flac_parser.c File Reference

FLAC parser. More...

#include "libavutil/attributes.h"
#include "libavutil/crc.h"
#include "libavutil/fifo.h"
#include "bytestream.h"
#include "parser.h"
#include "flac.h"

Classes
struct	FLACHeaderMarker
struct	FLACParseContext

Macros
#define	FLAC_MAX_SEQUENTIAL_HEADERS   4
	maximum number of adjacent headers that compare CRCs against each other
#define	FLAC_MIN_HEADERS   10
	minimum number of headers buffered and checked before returning frames
#define	FLAC_AVG_FRAME_SIZE   8192
	estimate for average size of a FLAC frame
#define	FLAC_HEADER_BASE_SCORE   10
	scoring settings for score_header
#define	FLAC_HEADER_CHANGED_PENALTY   7
#define	FLAC_HEADER_CRC_FAIL_PENALTY   50
#define	FLAC_HEADER_NOT_PENALIZED_YET   100000
#define	FLAC_HEADER_NOT_SCORED_YET   -100000
#define	MAX_FRAME_HEADER_SIZE   16
	largest possible size of flac header

Typedefs
typedef struct FLACHeaderMarker	FLACHeaderMarker
typedef struct FLACParseContext	FLACParseContext

Variables
AVCodecParser	ff_flac_parser

Detailed Description

FLAC parser.

The FLAC parser buffers input until FLAC_MIN_HEADERS has been found. Each time it finds and verifies a CRC-8 header it sees which of the FLAC_MAX_SEQUENTIAL_HEADERS that came before it have a valid CRC-16 footer that ends at the newly found header. Headers are scored by FLAC_HEADER_BASE_SCORE plus the max of its crc-verified children, penalized by changes in sample rate, frame number, etc. The parser returns the frame with the highest score.

Variable Documentation

ff_flac_parser

AVCodecParser ff_flac_parser

Initial value:

= {
    .codec_ids      = { AV_CODEC_ID_FLAC },
    .priv_data_size = sizeof(FLACParseContext),
    .parser_init    = flac_parse_init,
    .parser_parse   = flac_parse,
    .parser_close   = flac_parse_close,
}