8K TV broadcast trials: Do they mean 4K UHD TVs are obsolete already?

If you thought talk of 8K broadcasting was premature, you're right. 4K TVs are still expensive and broadcasting of UHD hasn't even begun yet. Nevertheless, Japanese TV station and tech company NHK is pushing 8K developments with plans to air the 2020 Tokyo Olympics in glorious 8K resolution.

The year 2020 might sound a long way off. But splashing out a few months' wages on a 4K TV now, only to have to upgrade in a few years, could feel like a waste of time. Remember 720p and the quick upgrade to 1080p? We do. But is that really the case this time around?

What is 8K?

As the name suggests 8K is four times the resolution of 4K. To scale that up, we've currently got HD broadcasts at 1920 x 1080 resolution known as Full HD or 1080p/i. The latest UHD televisions offer roughly four times that, featuring a resolution of 3840 x 2160 - a little shy of true 4096 x 2160 4K found in cinemas. But this isn't transmitted by any UK broadcasters yet.

That being said, Netflix does offer its House of Cards season two in 4K when streamed over a decent broadband connection. And YouTube is building up its 4K library daily, so there is native content available.

In comparison, 8K comes in at a mind-boggling sixteen times the resolution of Full HD at 7680 x 4320 – a little over 33 million pixels. Streaming or broadcasting that much data is currently not easy to deliver.

To put 8K in perspective: On a 42-inch television 1080p offers 52ppi, 4K offers 105ppi and 8K will deliver 210ppi. By comparison, the Oppo Find 7 mobile, with a 5.5-inch 2K screen (1440 x 2560) will offer 538ppi. But on a screen that small it's getting to the point where detecting a difference is tough.

Before the thought of watching everything on a mobile starts to appeal it must be said big screens work differently.

An IMAX screen is around a 1,071-inch display which means, using two projectors each at 4000 x 2000 resolution for a total 8000 x 4000 resolution picture, that delivers just 8ppi. But it's viewed from further away so it looks really clear. Of course IMAX digital and film formats vary so that resolution is just a rough way of equating the values, there's actually a lot more to take into account but for now this makes the point.

So without going in too deep, 8K in the home represents a clarity that will make 1080p look as granular as standard definition now looks after watching a Blu-ray.

How can 8K be captured?

Filming an 8K video requires a very special camera, one that Japan's NHK has created and managed to compress to a 2KG unit. The reason this camera is exciting is it's made for broadcast, meaning it can record ready for transmission footage. Current 70mm IMAX film cameras can, theoretically, record at 18K resolution. But once this has gone through the process of being made ready for projection the end result is a far lower resolution.

The NHK camera uses a 33-megapixel sensor and can record at up to 60fps using the latest H.265 (HEVC) codec. Broadcasts using this wonder-camera are planned to begin in Japan from 2016.

Will it broadcast?

One of the major hurdles in upgrading video quality is transmission. It's for this reason 4K, which has been around for years, still isn't being broadcast by British companies. Nor can it be found on any disc format presently.

But we're at a time when broadband is getting so fast it may kill solid-state media and, if BBC 3 is anything to go by, even access entire TV channels online only. So it's with great trepidation that broadcasters like Sky and the BBC test their 4K signal transmission kit, possibly waiting to see if a better solution appears.

Despite that, these broadcasters have already started testing 4K signals. Sky broadcast a premiership football game in September 2013 but it was only sent from the stadium to one 84-inch Sony UHD TV at Sky's headquarters. A far cry from sending to homes en masse.

The use of the H.265 HEVC codec is also a huge factor in 4K and 8K distribution. This relatively new compression software (2013) can send similar quality video to current H.264 but at half the bitrate. That means that Sky, for example, won't need to use up much more bandwidth when transmitting the higher quality 4K signal.

For 4K, at four times the quality of current Full HD, Sky will only need to double the bandwidth for transmission using HVEC – rather than times it by four. Whereas 8K, at a massive 16 times the size of Full HD, will require a bit more room even with HEVC encoding and decoding.

That being said the BBC, with NHK, filmed the London Olympics in 8K and broadcast it to the UK and Japan in a world first. So it can be done. But doing this at a larger scale, because of bandwidth issues and camera costs, isn't going to happen any time soon.

Can a screen do 8K justice?

In reality, anything less than an 84-inch screen isn't going to be able to handle an 8K feed and look good. This is another reason 8K is far from ready. But 4K projectors were around before 4K TVs so we could see them appear as a way for 8K to make it into homes. A projector also means owners won't have a screen taking up a whole wall when turned off.

At the moment larger screens are still more expensive as fewer are made so the production costs are higher. But in the same way we saw 42-inch screens become the norm when factories were built to roll out larger glass panels, we could see that happen with 84-inch screens for 8K.

We saw an 8K screen at CES a while back and were blown away by the realism. On the display was a lion in a cage and owing to the huge screen it really was lifelike - as if we were looking through real bars at the beast. But this screen was over 100-inches, something most people won't be able to squeeze into their lounge unless it's load-bearing and can replace a wall.

So should I upgrade to 4K?

In a word, yes. 4K is the next format shift and, just like Full HD, will be around for quite some time before 8K arrives. Netflix and YouTube have opened the floodgates on 4K streaming with the BBC and Sky almost ready to do the same over broadcast, if not through IPTV. Screens are dropping in price as more and more 4K TVs hit the market.

While buying right now might not be the best idea as there's still very little to watch, 2014 will be an interesting time for 4K. If an upgrade is on your radar it's worth sitting tight a little longer until prices drop. Then you've got at least five years of use before you even need to start thinking about upgrading to an eye-watering 8K screen.

READ: Japan plans 8K TV broadcast testing in 2016, with full service by 2020 Tokyo Olympics