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Old 02-04-2015, 04:50 AM
Cheesehead Cheesehead is offline
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Default Strange Video Sync Issue?

I have a PT11 film session which has a Pro Res 422 video file in the timeline.
Because of a short notice re-conform I was sent an H264 file as a reference for a new cut.

With both the files on separate video tracks when i switch from one to the other on a still frame the H264 is 2 frames earlier than the Pro Res.
They both start at the same place and are the same length.

But when I look at the files in Quicktime their cuts happen at exactly the same frames according to QT's timecode! Start points of the files are the same etc etc.

I was worried that the sync may have changed or it was finger trouble from the video editor, but according to Quicktime they are the same, just different codecs.

Is this a known issue with PT11 and H264?
Has anyone else seen this happen?
Its driving me nuts.
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Old 02-04-2015, 06:59 AM
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Question Re: Strange Video Sync Issue?

Was the H264 encoded as intraframe? If it was encoded as interframe, then not every frame is fully encoded. This is the first thought that comes to mind for the discrepancy. It could be related to reading the I/P/B frames and not accurately showing what it should when you park at that particular frame.
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Old 02-04-2015, 09:10 AM
Cheesehead Cheesehead is offline
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Default Re: Strange Video Sync Issue?

Thanks Jonathan,
I don't know if it was, I doubt the Editor will know either.
Would that cause a 2 frame discrepancy accross a whole 2 hour film?

I suppose the answer is not to use H264 apart fom as a rough guide.
Cheers
Martin
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Old 02-04-2015, 09:37 AM
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Question Re: Strange Video Sync Issue?

Possibly. Are they both consistently two frames apart from start to finish? Are they fine up to a certain frame, and then after that frame they are consistently two frames apart?
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Old 02-04-2015, 12:13 PM
Cheesehead Cheesehead is offline
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Default Re: Strange Video Sync Issue?

Yes, consistently 2 frames different when parked.
Even though they start and end on the same frames in the timeline.
Spooky!
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Old 02-04-2015, 05:04 PM
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Post Re: Strange Video Sync Issue?

Indeed. Is there a countdown or a slate before program start that might possibly have had two frames added or removed?

FCP had an issue when performing a digital cut where it would skip a frame or repeat a frame. The only way you knew this was if you went back and checked the tape. Your sequence would always be fine. I know we are talking about files here. Something doesn't add up though. Two frames off from start to finish makes me think one of them is missing two frames, even though their length is the same.
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Old 02-12-2015, 09:47 AM
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Default Re: Strange Video Sync Issue?

Just updating this as it might help someone who see's this issue and thinks they are going crazy, like I did.

I transcoded the H264 to Pro res proxy, removed the H264 from the session and added the Proxy version of the same file on a new video track.

The new transcoded version is frame accurately in sync with my original pictures.

So beware, if you use H264 in a session with a different video file type in it, the H264 may not show the correct frame when parked!

Pesky H264's!
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