Video playback Issue

I was watching shows on netflix online streaming and when I select Allow HD it buffers in hd than plays hd, but the video laggs and audio plays normal untill it catches up then it plays the show for a while then repeats.
But the weird thing is when the video file is downloaded I can watch full 1080p with no lagg at all and this show i watch has 720p hd so i need help Identifining
the problem. If you can could you give info on the entire process of video streaming from the video down to the graphics card cpu and memory.

If you could help that would be great and I know i little about the subject so please be technical

If this will help the show is called Stargate Atlantis
If you need more info please ask

SledgeDG said:

Your problem lies in your internet connection!! For some reason your computer doesn't receive enough data to guarantee uninterrupted playback.
You sure know that the amount of data transferred for HD content is bigger than that for non-HD content.
There is not much you could do...perhaps shutting down other processes that use the internet or pause the clip for 5-10minutes to give it enough time to buffer. Or you use a different player where you could change the buffering settings. On the other hand you go with a download first (which poses another problem as long as it's about Netflix)
The technical aspect in streaming is fairly simple: Some server offers streamable content, your browser (or player) connects to it and (after a successful handshake) starts to buffer the incoming stream, which now gets sorted out by one of your codecs and sent to whatever playback device is set up.

You could check here if the stream is better

Stargate Universe Season 1 Episode 1

-DG

that is not the problem for sure cause i have fast internet and it usualy starts lagging when buffer is far ahead.