Movies lose audio/video sync as they progress

I partially fixed my audio synch problem by splitting the movie into clips no largter than 10 minutes. But I did notice that while I don't have a synch problem anymore, I do get a slight audio "pause" at the point where the clips are broken. This is akin to what iTunes does when you convert a live album and you get a small dead spot between tracks.

I don't notice this when I bring in video directly from the TV going through the DAC box. But I notice it on some VHS tape transfers. I was transferring the Star Wars saga (original, letterbox) and if I leave it as 2 long clips I get the audio sync.

If I split it into clips less than 10 minutes, there is no sync but a gap where each clip is divided. It's fine in iMovie.

I've doen a full quality QuickTime DV export and then brought it into Toast to burn to a DL DVD.

The reason that shorter clips aren't as bad, is because the clips resync properly at the beginning of each clip. That means that by the end of the clip, there's a smaller sync error (2-4 frames)than at the end of a long (1hr) clip (20-30 frames).

I've also tried to use Quicktime Pro to expand the audio (Edit>Add Scaled) to match the length of the video. This works... almost.

The sync is very good, but the audio is 1 frame short. That means that if you have video across multiple clips, there is a noticable 'tick' when you jump that one empty frame of audio to the next clip.

This is fine for a single clip, or even two: you can align the audio to start at the end of the audio on the first clip, instead of the second. You'll be 1 frame off on audio sync of the second clip, but you'll never notice. As you add additional clips, however, you'll get more and more out of sync. VERY annoying.

I'm still searching for a viable workaround.

jf

Hmmm. I'm starting to think it may not be Apple after all. Well, not entirely.

I've been doing some tests with a friends copy of Final Cut Express, and it appears to have the same issues. It's not as apparent, because Final Cut makes a heroic effort to match the audio rate and the video length, which works okay for about the first hour of video, but slowly loses sync. I also get this capturing directly in Quicktime 7.

(In a side note, upgrading to Tiger and QT 7 did not help things. Now, instead of the audio being a bit short when extracted, QT helpfully pads the audio to the same length as the video with silence. Grrrr. Oh well, at least Spotlight is neat)

Both Final Cut Express and my own testing shows that the extracted audio is about 47.970Khz, instead of 48Khz. This could either be an incompatibility with Quicktimes Dv->AIFF conversion, or it could be a problem with the hardware.

Could we get a quick poll of what kind of converters we're seeing this with? I've seen the DAC-100 mentioned twice.

I have a Datavideo DAC-100, firmware version H531 (on white sticker on the bottom)

jf

I am happy to read this thread. It sort of answers some of my questions from my post yesterday (that noone replied to) 😟

I don't understand all the technical aspects of what you are all saying. I videotaped one of my concerts (I am a band director) and imported it into imovie in small clips (2-3 minutes) and everything was great until I moved it to idvd to burn it. Then it is completely out of synch. Is this the same problem?

So basically, there is no easy fix or answer. Bummer.

Becky,

What kind of capture device do you have? Or is this straight from a DV camera?

BTW, there is a workaround of a sort, but it only works well for single clips of less than 1hr. I wrote a workaround document a week or two back, but Tiger and QT 7.0 conspired to make it invalid.

I may redo it to reflect the 1hr limitation.

BTW, can you tell if the sound is ahead of the video or behind the video?

jf

I was importing straight from the camera.

I don't have Tiger or QT 7.0.

The video is ahead of the audio. The same thing happened on my wedding video done by a friend (an excellent professional-type job) on one portion of the DVD. This video was made for us 3 years ago.

Our computer was purchased in January right before the new ilife came out, so it is a more updated version than what they used.

I would appreciate any workarounds because I plan on doing some projects with videos of my son soon.....

THANK YOU!

I've been looking for a solution for this audio sync glitch for about a week now, since discovering that longer iMovie 5 projects, say more than 30 min that are burnt to a DVD via iDVD end up out of sync.
Unfortunately I have a project that I already had many hours of editing into and is about to go over an hour in length before I discovered this audio sync problem. The solution I've come up with isn't really a solution, but I've discovered that If I put the video from the camera into iMovie 4 instead of iMovie HD it will burn in iDVD 5 without a hitch! Perfectly in sync. Which makes me feel that the audio sync problem lies more with iMovie 5 HD rather that with iDVD 5.
I did try the one step movie option in iDVD 5 where you feed the video from the camera straight into iDVD to burn a DVD and that also ended up out of sync just as badly as using iMovie 5.
The problem with my project is that you can't take the files from a project in iMovie 5 back to iMovie 4, so I may try exporting the files into DVD Pro and seeing if that will work or into Final Cut Express and then into DVD pro 3.
I did try going through Apple help line for 2 days eventually after everything was tried with no solution they sent me to a product specialist... I thought for sure that he would be able to help but all the solutions that he offered were the same things I'd already tried with the other lower level tech help, who I might say, were very concerned about my problem and tried their very best to solve the issue. The specialist almost seemed miffed that every suggestion that he made I'd already tried. The only new thing he seemed to offer was that it may be a problem with the camera. When I told him that I'd actually used two different Apple approved Canon cameras and that I'd never had the problem before I'd upgraded to the iLife suite he said that it was still probably a problem with the cameras not the software. I offered to call back if I found a solutiion and let them know and he flatly said "No." So much for Apple Product Specialists. (He was probably just having a bad day.)

I just installed the Quicktime update and my audio problems are the same. I import footage from a DV tape and the audio doesn't work. I export the footage from iMove HD to QT7 Pro and the audio is fine!!?? This problem didn't happen in earlier versions of iMovie. I hope apple comes up with a fix soon.
Paul