Google’s Youtube now supports 4k resolution
Google’s YouTube today announced in VidCon 2010 support for videos shot in 4K (4096 x 3072 ).Now it options from 360p all the way up to 4096p .”The ideal screen size for a 4K video is 25 feet ,IMAX movies are projected through two 2k resolution projectors.” Ramesh Sarukkai, a YouTube engineer .
To demonstrate the power of 4K,youtube has created by a filmmaker with access to a 4K camera check out the videos in this playlist(Be warned: watching videos in 4K, even on YouTube, will require ultra-fast high-speed broadband connections). To view any video in a source resolution greater than 1080p, select “Original” in the video quality pulldown menu:

Video add by youtube are :
1). Life in the Garden (4k resolution)
3).2nd Movement for Violin (4k resolution)
5).(( Secret World )) 4k Footage
Because 4K represents the highest quality of video available, there are a few limitations that you should be aware of. First off, video cameras that shoot in 4K aren’t cheap, and projectors that show videos in 4K are typically the size of a small refrigerator. And, as we mentioned, watching these videos on YouTube will require super-fast broadband.
Click Here to go to official blog of youtube blog