Introduction: HDMI standards have been a mess for years, with inconsistent support among TV manufacturers, cable makers, and devices that make it challenging to set up, for instance, 120Hz gaming on a PS5 or Xbox Series X. However, the HDMI Forum has recently come up with a revision to the HDMI specification stack, HDMI 2.1a, which is meant to make things better and more straightforward. In this article, we will explore the new features of HDMI 2.1a and the Source-Based Tone Mapping (SBTM) feature and its impact on the industry.
The Good: HDMI 2.1a and SBTM
HDMI 2.1a is a revision to the HDMI 2.1 stack that introduces a new prominent feature, Source-Based Tone Mapping or SBTM. SBTM is a new HDR feature that enables the content source, like a computer or set-top box, to optimize the content it passes to the display. This feature helps existing HDR setups work better by allowing the content source to optimize the content better, removing the need for manual calibration of screens for HDR. The HDMI Forum has noted that it will be possible for set-top boxes, gaming companies, and TV manufacturers to add support through firmware updates for HDMI 2.1a and its source-based tone mapping.
The Bad: Optional Features of HDMI 2.1a and SBTM
Like other unique HDMI 2.1 features, including variable refresh rates, automatic low latency connections, and the bandwidth necessary to offer 10K resolution or 120Hz refresh rates, SBTM will be an optional feature that manufacturers can support, but not something they are required to keep. The HDMI Forum and HDMI Licensing Administrator run the standards as a set that contains all previous standards.
Once the HDMI 2.1a standard is released, all new ports will be labeled HDMI 2.1a; they won’t have to offer the new SBTM or any HDMI 2.1 features. The HDMI Forum argues that optional features allow manufacturers to have flexibility in their functionality, and companies must list what features their hardware supports so that customers are aware of their hardware capabilities.
Confusion Around Port Labeling
The argument for the HDMI Forum needs to be revised, as the whole point of standards is to simplify things by standardizing across devices. It needs to be more apparent when customers have to dig into a spec sheet to determine if a specific refresh rate feature is supported on a new TV. Moreover, most manufacturers must follow the HDMI licensing recommendations for port labeling.
TV companies have mainly listed HDMI 2.0 ports as “HDMI 2.0” and reserved the HDMI 2.1 labeling for ports that support the newer features. However, under the rules of the licensing organization, these companies don’t have to do this, and less scrupulous or ignorant companies could start marketing HDMI 2.1 ports that don’t offer any 2.1 or 2.1a features.
Impact on the Industry
The HDMI 2.1a standard and its new SBTM feature are in much the same place as the rest of HDMI 2.1 and its feature set: a potentially valuable new part that could make the content look better but will likely require buying new hardware and cables, and may not even be supported. The HDMI Forum and HDMI Licensing Administrator need to simplify the standards and ensure that customers are aware of the features that their hardware supports, as it is the only way to ensure that HDMI 2.1a and its SBTM part will have a positive impact on the industry.
Conclusion
HDMI 2.1a and its SBTM feature are a step in the right direction for the HDMI standards, but there are still some hurdles that need to be overcome to ensure that it will be successful. The lack of mandatory support for SBTM and other HDMI 2.1 features, as well as the confusion around port labeling, are issues that need to be addressed by the HDMI Forum and HDMI Licensing Administrator.
Additionally, the fact that customers will likely need to buy new hardware and cables to take advantage of these new features also limits their appeal. However, if the HDMI Forum can simplify the standards and clarify what features are supported by each piece of hardware, the HDMI 2.1a and SBTM features could significantly improve the experience for users looking for a better HDR experience.
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