Strange Chroma Key Issue - See video link. . . .

Posted by Scott_r 
Strange Chroma Key Issue - See video link. . . .
November 16, 2010 01:21PM
Hi All,

I'm just stared to do more work with chroma keying. But tried and experiment where I put my talent up against a wall that was green but not green enough. I had some holes pop in my subject. I cleverly (I think anyway) was to layered the same clip (but cropped) over the problem areas worked great.

Next I rendered out the clip with a correct green screen back ground. Hoped this would save some time.

Here's the very weird part: Everything looks fine in the sequence until I render the sequence. The rendered part of the sequence only keyed out the area where I softened the edges around my subject, the rest of the frame is all green, as if I've never keyed out the rest of the frame!

If I cause FCP to dump the rendered portion, then it looks correct.

What the heck could I be doing wrong???

I'm using FCP 6.0.6 and this is the first time I've ever had an issue like this.

Thought it might be because I was rendering over a Motion project, but tried it over just a white matte background and an having the same issue!

I went back to the multi-layered clip and tested it. It keys out everything correctly, but says it going to take 2 hours to render! This is a one minute and six second clip! Yikes! The other clip that isn't keying properly says that it will take 45 minutes to render.

Any ideas on what might be causing this?

Link to video showing the strange behavior: []

- Scott
Re: Strange Chroma Key Issue
November 16, 2010 05:49PM
Have you tried simply using motion to key. I use ta key in FCP all the time but the result was never exactly what i wanted.

Motion3 with be my 2nd choice for render and it does a nice job on those edges. the long render is due to your stacking in the v-trks. I would bet that that 2 hours is more like 30-45mins.
Never trust what the render says at the beginning. I have seen 3.5hrs turn into 1m15s.

Just guessing but...

... it seems to me that FCP6 recognizes the in and out points (duration), then it reads the 1st potion (or the most complicated area) then uses that to calculate the total render time. Once its through the 1st clip it may speed up or slow down depending on the composition of your TL.

I could be wrong but you will quickly know as the mods here are lightening quick.

""" What you do with what you have, is more important than what you could do, with what you don't have."

> > > Knowledge + Action = Wisdom - J. Corbett 1992
Re: Strange Chroma Key Issue
November 16, 2010 07:25PM
Hi J,

Will have to give that a try. I have played with clips in Motion and found it a bit tedious. I have Motion 3, so 4 might have some better ways of handling video(?).

I just ran test with myself against a proper color green screen and now it properly keying out the green. So maybe it's an issue with the file. I've added a video to my original post so you can see exactly what is happening. Really think it's a software issue!


Re: Strange Chroma Key Issue - See video link. . . .
November 18, 2010 05:08PM
I had similar problem with my G5 and it ended up being my graphic card after I installed Magic Bullet Quick Looks.
I had to disconnect my second monitor that I had since the G5 Quad came out in1995.
What have you change or added lately?

God Bless,

Douglas Villalba
Miami, Florida

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