FORMAT



Autor: Redaktion


Ultra High Definition (UHD)

Ultra High Definition video (UHD) became a broadcast reality in 2014.

While recording technologies had supported acquisition of UHD formats for some time, the technical capabilities of the media distribution chain are now sufficiently mature to allow the delivery of UHD materials over IP, Cable, Satellite and Terrestrial transmissions. However these services are rolling out in a phased approach as broadcasters migrate their commissions and technologies across to UHD.

In 2015, the UHD Alliance (an 35 member-coalition of movie studios, technology providers, electronics manufacturers and content distributors) formed with the aim to recommend common specifications for the entire production chain of UHD content under a common logo.

UHD will be introduced in several phases:

UHD 1 Phase 1 introduced the new resolution of 3840x2160 pixels delivered in 10 bits at up to 60 frames per second.

UHD 1 Phase 2 was agreed in 2016. Phase 2 builds on the initial specification to include frame rates up to 120fps (Higher frame rate / HFR), and the introduction of the new colour space specification ITU-R BT.2020 to be added to the standard (This is referred to as Wider Colour Gamut). This allows the production of high-contrast image content, described as High Dynamic Range (HDR ). There are a number of different HDR standards and it’s important to plan for the delivery requirements of commissioners, as different broadcasters and online streaming services will require differing HDR standards.

In terms of sound, 5.1 Surround Sound and beyond, channel or object-based 3D positional audio signals are possible. In UHD 1 phase 1 – Next Generation Audio was introduced via ITU-Recommendation BT.2051, which allows for audio and sound items to be controlled by metadata delivered to the viewers reception device.

Conceptually UHD is very often equated with 4K, although this is not technically accurate. 4K refers to the resolution of 4096x2160 pixels used in Digital Cinema, while the UHD resolution of 3840x2160 pixels is used for ultra high-definition TV distribution.

The vast increase in the amount of information, through expanded colour and contrast range, higher frame rates and new sound formats, also mean skyrocketing data rates for production and distribution.

This challenge is addressed in the production environment using new XAVC or AVC-Ultra codecs, and in the distribution and transmission space through the HEVC / H.265 codec as the successor to the widely used H.264 . This codec is becoming the industry standard for the compression of UHD content.

The UHD specifications won’t be compatible with a number of existing displays, both in the home, and for professional review on location.

It’s not only the increased resolution that will be the challenge, it’s the high dynamic range (HDR) , as well as the high frame rate (HFR). HFR requires HDMI 2.0 as one of the minimum requirements. HDMI 1.4 can only transmit UHD resolutions up to 30Hz, while HDMI 2.0 supports the transfer of the necessary resolution to 60Hz.

What qualifies as a UHD display is a challenging topic. The UHD Alliance define UHD displays (based on SMPTE ST2084) as either at least 1000 nits peak brightness and less than 0.05 nits black level, or at least 540 nits peak brightness and less than 0.0005 nits black level (compared to HDTV standard Rec.709 defined 100 nits brightness peak and 0.05 nits black level). This is sometimes referred to as Ultra HD Premium on consumer TV sets.

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