ac3dec.c File Reference

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Classes

struct AC3DecodeContext

struct mant_groups

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

Functions

static void ac3_window_init (float *window)

Generate a Kaiser-Bessel Derived Window.

static float 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.

static void ac3_tables_init (void)

static int ac3_decode_init (AVCodecContext *avctx)

AVCodec initialization.

static int ac3_parse_header (AC3DecodeContext *ctx)

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

static void decode_exponents (GetBitContext *gb, int expstr, int ngrps, uint8_t absexp, int8_t *dexps)

Decode the grouped exponents according to exponent strategy.

static void uncouple_channels (AC3DecodeContext *ctx)

Generate transform coefficients for each coupled channel in the coupling range using the coupling coefficients and coupling coordinates.

static int get_transform_coeffs_ch (AC3DecodeContext *ctx, int ch_index, mant_groups *m)

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

static void remove_dithering (AC3DecodeContext *ctx)

Remove random dithering from coefficients with zero-bit mantissas reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0).

static int get_transform_coeffs (AC3DecodeContext *ctx)

Get the transform coefficients.

static void do_rematrixing (AC3DecodeContext *ctx)

Stereo rematrixing.

static void do_imdct_256 (AC3DecodeContext *ctx, int chindex)

Perform the 256-point IMDCT.

static void do_imdct (AC3DecodeContext *ctx)

Inverse MDCT Transform.

static void ac3_downmix (float samples[AC3_MAX_CHANNELS][256], int nfchans, int output_mode, float coef[AC3_MAX_CHANNELS][2])

Downmix the output to mono or stereo.

static int ac3_parse_audio_block (AC3DecodeContext *ctx, int blk)

Parse an audio block from AC-3 bitstream.

static int ac3_decode_frame (AVCodecContext *avctx, void *data, int *data_size, uint8_t *buf, int buf_size)

Decode a single AC-3 frame.

static int ac3_decode_end (AVCodecContext *avctx)

Uninitialize the AC-3 decoder.

Variables

static const uint8_t rematrix_band_tab [5] = { 13, 25, 37, 61, 253 }

Table of bin locations for rematrixing bands reference: Section 7.5.2 Rematrixing : Frequency Band Definitions.

static float scale_factors [25]

table for exponent to scale_factor mapping scale_factors[i] = 2 ^ -i

static uint8_t exp_ungroup_tab [128][3]

table for grouping exponents

static float b1_mantissas [32][3]

tables for ungrouping mantissas

static float b2_mantissas [128][3]

static float b3_mantissas [8]

static float b4_mantissas [128][2]

static float b5_mantissas [16]

static const uint8_t qntztab [16]

Quantization table: levels for symmetric.

static float dynrng_tab [256]

dynamic range table.

static float dialnorm_tab [32]

dialogue normalization table

static const float gain_levels [6]

static const uint8_t clevs [4] = { 2, 3, 4, 3 }

Table for center mix levels reference: Section 5.4.2.4 cmixlev.

static const uint8_t slevs [4] = { 2, 4, 0, 4 }

Table for surround mix levels reference: Section 5.4.2.5 surmixlev.

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.

AVCodec ac3_decoder

Function Documentation

static void ac3_window_init ( float * window ) [static]

Generate a Kaiser-Bessel Derived Window.

Definition at line 205 of file ac3dec.c.

Referenced by ac3_decode_init().

static float symmetric_dequant	(	int	code,
		int	levels
	)			`[inline, static]`

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

Definition at line 232 of file ac3dec.c.

Referenced by ac3_tables_init().

static void ac3_tables_init ( void ) [static]

Definition at line 240 of file ac3dec.c.

Referenced by ac3_decode_init().

static int ac3_decode_init ( AVCodecContext * avctx ) [static]

AVCodec initialization.

Definition at line 306 of file ac3dec.c.

static int ac3_parse_header ( AC3DecodeContext * ctx ) [static]

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

GetBitContext within AC3DecodeContext must point to start of the synchronized ac3 bitstream.

Definition at line 336 of file ac3dec.c.

Referenced by ac3_decode_frame().

static void decode_exponents	(	GetBitContext *	gb,
		int	expstr,
		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 437 of file ac3dec.c.

Referenced by ac3_parse_audio_block().

static void uncouple_channels ( AC3DecodeContext * ctx ) [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 468 of file ac3dec.c.

Referenced by get_transform_coeffs().

static int get_transform_coeffs_ch	(	AC3DecodeContext *	ctx,
		int	ch_index,
		mant_groups *	m
	)			`[static]`

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

Definition at line 504 of file ac3dec.c.

Referenced by get_transform_coeffs().

static void remove_dithering ( AC3DecodeContext * ctx ) [static]

Remove random dithering from coefficients with zero-bit mantissas reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0).

Definition at line 580 of file ac3dec.c.

Referenced by get_transform_coeffs().

static int get_transform_coeffs ( AC3DecodeContext * ctx ) [static]

Get the transform coefficients.

Definition at line 612 of file ac3dec.c.

Referenced by ac3_parse_audio_block().

static void do_rematrixing ( AC3DecodeContext * ctx ) [static]

Stereo rematrixing.

reference: Section 7.5.4 Rematrixing : Decoding Technique

Definition at line 655 of file ac3dec.c.

Referenced by ac3_parse_audio_block().

static void do_imdct_256	(	AC3DecodeContext *	ctx,
		int	chindex
	)			`[static]`

Perform the 256-point IMDCT.

Definition at line 679 of file ac3dec.c.

Referenced by do_imdct().

static void do_imdct ( AC3DecodeContext * ctx ) [inline, static]

Inverse MDCT Transform.

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

Definition at line 722 of file ac3dec.c.

Referenced by ac3_parse_audio_block().

static void ac3_downmix	(	float	samples[AC3_MAX_CHANNELS][256],
		int	nfchans,
		int	output_mode,
		float	coef[AC3_MAX_CHANNELS][2]
	)			`[static]`

Downmix the output to mono or stereo.

Definition at line 754 of file ac3dec.c.

Referenced by ac3_parse_audio_block().

static int ac3_parse_audio_block	(	AC3DecodeContext *	ctx,
		int	blk
	)			`[static]`

Parse an audio block from AC-3 bitstream.

Definition at line 786 of file ac3dec.c.

Referenced by ac3_decode_frame().

static int ac3_decode_frame	(	AVCodecContext *	avctx,
		void *	data,
		int *	data_size,
		uint8_t *	buf,
		int	buf_size
	)			`[static]`

Decode a single AC-3 frame.

Definition at line 1093 of file ac3dec.c.

static int ac3_decode_end ( AVCodecContext * avctx ) [static]

Uninitialize the AC-3 decoder.

Definition at line 1188 of file ac3dec.c.

Variable Documentation

const uint8_t rematrix_band_tab[5] = { 13, 25, 37, 61, 253 } [static]

Table of bin locations for rematrixing bands reference: Section 7.5.2 Rematrixing : Frequency Band Definitions.

Definition at line 46 of file ac3dec.c.

Referenced by do_rematrixing().

float scale_factors[25] [static]

table for exponent to scale_factor mapping scale_factors[i] = 2 ^ -i

Definition at line 52 of file ac3dec.c.

Referenced by ac3_parse_audio_block(), ac3_tables_init(), compute_scale_factors(), get_transform_coeffs_ch(), mp_decode_layer1(), and mp_decode_layer2().

uint8_t exp_ungroup_tab[128][3] [static]

table for grouping exponents

Definition at line 55 of file ac3dec.c.

Referenced by ac3_tables_init(), and decode_exponents().

float b1_mantissas[32][3] [static]

tables for ungrouping mantissas

Definition at line 59 of file ac3dec.c.

Referenced by ac3_tables_init(), and get_transform_coeffs_ch().

float b2_mantissas[128][3] [static]

Definition at line 60 of file ac3dec.c.

Referenced by ac3_tables_init(), and get_transform_coeffs_ch().

float b3_mantissas[8] [static]

Definition at line 61 of file ac3dec.c.

Referenced by ac3_tables_init(), and get_transform_coeffs_ch().

float b4_mantissas[128][2] [static]

Definition at line 62 of file ac3dec.c.

Referenced by ac3_tables_init(), and get_transform_coeffs_ch().

float b5_mantissas[16] [static]

Definition at line 63 of file ac3dec.c.

Referenced by ac3_tables_init(), and get_transform_coeffs_ch().

const uint8_t qntztab[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 69 of file ac3dec.c.

Referenced by get_transform_coeffs_ch().

float dynrng_tab[256] [static]

dynamic range table.

converts codes to scale factors.

Definition at line 75 of file ac3dec.c.

Referenced by ac3_parse_audio_block(), and ac3_tables_init().

float dialnorm_tab[32] [static]

dialogue normalization table

Definition at line 78 of file ac3dec.c.

Referenced by ac3_parse_header(), and ac3_tables_init().

const float gain_levels[6] [static]

Initial value:

 {
    LEVEL_ZERO,
    LEVEL_ONE,
    LEVEL_MINUS_3DB,
    LEVEL_MINUS_4POINT5DB,
    LEVEL_MINUS_6DB,
    LEVEL_MINUS_9DB
}

Definition at line 88 of file ac3dec.c.

Referenced by ac3_parse_header().

const uint8_t clevs[4] = { 2, 3, 4, 3 } [static]

Table for center mix levels reference: Section 5.4.2.4 cmixlev.

Definition at line 101 of file ac3dec.c.

Referenced by ac3_parse_header().

const uint8_t slevs[4] = { 2, 4, 0, 4 } [static]

Table for surround mix levels reference: Section 5.4.2.5 surmixlev.

Definition at line 107 of file ac3dec.c.

Referenced by ac3_parse_header().

const uint8_t ac3_default_coeffs[8][5][2] [static]

Initial value:

 {
    { { 1, 0 }, { 0, 1 },                               },
    { { 2, 2 },                                         },
    { { 1, 0 }, { 0, 1 },                               },
    { { 1, 0 }, { 3, 3 }, { 0, 1 },                     },
    { { 1, 0 }, { 0, 1 }, { 4, 4 },                     },
    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 5, 5 },           },
    { { 1, 0 }, { 0, 1 }, { 4, 0 }, { 0, 4 },           },
    { { 1, 0 }, { 3, 3 }, { 0, 1 }, { 4, 0 }, { 0, 4 }, },
}

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

Definition at line 113 of file ac3dec.c.

Referenced by ac3_parse_header().

AVCodec ac3_decoder

Initial value:

 {
    .name = "ac3",
    .type = CODEC_TYPE_AUDIO,
    .id = CODEC_ID_AC3,
    .priv_data_size = sizeof (AC3DecodeContext),
    .init = ac3_decode_init,
    .close = ac3_decode_end,
    .decode = ac3_decode_frame,
}

Definition at line 1197 of file ac3dec.c.


Classes
struct	AC3DecodeContext
struct	mant_groups
	Grouped mantissas for 3-level 5-level and 11-level quantization. More...
Functions
static void	ac3_window_init (float *window)
	Generate a Kaiser-Bessel Derived Window.
static float	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.
static void	ac3_tables_init (void)
static int	ac3_decode_init (AVCodecContext *avctx)
	AVCodec initialization.
static int	ac3_parse_header (AC3DecodeContext *ctx)
	Parse the 'sync info' and 'bit stream info' from the AC-3 bitstream.
static void	decode_exponents (GetBitContext gb, int expstr, int ngrps, uint8_t absexp, int8_t dexps)
	Decode the grouped exponents according to exponent strategy.
static void	uncouple_channels (AC3DecodeContext *ctx)
	Generate transform coefficients for each coupled channel in the coupling range using the coupling coefficients and coupling coordinates.
static int	get_transform_coeffs_ch (AC3DecodeContext ctx, int ch_index, mant_groups m)
	Get the transform coefficients for a particular channel reference: Section 7.3 Quantization and Decoding of Mantissas.
static void	remove_dithering (AC3DecodeContext *ctx)
	Remove random dithering from coefficients with zero-bit mantissas reference: Section 7.3.4 Dither for Zero Bit Mantissas (bap=0).
static int	get_transform_coeffs (AC3DecodeContext *ctx)
	Get the transform coefficients.
static void	do_rematrixing (AC3DecodeContext *ctx)
	Stereo rematrixing.
static void	do_imdct_256 (AC3DecodeContext *ctx, int chindex)
	Perform the 256-point IMDCT.
static void	do_imdct (AC3DecodeContext *ctx)
	Inverse MDCT Transform.
static void	ac3_downmix (float samples[AC3_MAX_CHANNELS][256], int nfchans, int output_mode, float coef[AC3_MAX_CHANNELS][2])
	Downmix the output to mono or stereo.
static int	ac3_parse_audio_block (AC3DecodeContext *ctx, int blk)
	Parse an audio block from AC-3 bitstream.
static int	ac3_decode_frame (AVCodecContext avctx, void data, int data_size, uint8_t buf, int buf_size)
	Decode a single AC-3 frame.
static int	ac3_decode_end (AVCodecContext *avctx)
	Uninitialize the AC-3 decoder.
Variables
static const uint8_t	rematrix_band_tab [5] = { 13, 25, 37, 61, 253 }
	Table of bin locations for rematrixing bands reference: Section 7.5.2 Rematrixing : Frequency Band Definitions.
static float	scale_factors [25]
	table for exponent to scale_factor mapping scale_factors[i] = 2 ^ -i
static uint8_t	exp_ungroup_tab [128][3]
	table for grouping exponents
static float	b1_mantissas [32][3]
	tables for ungrouping mantissas
static float	b2_mantissas [128][3]
static float	b3_mantissas [8]
static float	b4_mantissas [128][2]
static float	b5_mantissas [16]
static const uint8_t	qntztab [16]
	Quantization table: levels for symmetric.
static float	dynrng_tab [256]
	dynamic range table.
static float	dialnorm_tab [32]
	dialogue normalization table
static const float	gain_levels [6]
static const uint8_t	clevs [4] = { 2, 3, 4, 3 }
	Table for center mix levels reference: Section 5.4.2.4 cmixlev.
static const uint8_t	slevs [4] = { 2, 4, 0, 4 }
	Table for surround mix levels reference: Section 5.4.2.5 surmixlev.
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.
AVCodec	ac3_decoder