There's an mkv file I have that the audio, according to Mediafile, is ogg-flac.
How can I do to convert it to wav or AC3? My FLAC Frontend program is not recognizing it and says there's a sync error.
VLC plays it, but I need to convert it.
I've never had my hands on that format... If you are going to mess-around with odd formats, or randomly downloaded formats, you should probably load-up on conversion tools & CODECS, etc. Sometimes, you just have to try a bunch of conversion programs 'till you find one that works.
...to wav or AC3?
AC3 isn't popular as a stand-alone format either. Unless you are making a DVD or you've got a really good reason to use AC3, I recommend sticking with something more standard (WAV, FLAC, AAC, MP3, or audio CD). I use AC3 files for DVDs all the time, but I never use them for "listening"... Once the DVD is done, I either delete the AC3 file, or archive it with the other resource files for the DVD.
VLC plays it, but I need to convert it.
I've never used VLC to convert files, but it's one of its features. I found
this page (http://www.guidingtech.com/8848/use-vlc-player-to-convert-videos-from-one-format-to-another/) showing how to convert audio/video files, and I assume it will work on audio-only files.
When I run across a "problem" audio/video file (usually an A/V file from a "still" camera),
SUPER (http://www.erightsoft.com/SUPER.html) can often transcode or re-encode it. (If you try it, make sure to download SUPER... Their website is tricky... Don't get fooled by the ads for other software on the site.)