mp4getsampleidfromtime.3

完整的RTP RTSP代码库

.TH "MP4" "3" "Version 0.9" "Cisco Systems Inc." "MP4 File Format Library"
.SH "NAME"
.LP 
\fBMP4GetSampleIdFromTime\fR \- Get the sample id of a specified time
.SH "SYNTAX"
.LP 
#include <mp4.h>
.LP 
MP4SampleId \fBMP4GetSampleIdFromTime\fR(
.br 
	MP4FileHandle \fIhFile\fP,
.br 
	MP4TrackId \fItrackId\fP,
.br 
	MP4Timestamp \fIwhen\fP,
.br 
	bool \fIwantSyncSample\fP = false
.br 
);
.SH "ARGUMENTS"
.LP 
.TP 
\fIhFile\fP
Specifies the mp4 file to which the operation applies.
.TP 
\fItrackId\fP
Specifies the track to which the operation applies.
.TP 
\fIwhen\fP
Specifies the time in the track time scale that is desired.
.TP 
\fIwantSyncSample\fP
Specifies if the returned sample id must correspond to a sample whose sync/random access flag is true.

.SH "RETURN VALUES"
.LP 
Upon success, the sample id that occurs at the specified time. Upon an error, MP4_INVALID_SAMPLE_ID.
.SH "DESCRIPTION"
.LP 
\fBMP4GetSampleIdFromTime\fR returns the sample id of the track sample in which the specified time occurs. 
.LP 
The specified time should be in the track time scale. See MP4ConvertToTrackTimestamp() for how to map a time value to this time scale.
.LP 
It is wise to use MP4GetSampleTime() with the returned sample id so one can adjust for any difference between the specified time and the actual start time of the sample.
.LP 
If the calling application needs a sample that can be accessed randomly then the 'wantSyncSample' argument should be set to true. This could be the case for a player that is implementing a positioning function and needs to be able to start decoding a track from the returned sample id.

.SH "SEE ALSO"
.LP 
MP4(3) MP4GetSampleIdFromEditTime(3)