• Adobe After Effects

  green screen and deinterlacing

  Posted by Malcolm Desoto on August 2, 2007 at 10:17 pm

  Hey,

  so I’m doing some test with keylight (pretty impressive effect).

  Everything’s going pretty good. However, one of my main problems is this interlaced look. Now, I went to my project window, right click, interpret footage, seperate fields, lower field first.

  Even after doing this, you can still see some definite vertical lines.

  

  I’m shooting with a canon XL1S (DV25) until Monday. I know this is the suck to work with when you’re trying to pull a decent key, but is there anything else I can do to improve this interlacing issue?

  Thanks.

  Ps, I’m still workin’ on that spill you see there.

  Brendan Coots replied 19 years ago 3 Members · 4 Replies
• 4 Replies

• 

  Malcolm Desoto

  August 2, 2007 at 10:40 pm

  Yeah, I’m still messin with the parameters as we speak. Pre-blur seems to help a little.
• 

  Darby Edelen

  August 2, 2007 at 11:10 pm

  You should also look into smoothing the chroma channels of your footage a bit. The easiest way to do this is to apply a Channel>Channel Combiner effect and go from RGB>YUV, then apply a Blur & Sharpen>Channel Blur effect and blur the ‘Green’ and ‘Blue’ (the chroma channels in YUV) some. Then apply another Channel Combiner effect to go back from YUV to RGB.

  The more complicated but technically more correct way to do this is to use Median to smooth the chroma components. This becomes more complicated because you can only apply Median to all of the channels of the footage at once (in YUV this means both the Luma (R) and two Chroma (G & B) channels) so you have to apply more effects to round-trip the footage:

  Channel Combiner:
  RGB>YUV

  Median:
  2-3

  Set Channels:
  Source Layer 1 = Your Layer
  Set Red To Source 1’s = Luminance
  (this takes the luminance from the source RGB footage and replaces the smoothed ‘red’/luma channel of the YUV with it)

  Levels:
  For the Red/Luma Channel Only!
  Red Output Black = 16
  Red Output White = 235
  (this is necessary to bring the RGB luminance values from the previous step back into the YUV range)

  Channel Combiner:
  YUV>RGB

  That might be more trouble than it’s worth, but the results should be good!

  Darby Edelen
  DVD Menu Artist
  Left Coast Digital
  Aptos, CA
• 

  Malcolm Desoto

  August 2, 2007 at 11:36 pm

  Wow, thanks for that excellent advice!

  I’ll try that out. I do want this to look as good as it possibly can.

  Thanks.
• 

  Brendan Coots

  August 3, 2007 at 10:30 pm

  The artifacts you’re seeing are not from interlacing, but are the result of poor color sampling inherent in all DV footage. That blockiness is actually the color information in your video clip. When you key footage out, the edges of your matte tend to reveal this poor sampling whereas you might not ever notice it with standard footage.

  The best thing to do is the chroma blur trick Darby mentioned.

  Brendan Coots
  Splitvision Digital
  http://www.splitvisiondigital.com

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