how to change gamma in avisynth?

[marcorocchini]

(f.c.o) please how y gamma can be changed inside avisynth? thanks

[LMotlow]

Use the gamma_y setting in Avisynth's internal filter, ColorYUV().
http://avisynth.org.ru/docs/english/corefilters/coloryuv.htm

Or use Avisynth's built=in Levels() function.
http://avisynth.nl/index.php/Levels

[El Heggunte]

That's a very-trivial task

[LMotlow]

You can get to Avisynth's installed documentation a little faster by going to Start ->, look for the All Programs or Programs listing, find AVisynth 2.5, expand the Avisynth program group an click Avisynth Documentation. Or do what lots of folks do and make a desktop shortcut to the "Index.htm" file shown in the above image. The online documentation page has an A-to-Z index in the upper left hand corner.

[jagabo]

marcorocchini isn't interested in reading documentation to learn anything. He wants all of you to write his scripts for him. That's why I've stopped responding to his posts. Next he'll be pointing you to one of his videos and asking you what gamma setting he should use.

[LMotlow]

Yep. Still waiting for the other shoe to drop.

[jagabo]

And then he'll be asking for a script to automate gamma adjustments for all his videos in a batch process.

[LMotlow]

Yep. Then he'll get a new batch of videos, won't remember a thing that anyone posted, and it'll start all over again.

As it is, there's already some confusion about gamma anyway. https://forum.videohelp.com/threads/367549-same-mp4-opened-in-VD-and-avisynth-is-differ...=1#post2349845

[El Heggunte]

Yep. Then he'll get a new batch of videos, won't remember a thing that anyone posted, and it'll start all over again.

Very true I daresay he is an Italian gamemaniaco who sniffs cats instead of DVD-fungus

[marcorocchini]

OH, first of all I'm a cat: a beautiful cat. "Italian gamemaniaco" ?!?
It is a fact that in avisynth gamma correction does not have an elementary syntax command: is a fact that avisynth is not easy to use.
Hell Heggunte is an anti-cats and anti-my-nle, but also thanks to all

[marcorocchini]

And then he'll be asking for a script to automate gamma adjustments for all his videos in a batch process.

however I try to change gamma in a fixed point, not autogamma or autolevels.

I would do a batch that to this: if recognized that input file is a GOPRO MP4 file

        Set "TokenS=0"
        Set "isMP4GOPRO=0"
        IF "%~x1"==".MP4" Set "TokenS=1" 
        IF "%~x1"==".mp4" Set "TokenS=1"
        If "%TokenS%"=="1" Set "isMP4=1"
        IF "%isMP4%"=="1" (v:\automazioneclip\virtualdub\mediainfo.exe "%CD%\%~n1.mp4" dumpinfo:unicodefile.txt
        TYPE unicodefile.txt>mediainfo.txt)
        findstr /c:"Title                                    : GoPro AVC" "mediainfo.txt"
        IF NOT ERRORLEVEL 1 (set "GoPROAVC=1")
        if "%ismp4%"=="1" if "%Goproavc%"=="1" (set "MP4gopro=1")
        findstr /c:"Frame rate                               : 50.000 fps" "mediainfo.txt"
        IF NOT ERRORLEVEL 1 (set "gopro50fps=yes")
        findstr /c:"Scan type                                : Progressive" "mediainfo.txt"
        IF NOT ERRORLEVEL 1 (set "goproProgressive=yes")
        IF "%MP4gopro%"=="1" if "%gopro50fps%"=="yes" if "%goproProgressive%"=="yes" (set "MP4gopro50fpsProgressive=1")

do: gamma correction (in a fixed point)

[Alex_ander]

I use SmoothAdjust plugin (it works with internal bit-depth upconversion), like this:

SmoothLevels(gamma=1.2)

[LMotlow]

Yep. The shoe drops.

It is a fact that in avisynth gamma correction does not have an elementary syntax command

Sure it does. Avisynth's ColorYUV(), Levels(), and RGBAdjust() functions have parameters for gamma adjustment.

Sample: ColorYUV(gamma_y=10)
Sample: Levels(gamma=1.2)
Sample: RGBAdjust(rg=1.2, gg=1.2, bg=1.2)

[jagabo]

Hint: VirtualDub Levels filter ~= AviSynth Levels().

[LMotlow]

All of the filters mentioned will adjust gamma. The problem with automation is deciding how much or how little to adjust. It will be different for different videos. The GOPRO video submitted has serious problems with gamma, which varies during the video from too low to too high because of the GOPRO's autogain feature. Using autogain under widely varying light conditions is a serious mistake commonly made by amateurs. There is no remedy for it. "Auto" filters either don't improve it or make it look worse.

[marcorocchini]

thanks alex_ander, SmoothLevels(gamma=1.2) work easy

for YUY2:
ColorYUV(gamma_y=-15, gamma_u=-15, gamma_v=-15)

[jagabo]

gamma_u and gamma_v do nothing in ColorYUV(). Gamma adjustments make no sense for the chroma channels.

[marcorocchini]

ops, using ColorYUV(gamma_y=1.2) it seemed to me give back an error but not, work well and work well in YUY2

[jagabo]

ColorYUV() requires integers, scaled by 256.

[LMotlow]

ColorYUV() requires integers, scaled by 256.

Yep, you're right. Sharp eye for spotting that one. I changed my code with ColorYUV a couple of posts back. gamma_y is defined in the docs as float rather than integer, but with a range of -256 to +256 a decimal value like 1.2 doesn't make much sense, even if it worked (maybe the online Help needs correction?).

[jagabo]

gamma_y is defined in the docs as float rather than integer, but with a range of -256 to +256

You're right, all the numeric arguments are floats. I wonder if it used to be integers, otherwise why would they use scaled values? That's normally done so that program doesn't have to use floating point calculations (which used to be interminably slow).

[marcorocchini]

ColorYUV(gamma_y=-15)