Increasing Brightness of Videos?

[kolamorx]

Some videos are just too dark and it's sometimes hard to see clearly what is going on.
How can I improve video brightness without making the videos too pale or washed out? (for free.)

[Emulgator]

AviSynth:

<yoursourcefilter> "<yoursourcepath>"
smoothdebug=0 #0 no Diagram, 1 = Curve only, 2: Tweak only, 3: Both
ShowSmoothCurveDiagram=smoothdebug==1 ? true : smoothdebug==3 ? true : false
ShowSmoothTweakDiagram=smoothdebug==2 ? true : smoothdebug==3 ? true : false
smoothdebugwidth=1920
smoothdebugheight=1080
linear3="0-0;32767-32767;65535-65535"
linear5="0-0;16383-16383;32767-32767;49151-49151;65535-65535"
linear9="0-0;8191-8191;16383-16383;24575-24575;32767-32767;40959-40959;49151-49151;57343-57343;65535-65535"
your9="0-0;8191-12000;16383-20000;24575-30000;32767-35000;40959-40959;49151-49151;57343-57343;65535-65535"
SmoothCurve16(ConvertTo16bit().ConvertToStacked(), \
Ycurve=your9, \
Ucurve=linear3, \
Vcurve=linear3, \
limiter=false, HQ=true, interp=100, debug=ShowSmoothCurveDiagram, screenW=smoothdebugwidth, screenH=smoothdebugheight)
#SmoothTweak(HQ=true, brightness=0, contrast=1.0, saturation=1.0, hue1=-0, hue2=+0, limiter=false, debug=ShowSmoothTweakDiagram, screenW=smoothdebugwidth, screenH=smoothdebugheight)
ConvertFromStacked()