.TH "MP4" "3" "Version 1.0" "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 	u_int32_t \fIflags\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 \fIflags\fPCurrently ignored. .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)