.TH "MP4" "3" "Version 0.9" "Cisco Systems Inc." "MP4 File Format Library".SH "NAME".LP \fBMP4Modify\fR \- Modify an existing mp4 file.SH "SYNTAX".LP #include <mp4.h>.LP MP4FileHandle \fBMP4Modify\fR(.br 	const char* \fIfileName\fP, .br 	u_int32_t \fIverbosity\fP = 0,.br 	bool \fIuseExtensibleFormat\fP = 0.br );.SH "ARGUMENTS".LP .TP \fIfileName\fPSpecifies the path name of the file to be modified..TP \fIverbosity\fPSpecifies a bitmask of diagnostic details the library should print to stdout during its functioning. See MP4SetVerbosity() for values..TP \fIuseExtensibleFormat\fPCurrently ignored. When implemented it will use extensions to the mp4 file format to allow incremental additions to media tracks..SH "RETURN VALUES".LP Upon successful completion the function returns a handle to the mp4 file. This is used in subsequent calls to the library to modify the file.Upon an error, MP4_INVALID_FILE_HANDLE is returned..SH "DESCRIPTION".LP \fBMP4Modify\fR is the first call that should be used when you want to modify an existing mp4 file. It is roughly equivalent to opening a file in read/write mode..LP Since modifications to an existing mp4 file can result in a sub\-optimal file layout, you may want to use MP4Optimize() after you have modified and closed the mp4 file..SH "SEE ALSO".LP MP4(3)