The official body that sets the specifications for Blu-ray has finally agreed on a standard that will allow 4K material, or ultra HD, to be stored on Blu-ray disks - after previously announcing that we'll have 4K Blu-rays by Christmas time.
So why has all of this taken so long when there is really no surprise about what 4K is? Well, thanks for asking. It has a lot to do with a new approach to how we see images.
Rather than just increasing the resolution, which is easy, the BDA has also taken the option of giving us better colour reproduction, and the potential for three different types of HDR video.
Physically, there will be a change in the Blu-ray discs. A 66GB dual-layer and a 100GB triple-layer Blu-ray disc will be the medium for Ultra HD Blu-ray.
Video will be encoded with the super-efficient h.265, or HEVC (High Efficiency Video Codec) as it's more often known. Audio, it seems, won't be seeing much change but that's not a massive issue as Dolby TrueHD and DTS HD-MA are both lossless and studio quality anyway.
Colour gets an upgrade
Colour is important, but has been ignored for a long time but modern TVs have an enormous amount of potential that is wasted on most formats. Blu-ray uses something called a 4:2:0 colour while UHD Blu-ray can mange 4:4:4.
The only problem with this is that most TVs and most AV receivers don't yet do 4:4:4 so seeing any benefit from it will require new equipment from end-to-end. We've covered some of these issues before, and it's worth having a look to understand what's going on here.
Also included in the Blu-ray ultra HD spec is support for 10-bit sampling. This makes a difference to the quality, but Blu-ray is currently tweaked so it's not obvious it uses 8-bit sampling. This will improve the quality, but there's only a small chance you'll actually notice.
HDR comes to video
High Dynamic Range, or HDR is also important because it will allow TVs to show much more detail in both areas that are bright, and areas which are dark. The human eye has a great range, around 1000:1 and the same is true of modern digital video cameras. Flat panel TVs also have a theoretically great dynamic range, but are hampered by other factors.
So the idea here is for Ultra HD Blu-ray to enable HDR formats, and for modern TVs to remove the bits that can't handle an improved dynamic range.
At CES this year Netflix and LG announced that they would be collaborating to bring HDR via streaming video. Adding it to Blu-ray makes a lot of sense, and may well be more significant than the resolution increase. Yes - it's really that important.
Oh, and one more thing: 3D is dead. It's not included in the spec. Presumably 1080p 3D is fine, but there's no mention of 4K 3D. Will it be added in the future? Who cares.
Copy protection isn't really mentioned in any of the news about this. Given Hollywood's paranoia about such matters, you can bet that Blu-ray players will require HDCP 2.2. This means that to see 4K you'll need a TV that supports that system.
The options for TVs that don't have HDCP 2.2 might include fallback to 1080p, but that's really just a guess. Only time will tell what horrors of copy protection await us on this new format.