DVD Audio Drift - the wierdest problem at DVinfo.net
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Old March 21st, 2008, 03:07 PM   #1
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DVD Audio Drift - the wierdest problem

OK I don't have a expalantion for this, but I wanted to ask if anyone has ever run into this before?

I shot a live concert of 3 bands with a XHA1 in 24f. Brought the files into vegas Pro 8 as native m2t files. The audio was recorded on a Olympus voice recorder with a stereo mic and synced to the video in post.

Note here - the Olympus did drift compared to the on camera audio which I synced back together in post by stretching the Olympus audio.

Rendered out as a cineform 1080p, 23.97fps avi. Then downrezzed it to MPEG2 DVD architect 23.97fps widescreen file. Audio rendered along with video (I know it's not the best way but it's what I did).

Brought this into DVD architect 4.5, added chapters and such and burned the disc.

The entire edit runs 2hours 2minutes. In all the steps above other than the initial syncing of the audio to video everything at each step remained in sync.

I had checked the DVD's on my set top player and all was good. Sync was complete throughout.

However....when I brought the disc to one of the bands we watched it in it's entirety front to back. The last bands performance had started to drift with the audio being almost a full second out from the video. This was easy to see as the drummer's snare drum actions were clearly not syncing up to the snare drum hits.

The only two things that I can think of that would contribute to this is that when I checked the discs I would not watch the disc front to back but rather watch a portion and fast forward as well as chapter skip to the next sections. So this is one area I need to check again to see if continuous playing was a factor.

The second thing was the quality of the band members DVD player. It was a horribly cheap little DVD player (brand name not checked at the time). When I say cheap I mean cheap....we actually watched it on a television no bigger than about 15" big with this cheap DVD player connected. I was double taking the video by the time the drift started to really get noticable, because it just wasn't making sense. It occurs to me that if this is the case than that poor band guy must have a hell of a time watching a movie as by the end of it dialog would look like a badly dubbed Kung Fu movie.

So does anyone have any thoughts or similar noticeable occurances of something like this?

If it's my technical steps that may be unsound (more info may be needed here as well to suss that out) then where would I have gone wrong?

I've never seen/noticed this before in any of my projects, included wedding videos I have shot. The only difference between previous projects and now is that I also stayed completely within a 24f workflow.

Help please!
James Hooey
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Old March 21st, 2008, 06:22 PM   #2
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I don't know where the cause of your issue lies nor mine. I have just finished editing a wedding where I had four video tracks and ten audio tracks. Most of the six independant audio tracks drifted but this is no real issue in Vegas as you can stretch and shrink the tracks so easily.

I went to considerable pains - I thought - to syn everything at the start, and then adjust each track so they were all in sync at the end.

I then converted my video tracks to a multicam track and went right though the wedding making my angle selection via multicam editing.

Then I went right through the whole thing again to fine tune the camera changes I had made and lo and behold I discovered video from three of the cameras had drifted from the master audio track I used as my bench mark, even though they were in sync beginning and end. The amount varied from a couple of frames up to about eight which was very noticably out of sync with lip movements.

I have no idea why this happens and have resigned myself to the fact that it does happen, and therefore I will/may have to bring individual events into sync after I have made my multicam camera selections. It is quite easy to do and doesn't faze me any more, but I wish it didn't happen.

It means every event needs to be scrutinised for sync towards the end of the project and not just at the beginning.
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Old March 21st, 2008, 06:44 PM   #3
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I'm not sure if this is exactly your problem but I've had similar issues. I had a client who had shot video from one position but recorded the audio with a DigiVoice Recorder at a different position and he wanted them synched. When I lined them up on the timeline they would play well for a few minutes then start to drift.

After a LOT of testing and trial and error I found that since the video was shot with an audio sample rate of 48khz and the voice recorder recorded at 41.1khz, if I used SoundForge and resampled the audio track to 48 it synced up fine.

I didn't hear any discernible change in the quality of the sound and once I found a common sync point the whole track lined up without any drift. I don't know if this is an answer to your problem but I thought I'd throw it out there.
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Old March 21st, 2008, 08:17 PM   #4
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Syncing up remote recorders in post is a bit of a pain but easy to do, although I'm sure dialog would be harder than music with drums.

However this is not exactly my issue. I did sync the audio to video in post and my pre DVD MPEG2 file confirms that the sync was maintain through all my steps.


Same thing. It's not the audio and video sync in editing that is causing me the problem. It is the actual finished DVD burn that is showing a loss of sync in audio on at least one particular set top player.

Hope that clarifies the issue a bit, and thanks for your responses.

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Old March 23rd, 2008, 11:44 AM   #5
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Anyone have any thoughts?
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