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Keylight inter-frame problem
I’m calling it an inter-frame problem not because I know what is going on but because I only see the problem when viewing the interlaced result on an NTSC monitor.
I don’t see this as a dv edge problem. I know the edges aren’t great looking in that steppy way you see in dv, this is different.
What I’m doing is keying some dv footage, laying it over another piece of dv footage. AE is de-interlacing the footage (lower) on import and I’m rendering out to dv.
What I’m seeing is a shudder/stutter on the edges of the keyed subject only when they move (i.e. wave an arm or walk across the frame) when they are standing still with relatively no motion the shudder/stutter on the edges is not apparent.
This is not seen on playback in the canvas viewer in AE or in FCP but neither show you interlaced fields on playback (as well as my computer monitor is a progress display).
I have tried de-interlacing/Not de-interlacing the footage on import, Selecting/Not Selecting Preserve Edges. I even tried setting Pixel Motion to on for the keyed layer (it helped but wasn’t fixing it just hiding it). I tried rendering just the keyed piece over a solid and it seemed to get better but it didn’t go away completely.
In some cases I’m placing the keyed footage centered in the comp. In others they are scaled and moved to place them in the environment. And with others I’m parenting the keyed footage to a null with tracking data. They all exhibit varying amounts of the shudder/stutter on the edges. Also The background piece varies in is use, sometimes it’s a still from dv(a hold key in time remapping), sometimes it just motion footage, sometimes it is scaled and repositioned.
I know it’s hard to tell what is going on without a look at the render clip but any suggestions?
TonyTony
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5 Replies
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[Dave LaRonde] “You’re NOT deinterlacing footage when you use that lower-field first button in AE, you’re interpreting the footage.”
Well… you are actually…
When After Effects separates fields, it shows de-interlaced video in the comp window.
Only when rendering to fields, After Effects will render every field separately, but when rendering without fields, the de-interlaced source is being used, resulting in de-interlaced footage.
TonyTony: how about a couple of sample frames so we can see what you’re seeing?
Bar3nd
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Dave your right I’m technically “NOT deinterlacing footage” I misspoke (typed). I am in-fact as you said “interpreting the footage”. AE is doing the separating and I am then asking it to re-interlace the footage when rendering. (AE User Guide: “After Effects creates field-separated footage from a single formerly interlaced field by splitting fields into two independent frames…”)
My point was that I feel I’m handling the fields properly and is not the cause of my problem.
As far as “What you’re seeing is how the key differs from one field to the next. That’s DV for you.” Differing from one field to the next is a problem for any interlaced format and I am seeing some of that but this is (it seems to me) much more.
And to had to the weirdness. As part of the final rendering I added an adjustment layer with a small amount of wave warp (hot day kind of thing) and test rendered a section and now it seems as if the shudder/stutter has gone away.
I’m rendering a longer section tonight and will report back tomorrow on the render results.
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The problem doesn’t show up in any one frame or I should say any one field that I might export from AE or FCP it only is visible on an Interlaced display (NTSC Monitor). Tomorrow I could render out a small dv file (~12meg) that you could then playback.
TonyTony
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So rendering with a small a mount of wave warp has greatly reduced the shudder/stutter seen on an interlaced display at the edges of the keyed subject when they’re in motion.
I have done a number of keying projects that used dv footage but never have I seen this kind of a problem until using AE 7 and Keylight. I’ve used Keylight in 6.5 and it looked fine, as well as using color difference keyer to some success.
I’ll try the foundry forums as well as some more tests.
TonyTony
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Was there a solution to this problem? I’ve just come across this problem for the first time.
Cheers
Mark Smith
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