YUV Curves Plugin

[joshbm]

Hello,

I was wondering how I can use the adjust plugin (YUV for curves) and mimic this curve (http://www.videocdpro.com/josh/s-curve.amp).

Regards,
joshbm

[krieger2005]

ConvertToRGB24.GiCoCU("X.amp",photoshop=true).ConvertToYUY2
try to find it here in the forum.

krieger2005

[joshbm]

Thanks, but I'd like to keep it in the YUV colorspace without any color conversions. I already have used GiCoCU, but like I said YUV color space, no conversions. This is why I said adjust.

Regards,
joshbm

[joshbm]

Anyone? I know that Didee talked about this filter before.

Regards,
joshbm

[E-Male]

if the curve is RGB and the video is YUV you won't get around converting
unless some pro comes up with a great idea i haven't thought of

[joshbm]

This plugin: http://www.avisynth.org/warpenterprises/files/adjust_25_dll_20031110.zip is a curves plugin, no? YUY2 only, but you have to know the equation for your curve.

Regards,
joshbm

[mg262]

I looked at the .AMP file format recently; I think they include R, G, B and luma curves -- so either the R,G,B are applied and then the luma is applied, or vice versa. In the one you attach, R,G,B seem to be straight lines (i.e. don't change the input), so it's just really a Y curve (I think).

There is a VDub plug-in by BugsBunny (discussed on neuron2's forums) which might be able to load that .AMP up. I meant to add .AMP importing/exporting to the colouring filter I wrote, but I decided to try and get in touch with BugsBunny to ensure compatibility first (parts of the AMP specifications aren't very clear, at least to me)...

[joshbm]

Yes I downloaded his plugin, but the only problem is I need YUV in AviSynth. When I use "LoadVirtualDubPlugin" I get the "Virtual Dub Plugs are for RGB32 colorspace only... blah blah" :-P.

Regards,
joshbm

[E-Male]

if onyl the first curve is used it can be applied to Y and should(!) be correct

i currently don't have the time to implement that into gicocu, anyone else is welcome to do so

[mg262]

Is it just that one curve you want to apply? If so, we could extract the values (the .AMP file just contains blocks of 256 bytes, each one specifying a curve) and try to guess the function, if it comes from something nice. If that fails or if it's lots of curves I'll try to stick something into ColourLike...

Edit: It looked so regular that it was worth a try...

http://people.pwf.cam.ac.uk/mg262/posts/randomcurve.jpg

but that's not quite right. (That's a linear function + sine curve that I tried fitting.)

[joshbm]

It is just an S-Curve... It enhances mid-tones and such, mostly for dv to digital film purposes.

http://www.c-f-systems.com/Docs/GammaCFS-242.pdf

That document may help. Except it shows some graphics on film negatives, you must obviously flip it, as to not have the negative image.

Regards,
joshbm

[E-Male]

why gues functions when you can j ust aply the LUT

[joshbm]

So you don't have to convert colorspaces. If this helps anyone see the values of this curve you can download PS_Curves.exe to view the values.

http://www.gcogger.dsl.pipex.com/stuff/PS_Curves.exe

From:

http://www.forum4designers.com/message180657.html

@E-Male:

You might be able to easily add YUV support to GiCoCu. Have you seen this thread? It looks like it shows the Y from RGB:
http://forum.doom9.org/showthread.php?t=16662&goto=nextnewest#post431971

Regards,
joshbm

[mg262]

I looked at the .AMP file format recently; I think they include R, G, B and luma curvesI just implemented .AMP import/application based on that assumption and it doesn't produce the correct results ... I am really sorry, @joshbm. I think I must have misremembered/misunderstood the specification; I suspect what is happening is that it includes not a luma curve but a curve which is applied to each channel in RGB. Unfortunately I can't find the specification again to check (via Google or Adobe's website).

If it is something being applied to each RGB channel separately, there really is no way to apply but to convert to RGB, apply it, and then convert back. That's not to say you couldn't build a YV12 filter to do it -- it would do the conversion internally at higher than 8-bit accuracy. (That would requiring interpolating the curves, but that can be done.)

Edit: I tried applying it to each of RGB separately...

http://people.pwf.cam.ac.uk/mg262/posts/colour/ampcheck.jpg

[joshbm]

No I believe it is JUST the RGB channel. No separate channels.

Regards,
joshbm

[mg262]

What is the RGB channel?

[E-Male]

You might be able to easily add YUV support to GiCoCu. Have you seen this thread? It looks like it shows the Y from RGB:
http://forum.doom9.org/showthread.php?t=16662&goto=nextnewest#post431971

looks to me that it would just do the same conversions, but internally in the plug-in
you can just do them in avisynth