Why is AVStoDVD saying my audio will "be very likely out-of-sync"?

[seanmcnally]

Wondering why AVStoDVD is giving me grief about audio being out of sync. Getting a message that says:

Audio Track #1 is DVD compliant but has a delay of -17ms. Resulting DVD will be very likely out-of-sync, unless audio will be re-encoded.

The file is an MPG exported from Adobe Premiere Pro, using the MPEG2-DVD setting. Could someone give me a primer on why this message occurs? What accounts for that supposed 17ms delay? As far as I know, the DVD audio and video should start at the same time for this file...

[usually_quiet]

There are some authoring programs that can't cope with negative audio delays. Maybe AVStoDVD is one of them.

Audio delays are not unusual for DVDs. This post explains the technical reasons for DVD audio delays: https://forum.videohelp.com/threads/302180-Audio-to-video-delay-value-on-a-DVD#post2125315

[davexnet]

Hello -
this is the answer from the main program thread, courtesy manolito
https://forum.videohelp.com/threads/277852-AVStoDVD-Support-Thread/page114#post2491121

In your case, 17ms is such a small amount you may not notice. Or use one of the workarounds mentioned

[seanmcnally]

Thank you both for the explanations!

This post explains the technical reasons for DVD audio delays: https://forum.videohelp.com/threads/302180-Audio-to-video-delay-value-on-a-DVD#post2125315

I've read through that, thank you. It seems the delay is there to give the DVD player time to read and decode the audio data.

As an experiment, aside from the MPG I rendered from Premiere, I've also attempted importing an MKV ripped from a DVD using MakeMKV. AVStoDVD didn't give me the error. Is this because the DVD is professionally muxed with a 0ms delay, or because MakeMKV has done some magic to eliminate the delay without re-encoding? And if it's the latter, can I use this same kind of magic on my MPG file?

[davexnet]

Thank you both for the explanations!

This post explains the technical reasons for DVD audio delays: https://forum.videohelp.com/threads/302180-Audio-to-video-delay-value-on-a-DVD#post2125315

I've read through that, thank you. It seems the delay is there to give the DVD player time to read and decode the audio data.

As an experiment, aside from the MPG I rendered from Premiere, I've also attempted importing an MKV ripped from a DVD using MakeMKV. AVStoDVD didn't give me the error. Is this because the DVD is professionally muxed with a 0ms delay, or because MakeMKV has done some magic to eliminate the delay without re-encoding? And if it's the latter, can I use this same kind of magic on my MPG file?

It's possible MakeMKV does something, I don't know for sure - you'll have to try it

[seanmcnally]

Done some experimenting. I've been able to export from premiere to separate files, movie.m2v and movie.wav. I've then tried combining the two with FFMpeg, using

ffmpeg -i movie.m2v -i movie.wav -vcodec copy -acodec ac3 -f dvd movie.mpg

...but this causes AVStoDVD to report a delay. My question is, how can I use FFmpeg to mux a file that wont have a delay like that?

[davexnet]

I don't know, but if you're converting WAV to AC3, allow A2d to do it, add as it as a separate audio and run the project

[seanmcnally]

Good idea in theory, but not useful for my specific use-case. Within the same project, I have correctly muxed files (0ms delay), and incorrectly muxed files (35ms delay). It’s silly to re-encode the audio on all the correctly muxed files (which I didn’t mux myself), just to fix the delay on the incorrectly muxed files. I want to know how to correctly mux them in the first place. Maybe I should start another thread?

Edit: to clarify, AVStoDVD is all-or-nothing when it comes to re-encoding audio, you can’t just do it for specific files and stream copy for others.

[davexnet]

Good idea in theory, but not useful for my specific use-case. Within the same project, I have correctly muxed files (0ms delay), and incorrectly muxed files (35ms delay). It’s silly to re-encode the audio on all the correctly muxed files (which I didn’t mux myself), just to fix the delay on the incorrectly muxed files. I want to know how to correctly mux them in the first place. Maybe I should start another thread?

Edit: to clarify, AVStoDVD is all-or-nothing when it comes to re-encoding audio, you can’t just do it for specific files and stream copy for others.

Actually you can do it on a title by title basis, on the edit title/audio tab

[seanmcnally]

Thanks for this, Dave. The solution I went with was losslessly fixing the delay using FFMpeg. Here's the command I used:

ffmpeg -i movie.mkv -itsoffset 0.017 -i movie.mkv -map 0:v -map 1:a -c:v copy -c:a copy -f dvd movie_fixed.mkv

[davexnet]

Thanks for this, Dave. The solution I went with was losslessly fixing the delay using FFMpeg. Here's the command I used:

ffmpeg -i movie.mkv -itsoffset 0.017 -i movie.mkv -map 0:v -map 1:a -c:v copy -c:v copy -f dvd movie_fixed.mkv

Thanks for the info, similar to the method that was discussed in the main thread regarding this problem and the usage of DelayCut
https://www.videohelp.com/software/delaycut

You have "-c:v copy" twice in your ffmpeg line above

[seanmcnally]

Oops, second one was meant to be c:a. Thanks, I've edited it!