HDMI Hikes Rates—Boosts Bandwidth for UHD
HDMI 2.0 extends bandwidth up to 48Gb/s for high frame rate and high resolution video.
A quick look at the lens to display pipeline highlights some trivial-seeming bottlenecks that place important constraints on motion imaging systems. One of these is the connection to the consumer display. The announcement of HDMI 2.1 is key to advancing to 4K and beyond, with additional support for HDR, and increased frame rates for UHD video.
HDMI 2.1
The HDMI Forum has announced the release of the HDMI 2.1 specification. Supporting a bandwidth up to 48Gb/s, it is a big increase over the 18Gb/s of the previous HDMI 2.0 and over 4x the bandwidth of HDMI 1.4, which is still commonplace in the home.
The wider bandwidth now supports 8K to 60fps and 4K to 120fps. Resolutions up to 10K are also supported for other applications.
As developers of HDR transmission soon found, without the release of HDMI 2.0, it was difficult to display UHD video without multiple connectors, a no-no for consumer applications. The first UHD content I saw was on a monitor with four DVI connectors, carrying four HD quadrants.
It wasn’t just the video bandwidth either, support for HDR static metadata (added in 2.0a) and HLG signalling (2.0b) also awaited updates to the interface specification. HDMI 2.1 now adds support for dynamic HDR metadata.
Dynamic HDR support ensures every moment of a video is displayed at its ideal values for depth, detail, brightness, contrast and wider color gamuts—on a scene-by-scene or even a frame-by-frame basis.
The step from 1.4 to 2.0 was key for UHD displays, increasing the frame rate for 4K images from 24fps (OK for movies) to 60 fps for the new higher frame rate UHD sports programming. 2.1 now means that all the planned HDR features can be utilized in the next generation of displays.
A new cable specification was required for such a high speed interconnection. It should exhibit exceptionally low EMI (electro-magnetic interference) which reduces interference with nearby wireless devices. The cable is backwards compatible and can be used with the existing installed base of HDMI devices. The Forum designates the maximum speed of HDMI cables as follows:
| Designation | Data Rate | Typical application |
|---|---|---|
| Standard | 2.23 Gb/s | 1080P30 and 1080i60 |
| High Speed | 8.9 Gb/s | 1080P60 and 2160P24 |
| Premium | 17.8 Gb/s | 2160P60, 8, 10 &12 bit 4:2:2 |
| Ultra | 48Gb/s | 2160P120 12 bit 4:4:4 |
To support the higher data rates a new 'Ultra' cable is specified.
Since the connector form-factor is basically the same, the label—Ultra or whatever—indicates whether that cable will support the necessary video data rate. Consumer beware! Many of the early adopter of UHD display riushed out and purchased receivers with 1.4 connectors, and soon found that they are not much use for watching 50 or 60 fps sportscasts.
Display Stream Compression (DSC)
Resolutions up to 8K (4320P120) are supported with DSC, a Video Electronics Standards Association (VESA) standard. DSC is visually lossless compression that is also used with DisplayPort connections.
You might also like...
Designing IP Broadcast Systems: Integrating Cloud Infrastructure
Connecting on-prem broadcast infrastructures to the public cloud leads to a hybrid system which requires reliable secure high value media exchange and delivery.
Video Quality: Part 1 - Video Quality Faces New Challenges In Generative AI Era
In this first in a new series about Video Quality, we look at how the continuing proliferation of User Generated Content has brought new challenges for video quality assurance, with AI in turn helping address some of them. But new…
Minimizing OTT Churn Rates Through Viewer Engagement
A D2C streaming service requires an understanding of satisfaction with the service – the quality of it, the ease of use, the style of use – which requires the right technology and a focused information-gathering approach.
Designing IP Broadcast Systems: Where Broadcast Meets IT
Broadcast and IT engineers have historically approached their professions from two different places, but as technology is more reliable, they are moving closer.
Encoding & Transport For Remote Contribution At NAB 2024
As broadcasters embrace remote production workflows the technology required to compress, encode and reliably transport streams from the venue to the network operation center or the cloud become key, and there will be plenty of new developments and sources of…