-
frame lag on hd downconvert with kona
I have laid several HD projects off to digital beta tape recently in final cut and it has all been one frame off. I got 960×720 dvcpro hd 720p60 footage at 23.98 fps, and am downconverting to 29.97 sd. Usually working off a lacie firewire drive, usually on a dual 2.5 ghz G5 with 2GB ram, and using a Kona 3, 2, and LH. This has happened several times on several machines. It is perfect in my timeline, but when i lay it off it is a frame late. To fix it I have to shift everything one frame forward in my timeline, so that it is incorrect! and it comes out correct on the tape…
Has anyone experienced this problem, or have any ideas for me? -
3 Replies
-
Well, think about it. You are taking a 23.98 HD signal, adding a jitter frame or two, keeping the audio in sync and scaling down the image to fit in something a little less than half it’s size. All of that in a 30th of a second. Not too shabby, huh?
-
Ackerman,
There are all kinda of things that can cause signal delays. Down-converting is just one of them. Basically your video is not playing off or out of sync (you said it looks right when you play it back..it’s actually right on the tape too). The problem is that when you output to tape, FCP syncs up with your deck, playing video out in sync with the in points you’ve designated. The problem is that FCP is sending the signal at the appropriate time, but the downconvert is causing the signal to be delayed by 1 frame (if you were going out DVCPRO HD to an HD1400A or HDCAM deck, you’d have no problem, because no downconvert is needed).
You need to set the playback offset in the device control preset that you’re outputting with in your A/V settings (copy your expsting preset and edit the new copy – rename it something you’ll remember for future use). You should do a test with a few different offsets to make sure you’re using the right one, but when we downconvert with Kona 3 from HD to DigiBeta, we use an offset of +1 frame.
Hope that helps.
Ben
-
Thanks for the info Ben, I will give that a shot. Do you think it would make more sense for me to export a quicktime of my sequence at the downconverted settings and then just lay that off to tape?
Again, thank you for your response.
Reply to this Discussion! Login or Sign Up