Comment # 2 on bug 924971 from Bernhard Wiedemann

btw: this sounds like "tearing", which I observed on ATI in the past
and to make it more visible I once made this video
http://download.mikrom.com/ts/testpattern1_60.m2t
(and similar videos in 24 and 50 fps)

My video has nearly-vertical bars
that are moving at constant speed horizontally (and a bit downward)

Those tearing-artifacts go away when using for playback:
mplayer -fs -vo gl
or -vo gl_nosw
or -vo x11 (slow)

on my fglrx + Radeon HD 7750