If this is on a Mac the key values are in YUV. The green value is the lowest in the range (16,16,16) that's why the screen is green to begin with.
On 4/24/06, B. Bogart ben@ekran.org wrote:
Hey all,
I'm CCing a local artist, Teresa, who asked me this question.
In the process of playing with some keying footage she provided I seem unable to make pix_chroma_key actually work in this case...
We have two videos, a figure shot on a green screen (reading value 0, 240, 0), and a background to layer the figure into.
I'm using "value 0 240 0" to select the exact green of the background.
Now my understanding means that I should be able to see the green knocked out with a very low range, since it is more or less all the same exact color/shade, but instead I need to provide a very very high "range" to get a horrid result. I can start to see little bits of the figure with a range of "104 104 104", but going all the way up to "255 255 255" I don't see the whole figure (blacks parts are missing), and I get an approximate 1 pixel green halo around the figure. Some of this is due to compression, but that does not explain how bad this really looks. See attached screenshot of "value 0 240 0" "range 255 255 255"
Note I have sent colorspace RGB to both pix_film's so that I'm using RGB ranges and values.
It looks to me like the "range" I'm providing is trying to match not the green background, but the figure itself...
Since its a good green-screen, and pretty good footage, this should be a cinch to do, but I can't figure it out, after playing with the all the variables, direction, and which video goes to which pix_chroma_key inlet.
Please CC Teresa as it is her really trying to figure this out...
Thanks!
.b.
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