[doveman2]

It seems the Pi is still clipping my black levels, despite setting
hdmi_pixel_encoding=2
in config.txt, which is meant to be RGB Full (0-255). I'm testing with a black clipping pattern showing levels 0-25 and when I play it from a USB stick on my TV, if I increase the brightness the lower bars will show up as grey rather than black but via the RPi, it doesn't change which bars are visible at all. Is there another setting in XBMC which would cause this?

I've also found that with my TV (Panasonic X60B plasma) that playing the pattern via the RPi and setting the brightness to +2 - +4 shows noise/snow (dithering?) all over the picture but playing it via the TV's USB port this doesn't happen. I also see this noise on the XBMC menu background.

EDIT: Another thing I've noticed is that the thumbnails in Videos - Files look like they've had the brightness boosted, so that they look very different to how they do when played. I took these screenshots in the list and with the videos playing to show the difference.

Someone from the AV Forums was kind enough to take a look at my screenshots and has observed:

'The Black Clipping thumbnail screenshot has black at 16, whereas the XBMC UI all around it has black at zero. So it would seem that the XBMC thumbnail generator captured the image using Video Levels, and something about it eliminated BTB, converting all values below 16 to 16. That is not a useful thing for it to do, as it makes it more difficult to set Brightness. Viewed on my PC monitor, the pattern appears gray, which is expected, for my PC desktop is at PC Levels, where black is 0. The desktop would have to be using Video Levels for this pattern to appear correct.

OTOH, the screenshot taken while the video was playing is at PC Levels, because examining the pixel values, Bar 16 and below have been mapped to zero, 17 has been mapped to 1, etc. This is the bottom end of what is meant by expanding Video Levels (16-235) to PC Levels (0-255). It looks like it should on my PC monitor, which again is at PC Levels. If the desktop were at Video Levels, blacks would appear crushed.'

I hope that's helpful.