avisynth grammar and script?

[fjhdavid]

Dear all,

I would like to multiply the U channel by 1.1 in an YV12 clip.

My first attempt was to use colorYUV and write:

colorYUV(gain_u=1.1)

but in fact, U values, which may be positive or negative is summed with 128 to make it always positive.

I then tested: colorYUV(gain_u=1.1*(gain_u-128)+128 but it doesn't work!

What kind of script do I have to write to do the task?

Thanks for your help

Francois

[Gavino]

I think ColorYUV(cont_u=25.6) should do what you want.

You want to increase U by 0.1*(U-128) and 0.1*256 = 25.6

[fjhdavid]

It works. Thank you very much! really!

(I think, in addition, that cont_u or cont_v have been done for this purpose...next time I will read all the parameters description)

Francois