Need help creating program to tag MKV's

Hi,

I don't know if this is right section to post this, but basically I am trying to write a program to allow me to write tags to an MKV file (similar to tags in an MP3 file) and I am wondering if the MKV container has any tag system built in that I can write to.

The tags need to be completely internal, no XML files alongside or anything.

Failing that, is there another format that allows for multiple subtitle tracks, multiple audio tracks and actually has internal tags?

Thanks in advance.

You might want to read the specification: http://matroska.org/technical/specs/tagging/index.html
Mkv has a lot of official tags, but totally custom tags are possible,... and can be simply added through mkvmerge.

Of course, just because they're tagged doesn't mean any other program is going to use them. Especially if you use your own custom tags.

yup, even with the official tags not all players&tools support all of them,..

My apologies, I should have elaborated on the fact that I am using my own-built media player.
I just wanted to find out if it has an internal tagging system seeing as I can't find anything other than programs that utilize external XML files.

Also is there an API/SDK/Lib I can use to access MKV tags?

I'm afraid I don't entirely understand MKVToolnix, even for the tags it wants an XML file, will it embed this file into the MKV itself?