I assume you are trying to watch streaming video?
Despite your own settings and specifications, streaming video is also going to be affected by the network - which may be busy at any section of it. So, you might experience breaks due to buffering and network congestion.
You could try VLC player as an alternative to see if that makes any difference. Many people prefer VLC because it copes with all types and formats of video without the need to find codecs. It's free, download it from the link below:
http://www.videolan.org/vlc/
