The 4K TV revolution has been something of a slow-burner. The first 4K Ultra HD TVs made their way into shops a good few years ago, but it's only in 2015 that they are starting to feel like a viable proposition.
More realistic screen sizes in more affordable prices - like this Panasonic 40in 4K TV for £700 - and a just-about-decent selection of 4K content, means it's now fair to assume your next TV purchase might have a plethora of extra pixels.
But what about broadcast content? 4K films and TV shows from Amazon, Netflix and YouTube are good, and Ultra HD Blu-ray is on the way, but broadcast content is arguably the easiest way to bring Ultra HD to the mainstream. Enter BT Sport Ultra HD...
What is BT Sport Ultra HD?
The basics: BT Sport Ultra HD is the UK's first 4K TV channel. It launched in August 2015, with the first live 4K broadcast being the FA Community Shield football match on 2nd August between Arsenal and Chelsea.
For the uninitiated, Ultra HD promises "four times the detail" of HD. The resolution of Full HD is 1920 x 1080, sometimes known as 1080p. Ultra HD delivers video content in 3840 x 2160 resolution or 2160p.
Higher resolution equals more information, which should translate to a more detailed picture. Expect to see sharper edges, more detail in crowd scenes, more realistic faces, and so on.
The 4K content is delivered at 50 frames-per-second, which should help fast-moving action such as sport, and with 10-bit colour depth as opposed to the 8-bit used in HD video. This broader palette of colours should again make for more realistic, more colourful and more vivid pictures.
What does all this equal? As BT puts it: "Unbeatable picture quality." So if you're used to BT Sport HD or even Sky Sports HD, then expect to see a leap in picture quality.
More after the break
How can you get BT Sport Ultra HD?
BT Sport Ultra HD is only available, surprise surprise, if you have BT TV. To access it, you'll need to add the BT Entertainment Ultra HD package to your subscription.
And the Entertainment Ultra HD package isn't cheap: it will cost £15 per month extra, plus another £44 for an engineer installation and £49 for the new YouView Ultra HD box (worth £249).
The BT Ultra HD box has a 1TB hard drive and the package gives you access to "50 premium channels" of HD and SD content. There's currently a deal to save up to £500 off an LG Ultra HD TV, too.
You'll also need to have a BT Infinity broadband connection. BT tells What Hi-Fi? the service requires a 44Mbps connection, "which ensures a high quality TV viewing experience and concurrent internet usage".
Lastly, you'll need a compatible 4K TV, of course. Most 2014 and 2015 TVs from the likes of LG, Panasonic, Samsung and Sony will be supported.
As we noted ahead of the launch, BT Sport won't support older 4K TVs and products due to changes in the 4K spec over the last couple of years. This includes many 2014 AV receivers, with only Onkyo delivering AV amps with the necessary HDCP 2.2 spec.
There's no way to watch BT Sport Ultra HD online, on a laptop or on mobile (are you insane?), as you need the set-top box.
What's on BT Sport Ultra HD?
BT is promising "approx 1 live Ultra HD event per week across the season" - the reference to "the season" being something of a giveaway that the main focus of BT Sport Ultra HD is live football.
BT Sport has live Premier League and Champions League football during the 2015/16 season, and so far it's the English Premier League that has been featured in Ultra HD.
The channel will also be showing live MotoGP in 4K, with the British MotoGP Grand Prix scheduled for the weekend of 29th and 30th August.
BT promises that Champions League and FA Cup football, Aviva Premiership rugby and NBA basketball will all get the Ultra HD treatment over the coming year.
For now, look out for one live 4K sports event each weekend - and remember to record it if you want to wallow in 4K goodness during the week...
What about 4K on Sky? Virgin? BBC?
It would feel remiss not to mention BT's main rivals, Sky and Virgin. Sky was crucial in the launch of HD, rolling out content arguably faster than anyone, and both Sky and Virgin offer a wealth of HD sport, films, TV series and more.
The BT Sport Ultra HD channel is exclusive to BT TV at present, and therefore not available on Sky or Virgin.
Instead, Sky is working on its own 4K offering, dubbed SkyQ. Though rumoured to be launching later in 2015 - Sky actually delivered the first 4K broadcast back in 2013 - it seems it's not yet ready to roll out to consumers.
Back in April, the BBC revealed plans to broadcast in 4K as standard by 2016, with the 2016 Rio de Janeiro Olympics seen as a key event for a potential launch.
But for now, BT Sport Ultra HD remains the only broadcast option. Want more 4K content? Check out our Ultra HD content guide...
MORE: 7 of the best 4K TVs
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