https://bugs.freedesktop.org/show_bug.cgi?id=84944
--- Comment #5 from Christian König deathsimple@vodafone.de --- The deinterlacer is hardware independent and so it's rather unlikely that it is the source of the problem.
Can you grab a trace of MythTV with VDPAU_TRACE=1 in the environment once with and once without deinterlacing enabled? This way we can see what MythTV is actually doing.