public void tag_register
Registers a new tag type for the use with GStreamer's type system.
If a type with that name is already registered, that one is used. The old registration may have used a different type however. So don't rely
on your supplied values.
Important: if you do not supply a merge function the implication will be that there can only be one single value for this tag in a tag list and
any additional values will silenty be discarded when being added (unless
PREPEND is used as merge mode, in which case the new value will
replace the old one in the list).
The merge function will be called from copy_value when it is
required that one or more values for a tag be condensed into one single value. This may happen from
get_double etc. What will happen exactly in that case depends on how
the tag was registered and if a merge function was supplied and if so which one.
Two default merge functions are provided: tag_merge_use_first and
||the name or identifier string
||a flag describing the type of tag info
||the type this data is in
||a human-readable description about this tag
||function for merging multiple values of this tag, or NULL