Amazon today announced that they will begin offering select streaming video content in 4K Ultra HD resolution at no additional charge. This includes content available for free to Prime members. The selection of 4K content is a bit limited at the moment, including only a small selection of TV shows and Movies from Amazon Studios, BBC, and Sony Pictures. In order to view the new 4K content, you must use one of 33 compatible 4K TVs with Amazon Instant Video built in.
The new higher resolution streams are not compatible with the Fire TV. About a month ago I came across a “[Ultra HD]” version of Hitch when browsing through the results of a voice search. Trying to play the video on the Fire TV resulted in an error message. The 4K videos have since been filtered out of the Fire TV listings to avoid any confusion. Lets hope the Fire TV 2 will be a 4K device.