Audio Sync Drifts With Editing

[megamachine]

After capturing video from a VCR, I have a PAL VCD file on my hard drive that I wish to edit. Mostly, I want to remove the titles and credits at the beginning and end, and occasionally remove some commercials within a program. The problem is, once I render the edited video, the sound drifts out of sync. It begins in sync, but by the end of a half hour program it is noticeably off, and at the end of an hour program there is a full one second gap between sound and video. As far as I can tell, the picture is behind the sound. There is no problem with the original captured video, the sync is fine. It is only after editing and rendering that I notice the problem. So, I am assuming it has something to do with the editing software settings and procedure I am using, or the codecs I am using for rendering the finished product. I have tried editing projects on three different softwares, VideoStudio6, MediaStudioPro6.5 Trial, and Premiere 6.5. Actually, Premiere was the worst, and not only was the audio out of sync, but the picture ended up looking more like a slide show, which is probably some problem with codec or framerate. Anyway, I am a newbie to all this, but know, or hope, there must be a simple way to solve this annoying problem. Your kind advice will be greatly appreciated.

[rsquirell]

There are simple ways to adjust "displacement synch" where audio is off by the same amount at the beginning and end of a video...but you have what Nicky calls "stretching synch" where the video is being processed at a different rate than the audio due to frame dropping (See Nicky's FAQ in Beginners Start here). He has ways of correcting it...but no video is worth that much hassle. It's best to scrap the project and attempt to identify what caused the problem to begin with and reedit.

[setarip]

In what format are you initially capturing from your VCR?

[megamachine]

Thanks for the replies. I can scrap the project, no problem, actually this is just some testing for a bigger project that won't be as easily scrappable later, so I would like to figure out what I am doing wrong to avoid the stretching sync. I did find something about frame rate and dropping frames, but no advice on how to avoid it. Anyway, here are the steps I took for this project:

1) Play a PAL video on my VCR and capture it with ADS Instant DVD CapWiz, which allows 4 levels of capture. I set it for PAL video input and use the VCD level of capture, which as far as I can tell has fixed attributes. The resulting file ends up as 352x288, 25fps, 44.1Hz and is about 10MB per minute.

2) Play the resulting video on Windows Media Player and Power DVD (in VCD mode) and it plays fine, no sync problems visible.

3) Load the video file into one of the above mentioned video editing softwares, and do some mild editing. Mostly, I am just trimming off the titles at the beginning and the credits at the end, mainly to save space, but I also tried clipping out a middle section.

4) Render the edited video in one of the programs mentioned above, which each has its own way of doing that. In VS6, I select "Create Video File" and save it as PAL VCD. After rendering, I play the video and notice the stretching. In MSP, the rendering options are more complicated, but I think I am using the right method. In the end, the result is the same as with VS.

5) In Premiere, I have a worse problem, in that the video comes out looking like a slide show, after rendering with the Adobe MPEG encoder feature set to PAL VCD. I tried it several ways.

I don't know if this is too much info, but I have been spending a lot of time on this and can't seem to get beyond the problem. Do you think it's a software problem, or my use of the software or a codec, or something else. The rendering is really slow, about an hour for half hour of video in VS and MSP, and two hours for AP. So could it be my hardware? I am using W2K, P4 with 256 RAM.

With many humble thanks for all your time and kind assistance.

[setarip]

For such routine editing (cutting and pasting), I'd suggest that you try using TMPGEnc as follows:

TMPGEnc>>MPEGTools>>Merge&Cut (Set mode to "MPEG1-VideoCD)

[megamachine]

Great advice, TMPGEnc is much easier and faster for this type of project, and I clipped the beginning and end from two captured videos quite easily. I still need to try doing cuts within the video, and as far as I can tell the only way to do that is to save two parts as separate files and then merge them later, so I'll need a little more time to mess around with it for this purpose. Anyway, clearly I was using the wrong software, so that problem is solved.

But the other remains, regarding sound sync. I did two renders with TMPGEnc, and now there is a slight displacement sync, rather than the stretching sync I described earlier. In each case the problem was not there in the captured video, and only appears after rendering. So I am still doing something wrong.

Related to this, after having studied carefully the captures and renders I've done in recent weeks, using the softwares and methods mentioned above, it seems to me, unless I'm getting senile, that the sync problem is inconsistent among videos for which I used the same method of rendering. Can a mismatched Codec or incompatible DirectX cause sync problems in playing??

[megamachine]

BTW, where can I find Nicky's solution to displacement sync?

[setarip]

"Great advice, TMPGEnc is much easier and faster for this type of project"

My pleasure ;>}


The possibly outdated guides you're seeking can be found at:

http://nickyguides.digital-digest.com/

[rsquirell]

You can easily adjust displacement synch in TMPGenc "source range" (found under the "advanced" tab in "settings" when not using the Wizard...or when using the Wizard when you get to the settings area. Look for "audio gap correction" in the "source range" area and make your corrections in 200 Msec chunks (+ if audio after lip movement, - if before)...OK out and render just enough video to pass an area of lip movement and "stop" and abort render and check results. Continue to make adjustments until you have it lined up.

[megamachine]

Thanks, that did the trick, after a little experimetning. Great little program, TMPGEnc, and I'm relying on it a lot more these days.

[rsquirell]

Yeah...I use it to give me MPEG-2's that look as good as MPEG "lossless" capture (and the resultant MPEG-2 is up to 1/3 the size of the MPEG-2 capture file...which means you can easily fit a 3 hr movie on 1 disc.)