How to find out the real value of gamma correction applied?

[konstantin]

Hi!

I would like to transcode a video file with FFmpeg, and apply some gamma correction because the video is too dark. In FFmpeg I have to use this option syntax to apply the color filter: -vf 'mp=eq2=1.7:1.0:0.0:1.0:1.0:1.0:1.0'
Where the first real number (1.7) is the value of the gamma correction parameter. Other programs also use similar notation to define gamma correction. However in SMPlayer the gamma correction parameter is an integer number, for example 22. I would like to preview the video with SMplayer and to correct gamma, and than convert the applied gamma value to the format of FFMpeg. So my question is how can I convert the SMPlayer integer gamma value to the appropriate real number, usually in range 1.0-2.0.

[rvm]

SMPlayer uses integer values because the range for brightness, contrast, gamma, hue and saturation slave commands of mplayer is from -100 to 100.

I'm afraid SMPlayer doesn't have any option to automatically convert the values.

[konstantin]

Thx, I can convert the values for myself of course (assuming linear function), but I need to know what real gamma value correspond to -100 and what value to +100.