If you plan on picking up yourself one of those fancy new 4K Apple TV boxes, there's something you might want to consider first. It's not actually possible to use it to download 4K video from iTunes. Instead, you're stuck with streaming.
MacRumors found this bit of disappointing information in an Apple support document, which revealed that users can't download 4K video to watch offline. They can download HD video, and possibley even HD with HDR, but anything 4K is going to require a constant connection to Apple's servers.
Why this is the case isn't clear. The obvious reason is that 4K films take up a lot of storage space, which would likely fill up very quickly. The Apple TV is only available with 32GB or 64GB of storage, after all, with no option for expansion.
MacRumors also speculates that it could be a licencing issue. Apple announced that 4K video would not cost any more than HD, but rumours have suggested that film studios wanted to charge more. Limiting 4K to streaming only might have been a suitable compromise for all parties.
Apple recommends that you have a minimum internet speed of 25 mb/s for 4K streaming, otherwise it'll downscale the video - which defeats the purpose of 4K.
Another downside that was revealed is that Apple TV won't support 4K content from YouTube. That's because YouTube uses the VP9 codec, when Apple only supports H.264, HEVC (H.265), and MP4. Netflix's 4K content is supported, though, as will Amazon Prime Video's once the app launches later this year. [MacRumors via The Next Web]