High CPU usage playing videos

While in firefox I streamed a html5 video, let the video load completely and I looked at top in a terminal.
firefox hit up to 75% cpu
Xorg hit up to 41% cpu
pulseaudio hit 3%

Those are the high spikes, the low spikes would be half those numbers 35, 20 and 1 durring the video.

Videos look like they are in slow motion and skip every few seconds in all browsers. I tried ff, chrome and opera. It plays slow+skips in all flash and html5. Audio doesn't skip.
In youtube html5 i had a video in 480p, it was playing slow and skipping so i tued it to 144p and it got much worse.

Video does seem to play good if I reset my laptop and go directly to a video in any web browser but it will get really bad after playing a video or restarting the browser.

To put it into perspective in youtube i used to drop about 100 frames per minute in 480p and now i drop about 1500 frames per minute.

I did test it on puppy linux and it was much better, there was no slow motion video and a lot less frames dropped but videos still skipped a little every few seconds.