How can I get a playable audio track on an MKV with AC3?

[jeffreyabr]

I have a few MKV files with AC3 audio that I want to be able to play on a Roku using the Plex channel. Unfortunately, Roku does not support AC3, so Plex tries to transcode this, but ultimately fails.

I want to preserve the integrity of these MKV files, especially the video quality. I came across some threads that suggested using VLC to strip the audio (which I did to MP3) and then add that back into the MKV file using MKVToolNix, but when I did that, it generated a file with audio out of sync with the video.

Is there a good way to go about accomplishing what I'm trying to do? Is it even possible to create a good-quality audio file of a different format from an MKV and repack it into the original MKV?

Thank you for any and all help!

[jagabo]

Did you account for any audio delay in your original mkv file?

[manono]

Unfortunately, Roku does not support AC3, so Plex tries to transcode this, but ultimately fails.

What does that mean, 'ultimately fails? I've played a ton of MKVs with AC3 audio from my computer through the Plex channel on my Roku box to my television. And, as jagabo says, if you wind up with a delay for some reason, account for it when remuxing as MKV or whatever.

[jeffreyabr]

Unfortunately, Roku does not support AC3, so Plex tries to transcode this, but ultimately fails.

What does that mean, 'ultimately fails? I've played a ton of MKVs with AC3 audio from my computer through the Plex channel on my Roku box to my television. And, as jagabo says, if you wind up with a delay for some reason, account for it when remuxing as MKV or whatever.

Did you account for any audio delay in your original mkv file?

I didn't account for audio delay, and I suppose that I could have converted the audio from the MKV to MP3 without accounting for the frame rate too, which I saw on another thread. But another user on the Plex forums mentioned that there was a simple solution using Xmedia Recode.

You just need to convert the AC3 audio to AAC-LC with Xmedia Recode.
Format - MKV
Video - Copy
Audio - Convert
Should only take a few minutes.

Worked just fine, and I'm part of the way through "A New Hope." I've seen the movie stop and buffer only to return to the beginning twice so far, so I'm going to keep watching to make sure it was just a fluke, but I think I'm all set here! Glad it was this easy.