You can use mkvmerge from the MKVToolNix suite to remove unwanted audio tracks while keeping only the ones you need. Here’s how:

Step 1: Identify the Tracks in the MKV File

Run the following command to list all the tracks in the MKV file and identify the track numbers:

mkvmerge -i input.mkv

You’ll see output like this:

File 'input.mkv': container: Matroska
Track ID 0: video (V_MPEG4/ISO/AVC)
Track ID 1: audio (A_AC3) [English]
Track ID 2: audio (A_AC3) [French]
Track ID 3: audio (A_AAC) [Spanish]
Track ID 4: audio (A_AAC) [German]
...

Note the track IDs of the two audio tracks you want to keep (e.g., 1 and 3).

Step 2: Extract the Desired Tracks

To keep specific tracks, use the --audio-tracks option with their IDs:

mkvmerge -o output.mkv --audio-tracks 1,3 input.mkv

This command will create a new MKV file (output.mkv) with only the video and the specified audio tracks.

Step 3: Include Video and Subtitle Tracks (if needed)

By default, mkvmerge includes video and subtitle tracks along with the specified audio tracks. If you need to specify all the tracks explicitly (e.g., keep track 0 for video, 1 and 3 for audio, and specific subtitles), you can do this:

mkvmerge -o output.mkv --tracks 0,1,3,5 input.mkv

Here:

  • 0 is the video track ID.
  • 1 and 3 are the audio tracks you want to keep.
  • 5 is a subtitle track ID (if you wish to keep it).

Step 4: Verify the Output

Check the new file to ensure it contains the correct tracks:

mkvmerge -i output.mkv

Automating Track Selection

If you often work with MKV files with many audio tracks, you can use a script to automate selecting specific language tracks based on language codes (--language option) or track properties. Let me know if you’d like help creating such a script!