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24p sync issues
I am working in a 23.98p HD project- which is being down converted to SD upon capture- and have run into two problems regarding sync:
1) While uprezing a sequence from 14:1 to 2:1, I went through the normal process of duplicating my sequence, decomposing, and batch capturing the clips. The problem arose because I’m dealing with pulldowns so unless the clips that were cut in the sequence started at ‘0’ or ‘5’ frames, the image was jerky and since a majority didn’t start on either, I ended up having to capture these clips and splice them in. While doing this, I realized these clips were way off(I’m talking a second or two), even though the original low-rez clip had the exact same starting point as the up-rez’d clip. I don’t understand why this is happening and I want to know if there is a work around to this long, tedious process.
2) I’ve started capturing archival footage which originates at 30fps (DVDs and Beta tapes)and the audio seems to be just slightly off-sync. I’ve tried to offset audio by 1 frame in the capture window but this doesn’t appear to be doing the trick. Is it possible it just looks weird because of the pull-down? Would changing the audio speed help any? Or perhaps another option?
I appreciate any advice!
Ronnie
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4 Replies
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A recapture of the same clip will respect the Pullin log of the original clip so that should be the same. Is the connection or I/O different from the first and second captures?
Michael
Michael Phillips
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Same connection (SDI through Mojo), different in-points to avoid a jittery image on clips that didn’t start on a ‘0’ or ‘5’.
Ronnie
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I’m just coming onto a project that was captured in the same way – HDCam SR SDI through Mojo and not logged to start on the “0” or “5”. Just curious, when you changed the starts, did the jittering problem go away?
Also – were the cuts themselves off by a frame or 2? Or by more than a frame?
Thanks, Cecily
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I’ve been finding, generally, that ‘0’s and ‘5’s will do the trick. Sometimes though the deck doesn’t catch the right frame in which case it will be a game of trial and error. (I found ones worked sometimes when zeros didn’t.) It also depends on whether the footage was shot using a standard or advanced pull-down.
As for recapturing, my shots were off by roughly a second (+ or -).
Here’s what I believe is happening: The tapes we’re using had a pull-down applied to them withing the camera during shooting to match the rate of video- 29.97 fps. When we capture them into the Avid, we’re removing the pull-down and 6 frames are dropped per second to match the 23.98 time frame of the project. Therefore, over time all of those dropped frames add up and will throw off the time code in the project from that of the tape. (Similar to the concept of trying to match a DF sequence with an EDL that was exported as NDF; at first it will match up but after some time, the gap between the two will become larger and larger.)
Hope that helps!
Ronnie
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