Strange Avisynth sound glitch

kearlywi · Post by **kearlywi** » Mon May 19, 2003 12:02 am

When I use avisynth (thru virtual dub) to encode my video (using XVID) i get a very peculiar sound problem. It is out of sync, even though my frame rates match, and skewing the sound by delaying it or advancing doesnt work either.

Whats happening is the sound is off by 1/2 second, then 3 seconds, then 1 second, then 4 1/2 seconds in that order (in other words, the speed of the audio is speeding up and slowing down erratically) (it is also possible that the video is speeding up and down eratically as well, altho I suspect the audio). I use the avisynth provided with AMV app on this website. I used files from two different versions of DVD2AVI (1.76 and 2.06 (the latter is a guess)). Both have the same problem.

Ok, now the strange part. When I encode my d2v and wav files thru TMPGEnc, i get no dubbing problems whatsoever. Everything works great (cept for the lame TMPGEnc quality that is

)! What this tells me is that the problem does not lie in my dvd2avi files, but avisynth itself (or possibly an obscure setting in virtual dub).

AbsoluteDestiny · Post by **AbsoluteDestiny** » Mon May 19, 2003 1:11 am

Are you sure the dvd audio doesnt have an offset?

If you are getting the audio from dvd2avi te filename includes an offset which you need to add in order to make it sync.

jbone · Post by **jbone** » Mon May 19, 2003 6:36 am

It sounds like a framerate issue - possibly the video contains 29.97 frames per second, but was slowed to 23.976fps without removing additional frames, with the audio playing at 23.976fps - effectively the video slowed while the audio not.

That's my first guess.

kearlywi · Post by **kearlywi** » Mon May 19, 2003 9:00 pm

Skewing the audio one direction or another had no effect.

I told VDUB to make it so that video and audio framerates match, so its not that either. Keep guessing.

jbone · Post by **jbone** » Mon May 19, 2003 9:09 pm

kearlywi wrote:I told VDUB to make it so that video and audio framerates match, so its not that either. Keep guessing.

That might be the problem, you may need to tell it to make the _durations_ match, or just do nothing.

kearlywi · Post by **kearlywi** » Mon May 19, 2003 9:42 pm

That might be the problem, you may need to tell it to make the _durations_ match, or just do nothing.

"_durations_ match"? Is that avisynth or Virtual dub and where?

OK update. I played the avisynth file in windows media player, and even though the video quality was unspeakable (it dropped frames like a maniac) the sound dubbing did a decent job of being where it was supposed to be. So apparently, the problem lies within Virtual dub (1.5.1) (although the avisynth file was still terrible, and was slightly off twice in the first five minutes of my file[probably due to computer lag]).

kearlywi · Post by **kearlywi** » Mon May 19, 2003 9:45 pm

does it matter that I use Windows 2000? (for the programs we discussed)

I recently "upgraded" (laughs) from xp to 2000. Strangely enough Im getting all these new bugs that never surfaced before. The problem posted in this thread is the only one so far I havent debugged.

kearlywi · Post by **kearlywi** » Mon May 19, 2003 11:48 pm

Can anyone tell me their exact audio and video settings that they use for dvd2avi? (i.e. mpeg audio or dolby, rgb or yuv, forced film or swap field order, etc) It may be that my settings are off.

kearlywi · Post by **kearlywi** » Wed May 21, 2003 11:55 am

ok ok I solved the problem: In dvd2avi I set my video settings to "forced film" (it was previously on "none", and this setting has worked just fine for the last 2 months until it inexplicably started having sync problems for no apparent reason on my most recent dvd)

Its only 24 fps but with filters it looks just like the real thing (awesome quality)

So in the end it was a video syncing problem and not an audio syncing problem.