The HDMI Forum started the clock on the next generation of television and video performance when it formally released completed specifications for version 2.1 of the High Definition Multimedia Interface (HDMI) on Nov. 29. With compliance testing still in the works, however, many supporting products are probably still a year away from full integration.
The latest version brings a list of advancements for the ubiquitous digital HDMI connector that has been the main interface for digital video and audio connections for more than a decade.
Version 2.1 offers several new and improved capabilities, while still allowing the physical 19-pin plug to work with legacy products and features. The new features and improvements include:
- Nearly triple the Gbps with 48 Gbps, using four lanes. The lane speed is raised from 6 Gbps to 12 Gbps, and the encoding changes from 10B to 16B/18B—providing approximately an 11% improvement in efficiency.
- A connector that includes three twisted pairs and a clock, translating to four twisted pairs sending RGB or Y and Cb and Cr. It can be packetized and run in an inverted clock mode that uses all four lanes.
- Support for 4K Ultra HD at up to 120 fps. It will transport future technologies up to 10K video resolutions.
- Support for a Variable Refresh Rate (VRR) to reduce or eliminate lag, stutter and frame-tearing for more fluid video gameplay.
- Enhanced Audio Return Channel (eARC) that affords up to 37 Mb/s bandwidth. This allows pass- through of new high resolution surround sound and object-based audio formats such as Dolby Atmos and DTS:X.
- Low electro-magnetic interference (EMI) to reduce interference with nearby wireless devices.
Keeping with past practices, no additional license will be required to add HDMI 2.1. Manufacturers using existing HDMI 2.0 licensees will automatically have access to 2.1 with the same terms and annual fees.
The release of the specification was only the next step before delivery of the HDMI 2.1-supporting products will be ready for market. Integrated circuit developers are now planning silicon to accommodate the huge bandwidth requirements. The HDMI Forum is now developing the compliance test specifications for finished products. The test specs are to be released in layers between the first and third quarters of 2018, although the Forum is still deciding exactly how to roll it out.
A spokesman with the HDMI Licensing Administrator said the goal is not to produce test specifications in a piecemeal way. Rather, the test specifications are likely to arrive “in chunks.” The Forum assures testing protocols will be as thorough and rigorous as they have always been to ensure compatibility and interoperability between devices, brands and models.
The HDMI interoperability problems that have plagued some past devices were primarily related to issues with the necessary High-bandwidth Digital Copy Protection (HDCP) system developed by Intel and mandated by Hollywood studios. HDMI 2.1 will continue to work with the latest versions of HDCP (version 2.2 is the most current), but compliance testing for that is handled independently of the HDMI 2.1 compliance testing program.
HDMI 2.1 will require a new “Ultra High Speed” cable, which will be identifiable by a new logo. Some early versions were introduced in late 2017. The Ultra High Speed HDMI 2.1 cable is initially limited to lengths of between 6.5 and 9.8 feet. However, longer runs are expected to be supported by powered HDMI cable implementations, as has been the case with past versions. In addition, HDMI 2.1 will use Display Stream Compression (DSC) 1.2a for resolutions above 8K with 4:2:0 chroma subsampling. The lossy scheme can also be applied to lower resolution signals for more efficient bandwidth requirements and longer cable runs.
As to whether any existing products will be upgradeable to HDMI 2.1 via a firmware update, spec developers said it is feasible in certain cases, such as the replacement of an outboard connector hub (e.g., One Connect boxes used in certain Samsung televisions; Samsung has not yet said if an upgrade will be forthcoming or even possible). But, as with any other system, a product has to be designed from the beginning to support upgradeability.
In all cases, upgradeability will be up to manufacturers, and not required through the specification. One of the problems preventing simple firmware upgradeability is that the new higher speeds need different silicon architectures. Certain features within HDMI 2.1, like some dynamic HDR profiles, might be upgradeable through firmware alone, depending on the architecture of the system in the product.
So, for the most part, the new HDMI 2.1 future has arrived, but its true impact is yet to be revealed.