Vegas 6.0 output A/V Sync Issue

[vvume]

I am using Vegas 6.0c to edit a AVI video. It has multiple video and audio channels. The main video has been chopped up at different points to introduce titles. When I preview the editing, the Audio/Video are perfectly synced. However whenever I render the project, the output has a huge sync problem. I tried to render just the audio seperately as a wav/mp3 and use it in DVD Architect 3.0c and the A/V Sync issue remains. I simply can't figure out why Vegas will show perfect sync in preview mode, but cause A/V sync when doing a full render of the project. Any tips??

[guns1inger]

What was the source audio ?

[vvume]

Video=MPEG-2 (DVD Compliant)
Audio=AC3 (Stereo/224Kbps)

I also tried Audio=MP3(Stereo/224Kbps)

[slacker]

This is an interesting case because Vegas is known for its auto-correcting audio features. In fact, if your video and audio are out of sync, the software is supposed to hit you over the head with pop ups. Hmmm...

Mark

[mikiem]

Is it possible that there's some fps conversion going on? If the clip's fps is listed or set incorrectly, it could still preview OK matching project setting, but if the render also included a fps conversion, not sure how it would work, except that it would probably be wrong.

Vegas works well with wav files, creates temp wav files for mp3 I think, but not sure how it handles vbr mp3 -- if that's what you've got. Another potential issue is the use of mpg2 video, if you put that on the timeline.

Have you tried rendering just a few sections of your vegas project as avi using dv or mjpeg, or mpg2 with audio to check sync.

Anyway, those are guesses of maybe where to start looking. Since the beta of vegas 3 haven't seen, heard of, or experienced a sync prob. 'Bout the only think I could add is don't rely on DVDA to preview for sync. The way it buffers output to allow ac3 playback, sub preview, and video, it's not terribly accurate. If DVDA is the only place you've seen sync prob., I'd suggest rendering a short section of your project in Vegas with audio, or muxing your output and testing that.

[guns1inger]

I asked what the source audio was, not what you are outputting to. What is the format of the audio you are loading into Vegas ?

[vvume]

The SOURCE audio was tried in both AC3/WAV & MP3 formats. Yes the source audio.

This is the sequence of steps I used:

(1) A home video was transferred to a DVD using a home DVD recorder and given to me (I had no other choice).

(2) I used TMPEG XPress to convert all the titles into DV AVI format/WAV format [I later tried to export the video to MPEG-2 and audio to AC3/MP3].

(3) For an unknown reason Sony Vegas 6.0c rendered 4 second blank video spots all over my DV AVI when it was rendered to DVD NTSC output. Even the preview showed the bank 4 second videos (audio was intact) at 5-6 spots in the stream. Otherwise A/V sync was good. Output A/V sync was also good. I couldn't figure out why I was having the black spots. Figuring AVI corruption, I first converted the TMPEG video into DVD complaint MPEG-2 video. The black spots were gone. The Preview also showed correct A/V sync. However when I rendered the output there was serious A/V problem with the audio running faster.

(4) To attempt to fix the A/V problem I used TMPEG Express to output the audio in AC3/MP3 formats. The A/V problems in the OUTPUT alone persisted.

I don't get a A/V problem indication from Sony Vegas because the audio/video lengths are the same. My suspicion is that the output audio is somehow being rendered with an incorrect (higher) fps than the video. Since I am using the standard Vegas DVD template, I don't see what I could be doing wrong.

When I try to render small sections of the video, then A/V sync is ok (even when rendering a small clip from the end of the timeline the audio and video matches correctly). The longer the clip I render, the clearer the A/V problem shows. Given that the video is 1hr 24mins long, I want to avoid rendering the whole video into 5 min clips for maintaining A/V sync (unless someone can show me a simple way to script it).

[kschang]

If the home video was recorded onto DVD and given to you... Does that mean you got VOB and all that?

I'd say demux the audio here, directly from the source, re-encode as CBR. Then find something that'll load your DV-AVI properly into Vegas (video only), then sync them together in Vegas.

[vvume]

Yes, the DVD video disk contained VOB files (I had to extract based on titles since the VOB was all mixed up).

I did do exactly what you said. I extracted the audio seperately and made them into a WAV, CBR MP3 and AC3 and added it seperately to Vegas. I still got the A/V sync problem.

Since I chop the Video and Audio at specific spots to introduct tiles and background audio, I wonder if the A/V sync problem is caused because of that. I fade in and out the title background audio.

Vegas 6.0 Preview:

Video: [Main][Title][Main][Title][Main][Title][Main][Title][Main][Title]
Audio: [Main][Title][Main][Title][Main][Title][Main][Title][Main][Title]

After rendering:

Video: [Main][Title][Main][Title][Main][Title][Main][Title][Main][Title]
Audio: [OOS][Title][OOS][Title][OOS][Title][OOS][Title][OOS][Title]

OOS = Out Of Sync
Notice how only the main audio is out of sync. The title audio plays at the right spot. Thats what surprises me

[guns1inger]

So why don't you manually sync the audio ? Just zoom in on the time line and shift the audio as required, left or right.

Are all the main sections out by the same amount ?

[lacywest]

Back in the days when I messed with Vegas 3 - 4 and 5 ... I remember I had problems with audio sync with AVI files ... but not with mpeg files.

[guns1inger]

I have never had sync problems with Vegas 5 or 6, and I use it a lot. I know that some audio files can be problematic, but they should not be in this case.

[harley2ride]

I know in Vegas 5 there is a setting to lock the video to the audio, so when you make cuts, everything stays in sync. I found that out, because I was cutting some frames, and my audio went out of sync. Could this possibly be the problem here. Are you locking the audio and video before you start editing?

[mikiem]

More guessing...

If the snapshot renders are in sync, that eliminates I guess any big fps or playback rate issues. The black spots you mentioned -- I've seen similar if Vegas didn't agree with or like the codec in use, & the reason for my comments on it not likeing mpg2. For that I would try disabling other DV codecs temporarily, &/or try option settings re: DV codec.

Focussing on the result, you posted the audio ran faster at a fixed rate. If this were a regular avi file with wav, first thing I'd look at was length of audio, stretching it to length of video. If the lengths are different with rendered mpg2 and ac3, don't know of many ways the audio could have been rendered at an incorrect rate, so would double check the video -- can't timestretch ac3 anyway.

In rendering mpg2, from mpg2 on the timeline, Vegas (or I guess most editors) has to create the frames from the timeline. If reading this mpg2 source, it gets maybe incorrect instructions to draw or repeat frames, or misunderstands them, that could mean longer video. At any rate, what about dgpulldown on the original or rendered mpg2's to make sure set correctly?

[vvume]

The Audio and Video tracks are locked in Vegas. Since I don't see any A/V sync problem within Vegas itself, there is no A/V correction that I can do. And I would like to avoid the headache of doing A/V corrections on a rendered mpeg2 file if possible.

I also have Adobe Premier Elements 2.0 and that renders the exact same source video and editing into mpeg files without a single issue. However I like the quality of Vegas output and additional plugins that it has.

For a short term solution, I rendered only the parts that I have edited and then replaced the original vob video segments with the rendered ones using VideoRedo. Worked very well and I get to maximize the video quality by not re-rendering the entire video.

The A/V sync still remains a mystery. Perphas Vegas does like the TMPEG MPEG2 output and the AVI codec I use for video editing. I am kind of new to Vegas (though I have learned quite a bit in a short time), and I hope this is a stray problem.