Have an MKV with a default audio track in Russian or subtitles in Chinese? Maybe from ripping an anime you found at a yard sale (who are we to judge)? In any case you could use Media Control to switch the tracks each time you load it up or we could just change the default tracks and not worry about it again. For that matter we don’t even speak Russian and never plan to, why not just remove it completely?
To get started you’ll need your video file, which doesn’t have to be an MKV but will be when we are done, and a copy of MKVMerge. Download and install the MKVToolnix package for Windows (v.2.9.5) then open MKVMerge from the programs menu.
Add the file you want to change the defaults for by pressing the add button on the right of the Input Files box or drag and drop the file into the Input Files box. It may take a few moments but the Tracks available for the file should appear under the Tracks box.
Above you can see that this file contains multiple subtitle files. The principal will be the same with multiple audio tracks. They will be listed as A_ followed by the encoding type.
Now to completely remove any given track from the file simply uncheck the box next to that track under the track listing. Those tracks will now be excluded when we remux (rebuild) our MKV file.
Once you’ve decided which tracks to keep with your new MKV file it’s time to determine which tracks will play by default. To determine this select each track and examine the General track options below the tracks box.
Here you’ll find the Language, Default track flag and Forced track flag. These settings are read by the decoder, such as FFDShow, when the file is loaded. Then depending on the settings set in the decoder the track that is played will be selected. For example, if you have set FFDShow (VobSub) to choose English by default English should be loaded by default.
Barring any such setting, the Default track flag will determine the default track to be played. The Forced track flag comes into play if you need to force a particular audio or subtitle file to play always. For instance in a movie with foreign dialog there would be a subtitle stream specifically for this portion of the movie. This subtitle stream should be set to forced, otherwise there would be no subtitles during this portion of the movie, leaving the audience scratching their heads.
Now you should have one stream of each type marked as the default stream. Set an output filename at the bottom of MKVMerge (which must be different than the input file) and press the Start Muxing button. The process should normally only take a few minutes then you’ll have your output MKV file with the proper default tracks.