Audio sync problem, dvdmpeg2enc

[dwil3000]

I recently converted an avi file to dvd2mpeg, however when i played it back on my mac dvd player the audio was not in sync with the video.
the avi file was: 23.976 fps, 737.2 kbps (don't know if that matters) and dont know what other settings that it had which are relevant. can anyone help me out? thanks!

[tomlee59]

Does the sync get progressively worse as the movie proceeds? Or does it jump in steps? Or is it off by a constant amount? Are the input and output framerates equal?

[dwil3000]

its pretty much constant throughout,
im not exactly sure how to change the framerate, here's what i did; in 'info' audio is = 441000 bits, on ffmpegx audio bitrate is set automatically to 448 kits/s, so i changed it to 441kbits/s and after converting to dvdmpeg2enc there was no audio ts or video ts folders!

[tomlee59]

If the sync does not drift, then it's not a framerate problem. You can fix a truly constant offset by demuxing, then remuxing with a compensating delay. ffmpegX, among others, has an option for doing just that. No re-encoding needed, so this is a very fast operation.

To determine the right number to use, play it in VLC. Under the Preferences menu, you'll find an option to dial in a sync offset (you may have to enable the advanced menus option; I don't remember). Type in your best guess (a positive number delays the audio), and play the clip again. To help guide you in what numbers to use, note that a 100ms error is just barely noticeable when characters are talking (but easily noticeable with door slams and the like), and 200ms is annoyingly noticeable. When you think you've got it, check sync at various points in the movie (beg, middle and end, at minimum), just to make sure that the sync error truly was a constant one. If it all looks good, then you're pretty much set. If you use ffmpegx's muxing tool, type in the *negative* of the number you used in VLC. Remux, author, and burn.

If you find, on closer examination, that there is both a drift and an offset, post back. There are several options for fixing those, depending on the magnitude and cause.

[dwil3000]

ok sounds good, but i cant figure out how to do the audio delay in vlc, im pretty sure you have to apply the advanced menu, but i can really figure out what to do after that, any tips?

[tomlee59]

Under Preferences, look at the Audio options. You will see something labeled "audio desynchronization" or "synchronization" or some such thing. Type in a value in milliseconds, save the prefs, close the prefs pane, and you're off to the races.

[dwil3000]

thanks for the help, but i've run into some trouble
the value i get from vlc is 455
but when i use the ffmpegx muxing tooling im not sure that im opening the right
files to re-mux. im opening the video ts folder and audio ts folder (which actually has nothing
in it). so then i hit mux, it works really fast then i open to video ts in the apple dvd player and the audio is out of sync just like when i began. maybe i am using the muxing tool wrong?

[tomlee59]

You can only mux elementary streams, which the vob files inside of the video_ts folder are not. So, you will first need to demux into elementary streams.

Most likely, you have multiple vob files. So, the first order of business is to rip your dvd as a single vob. Another option is to join the separate vobs yourself (using, e.g., the joining tool from D-Vision3), and then proceed from there. Do this for just the title you're working on.

Then, use the demux tool in ffmpegx. That will get you separate video and audio files.

Next, use the muxing tool in ffmpegx, and input -455 as the offset. Author, and burn.

[dwil3000]

thanks so much for the help, that worked great!
D-Vision 3 seems like a good program, have you used it to convert
framerates at all? that seems like a good feature
thanks again!

[tomlee59]

D-Vision 3 is a very well-written app. It's the only utility I use to convert into DivX/XviD, because it just works, and with a minimum of fuss (and with a minimum of opportunities for pilot error). I don't think I've ever used its framerate conversion feature, but I'd expect it to work as well as everything else does in D-Vision.

Glad to hear that you were able to resolve your sync problem!