libavcodec/flac_parser.c File Reference

FLAC parser. More...

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

Go to the source code of this file.

Data Structures

struct FLACHeaderMarker

struct FLACParseContext

Defines

#define FLAC_MAX_SEQUENTIAL_HEADERS   3

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

Functions

static int frame_header_is_valid (AVCodecContext *avctx, const uint8_t *buf, FLACFrameInfo *fi)

static uint8_t * flac_fifo_read_wrap (FLACParseContext *fpc, int offset, int len, uint8_t **wrap_buf, int *allocated_size)

Non-destructive fast fifo pointer fetching Returns a pointer from the specified offset.

static uint8_t * flac_fifo_read (FLACParseContext *fpc, int offset, int *len)

Return a pointer in the fifo buffer where the offset starts at until the wrap point or end of request.

static int find_headers_search_validate (FLACParseContext *fpc, int offset)

static int find_headers_search (FLACParseContext *fpc, uint8_t *buf, int buf_size, int search_start)

static int find_new_headers (FLACParseContext *fpc, int search_start)

static int check_header_mismatch (FLACParseContext *fpc, FLACHeaderMarker *header, FLACHeaderMarker *child, int log_level_offset)

static int score_header (FLACParseContext *fpc, FLACHeaderMarker *header)

Score a header.

static void score_sequences (FLACParseContext *fpc)

static int get_best_header (FLACParseContext *fpc, const uint8_t **poutbuf, int *poutbuf_size)

static int flac_parse (AVCodecParserContext *s, AVCodecContext *avctx, const uint8_t **poutbuf, int *poutbuf_size, const uint8_t *buf, int buf_size)

static int flac_parse_init (AVCodecParserContext *c)

static void flac_parse_close (AVCodecParserContext *c)

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 it's crc-verified children, penalized by changes in sample rate, frame number, etc. The parser returns the frame with the highest score.

Definition in file flac_parser.c.

Define Documentation

#define FLAC_AVG_FRAME_SIZE 8192

estimate for average size of a FLAC frame

Definition at line 46 of file flac_parser.c.

Referenced by flac_parse(), and flac_parse_init().

#define FLAC_HEADER_BASE_SCORE 10

scoring settings for score_header

Definition at line 49 of file flac_parser.c.

Referenced by check_header_mismatch(), and score_header().

#define FLAC_HEADER_CHANGED_PENALTY 7

Definition at line 50 of file flac_parser.c.

Referenced by check_header_mismatch().

#define FLAC_HEADER_CRC_FAIL_PENALTY 50

Definition at line 51 of file flac_parser.c.

Referenced by check_header_mismatch().

#define FLAC_HEADER_NOT_PENALIZED_YET 100000

Definition at line 52 of file flac_parser.c.

Referenced by check_header_mismatch(), find_headers_search_validate(), and score_header().

#define FLAC_HEADER_NOT_SCORED_YET -100000

Definition at line 53 of file flac_parser.c.

Referenced by score_header(), and score_sequences().

#define FLAC_MAX_SEQUENTIAL_HEADERS 3

maximum number of adjacent headers that compare CRCs against each other

Definition at line 42 of file flac_parser.c.

Referenced by check_header_mismatch(), find_headers_search_validate(), and score_header().

#define FLAC_MIN_HEADERS 10

minimum number of headers buffered and checked before returning frames

Definition at line 44 of file flac_parser.c.

Referenced by flac_parse(), and flac_parse_init().

#define MAX_FRAME_HEADER_SIZE 16

largest possible size of flac header

Definition at line 56 of file flac_parser.c.

Referenced by find_headers_search_validate(), find_new_headers(), flac_parse(), and frame_header_is_valid().

Function Documentation

static int check_header_mismatch	(	FLACParseContext *	fpc,
		FLACHeaderMarker *	header,
		FLACHeaderMarker *	child,
		int	log_level_offset
	)			`[static]`

Definition at line 268 of file flac_parser.c.

Referenced by get_best_header(), and score_header().

static int find_headers_search	(	FLACParseContext *	fpc,
		uint8_t *	buf,
		int	buf_size,
		int	search_start
	)			`[static]`

Definition at line 200 of file flac_parser.c.

Referenced by find_new_headers().

static int find_headers_search_validate	(	FLACParseContext *	fpc,
		int	offset
	)			`[static]`

Definition at line 162 of file flac_parser.c.

Referenced by find_headers_search(), and find_new_headers().

static int find_new_headers	(	FLACParseContext *	fpc,
		int	search_start
	)			`[static]`

Definition at line 224 of file flac_parser.c.

Referenced by flac_parse().

static uint8_t* flac_fifo_read	(	FLACParseContext *	fpc,
		int	offset,
		int *	len
	)			`[static]`

Return a pointer in the fifo buffer where the offset starts at until the wrap point or end of request.

len will contain the valid length of the returned buffer. A second call to flac_fifo_read (with new offset and len) should be called to get the post-wrap buf if the returned len is less than the requested.

Definition at line 151 of file flac_parser.c.

Referenced by check_header_mismatch(), and find_new_headers().

static uint8_t* flac_fifo_read_wrap	(	FLACParseContext *	fpc,
		int	offset,
		int	len,
		uint8_t **	wrap_buf,
		int *	allocated_size
	)			`[static]`

Non-destructive fast fifo pointer fetching Returns a pointer from the specified offset.

If possible the pointer points within the fifo buffer. Otherwise (if it would cause a wrap around,) a pointer to a user-specified buffer is used. The pointer can be NULL. In any case it will be reallocated to hold the size. If the returned pointer will be used after subsequent calls to flac_fifo_read_wrap then the subsequent calls should pass in a different wrap_buf so as to not overwrite the contents of the previous wrap_buf. This function is based on av_fifo_generic_read, which is why there is a comment about a memory barrier for SMP.

Definition at line 111 of file flac_parser.c.

Referenced by find_headers_search_validate(), flac_parse(), and get_best_header().

static int flac_parse	(	AVCodecParserContext *	s,
		AVCodecContext *	avctx,
		const uint8_t **	poutbuf,
		int *	poutbuf_size,
		const uint8_t *	buf,
		int	buf_size
	)			`[static]`

Definition at line 474 of file flac_parser.c.

static void flac_parse_close ( AVCodecParserContext * c ) [static]

Definition at line 661 of file flac_parser.c.

static int flac_parse_init ( AVCodecParserContext * c ) [static]

Definition at line 652 of file flac_parser.c.

static int frame_header_is_valid	(	AVCodecContext *	avctx,
		const uint8_t *	buf,
		FLACFrameInfo *	fi
	)			`[static]`

Definition at line 90 of file flac_parser.c.

Referenced by find_headers_search_validate(), and flac_parse().

static int get_best_header	(	FLACParseContext *	fpc,
		const uint8_t **	poutbuf,
		int *	poutbuf_size
	)			`[static]`

Definition at line 445 of file flac_parser.c.

Referenced by flac_parse().

static int score_header	(	FLACParseContext *	fpc,
		FLACHeaderMarker *	header
	)			`[static]`

Score a header.

Give FLAC_HEADER_BASE_SCORE points to a frame for existing. If it has children, (subsequent frames of which the preceding CRC footer validates against this one,) then take the maximum score of the children, with a penalty of FLAC_HEADER_CHANGED_PENALTY applied for each change to bps, sample rate, channels, but not decorrelation mode, or blocksize, because it can change often.

Definition at line 395 of file flac_parser.c.

Referenced by score_sequences().

static void score_sequences ( FLACParseContext * fpc ) [static]

Definition at line 428 of file flac_parser.c.

Referenced by flac_parse().

Variable Documentation

AVCodecParser ff_flac_parser

Initial value:

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

Definition at line 676 of file flac_parser.c.


Data Structures
struct	FLACHeaderMarker
struct	FLACParseContext
Defines
#define	FLAC_MAX_SEQUENTIAL_HEADERS 3
	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
Functions
static int	frame_header_is_valid (AVCodecContext avctx, const uint8_t buf, FLACFrameInfo *fi)
static uint8_t *	flac_fifo_read_wrap (FLACParseContext fpc, int offset, int len, uint8_t wrap_buf, int allocated_size)
	Non-destructive fast fifo pointer fetching Returns a pointer from the specified offset.
static uint8_t *	flac_fifo_read (FLACParseContext fpc, int offset, int len)
	Return a pointer in the fifo buffer where the offset starts at until the wrap point or end of request.
static int	find_headers_search_validate (FLACParseContext *fpc, int offset)
static int	find_headers_search (FLACParseContext fpc, uint8_t buf, int buf_size, int search_start)
static int	find_new_headers (FLACParseContext *fpc, int search_start)
static int	check_header_mismatch (FLACParseContext fpc, FLACHeaderMarker header, FLACHeaderMarker *child, int log_level_offset)
static int	score_header (FLACParseContext fpc, FLACHeaderMarker header)
	Score a header.
static void	score_sequences (FLACParseContext *fpc)
static int	get_best_header (FLACParseContext fpc, const uint8_t poutbuf, int poutbuf_size)
static int	flac_parse (AVCodecParserContext s, AVCodecContext avctx, const uint8_t *poutbuf, int poutbuf_size, const uint8_t *buf, int buf_size)
static int	flac_parse_init (AVCodecParserContext *c)
static void	flac_parse_close (AVCodecParserContext *c)
Variables
AVCodecParser	ff_flac_parser