Even though most of the attention has been focused on its famous handset recently, Apple talked about more than just the iPhone X at its September 12 event; the company also announced the Apple TV 4K. It may be twice as fast as the current Apple TV and offer 4K movies at the same price as their HD versions, but there are some caveats.

As noted in Apple's support documents (via MacRumors), 4K content from the iTunes store can only be streamed. While it's possible to download HD movies, and occasionally HD movies that support HDR and Dolby Vision, titles in the 4K resolution can't be downloaded to a device.

Apple had announced that it would upgrade HD movies already bought on iTunes to 4K at no extra cost, but as these can also only be streamed, they can't be viewed offline.

Apple isn't clear about why it added this restriction, though it's thought to be either a licensing issue --- Apple is charging the same price for 4K movies as the HD versions --- or it could simply be due to the large 4K file sizes taking up too much of the Apple TV's built-in storage.

While some users might not be put off by the restrictions, most Apple fans will likely be disappointed by the next bit of bad news: the Apple TV 4K can't play YouTube's 4K videos. This is because the device currently doesn't support Google's VP9 codec, relying instead on H.264/HEVC. It's the same reason why the Mac and iOS versions of safari can't play recently uploaded 4K YouTube content.

The Apple TV 4K ships today. Prices start at $179 for the 32 GB model.