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Old 11-07-2018, 07:22 AM   #1
wwwmaze
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Default Video-processor: parameter 1 of gfx_keyedblit (kv1) sets yellow-factor not green

In the docs of video-processor it is stated:
Quote:
gfx_keyedblit(input[,x,y,w,h,srcx,srcy,kv1,kv2,kv3,kv4])
chroma-key blits, using the source color as key. kv1-kv4 meaning depends on colorspace:

YV12/YUY2: kv1 is U target (-0.5 default), kv2 is V target (-0.5 default), kv3 is closeness-factor (0.4 default), kv4 is the gain (2.0 default)
RGBA: kv1 is green-factor (1.0 default), kv2 is blue-factor (-1.0 default), kv3 is offset (-1.0 default), kv4 enables spill removal (1.0 default)
In contrary kv1 adjusts yellow here (Linux native 64bit) if video output is set to RGBA mode.
This would make it hard (impossible?) to chroma-key green screens in RGBA mode.

reproduce:
  1. download a color-wheel image or similar (e.g. this post attachment) and insert on track in empty project
  2. set video colorspace to RGB in project settings
  3. insert video processor and open "simple source chroma-key" preset
  4. set k1 all the way to the right (16)
  5. set k2 (blue-factor) to 0
  6. adjust k3 (offset)

You'll notice that yellow is faded out first.
Attached Images
File Type: jpeg colorwheel2.jpeg (29.1 KB, 50 views)

Last edited by wwwmaze; 11-07-2018 at 08:07 AM.
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Old 11-07-2018, 08:27 AM   #2
Eliseat
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There is definitely something wrong because the base colors shift in RGBA rather then get transparent. So if I turn k2 to -16 and turn k1 slowly to the right, yellow turns red and green turns to black. If I go further the red and black turn transparent.
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Old 11-07-2018, 09:16 AM   #3
wwwmaze
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Quote:
Originally Posted by Eliseat View Post
yellow turns red
This may be a feature (spill removal), not sure. Turn it off by setting k4 to 0.
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Old 11-27-2018, 09:33 PM   #4
Justin
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Hmm yeah the RGBA mode is completely broken... It completely ignores the red channel when keying, oops.
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Old 11-29-2018, 01:03 PM   #5
wwwmaze
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Hey, thank you. Also for the new preset. Having a short glimpse at it I think I also misunderstood how to use gfx_keyedblit.
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