BBC iPlayer launch Ultra HD trial

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As well as testing the quality and performance of the broadcaster's Ultra HD capabilities, the trial is also showcasing a particular type of HDR technology, known as Hybrid Log-Gamma (HLG).

Ultra HD screens have a much greater resolution (3840 x 2160 pixels) than normal 1080p high definition screens; HLG supposedly improves on that by making those thousands of extra pixels of better quality.

That means that at present, only those with certain TVs - most likely the newest Panasonic models - will be able to view the video, which features a tiny red frog in the rain.

The trial will be running until early next year, and the BBC say they hope more TVs will be made compatible with the technology used to make and stream this and future Ultra HD videos.

HLG vs other HDR

The attraction of HLG for viewers is that it's a clever version of HDR, with the TV screen adapting the picture to best suit the lighting in which we're viewing.

It's clever enough that when we're watching a live sporting event where half the pitch or stadium is in shadow, while the other half is in bright sunlight, none of the picture is washed out or too dark to see what's happening.

It's also far better suited to live TV than the existing types of HDR processing, both of which rely on a lot of metadata being streamed with the content - which just doesn't exist when that content is being filmed at the same time as it's being broadcast or streamed.

HLG also works whether the receiving set is HDR-compatible or not: if the TV can show HDR content, it will, but if it's boring old SDR (standard dynamic range), the HDR part of the signal can and will be ignored.

At the moment owners of the newest Panasonic Ultra HD sets are the only people who have HLG-compatible screens, although other manufacturers are already building TVs that should be able to show HLG content with not much more than a firmware update.

Samsung, for example, say that all their 2016 Ultra HD TV sets should be capable of upgrading to HLG, but they'll only push the necessary update once HLG is more widely available.

Streaming requirements

The TV isn't the only issue, however. Because the video is only available through iPlayer, would-be viewers will also need a broadband connection fast enough to be able to stream the image without losing any of that superior quality.

It's not clear just how fast a connection that will be, but the extra data required for the HLG part of the signal will have an impact - and going by the demands of other Ultra HD streaming services, we could expect to need a good fibre connection at the very least.

Netflix and Amazon, for example, both recommend that viewers wanting to watch Ultra HD content will need a connection of at least 25Mb; Youtube, who also offer video in 4KHD suggest that viewers with a consistent connection of at least 15Mb should be fine.

That's way below the minimum connection required by BT for those wanting to get their top tier TV package, which includes BT Sport Ultra HD. They say subscribers will need a line "technically capable" of a minimum 44Mb - which means being in an area that can get BT Infinity 2.

To be fair to them, they say users will need a connection that fast to allow them to view or record the ultra HD stream, while watching, recording or streaming another channel and using other online services without anything grinding to a halt.

It's likely that given the source of the most widely available Ultra HD content at present, those who are likely to be able to watch the BBC's four minute epic will already have a suitably fast connection - which just leaves the small matter of whether it's worth getting a new HLG-capable TV.