Ubuntu :: VLC Stops For 5 Seconds While Doing Fullscreen?

1. while playing any video file in VLC or any other player, i try to fullscreen or back to normal then the VLC just stopped for 5-7 seconds, video is running but in the screen it does not show running just sound comes.

2. while i open firefox or maximize it from clicking on taskbar, it take time similar thing the nautilus do when its going to maximize.

i don't know what the problem is, sometimes i feel it is because of compiz and emerald effact, but when i was ubuntu8.10 user, there was not such problem, it runs smooth.