Adding AC3 audio to MKV video

[switch_foot4]

I am a complete noob when it comes to this stuff. I have an MKV video file that has one audio track on it...and I have a seperate AC3 file which has the audio i want in the MKV. I really want to add that audio to the MKV file and make it the primary audio. I don't know anything about formats or codecs or have any programs...I was hoping someone could lay this all out for me?

[minerva.thegift]

The good news is that the .mkv container can hold AC3 audio so you don't need to worry about doing anything to that audio file (no converting or anything.) A nice tool for putting something into an .mkv file is the mkvmerge GUI (part of the mkvtoolnix package.) With it, you can just drag and drop your two files into the upper white box area labeled "Input files:" and all the track will show up in the box below it (labeled "Tracks, chapters and tags:"). From there, you can select the AC3 audio track and set the "Default track flag:" to "yes" and if the .mkv file already has an audio track you can select it and set the "Default track flag:" to "no" and you should be all set. Let me know if that works for you, but I think that oughta do the trick

[switch_foot4]

This worked perfectly and only took about ten minutes! Thanks so much for your helpful and very clear instructions!