ac3enc.c File Reference

The simplest AC-3 encoder. More...

#include <stdint.h>
#include "libavutil/attributes.h"
#include "libavutil/avassert.h"
#include "libavutil/avstring.h"
#include "libavutil/channel_layout.h"
#include "libavutil/crc.h"
#include "libavutil/internal.h"
#include "libavutil/opt.h"
#include "avcodec.h"
#include "internal.h"
#include "me_cmp.h"
#include "put_bits.h"
#include "audiodsp.h"
#include "ac3dsp.h"
#include "ac3.h"
#include "fft.h"
#include "ac3enc.h"
#include "eac3enc.h"

Classes
struct	AC3Mant

Macros
#define	CMIXLEV_NUM_OPTIONS   3
#define	SURMIXLEV_NUM_OPTIONS   3
#define	EXTMIXLEV_NUM_OPTIONS   8
#define	EXP_DIFF_THRESHOLD   500
	Exponent Difference Threshold. More...
#define	CRC16_POLY   ((1 << 0) | (1 << 2) | (1 << 15) | (1 << 16))
	CRC-16 Polynomial.
#define	FLT_OPTION_THRESHOLD   0.01

Typedefs
typedef struct AC3Mant	AC3Mant

Functions
void	ff_ac3_adjust_frame_size (AC3EncodeContext *s)
	Adjust the frame size to make the average bit rate match the target bit rate. More...
void	ff_ac3_compute_coupling_strategy (AC3EncodeContext *s)
	Set the initial coupling strategy parameters prior to coupling analysis. More...
void	ff_ac3_apply_rematrixing (AC3EncodeContext *s)
	Apply stereo rematrixing to coefficients based on rematrixing flags. More...
void	ff_ac3_group_exponents (AC3EncodeContext *s)
	Group exponents. More...
void	ff_ac3_process_exponents (AC3EncodeContext *s)
	Calculate final exponents from the supplied MDCT coefficients and exponent shift. More...
int	ff_ac3_compute_bit_allocation (AC3EncodeContext *s)
void	ff_ac3_quantize_mantissas (AC3EncodeContext *s)
	Quantize mantissas using coefficients, exponents, and bit allocation pointers. More...
void	ff_ac3_output_frame (AC3EncodeContext *s, unsigned char *frame)
	Write the frame to the output bitstream. More...
int	ff_ac3_validate_metadata (AC3EncodeContext *s)
	Validate metadata options as set by AVOption system. More...
av_cold int	ff_ac3_encode_close (AVCodecContext *avctx)
	Finalize encoding and free any memory allocated by the encoder. More...
av_cold int	ff_ac3_encode_init (AVCodecContext *avctx)

Variables
const uint64_t	ff_ac3_channel_layouts [19]
	List of supported channel layouts. More...

Detailed Description

The simplest AC-3 encoder.

Macro Definition Documentation

EXP_DIFF_THRESHOLD

#define EXP_DIFF_THRESHOLD   500

Exponent Difference Threshold.

New exponents are sent if their SAD exceed this number.

Function Documentation

ff_ac3_adjust_frame_size()

void ff_ac3_adjust_frame_size

(

AC3EncodeContext *

s

)

Adjust the frame size to make the average bit rate match the target bit rate.

This is only needed for 11025, 22050, and 44100 sample rates or any E-AC-3.

Parameters

s	AC-3 encoder private context

ff_ac3_apply_rematrixing()

void ff_ac3_apply_rematrixing

(

AC3EncodeContext *

s

)

Apply stereo rematrixing to coefficients based on rematrixing flags.

Parameters

s	AC-3 encoder private context

ff_ac3_compute_coupling_strategy()

void ff_ac3_compute_coupling_strategy

(

AC3EncodeContext *

s

)

Set the initial coupling strategy parameters prior to coupling analysis.

Parameters

s	AC-3 encoder private context

ff_ac3_encode_close()

av_cold int ff_ac3_encode_close

(

AVCodecContext *

avctx

)

Finalize encoding and free any memory allocated by the encoder.

Parameters

avctx

Codec context

ff_ac3_group_exponents()

void ff_ac3_group_exponents

(

AC3EncodeContext *

s

)

Group exponents.

3 delta-encoded exponents are in each 7-bit group. The number of groups varies depending on exponent strategy and bandwidth.

Parameters

s	AC-3 encoder private context

ff_ac3_output_frame()

void ff_ac3_output_frame	(	AC3EncodeContext *	s,
		unsigned char *	frame
	)

Write the frame to the output bitstream.

Parameters

s	AC-3 encoder private context
frame	output data buffer

ff_ac3_process_exponents()

void ff_ac3_process_exponents

(

AC3EncodeContext *

s

)

Calculate final exponents from the supplied MDCT coefficients and exponent shift.

Extract exponents from MDCT coefficients, calculate exponent strategies, and encode final exponents.

Parameters

s	AC-3 encoder private context

ff_ac3_quantize_mantissas()

void ff_ac3_quantize_mantissas

(

AC3EncodeContext *

s

)

Quantize mantissas using coefficients, exponents, and bit allocation pointers.

Parameters

s	AC-3 encoder private context

ff_ac3_validate_metadata()

int ff_ac3_validate_metadata

(

AC3EncodeContext *

s

)

Validate metadata options as set by AVOption system.

These values can optionally be changed per-frame.

Parameters

s	AC-3 encoder private context

Variable Documentation

ff_ac3_channel_layouts

const uint64_t ff_ac3_channel_layouts[19]

Initial value:

= {
     AV_CH_LAYOUT_MONO,
     AV_CH_LAYOUT_STEREO,
     AV_CH_LAYOUT_2_1,
     AV_CH_LAYOUT_SURROUND,
     AV_CH_LAYOUT_2_2,
     AV_CH_LAYOUT_QUAD,
     AV_CH_LAYOUT_4POINT0,
     AV_CH_LAYOUT_5POINT0,
     AV_CH_LAYOUT_5POINT0_BACK,
    (AV_CH_LAYOUT_MONO     | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_STEREO   | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_2_1      | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_SURROUND | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_2_2      | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_QUAD     | AV_CH_LOW_FREQUENCY),
    (AV_CH_LAYOUT_4POINT0  | AV_CH_LOW_FREQUENCY),
     AV_CH_LAYOUT_5POINT1,
     AV_CH_LAYOUT_5POINT1_BACK,
     0
}

List of supported channel layouts.