Thread: VirtualDub2
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Old 22nd October 2018, 10:52   #713  |  Link
shekh
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Join Date: Mar 2015
Posts: 775
Sorry for confusion, here is illustration



I did not write the original algorithm in VD, only filled missing parts to communicate with higher precision formats. Overall it is the same in 8-bit, I don't think you have to stick to high bit depth to experiment with resampling.
By nature downsampling and upsampling are resizing of image applied to chroma planes. The differences are in small detail what filters are selected, subpixel offsets etc.

It seems I used wrong terms in wrong places.
All chroma resampling in VD is called "linear" and applied independently in with/height. Also there is "interpolation only". It seems Avisynth bilinear is exactly the same as VD "linear".
The second picture ("sony") should be called "bilinear interpolation" (not same as "bilinear resampling"). Or is it plain averaging?

This definition sounds correct: "Bilinear interpolation uses a 2x2 environment of a pixel and then takes the average of these pixels to interpolate the new value. It's not the best algorithm, but rather fast." = "sony".

Bilinear resampling averages more pixels by applying weights which fall off in linear law. By coincidence, in this example 0.5, 1, 0.5 are exactly pixel areas if you draw a box around them. Thus you could call it "Area averaging" but it behaves differently with other scales.
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VirtualDub2
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