Video Capture - audio/video out of sync

DarrenD · Post by **DarrenD** » Sat May 05, 2007 8:36 pm

I searched for Video Capture Sync before posting thinking this might have been a common problem, but it came up blank so here goes...

I am playing a VHS tape from a VCR into my Mini-DV camcorder that has AV-in->DV-out which is then piped down the DV cable into my PC. I have used Video Capture to get the VHS on my PC using the DV type-1 recording setting. Twice now I have noticed that the audio/video are out of sync in the Video Capture window after a while (1/2 an hour). The first time I stopped the recording and loaded up the recorded section in Video Editor but could not find any sync errors; it played fine. I carried on recording a second session and put them together and burned it to DVD. The DVD played fine.

The same thing happened on the next VHS tape but I left it to record to completion (3 hours). Video Capture was well out of sync but again Video Editor played it fine. I am guessing this is just a quirk of Video Capture and as the final recording is OK then I should simply accept this as a quirk/feature/bug-ette that does not matter in the long-run. I would certainly wish it this way (out-of-sync in Video Capture display than in the rendered DVD).

Has anyone else seen this effect? If you need more setup info please ask.
Cheers
Darren

heinz-oz · Post by **heinz-oz** » Sat May 05, 2007 11:46 pm

During capture, the preview window only receives limited resources and cannot be used to judge capture quality. It only serves as a visual pointer to the current capture position within your original clip.

More often than not I capture unattended and have the preview turned off. What matters is the final result.

Devil · Post by **Devil** » Sun May 06, 2007 8:45 am

Your problem may very well be due to the camera. I have heard of someone who had the same difficulty but he cured it by not using the cam as a pass-through. He actually DV-taped the analogue input in the cam and then captured from the tape with zero problem. Don't ask me why! May be worth the try.

DarrenD · Post by **DarrenD** » Sun May 06, 2007 9:55 am

Heinz
That is what I hoped happens. I am not fussed so long as that is expected behaviour and as you say the final capture being in sync is what matters.

Brian
Thanks for that suggestion. However, since the final capture is OK I will stick with my current method as it is easier to record 3 hour VHS in one go.

By the way guys, I forgot to mention that after capture I load the .AVI file into VirtualDub-MPEG2 and locate any dropped frames. With the list of dropped frames I locate them in Video Editor source window and either cut around them if they are at the end/start of a scene (i.e. DV got confused over VHS end-recording/start-recording next bit, or switch from short to long play - yes I know long play was bad but these are our first few VHS tapes - 16 years ago). The other dropped frames seem to be single frames pin the middle of a scene probably due to the age of the tapes so I simply leave them in the final DVD.

Does Video Capture give a list of dropped frames? In VirtualDub-MPEG2 I have to use the } key to go to the next one and then write them down on paper. I don't suppose Video Editor has a goto next dropped frame? Not too bad if neither do as there are only a handful of dropped frames, I am just curious. When I get up to my Hi-8 and Mini-DV tapes (done 3 VHS out of 17) I don't expect any dropped frames due to the better source format and younger age of the material.

Cheers
Darren

GeorgeW · Post by **GeorgeW** » Sun May 06, 2007 4:29 pm

Devil wrote:Your problem may very well be due to the camera. I have heard of someone who had the same difficulty but he cured it by not using the cam as a pass-through. He actually DV-taped the analogue input in the cam and then captured from the tape with zero problem. Don't ask me why! May be worth the try.

The reason that might be working is when recording to camcorder tape first, some dv cams have a builtin TBC -- and so dropouts from the analog video are recorded/handled properly using the TBC. But when you use the pass-through feature, the TBC is not active, and so you can get audio/video sync issues.

Is the VHS signal "clean" -- without dropouts or those snowy gaps between recording sessions on the VHS tape

Regards,
George

DarrenD · Post by **DarrenD** » Tue May 08, 2007 12:37 pm

I am not sure how "clean" the VHS signal is; it seems pretty good to me considering the tapes are about 15 years old. My camcorder is a Canon MV600i (PAL UK model) but I don't know if it has a TBC built-in.

As I said, I am happy to accept the preview going out of sync so long as the final capture is in sync, just like Heinz said.

Thanks
Darren

heinz-oz · Post by **heinz-oz** » Tue May 08, 2007 11:25 pm

You mentioned dropped frames. Find out why you get dropped frames. I have captured many, many hours of DV and analog (pass through) without a single dropped frame.

Something is not right if you are dropping frames. What is running in the background?

DarrenD · Post by **DarrenD** » Wed May 09, 2007 12:42 pm

Heinz

The (type 1) dropped frames are where my old VHS tapes stop/start between recordings (made several days apart 15 years ago). I accept these as drops and just use Video Editor to cut a frame before and after. This is OK in my book especially since recording to VHS (from our old camcorder) was never frame accurate in the first place (unlike Print To Tape).

The second set (type 2) of dropped frames that I am seeing are the odd square blocks (about 5-15) on a single frame. Again I put these down to the age of the tape/VHS.

On my last VHS tape recording I had 0.07% dropped frames over a 3 hour tape. Most of them occurred at a very bad stop/start sequence so the real type 2 drop rate is even lower.

I have been using Video Capture on a dedicated Windows XP Home partition so I have nothing else running. I have successfully managed to record similar effects on my main XP partition with Trend Internet Security running as well.

Jst some background work-flow information
I see the Video Capture as the critical part of the whole process. The VirtualDub-MPEG2 drop frame collection and Video Editor slicing clips and creating .MPG files can be done in parallel with my normal PC stuff, i.e. web-browsing, e-mail etc. since I have the source info safely stored on the PC. I have been running a DVDWS 2 Full session audio/video multiplexing and burning a DVD whilst Video Editor is busy creating the next .MPG file. To prevent my DVD burn from failing I had raised the DVDWS priority to "Above Normal".