HDMI 2.1a to be announced at CES 2022


The standout new feature of HDMI 2.1a is reportedly Source-Based Tone Mapping, or SBTM. The technology diverts some of the HDR tone mapping of the content you’re watching to the source, instead of the display alone doing all the work. The feature will reportedly allow better mixing of HDR and SDR content. Fortunately, the HDMI Forum is swooping in ahead of CES with its latest revision to the HDMI specification stack, HDMI 2.1a, which is here to make everything better and simpler.

Good Part

  •  HDMI 2.1a is an upcoming revision to the HDMI 2.1 stack and adds a major new feature, Source-Based Tone Mapping, or SBTM.
  • SBTM is a new HDR feature that offloads some of the HDR tone mapping to the content source (like your computer or set-top box) alongside the tone mapping that your TV or monitor is doing.
  • SBTM isn’t a new HDR standard — it’s not here to replace HDR10 or Dolby Vision. Instead, it’s intended to help existing HDR setups work better by letting the content source better optimize the content it passes to the display or by removing the need to have the user manually calibrate their screens for HDR by having the source device configure content for the specific display.
  • The HDMI Forum does note that it’ll be possible for set-top box, gaming companies, and TV manufacturers to add support through firmware updates for HDMI 2.1a and its source-based tone mapping “depending upon their design.”
  • Given the usual trajectory of TV spec updates, though, it seems virtually guaranteed that in the majority of cases, users won’t be getting the new features until they buy a new TV that supports HDMI 2.1a right out of the box (which, as of now, is precisely zero of them, given that the spec has yet to be fully released).

Bad Part

  • Like every others feature, including variable refresh rates, automatic low latency connections, and the bandwidth necessary to offer things like 10K resolution or 120Hz refresh rates, SBTM will be an optional feature that manufacturers can support — but not something that they’re required to support.
  • That’s because the HDMI Forum and HDMI Licensing Administrator (the two organizations that define and license out HDMI standards, respectively) run the standards as a set that contains all the previous standards.
  • According to the HDMI Licensing Administrator, now that HDMI 2.1 exists, there is no HDMI 2.0 standard anymore: all new HDMI 2.0 ports should be lumped into the HDMI 2.1 branding, despite not using any of the new features included in the “new” 2.1 standard.



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