seek.c File Reference

#include "seek.h"
#include "libavutil/mathematics.h"
#include "libavutil/mem.h"
#include "internal.h"

Go to the source code of this file.

Data Structures
struct	AVSyncPoint
	helper structure describing keyframe search state of one stream More...

Functions
static int64_t	ts_distance (int64_t ts_hi, AVRational tb_hi, int64_t ts_lo, AVRational tb_lo)
	Compute a distance between timestamps.
static void	search_hi_lo_keyframes (AVFormatContext *s, int64_t timestamp, AVRational timebase, int flags, AVSyncPoint *sync, int keyframes_to_find, int *found_lo, int *found_hi, int first_iter)
	Partial search for keyframes in multiple streams.
int64_t	ff_gen_syncpoint_search (AVFormatContext *s, int stream_index, int64_t pos, int64_t ts_min, int64_t ts, int64_t ts_max, int flags)
	Search for the sync point of all active streams.
AVParserState *	ff_store_parser_state (AVFormatContext *s)
	Store current parser state and file position.
void	ff_restore_parser_state (AVFormatContext *s, AVParserState *state)
	Restore previously saved parser state and file position.
static void	free_packet_list (AVPacketList *pktl)
void	ff_free_parser_state (AVFormatContext *s, AVParserState *state)
	Free previously saved parser state.

Function Documentation

static int64_t ts_distance ( int64_t  ts_hi, AVRational  tb_hi, int64_t  ts_lo, AVRational  tb_lo  )

static

Compute a distance between timestamps.

Distances are only comparable, if same time bases are used for computing distances.

Parameters

ts_hi	high timestamp
tb_hi	high timestamp time base
ts_lo	low timestamp
tb_lo	low timestamp time base

Returns

representation of distance between high and low timestamps

Definition at line 63 of file seek.c.

Referenced by ff_gen_syncpoint_search().

static void search_hi_lo_keyframes ( AVFormatContext *  s, int64_t  timestamp, AVRational  timebase, int  flags, AVSyncPoint *  sync, int  keyframes_to_find, int *  found_lo, int *  found_hi, int  first_iter  )

static

Partial search for keyframes in multiple streams.

This routine searches in each stream for the next lower and the next higher timestamp compared to the given target timestamp. The search starts at the current file position and ends at the file position, where all streams have already been examined (or when all higher key frames are found in the first iteration).

This routine is called iteratively with an exponential backoff to find the lower timestamp.

Parameters

s	format context
timestamp	target timestamp (or position, if AVSEEK_FLAG_BYTE)
timebase	time base for timestamps
flags	seeking flags
sync	array with information per stream
keyframes_to_find	count of keyframes to find in total
found_lo	ptr to the count of already found low timestamp keyframes
found_hi	ptr to the count of already found high timestamp keyframes
first_iter	flag for first iteration

Definition at line 97 of file seek.c.

Referenced by ff_gen_syncpoint_search().

int64_t ff_gen_syncpoint_search	(	AVFormatContext *	s,
		int	stream_index,
		int64_t	pos,
		int64_t	min_ts,
		int64_t	ts,
		int64_t	max_ts,
		int	flags
	)

Search for the sync point of all active streams.

This routine is not supposed to be called directly by a user application, but by demuxers.

A sync point is defined as a point in stream, such that, when decoding start from this point, the decoded output of all streams synchronizes closest to the given timestamp ts. This routine also takes timestamp limits into account. Thus, the output will synchronize no sooner than ts_min and no later than ts_max.

Parameters

stream_index	stream index for time base reference of timestamps
pos	approximate position where to start searching for key frames
min_ts	minimum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
ts	target timestamp (or position, if AVSEEK_FLAG_BYTE set in flags)
max_ts	maximum allowed timestamp (position, if AVSEEK_FLAG_BYTE set)
flags	if AVSEEK_FLAG_ANY is set, seek to any frame, otherwise only to a keyframe. If AVSEEK_FLAG_BYTE is set, search by position, not by timestamp.

Returns

-1 if no such sync point could be found, otherwise stream position (stream is repositioned to this position)

Definition at line 244 of file seek.c.

AVParserState* ff_store_parser_state

(

AVFormatContext *

s

)

Store current parser state and file position.

This function can be used by demuxers before a destructive seeking algorithm to store the parser state. Depending on the outcome of the seek, either the original state can be restored or the new state kept and the original state freed.

Note

As a side effect, the original parser state is reset, since structures are relinked to the stored state instead of being deeply-copied (for performance reasons and to keep the code simple).

Parameters

s	context from which to save state

Returns

parser state object or NULL if memory could not be allocated

Definition at line 394 of file seek.c.

void ff_restore_parser_state	(	AVFormatContext *	s,
		AVParserState *	state
	)

Restore previously saved parser state and file position.

Saved state will be invalidated and freed by this call, since internal structures will be relinked back to the stored state instead of being deeply-copied.

Parameters

s	context to which to restore state (same as used for storing state)
state	state to restore

Definition at line 444 of file seek.c.

static void free_packet_list ( AVPacketList *  pktl )

static

Definition at line 478 of file seek.c.

Referenced by ff_free_parser_state().

void ff_free_parser_state	(	AVFormatContext *	s,
		AVParserState *	state
	)

Free previously saved parser state.

Parameters

s	context to which the state belongs (same as used for storing state)
state	state to free

Definition at line 489 of file seek.c.