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Old March 27th, 2004, 08:51 PM   #1
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resampling

What is the best way to resample minDV (4:1:1) to 4:2:2, b/c I understand it yields better qulity/better chroma-keying? I also heard that canopus A/D convertors can do that? Can anyone shed some light? Thanks.
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Old March 27th, 2004, 10:00 PM   #2
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Do it digitally. A lot of the good keyers will upsample 4:1:1 to 4:4:4. Which NLE are you using and on which platform?
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Old March 27th, 2004, 10:04 PM   #3
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I have Adobe Premiere Pro, After Effects 6.0
How do I do it?
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Old March 27th, 2004, 10:05 PM   #4
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Does up-sampling create a better image for chroma keying or does it produce banding? I'm not sure, because I've seen mixed results. Any links on this topic?
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Old March 27th, 2004, 10:44 PM   #5
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I'm pretty sure After Effects has a good keyer that will do the upsampling. I'm not familiar with AE so others can fill in here.

Quote:
Does up-sampling create a better image for chroma keying or does it produce banding?
I'm not sure, but I think banding refers to something else. Banding comes from rounding error. When you do an operation to a pixel and round the result, you lose a little tidbit of useful information. When you perform another operation, banding can occur. The way to see this is to go opposite directions with filters- darken and then brighten footage.

suppose your values are 1 2 3 4. You brighten by 50%.
That gives:
2 3 5 6 (round up)
Reduce the brightness by 33%. That gives
2 2 3 3

On a large scale this should cause bands of the same color to appear. Banding is avoided by using big intermediate numbers (i.e. 32-bit floating point numbers).


Does upsampling create a better image for chroma keying?
Yes according to Adam Wilt's DV FAQ.

http://www.adamwilt.com/DV-FAQ-tech.html#colorSampling
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