[lmyllari]

First, I created a python script to verify the colorspace conversion math. The numbers look good - even a bit more accurate than what VDPAU uses (although identical results with the rounding).

I tested various configurations, including my bluray player, with the avshd709 clips. I tested black level, white level, greyscale ramp and color clipping.

There are two problems as far as I can see. First, the RGB range is not signaled to the monitor. This can be worked around with the xrandr full range setting. The second problem is with colors - when VA-API decoding is in use, the color clipping test shows very different levels at the top. Green clips before 219 (where the pattern starts) and red extends almost all the way to 251 (all numbers approximate, read from the screen and in non optimal light conditions). These tests are available at w6rz.net - download the MP4 version and test 1 and 3 from Basic Settings/ and 1 and 4 from Misc Patterns/A - Additional.

Two options:

1) Full range output:

Code:

xrandr --output HDMI1 --set "Broadcast RGB" "Full"

, disable VA-API decoding

2) Limited range output (with nightly):

Code:

xrandr --output HDMI1 --set "Broadcast RGB" "Full"

, disable VA-API decoding, set 16-235 range in system -> video and set limited range RGB from your TV/monitor. This gives the best quality (no banding in greyscale ramp, blacks and whites don't clip).


My full testing results for those who might be interested:
ubuntu, mplayer2 vo gl
xrandr output range full
1 black clipping: 20 lowest visible
3 white clipping: 234 highest visible
misc a greyscale: banding visible (darker looking stripes)
misc a color clipping: red 233, green 233, blue 233 visible

ubuntu, mplayer2 vo gl
xrandr output range limited
1 black clipping: 20 lowest visible
3 white clipping: 252 highest visible
misc a greyscale: no banding visible
misc a color clipping: red 235, green 235, blue 237 visible

oe 3.2.3 xbmc 12.2 git:97a9f05
xrandr output range full
1 black clipping: 20 lowest visible
3 white clipping: 234 highest visible
misc a greyscale: banding visible
misc a color clipping: red 251, green below 219, blue 243 visible

oe nightly devel-20131109194305-r16358, git: f653098f0800c40375abc36ef1c669755e6f4f6e
xbmc 13.0-ALPHA git:b58612c
xrandr output range full
refresh rate matching off (to match ubuntu 60Hz)
1 black clipping: 20 lowest visible
3 white clipping: 234 highest visible
misc a greyscale: banding visible (darker looking stripes)
misc a color clipping: red 251, green below 219, blue 243 visible

oe nightly devel-20131109194305-r16358, git: f653098f0800c40375abc36ef1c669755e6f4f6e
xbmc 13.0-ALPHA git:b58612c
xrandr output range full, no vaapi decoding
1 black clipping: 20 lowest visible
3 white clipping: 234 highest visible
misc a greyscale: banding visible (darker looking stripes)
misc a color clipping: red 231, green 233, blue 231 visible

oe nightly devel-20131109194305-r16358, git: f653098f0800c40375abc36ef1c669755e6f4f6e
xbmc 13.0-ALPHA git:b58612c
xrandr output range full, no vaapi decoding, system -> video -> use 16-235
1 black clipping: 20 lowest visible
3 white clipping: 252 highest visible
misc a greyscale: no banding visible
misc a color clipping: red 237, green 235, blue 237 visible

oppo bdp93
rgb limited range output, no dithering
1 black clipping: 20 lowest visible
3 white clipping: 252 highest visible
misc a greyscale: no banding visible
misc a color clipping: red 235, green 233, blue 237 visible



edit: I just noticed that this issue has been seen earlier at http://openelec.tv/forum/116-vaapi-intel...saturation