some small additions:
I cannot reproduce it anymore with xine-ui.
And more important, another workaround is to start with this environment:
$ VDPAU_NVIDIA_NO_OVERLAY=1 kaffeine
But unfortunately then I think tearing gets visible.
>From the nvidia driver readme :
Both the overlay and blit methods sync to VBLANK. The overlay path is
guaranteed never to tear, whereas the blit method is classed as "best effort".
And still the issue is only visible with deactivated desktop effects, that's
mentioned in the nvidia driver readme :
The following conditions or system configurations will prevent usage of the
overlay path: ... The presentation target window is redirected, due to a
compositing manager actively running. ...
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