The UHD alliance is a working group that includes a number of well known brands.
In the board are directors of the following major players:
- Warner Bros
- Walt Disney
- Direct Tv
The members include companies like Sky, Amazon, Intel, Thx, Dts and others.
The key purpose is specifications mostly for high end use and the key pillars are:
- High dynamic range video (SMPTE ST2084 EOTF)
- Wide colour gamut (BT.2020)
- 4K resolution
- 10 bit colour depth
This is obviously a large improvement compared to the current specification of HD Video:
- BT.709 colour
- 1920×1080 Resolution
- 8 bit colour
Probably the most interesting feature is high dynamic range video as the human eye is more sensitive to contrast than it is to colour and resolution although surely the 10bit colour depth will make a difference.
Currently all professional recorders that manage 4K use 10 bit colour but none uses the BT.2020 colour gamut and the dynamic range is left to the sensor quality and has no minimum specifications.
So what will UHD premium mean to us? Well currently not much!
The key is that UHD alliance has also stayed clear from the major issue for distribution that are the video codecs.
Currently HEVC or H.265 has got royalty challenges but is the most efficient codec on the market and the widest in terms of diffusion in hardware.
To give an idea two minutes of 100 Mbps H.264 become 76.5 Mbps once you push the H.264 to the limit but the corresponding H.265 is only 13.6 Mbps only 18% of the size.
Google does not support HEVC and are distributing 4K using VP9 and H.264. From my tests VP9 is not as efficient as HEVC the same file came at 17 Mbps. The key issue of VP9 is playback that does not even work on a powerful home computer although some new Android TV have accelerated VP9 and so has the new Nvidia box.
Whilst this gets worked out it is likely that cameras will continue to record in H.264 and the key here is higher bitrate as H.264 is clearly inefficient with 4K.
If you are in the 4K space and you want to produce semipro or pro footage you need to have an external recorder working in Prores HQ or your device needs to be able to record higher than 100 Mbps.
Sony has just introduced the XQD memory cards that write 800 Mbps
This is potentially a way forward for higher bitrate recording as UHS 3 is limited to 240 Mbps and would only work with compressed footage.
Another thing to consider is that you need a pretty big Tv to notice UHD at the normal viewing distances we tend to watch.
Carlton Bale was on the scene few years ago when HD came about and the conclusion was you need 55″ or more at 8 feet to ‘see’ HD as your eyes can’t resolve more.
This distance becomes 120″ at 8 feet which is essentially the size of a projector screen.
Essentially UHD seems to be more for computer freaks watching clips very close to the screen that for the average user.
I did several test on my Tv with clips I had produced in 4K downscaled to HD and at my normal viewing distance I could not see any difference what so ever!
Essentially I have determined that 50 Mbps XAVC from the RX100 Mark IV looks actually better than 4K on my Tv.
I guess we will have to wait for HDR to see some real benefits meanwhile the clips from you tube look better simply because they have more information. There is a factor of 6x for UHD compared to HD and this shows a higher quality clip.
I don’t see a large future for UHD in TV broadcast it could die as 3D just did.