bitstream.h File Reference

Bitstream structures and inline functions. More...

Data Structures
struct	getbit_context
	Structure for bistream I/O. More...
struct	vlc
	A variable length code table. More...

Functions
void	init_vlc (struct vlc *vlc, int nb_bits, int nb_codes, const void *bits, const void *codes, int codes_size)
	Build VLC decoding tables suitable for use with get_vlc(). More...
void	free_vlc (struct vlc *vlc)
	Deallocate all resources of a VLC table. More...
int	get_vlc (struct getbit_context *gbc, const struct vlc *vlc)
	Parse a vlc code. More...

Detailed Description

Bitstream structures and inline functions.

Function Documentation

init_vlc()

void init_vlc	(	struct vlc *	vlc,
		int	nb_bits,
		int	nb_codes,
		const void *	bits,
		const void *	codes,
		int	codes_size
	)

Build VLC decoding tables suitable for use with get_vlc().

Parameters

vlc	The structure to be initialized.
nb_bits	Set the decoding table size (2^nb_bits) entries.
nb_codes	Number of vlc codes.
bits	Table which gives the size (in bits) of each vlc code.
codes	Table which gives the bit pattern of of each vlc code.
codes_size	The number of bytes of each entry of the codes tables.

The bigger nb_bits is, the faster is the decoding. But it should not be too big to save memory and L1 cache. '9' is a good compromise.

The wrap and size parameters allow to use any memory configuration and types (byte/word/long) to store the bits and codes tables.

References vlc::bits, PARA_INFO_LOG, vlc::table, vlc::table_allocated, and vlc::table_size.

free_vlc()

void free_vlc

(

struct vlc *

vlc

)

Deallocate all resources of a VLC table.

Parameters

vlc	Pointer to an initialized vlc structure.

The table given by vlc must have been initialized earlier via init_vlc().

References freep(), and vlc::table.

get_vlc()

int get_vlc	(	struct getbit_context *	gbc,
		const struct vlc *	vlc
	)

Parse a vlc code.

Parameters

gbc	The getbit context structure.
vlc	The vlc tables to use.

Returns

The vlc code.