode_exponents(), ff_ac3_compute_coupling_strategy(), ff_ac3_group_exponents(), ff_ac3_quantize_mantissas(), ff_eac3_parse_header(), output_audio_block(), remove_dithering(), and set_bandwidth().

#define AC3_MAX_COEFS   256

Definition at line 35 of file ac3.h.

Referenced by ac3_bit_alloc_calc_bap_c(), allocate_buffers(), compute_exp_strategy(), encode_exponents(), encode_frame(), extract_exponents(), ff_eac3_decode_transform_coeffs_aht_ch(), reset_block_bap(), scale_coefficients(), and set_bandwidth().

#define AC3_BLOCK_SIZE   256

Definition at line 36 of file ac3.h.

Referenced by ac3_decode_frame(), allocate_sample_buffers(), apply_mdct(), copy_input_samples(), ff_ac3_adjust_frame_size(), ff_ac3_encode_init(), and validate_options().

#define AC3_MAX_BLOCKS   6

Definition at line 37 of file ac3.h.

Referenced by ac3_compute_mantissa_size_c(), apply_channel_coupling(), count_mantissa_bits(), and count_mantissa_bits_init().

#define AC3_FRAME_SIZE   (AC3_MAX_BLOCKS * 256)

Definition at line 38 of file ac3.h.

Referenced by allocate_sample_buffers(), spdif_get_offset_and_codec(), spdif_header_ac3(), and validate_options().

#define AC3_WINDOW_SIZE   (AC3_BLOCK_SIZE * 2)

Definition at line 39 of file ac3.h.

Referenced by allocate_sample_buffers(), apply_mdct(), and normalize_samples().

#define AC3_CRITICAL_BANDS   50

Definition at line 40 of file ac3.h.

Referenced by ff_ac3_bit_alloc_calc_mask().

#define AC3_MAX_CPL_BANDS   18

Definition at line 41 of file ac3.h.

#define EXP_REUSE   0

Definition at line 48 of file ac3.h.

Referenced by bit_alloc(), bit_alloc_masking(), compute_exp_strategy(), count_exponent_bits(), count_frame_bits(), decode_audio_block(), encode_exponents(), ff_ac3_group_exponents(), ff_eac3_parse_header(), and output_audio_block().

#define EXP_NEW   1

Definition at line 49 of file ac3.h.

Referenced by compute_exp_strategy().

#define EXP_D15   1

Definition at line 51 of file ac3.h.

Referenced by compute_exp_strategy(), and exponent_init().

#define EXP_D25   2

Definition at line 52 of file ac3.h.

Referenced by encode_exponents_blk_ch().

#define EXP_D45   3

Definition at line 53 of file ac3.h.

Referenced by decode_exponents(), encode_exponents_blk_ch(), exponent_init(), and ff_ac3_group_exponents().

#define FIXR

(

x

)

((float)(x))

Definition at line 82 of file ac3.h.

#define FIXR12

(

x

)

((float)(x))

Definition at line 83 of file ac3.h.

Referenced by set_downmix_coeffs().

#define FIXR15

(

x

)

((float)(x))

Definition at line 84 of file ac3.h.

#define ROUND15

(

x

)

(x)

Definition at line 85 of file ac3.h.

#define AC3_RENAME

(

x

)

x

Definition at line 87 of file ac3.h.

Referenced by ac3_decode_init(), and decode_audio_block().

#define AC3_NORM

(

norm

)

(1.0f/(norm))

Definition at line 88 of file ac3.h.

#define AC3_MUL	(		a,
			b
	)		((a) * (b))

Definition at line 89 of file ac3.h.

#define AC3_RANGE

(

x

)

(dynamic_range_tab[(x)])

Definition at line 90 of file ac3.h.

Referenced by decode_audio_block().

#define AC3_HEAVY_RANGE

(

x

)

(ff_ac3_heavy_dynamic_range_tab[(x)])

Definition at line 91 of file ac3.h.

Referenced by ac3_parse_header(), and ff_eac3_parse_header().

#define AC3_DYNAMIC_RANGE

(

x

)

(powf(x, s->drc_scale))

Definition at line 92 of file ac3.h.

Referenced by decode_audio_block().

#define AC3_SPX_BLEND

(

x

)

(x)* (1.0f/32)

Definition at line 93 of file ac3.h.

Referenced by spx_coordinates().

#define AC3_DYNAMIC_RANGE1   1.0f

Definition at line 94 of file ac3.h.

Referenced by decode_audio_block().

#define AC3_LEVEL

(

x

)

ROUND15((x) * FIXR15(M_SQRT1_2))

Definition at line 101 of file ac3.h.

#define LEVEL_PLUS_3DB   M_SQRT2

Definition at line 104 of file ac3.h.

#define LEVEL_PLUS_1POINT5DB   1.1892071150027209

Definition at line 105 of file ac3.h.

#define LEVEL_MINUS_1POINT5DB   0.8408964152537145

Definition at line 106 of file ac3.h.

#define LEVEL_MINUS_3DB   M_SQRT1_2

Definition at line 107 of file ac3.h.

Referenced by ac3_decode_frame(), and set_downmix_coeffs().

#define LEVEL_MINUS_4POINT5DB   0.5946035575013605

Definition at line 108 of file ac3.h.

#define LEVEL_MINUS_6DB   0.5000000000000000

Definition at line 109 of file ac3.h.

#define LEVEL_MINUS_9DB   0.3535533905932738

Definition at line 110 of file ac3.h.

#define LEVEL_ZERO   0.0000000000000000

Definition at line 111 of file ac3.h.

#define LEVEL_ONE   1.0000000000000000

Definition at line 112 of file ac3.h.

Typedef Documentation

typedef float INTFLOAT

Definition at line 96 of file ac3.h.

typedef float SHORTFLOAT

Definition at line 97 of file ac3.h.

Enumeration Type Documentation

enum AC3DeltaStrategy

Delta bit allocation strategy.

Enumerator
DBA_REUSE
DBA_NEW
DBA_NONE
DBA_RESERVED

Definition at line 115 of file ac3.h.

enum AC3ChannelMode

Channel mode (audio coding mode)

Enumerator
AC3_CHMODE_DUALMONO
AC3_CHMODE_MONO
AC3_CHMODE_STEREO
AC3_CHMODE_3F
AC3_CHMODE_2F1R
AC3_CHMODE_3F1R
AC3_CHMODE_2F2R
AC3_CHMODE_3F2R

Definition at line 123 of file ac3.h.

enum AC3DolbySurroundMode

Dolby Surround mode.

Enumerator
AC3_DSURMOD_NOTINDICATED
AC3_DSURMOD_OFF
AC3_DSURMOD_ON
AC3_DSURMOD_RESERVED

Definition at line 135 of file ac3.h.

enum AC3DolbySurroundEXMode

Dolby Surround EX mode.

Enumerator
AC3_DSUREXMOD_NOTINDICATED
AC3_DSUREXMOD_OFF
AC3_DSUREXMOD_ON
AC3_DSUREXMOD_PLIIZ

Definition at line 143 of file ac3.h.

enum AC3DolbyHeadphoneMode

Dolby Headphone mode.

Enumerator
AC3_DHEADPHONMOD_NOTINDICATED
AC3_DHEADPHONMOD_OFF
AC3_DHEADPHONMOD_ON
AC3_DHEADPHONMOD_RESERVED

Definition at line 151 of file ac3.h.

enum AC3PreferredStereoDownmixMode

Preferred Stereo Downmix mode.

Enumerator
AC3_DMIXMOD_NOTINDICATED
AC3_DMIXMOD_LTRT
AC3_DMIXMOD_LORO
AC3_DMIXMOD_DPLII

Definition at line 159 of file ac3.h.

enum EAC3FrameType

Enumerator
EAC3_FRAME_TYPE_INDEPENDENT
EAC3_FRAME_TYPE_DEPENDENT
EAC3_FRAME_TYPE_AC3_CONVERT
EAC3_FRAME_TYPE_RESERVED

Definition at line 209 of file ac3.h.

Function Documentation

void ff_ac3_common_init

(

void

)

void ff_ac3_bit_alloc_calc_psd	(	int8_t *	exp,
		int	start,
		int	end,
		int16_t *	psd,
		int16_t *	band_psd
	)

Calculate the log power-spectral density of the input signal.

This gives a rough estimate of signal power in the frequency domain by using the spectral envelope (exponents). The psd is also separately grouped into critical bands for use in the calculating the masking curve. 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters determines the reference level.

Parameters

[in]	exp	frequency coefficient exponents
[in]	start	starting bin location
[in]	end	ending bin location
[out]	psd	signal power for each frequency bin
[out]	band_psd	signal power for each critical band

Definition at line 92 of file ac3.c.

Referenced by bit_alloc_masking(), and decode_audio_block().

int ff_ac3_bit_alloc_calc_mask	(	AC3BitAllocParameters *	s,
		int16_t *	band_psd,
		int	start,
		int	end,
		int	fast_gain,
		int	is_lfe,
		int	dba_mode,
		int	dba_nsegs,
		uint8_t *	dba_offsets,
		uint8_t *	dba_lengths,
		uint8_t *	dba_values,
		int16_t *	mask
	)

Calculate the masking curve.

First, the excitation is calculated using parameters in s and the signal power in each critical band. The excitation is compared with a predefined hearing threshold table to produce the masking curve. If delta bit allocation information is provided, it is used for adjusting the masking curve, usually to give a closer match to a better psychoacoustic model.

Parameters

[in]	s	adjustable bit allocation parameters
[in]	band_psd	signal power for each critical band
[in]	start	starting bin location
[in]	end	ending bin location
[in]	fast_gain	fast gain (estimated signal-to-mask ratio)
[in]	is_lfe	whether or not the channel being processed is the LFE
[in]	dba_mode	delta bit allocation mode (none, reuse, or new)
[in]	dba_nsegs	number of delta segments
[in]	dba_offsets	location offsets for each segment
[in]	dba_lengths	length of each segment
[in]	dba_values	delta bit allocation for each segment
[out]	mask	calculated masking curve

Returns

returns 0 for success, non-zero for error

Definition at line 118 of file ac3.c.

Referenced by bit_alloc_masking(), and decode_audio_block().