Some follow up on this: found on this thread that setting

CLUTTER_VBLANK=none

makes it a *whole* lot better. In fact, AFAICS the problem is gone -- even if NVidia driver is still set to sync to vblank. Other performance problems which were also very noticeable on GNOME 3.6 (eg. moving windows around) are also gone.

Not sure if this is a GNOME or a NVidia bug (or both), will dive deeper into it later.

Regards,

Andre


On Wed, Feb 6, 2013 at 9:20 PM, Andre Costa <blueser@gmail.com> wrote:

On Wed, Feb 6, 2013 at 5:03 PM, Joe Zeff <joe@zeff.us> wrote:
On 02/06/2013 04:26 AM, Andre Costa wrote:
Quite the contrary: this is a 8-core i7 desktop with a GeForce GT9800.
It should handle any videos just fine ;-) (as it always has done until
F18). There's clearly something wrong, I just don't know exactly what it
is. CPU usage doesn't spike too much while watching videos

Have you tried running top in a terminal while this is going on?  It can't hurt to know what process is using most of your CPU time when the videos slow down.

Thks Joe, I'll try that. But it doesn't look like it's a high CPU usage issue, it looks as if video decoding is buggy.

I just tested getting rid of totem-mozplugin and installing gecko-mediaplayer (which uses MPlayer). Firefox is now able to play videos just fine, so it does seem to be some issue with Totem (or, more specifically, GStreamer?). However, gecko-mediaplayer doesn't get along well with Chrome, it simply can't load the plugin. So, either I switch back to Firefox or I use it only when I want to watch Quicktime movies.

Damn :-/