BicubicResize (b=0, c=something>0.75)

[yingx2]

Hi,
My attemp is to use bicubic resizer to produce movies as sharp as possible. I've tried several values, and with c=5, the sharpness of my encodes was even better than that of the original DVD's.

With c=6 or 7, I might get green horizontal lines and wavering edges artifacts, so I guess 5 is somewhere close to the maximum.

My question:
Can I change b to a different value other than "0" to produce an even sharper picture? Or should I always stick to 0 in this case?

I've read the Avisynth_reference.txt, but I couldn't find what b and c stand for.

Can anyone offer an explaination on this, please?

[frank]

A long time before it was discussed by Steady.

You have to set:

b + 2*c = 1 !!!

That gives the most numerically accurate filter.
Default setting b=1/3, c=1/3 satisfies this formula.

Catmull-Rom spline b=0, c=0.5 is my suggestion for sharpness.

In general: Select c for sharpness, then use b = 1 - 2c

From c>0.6 the filter starts to "ring". You won't get real sharpness, what you'll get is crispening like on a TV set!

[yingx2]

So, If c = 5, I must set b to -9 (1-2*5) in order to get accurate filter effect, is that right?

I'll try it later. Thanks for your explaination.

By the way, I don't care about ringing that much since it's not that noticable when watching from an appropriate distance.

Have you encoded a movie using 100% quality-based method at full resolution, along with Vdub's sharp filter at maximum strengh (64)?

I was totally shocked when I first saw the result.

Someone may say "those details are fake", but at least they fake it beautifully. It's like you're watching a 3-D movie.

[DJ Bobo]

Originally posted by yingx2
Have you encoded a movie using 100% quality-based method at full resolution, along with Vdub's sharp filter at maximum strengh (64)?

I was totally shocked when I first see the result.

You mean shocked because of the bitrate? :p

[yingx2]

You mean shocked because of the bitrate?
Yeah, a little bit.:sly:

[frank]

Oh NOO. No negative values: Then stay on B=0.

You can cripple your pictures as you want. There are more nice filters to do such things like smoothing, sharpening... :)
But BicubicResize has basicly to maintain the picture quality without visual effects.
From bad sources you'll never get best results.

[yingx2]

BicubicResize has basicly to maintain the picture quality without visual effects

Hm..I think even bicucbic(0,0.75) would blur the original picture to some degree.

Maybe it's codec-related, I don't know. That's why I want my movies shaper--I'm trying to "recover", or even enhance the original sharpness of a movie without distorting its picture. "The shaper the better" is always true at least in my case.

From bad sources you'll never get best results
agree.