Additional info here, as 97119 is a duplicate of this. The flickering happens
even with R600_DEBUG=nodma. I don't even need to put the video to fullscreen.
This time flickering was just starting with the video. I've seen similar
flickering on a kabini system. Don't know, if this could be related. I've never
seen this on r600 systems (cedar, sumo), so I don't think it's a KDE bug.