I've posted about this before, but nobody seemed to know what was up, so I thought I'd check again. I've got a lot of MKV files, with DTS audio. All of them are in proper sync when viewed in VLC. When I use MKVTools to create an mp4/m4v, I always set video to pass through, and audio to AC3 5.1 Sometimes the audio ends up out of sync after 10 minutes or so of video. I absolutely cannot find the source of the problem. I've used other apps and ways to extract the DTS audio and convert to AC3, and then used MKVTools to remux everything, but still.. no go. Has anyone experienced this and found a solution? Any reason why the AppleTV won't play DTS files?