Quantcast Weird sync issue on copied tapes? - digitalFAQ Forum
  #1  
09-11-2020, 02:43 AM
koberulz koberulz is offline
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I have a tape, and what appears to be a copy of that tape (or two copies of a third tape I don't have, or something).

However, one is three minutes shorter than the other. Even though they seem to have the same content.

But looking at the ball in this clip, it looks like missing or duplicated fields or something? rather than an issue with frames.

I want to sync them up because the audio on one is far better than the audio on the other, but the good-audio tape looks horrendous.

-- merged --

If I did it right, these should be the individual clips from the above.

edit- Added sync1, sync2 attachments.


Attached Files
File Type: avi sync.avi (5.95 MB, 8 downloads)
File Type: avi sync1.avi (3.04 MB, 7 downloads)
File Type: avi sync2.avi (2.91 MB, 5 downloads)
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  #2  
09-11-2020, 02:33 PM
dpalomaki dpalomaki is offline
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You want to sync audio from one tape with video from another tape of the same event that has a different run time?

How long are the tapes?
Is the sync shift gradual and at a uniform rate (e.g., gains 1 sec every minute) or is it random jumps?
Have you played through the tapes to verify that the video is the same, except for perhaps duplicated or dropped frames?

- One approach is to load the two videos into an NLE that shows audio waveforms on the timeline.
- Selectively trim frames out of the longer track to obtain the desired degree of match to the shorter track based on the audio waveforms.
- mute the video in one track and audio on the other keeping the desired video and audio - they should be in sync.
- Save this edited file.
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  #3  
09-11-2020, 03:37 PM
hodgey hodgey is online now
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Are you using a JVC VCR with TBC/DNR on? The second jumpy vid looks a lot like what you get when the JVC in-VCR TBC has trouble, in addition to jumping it can give out duplicated or half-duplicated frames when that happens.
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  #4  
09-11-2020, 11:36 PM
koberulz koberulz is offline
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Quote:
Originally Posted by dpalomaki View Post
You want to sync audio from one tape with video from another tape of the same event that has a different run time?
Ideally.

Quote:
How long are the tapes?
2h17m for audio, 2h20m for video.

Quote:
Is the sync shift gradual and at a uniform rate (e.g., gains 1 sec every minute) or is it random jumps?
Have you played through the tapes to verify that the video is the same, except for perhaps duplicated or dropped frames?
Difficult to really tell.

Quote:
Originally Posted by hodgey View Post
Are you using a JVC VCR with TBC/DNR on?
It's a Philips rebadge, but yeah the tech is the same.
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  #5  
09-12-2020, 07:33 AM
hodgey hodgey is online now
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May be worth trying to capture the audio one with the VCR TBC off and see if you end up with less desync and if there is still duplicate/dropped frames. Maybe I've just been unlucky with the ones I got, but I've found the TBCs in the JVC-made decks to very easily act up if there are any issues on the tape so I tend very often use DVRs for the line-TBC part instead. The TBC in our Panasonic NV-HS1000 which came out a number of years before doesn't seem to have the same issue, though it's a tad less accurate.
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  #6  
09-15-2020, 04:18 AM
koberulz koberulz is offline
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I recaptured both with the ES10 in place of the VCR's TBC, and I've got perfect sync until half time at which point it seems the commercial breaks differ in length, which is probably where the three-minute difference comes from. It did seem way too much to be a result purely of dropped frames.

Is there an easy way to just drop a specific number of empty frames into the shorter one at various points, so I can quickly check for sync while I've still got the StackHorizontal thing set up, rather than running it through my whole process only to discover down the line at the NLE/audio sync stage that there's an issue in the second half?
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  #7  
09-15-2020, 10:53 AM
hodgey hodgey is online now
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Since it sounds like you're using avisynth, you can use the BlankClip to create blank clips and add them in the middle to line the clips up.
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  #8  
09-18-2020, 12:33 AM
koberulz koberulz is offline
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Yep, that all works. Still a three-frame difference but easy enough to duplicate/delete frames individually to fix that, and we're good to go.
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