Re-encoding dual audio mkv?

[Junpei]

I have two mkv files. They each have two audio tracks, two subtitle tracks, and ffmpegX claims they're PAL (25 fps) but I'm not sure about this.

Simply put, my PowerBook isn't fast enough to play these files (in VLC), so I want to re-encode them. I'd love to get them playing on my DVP642, but if the video is PAL, I dunno what issues would pop up. I'd settle for watching on my computer.

I only need one of the audio tracks (appears to be 6 channel mp4a) and one of the subtitle tracks, alongside the video. What do I need to do to accomplish this (ffmpegX can't deal with multiple audio tracks, and I need the subtitles too), if it's even possible?

[MikieV]

Have you tried extracting what you want, using the MKVToolnix (command-line only) and using ffmpegX to re-mux?

available via versiontracker, or directly from
http://www.bunkus.org/videotools/mkvtoolnix/downloads.html#macosx

Haven't used it myself, as I am just starting to run into mkv files - and this is only mkv-related tool for Mac that I have found.

[Junpei]

Thanks. I just read about MKVToolnix somewhere else too, looks like that will work, but I'm not quite sure what I have to enter to extract the right parts of the file.

Edit: I got it, now I need to figure out how to convert a 6 channel AAC audio file to 5.1 AC3.