Apple TV
A new version of the Apple TV is expected to be capable of 4K streaming Reuters

A major update is on the horizon for Apple TV and iTunes users, as Apple prepares to bring Ultra HD and HDR video to its digital store and set-top box.

Until now, Apple has only sold and rented digital copies of films and TV series in high definition, putting the iPhone maker at a disadvantage compared to Netflix and Amazon Prime Video. Both streaming services have offered a growing catalogue of Ultra HD content for over a year.

Also known as 4K, Ultra HD video has four times the resolution of high definition, making images sharper and clearer. HDR, short for high dynamic range, is a form of Ultra HD video which shows a higher range of colour, contrast, brightness and saturation. Details normally lost in the lightest and darkest parts of an HD or regular UHD picture are preserved with HDR.

Apple could be poised to join the Ultra HD, HDR bandwagon as some iTunes users in the UK have noticed references to the two technologies in their iTunes purchase history. One, called Thomas Jackson, created a thread on the popular MacRumors forum to share his discovery. Although the content cannot currently be viewed in 4K, some are described in the app as "Movie (4K, HDR)", suggesting a bump in resolution is on the horizon.

Not all purchases are appearing as 4K, but those spotted by iTunes customers so far include Passengers, and Fantastic Beats and Where to Find Them.

It was reported in February that Apple is working on a new fifth-generation Apple TV which will be capable of streaming 4K content. It isn't clear if Apple will only stream 4K content, as is the case with Netflix and Amazon, or if 4K titles will be offered for sale and download.

Unlike the annually-updated iPhone, it is more difficult to predict when the next Apple TV and its 4K capabilities will arrive. The most recent reports suggest it will launch before the end of the year.