Comment # 9 on bug 89987 from James Le Cuirot

Sincere apologies for this but it looks like this is actually a bug in VLC.
Several factors threw me off, namely that mplayer isn't playing ball either
(don't know why yet), that I upgraded the kernel around the same time, that UVD
was introduced in 3.18, and the error in dmesg, all of which made it look like
a kernel problem.

Doesn't that mean it would have still been broken when going back to 3.17?
Actually it kinda was but not nearly as badly so I guess I didn't notice when
filing this bug. Under that kernel version, it looks as though it drops every
other frame in a smooth manner. Under recent kernels, it barely moves at all. I
started downgrading various userspace components like libvdpau, Mesa, and
xf86-video-ati to see whether any of those made a difference but it wasn't
until I downgraded VLC from 2.2 to 2.1 that the problem went away, both under
3.17 and 4.1. I also tried VLC git master under 4.1 and strangely it behaves
like 2.2 does under 3.17, dropping every other frame. Very confusing.

I am now bisecting to track down the precise cause.