Reduce Pixelation in Keylight Composite

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Reduce Pixelation in Keylight Composite

I have composited video footage (shot on a professionally lit green screen with a pro level Sony DV camera) with a series of stills. The video (720) is an uncompressed, 10-bit Quicktime file which consists of 6 , 1 to 3 second clips. The stills were exported out of FCP in the same manner as a Quicktime file (and each still matches the length of the corresponding video clip).

The video file node and stills file node both pipe into the Keylight node; the Keylight node funnels down into the Fileout node. The whole thing works quite well, except there is heavy pixelation around the people in the long shots (the close-ups are clean).

Is there is node I an run the video file through to lower the pixelation? Also, after importing the file back into FCP (and then rendering it), I get approximately 5 horizontal lines running through the fast moving portions of the video. Any thoughts?

Thank you in advance!

iMac 24" 2.8GHZ INTEL CORE 2 EXTREME, Mac OS X (10.5.4), Optical Drive 065-6972 SuperDrive 8X(DVD+R DL/DVD+RW)

Posted on Sep 2, 2008 10:47 PM

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Answer 1

FLGB

Level 1

75 points

Sep 3, 2008 1:33 PM in response to Ahoog69

Even with the best green screen ever, if you shoot on DV tape, you'll always get the crappiest results ever. It's sub-sampled at 4:2:0 or 4:1:1 which basically means that you get in the U and V channels 1/4 pixels only.
If you want to use an intermediate codec, batch convert your chots to IFF files. It will be much more efficient than 10 bits quicktimes. (Just for info DV is only 8 bits).

So, to minimize aliasing effects on the edges of the matte, simply blur the U and V channels of your clips.

The lines you see in FCP can be the video fields. Did you shoot in some kind of progressive mode or is it interlaced? Double check you FCP projects settings to see if they match with your clips properties.

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Answer 2

Sep 13, 2008 6:23 AM in response to FLGB

I have a question for FLGB if i use a dv camera but record to a internal or external HD from quicktime via firewire. Will i have better results Than recording to the DV Tape.

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Answer 3

FLGB

Level 1

75 points

Sep 13, 2008 8:32 AM in response to Macbook91

No, the data sent through firewire are exactly the same as the ones sent to the tape. I don't remember exactly, but I think that there are mods for some hdv cameras to extract a HD-SDI signal. Maybe with some google you can find more infos.

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Answer 4

Sep 13, 2008 8:53 PM in response to FLGB

Oh ok.
If you could recommend me a web site to ask this question or if you know of a good kind of camera for a consumer price of around $400 that would be good or great for green screen video editing.

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Answer 5

FLGB

Level 1

75 points

Sep 14, 2008 4:36 PM in response to Macbook91

Unfortunately, to access a 4:2:2 format or better, you'll have to spend at least 5000$.
So, if you are using the DV, HDV, or some other strange sony format, use the method explained above about bluring the color components. It's not Hollywood but it can save the day.
Or you can sinply rent a professionnal camera with an experienced operator.
It all depends of your needs.

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Answer 6

Sep 14, 2008 9:06 PM in response to FLGB

I have one more question is mini-Dv the same or worse or better than dv. and is their a thing called mini-HDV as in high definition.

Well my main reason for the camera is at home i will have it firewire to my mac for recording straight to HardDrive. Maybe through Final Cut Pro. and for learning Final Cut Studio and Shake. And if some of the videos are to my liking or i made the for youtube i will put them on youtube and maybe a Hi-Def on my MobileMe Web site temporally. I said Hi-Def because it will look better before changed to 100MB of Flash Video.
So I'm saying i want my edited end result to look good or if possible great and then on youtube maybe look as good.
And maybe some family trips. will use mini dv tapes.
I will buy a 3ccd mini-Dv Camcorder tho. Since it has firewire and since a pro cam is way past pricing.

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Answer 7

FLGB

Level 1

75 points

Sep 16, 2008 3:37 AM in response to Macbook91

There are absolutely no difference between the datas recorded on DV and DVcam, but there is a difference on the tape speed. DVcam's tape runs faster to recond the datas on wider areas so it's less prone to drops. You get exactly the same picture quality on both formats (same codec, same data rate, etc).
If you are looking for a really really good DV camera, I suggest you the panasonic DVX 100. It's the best dv camera I've ever saw, but still a bit expensive for a consumer use (something around 1000 - 2000$ but really worth it). It has some cine like controls like it's progressive mode, and give great pictures.
Anyway, avoid sony cameras, they have too sharp and dersaturated images, that are typical of the video look.

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