mp4getnumberoftracks.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 
\fBMP4GetNumberOfTracks\fR \- Get the number of tracks
.SH "SYNTAX"
.LP 
#include <mp4.h>
.LP 
u_int32_t \fBMP4GetNumberOfTracks\fR(
.br 
	MP4FileHandle \fIhFile\fP,
.br 
	const char* \fItype\fP = NULL,
.br 
	u_int8_t subType = 0
.br 
)
.SH "ARGUMENTS"
.LP 
.TP 
\fIhFile\fP
Specifies the mp4 file to which the operation applies.
.TP 
\fItype\fP
Species the type of track for which a count is desired. A NULL value implies any type of track. See MP4GetTrackType() for predefined values.
.TP 
\fIsubType\fP
Specifies the subtype of the tracks to be counted. Subtypes are only defined for audio and video tracks, see MP4GetAudioTrackType() and MP4GetVideoTrackType() for predefined values. A zero value implies any subtype.
.SH "RETURN VALUES"
.LP 
The number of tracks of the specified type and subType in the mp4 file.
.SH "DESCRIPTION"
.LP 
\fBMP4GetNumberOfTracks\fR returns how many tracks of the specified type and subtype exist in the mp4 file. This can be used to determine if an mp4 file contains a track of a given type of media, for instance audio or video. It can also be used to determine if multiple options may be available. For instance multiple audio tracks in different languages.
.LP 
For audio and video tracks, a subtype can be specified to only count tracks of a particular encoding.
.SH "SEE ALSO"
.LP 
MP4(3)