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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