[AS3] High dimensions FLV playback issue

Hello, Everybody,
I have some issues with FLV playback which dimensions are 1280x720. It must be played in background and it must be scaled to fit stage width and stage height (imagine how big it becames if user has display 24" or 26"…). So then I’m scaling it to fit screen dimensions it becomes CPU sensitive and playback becames pretty choppy. Maybe some one is familiar with technology used in youtube or knows a good way to playback high dimesions FLV’s. Maybe it’s possible to divide FLV in to smaller screen’s and play them at the same time?

Thank You in advance!