Automatical color correction

[Terka]

Want to make an mkv from one my DVD and some scenes are greenish. Some more, some less. COuld you please suggest me how to process this automatically, without selecting them manually?

[martin53]

I think you ask for an automatic white balance filter? I also was looking for that. I did not find a native Avisynth plugin, nor did I ever read a theoretical approach about how to do it. These are the filters I know:
- native ColorYUV(autowhite=true)
- external plugin Autolevels() - you may separate the RGB channels and process them separately to do color correction, but in my experiments, the result was awful.
- Virtualdub filter ACOBW - I found it of no great use, but maybe I underestimate it.
function ACOBW(clip c, float "strength") {
strength= round(default(strength, 0.25)*100)
LoadVirtualDubPlugin("C:\_your_plugin_path_\ACOBW.vdf", "ACOBWVDF", 0)
c.ConvertToRGB().ACOBWVDF(strength, 1, 0)
}
I also started once to write a user function with runtime functions like AverageChromaU() etc, but i found no way how to determine the right color balance.

[lansing]

can you upload a sample?

[LemMotlow]

d l t d

[videoFred]

A very powerful color correction tool is tweak().

tweak(sat=1.0], hue= -5, starthue=20, endhue=169)

With starthue and endhue you can correct exactly the color range you want. Other colors will be untouched.

With colorbars() you can figure out what the starthue and endhue values are for the different colors.

Starthue - endhue:
---------------------
Red-Magenta: 20-169.
Green-Yellow: 170-280
Blue-Cyan: 281-360


And for color corrections we need sliders and real time preview: AvsPmod is very useful for this purpose.

Fred.