Tool for Editing MKV Without Re-Writing Entire File?

[Wardrop]

Often I deal with rather large MKV files, sometimes in excess of 30GB. Often I need to make a minor change to the file, such as making a subtitle track a non-default track. I imagine some modifications wouldn't add any more data to the MKV, so my question is, does anyone know of a tool that make certain changes to an MKV without re-writing the entire file?

I currently use MKVToolnix for all of my MKV needs.

[Baldrick]

Try mkvpropedit that is included in mkvtoolnix. Only a command line app though.

[Wardrop]

Thanks, I'll give that a go.

[Wardrop]

Ok, mkvpropedit kicks ass. Here's what I did to turn off the default subtitles track:

1) Open the file in MKV Merge GUI to easily view the properties of the file.
2) Note the number of the track that you want to modify (e.g. 1 for the first track)
3) Run the following command: mkvpropedit --edit track:1 --set flag-default=0 "E:\Example.mkv"
4) Marvel at the instant modification.

Some handy documentation can be found here: http://www.bunkus.org/videotools/mkvtoolnix/doc/mkvpropedit.html

Someone needs to write a GUI for this app though as I fear it's being severely under used.