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| george12 |
 Posted: Dec 9 2003, 10:54 AM |
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Unregistered
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Are b and c parameters in bicubic resize positive or negative? For example b=0 and
c= +- 0.5.
I noticed in VirtualDub it has parameters -0.6, -0.75 and -1 for bicubic resize.
Must I use in avisynth positive or negative values?
BicubicResize(x,y,0,0.5) or BicubicResize(x,y,0,-0.5) ?
What is the right thing to do? |
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| george12 |
| Posted: Dec 10 2003, 10:19 AM |
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Unregistered
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I was just curious(curiosity kill the cat) because of this:
VirtualDub documentation:
"Three different modes are given, A=-1.0, A=-.75, and A=-0.6 (notice the negative values). These vary the "stiffness" of the cubic spline and control the peaking of the filter, which perceptually alters the sharpness of the output. A=-0.6 gives the most consistent results mathematically."
and...
Avisynth documentation
"With b = 0 and c = 0.75 the filter is exactly the same as VirtualDub's "precise bicubic" and the results are identical (positive value). You have to set b + 2 * c = 1 for the numerically most accurate filter. This gives for b = 0 the maximum value for c = 0.5."
So if I use BicubicResize(x,y,0,0.75) this would be the same as in VirtualDub with A=-.75
But one value is positive and other is negative.
So I made some tests:
BicubicResize(x,y,0,0.75) - very sharp output like Lanczos
BicubicResize(x,y,0,-0.75) - very soft output like Bilinear
conclusion:
Higher c sharper output, lower c (even below zero) softer output.
Am i wrong? |
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