The slowdown is gone for me except in fullscreen HD videos (either VLC or flash - 720p+). I am quite sure this is a KWin bug because I tried downgrading to Mesa 8.0.4 (which was working fine before) and I experienced the same issues. So it is something in the 4.9.2 -> 4.9.3 transition (perhaps even the above patch).
I also noticed that low resolution videos (480p) play smoothly, as well as the HD videos but only when not viewed fullscreen.
The slowdown is gone for me except in fullscreen HD videos (either VLC or flash - 720p+). I am quite sure this is a KWin bug because I tried downgrading to Mesa 8.0.4 (which was working fine before) and I experienced the same issues. So it is something in the 4.9.2 -> 4.9.3 transition (perhaps even the above patch).
I also noticed that low resolution videos (480p) play smoothly, as well as the HD videos but only when not viewed fullscreen.
Mesa: 9.0
KDE: 4.9.3
Linux: 3.6.6
Intel Driver: 2.20.12
Intel HD Graphics 4000