HDMI Hikes Rates—Boosts Bandwidth for UHD

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.

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:

DesignationData RateTypical application
Standard2.23 Gb/s1080P30 and 1080i60
High Speed8.9 Gb/s1080P60 and 2160P24
Premium17.8 Gb/s2160P60, 8, 10 &12 bit 4:2:2
Ultra48Gb/s2160P120 12 bit 4:4:4
To support the higher data rates a new 'Ultra' cable is specified.

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.


Let us know what you think…

Log-in or Register for free to post comments…

You might also like...

Producing News in 360-degree

360-degree video is hot. Global 360-degree camera sales are expected to grow at an impressive CAGR of more than 35% through 2020. When will 360-degree news production begin? It’s happening now say some experts.

AJA & Colorfront Answer Questions on HDR Production

Many broadcasters and sports production companies are migrating to HDR production. However, this move is not straightforward. Just as the move from 4:3 to 16:9 raised many issues, the move to a high dynamic range (HDR) and a wider color gamut (WGC)…

H.264 Versus HEVC: Understanding the Differences

4K imagery has become the quality standard for many broadcast applications. A key requirement is that the transmission links be of sufficient bandwidth. Links using H.264 can be overwhelmed by the much higher bandwidth requirements of 4K video. HEVC is…

Smartphone Journalism

In the five months since The Broadcast Bridge published Frank Beacham’s article discussing Using the iPhone for Professional Video there have been many world events that offered ideal opportunities to cover events with smartphones rather than traditional ENG camcorders. O…

Articles You May Have Missed – November 8, 2017

More pixels, more audio channels and increased complexity. Those are some of the challenges facing today’s broadcast and media engineers. In this week’s review of technology briefs, we first examine a prediction of 8K cameras being used for the…