[MPlayer-users] sws affects color??

[Matthias Wieser]

Hi,

I found that "-sws X -vf scale=WxH" does not only scale but changes color 
slightly. Is this a known issue? (Mplayer-cvs)


You can see it clearly if you do more than two scalings after each other, 
for example  "-sws 2 -vf scale=640:480,scale=540:480,scale=320:240". 
Colors then become awful (, depending on the characteristics of the avi).

Even more strange is, that some interpolators (-sws 8 and at a lesser 
extent: -sws 10) produce wrong colors, even after only one single 
scaling.

How to reproduce:

mplayer inputfile.avi -ss 00:00:20 \
-vf scale=600:500,scale=550:427,scale=440:344,scale=340:264 \
-sws 2 -frames 2 -vo png
xv 00000002.png

and compare to

mplayer inputfile.avi -ss 00:00:20 \
-frames 2 -vo png
convert -scale 340x264 00000002.png 00000002_.png
xv 00000002_.png

-----------------------------------------
For sinc (-sws 8):

mplayer inputfile.avi -ss 00:00:20 \
-vf scale=340:264 \
-sws 8 -frames 2 -vo png
xv 00000002.png

and compare to
mplayer inputfile.avi -ss 00:00:20 \
-frames 2 -vo png
convert -scale 340x264 00000002.png 00000002_.png
xv 00000002_.png


Regards,
     Matthias