sharpeners and denoisers/smoothers together?

[N_F]

Yesterday while I was working on a source that's very blurry but also a bit noisy I ended up with something like
MPEG2Source(%source%)
crop(%values%)
lanczosresize(640,272)
asharp(1.5,6)
convolution3d("movielq")

I figure asharp will sharpen the edges and perhaps add some general noise (but hopefully this is kept to a minimum). The C3D will take care of the possible added noise and the "old" noise.

My questions:

1. Is a 'smoother' considered the same as a 'denoiser'?

2. I looked into avisynth's sharpen, Don's msharpen and Marc's asharpen and found I prefered asharpen (perhaps because it uses YV12). Are there any others that are considered good you'd suggest I look into?

3. Is it crazy using booth a sharpener and a smoother/denoiser in the same script? I can't recall ever seeing anyone else doing it. Is it a big "no-no" from a technical view?

4. How about the order of the filters? "Should" asharp be before the resizing or anything like that?

[mf]

Depends on the nature of the sharpening. I never use contrast-enhancing sharpening anyway, it's ugly. But I love combining sshiq with supersampled xsharpen.

[N_F]

Thanks for your reply mf. I'll have to find out what "contrast-enhancing sharpening" is :) and I'll take a look at xsharpen.

Noone else got any input?

[Didée]

"Contrast-enhancing" sharpening is (for me) that what almost all sharpeners do: compare a pixel with its environment, and enhance the difference. That's the basic principle of "normal" sharpening in AviSynth or any image processing tool, as well as unsharp masking (what Marc's asharp is also, in general, but with some twists), or what techniques there might be else.
"Not-contrast-enhancing" sharpening could be seen as sort of "geometric" sharpening: not comparing&altering pixel values, but searching for "boundaries" and making the edges of those thinner. That's the (very basic) nature of what Xsharpen and Warpsharp do.

The problem with the former group is, that they also enhance artefacts and noise, and lead to the famous "Edge Enhancement" effect that is, erh, problematic for encoding, compression-wise.
The latter group is pretty friendly to compression, doesn't enhance noise (but block artefacts), and looks simply different.

Generally, I have often used blurring and sharpening together, but admittedly more in plain image processing than video encoding.
Since I capture from relative clean source (DVB, but only composite cabel from receiver to PC), but my ATI8500DV delivers a little soft picture with captures, for me its relative easy:

- light denoising (ATM "dust", I get addicted to it)
- a *little* & *careful* Warpsharping
- thats it.

[edit]
Forgot to comment the smoother <--> denoiser question.

Don't know if there is any hard terminology ... so, again, for my personal understanding:
- a denoiser (tries to) reckognize what is noise, and what is actual image information (e.g. FluxSmooth, NoMoSmooth, Dust).
- a smoother doesn't care, and simply softens by threshold (e.g. Spatial/TemporalSoften, Convolution3d).

Obviously, the former retain more image detail, where the latter lead to better compressability.


Didée

[edit2]
Hi mf, simultaneous reply ;)

[mf]

Originally posted by N_F
Thanks for your reply mf. I'll have to find out what "contrast-enhancing sharpening" is :) and I'll take a look at xsharpen.

Noone else got any input?
Contrast-enhancing sharpening is actually sharpening that lightens surrounding pixels of dark edges and darkens surrounding pixels of light edges. This gives very ugly results. And supersampled xsharpen only works on anime, and it's super-slow. Sorry for giving you false hopes, I just said that's what I like to use, but I only do anime and I don't care if I get 1fps :D.

But you might wanna give warp sharp a try, it's not a contrast-enhancing sharpener either.

[N_F]

Thanks for your answers. I'll give warp sharp a shoot.

[Dreassica]

or give mshapren a try. :)

[mf]

Originally posted by Dreassica
or give mshapren a try. :)
Which is yet another contrast-enhancing sharpener *yawn*.

[wing1]

@N_F

If I am using asharp(and I do use it on all my scripts), I'd not use lanzcosresize, because it will definitely add all kind of edge artifacts. neutral or soft bicubicresize is best, and asharp will take care of the rest (asharp() will do fine). I'd soften the inputs with C3D or fluxsmooth before putting it through all the sharpening processes, and preferably do that in the luminance channel only. Asharp before resize causes stair stepping on edges for me, but the sharpening is more pronounced. Asharp after resize is much better IMO.

[N_F]

@wing1

I'll try once with lanczos and once with bicubic and see which one I prefer (thing is, in this case my compresabillity is already very high). Perhaps smooting it both before and after asharp() would be something to think about? (perhaps fluxsmooth before and C3D after or something like that).


@everyone

Is this (http://forum.doom9.org/showthread.php?s=&threadid=34076&highlight=warpsharp) the correct place for warpsharp (and xsharpen too for that matter)? Or is there a newer version I managed to miss?

[morsa]

The famous edge enhancement artifacts are created by contrast sharpenners not by Xsharpen or warpsharp.
Remember those ugly black lines on people´s shoulders.