How to sync up audio and video in mkvs?

[VidHunter]

Hi

I have an mkv with a really weird audio that I have never seen before. I have thrown my entire legion of audio software at it but not only have I not been able to convert it but also not able to even open it. I have thus given up on it. I have another mkv with the same audio track but is in AC3 format, but when I try to merge the audio track from the other mkv to this one, the sync is a little off. It is going to bug me when the video and audio is even off a little. So is there a mac program that can sync video and audio tracks in an mkv? I just hope it is simple and easy to use, so it doesn't matter if it is shareware or commercial software.


Vidhunter

[Baldrick]

You can try avidemux, under video choose copy, under audio choose copy and then change the shift value under audio so it syncs. Save as a new mkv.

But if the sync is progressive this wont work.

[jpschuck]

With MKVmerge, you can specify a delay in ms (positive or negative value), under the "Format specific options" tab of an audio track.

You may also try to open your original file with MediaInfo Mac in order to guess which audio format was used.

[tomlee59]

The fix depends on the nature of the sync problem. As Baldrick said, if your sync error is progressive (i.e., the amount of offset is not constant), you have more work to do. If the offset is fixed throughout, then following jpschuck's advice will solve it for you.

If you have drifting/jumping sync, you'll need to run your audio through a tool like Audacity. With it you can alter the speed (to correct a constant drift rate), insert/delete segments (to fix jumps in sync error), and offset the clip (to counteract a fixed sync error).

[VidHunter]

Thanks for the suggestions for syncing up mkvs. I will definately give them a try. It is always fun to learn new software. I got a copy of mediainfo, and it is awesome. I will be stashing that gem with my other treasures. The original file that I said was troublesome seem to use the codec Wavpack4. If there is a way to convert the original file to AC3 or something, maybe I can avoid the ugly work of trying sync up my video and the substitute audio track.

[ffooky]

I'd recommend XLD for converting the WavPack audio, which can be either lossy or lossless. Allow XLD to update itself.

[VidHunter]

Thanks for the suggestion ffooky. It worked. I totally forgot about that application. Somehow, the audio still seem a little off, so it looks like I will still have to mess around with the audio timing with the applications mentioned before. Thanks for all the help guys.