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

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

Classes
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

#define	AC3_MAX_CHANNELS 7
	maximum number of channels, including coupling channel

#define	CPL_CH 0
	coupling channel index

#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

typedef enum AC3DolbySurroundMode	AC3DolbySurroundMode
	Dolby Surround mode.

typedef enum AC3DolbySurroundEXMode	AC3DolbySurroundEXMode
	Dolby Surround EX mode.

typedef enum AC3DolbyHeadphoneMode	AC3DolbyHeadphoneMode
	Dolby Headphone mode.

typedef enum AC3PreferredStereoDownmixMode	AC3PreferredStereoDownmixMode
	Preferred Stereo Downmix mode.

typedef struct AC3BitAllocParameters	AC3BitAllocParameters

typedef struct AC3HeaderInfo	AC3HeaderInfo

Enumerations
enum	AC3DeltaStrategy { DBA_REUSE = 0, DBA_NEW, DBA_NONE, DBA_RESERVED }
	Delta bit allocation strategy.

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)

enum	AC3DolbySurroundMode { AC3_DSURMOD_NOTINDICATED = 0, AC3_DSURMOD_OFF, AC3_DSURMOD_ON, AC3_DSURMOD_RESERVED }
	Dolby Surround mode.

enum	AC3DolbySurroundEXMode { AC3_DSUREXMOD_NOTINDICATED = 0, AC3_DSUREXMOD_OFF, AC3_DSUREXMOD_ON, AC3_DSUREXMOD_PLIIZ }
	Dolby Surround EX mode.

enum	AC3DolbyHeadphoneMode { AC3_DHEADPHONMOD_NOTINDICATED = 0, AC3_DHEADPHONMOD_OFF, AC3_DHEADPHONMOD_ON, AC3_DHEADPHONMOD_RESERVED }
	Dolby Headphone mode.

enum	AC3PreferredStereoDownmixMode { AC3_DMIXMOD_NOTINDICATED = 0, AC3_DMIXMOD_LTRT, AC3_DMIXMOD_LORO, AC3_DMIXMOD_DPLII }
	Preferred Stereo Downmix mode.

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.

Function Documentation

§ ff_ac3_bit_alloc_calc_mask()

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

§ ff_ac3_bit_alloc_calc_psd()

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

Classes

Macros

Typedefs

Enumerations

Functions

Detailed Description

Function Documentation

§ ff_ac3_bit_alloc_calc_mask()

§ ff_ac3_bit_alloc_calc_psd()