Choppy video

Hello all,

I am experiencing choppy video playback for everything played on my system. I am using ubuntu 11.10 64 bit on an emachines d620 laptop. videos used to play fine but then I had a little trouble getting certain file extensions to even play so I got mixed up in installing codecs and then someone mentioned use VLC and I installed that and now the videos that used to play smoothly are really choppy. I am brand new to ubuntu so I was pretty lost to begin with. Can anyone help me?

These are local (not on a network share, for example) video files? What are they encoded with? If you could let us know the container and the codec, that'd be great. Also, another possible culprit would be the video driver, so if you could let us know what card you have and what driver is behind it, again that could help us.