Here's How HDMI 2.1a Could Make Movies And Games Look Better On Your PC

hero ultra high speed HDMI cable
CES 2022 is still nearly two weeks away, but plenty of companies and organizations are already teasing their upcoming announcements. The list of such groups includes the HDMI Licensing Administrator (LA). Apparently, is set to launch HDMI 2.1a soon, and one of the new features for the format will be Source-Based Tone Mapping (SBTM).

To understand what SBTM is, you need to understand tone mapping. Tone mapping is one part of the technique by which digital displays convert image data into visual output. To grossly oversimplify, image and video data can be stored in many different formats, and those formats may not match or "map" directly to the formatting that your display uses. Tone mapping, then, is the process by which a device "maps" the "tones" in the source data for final output.

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Image: HDMI LA

Source-Based Tone Mapping allows devices to perform tone mapping separately for individual sources. This feature is primarily useful for PCs, especially for gaming. It's easy to imagine the benefits of SBTM when you consider a Windows desktop with multiple applications open; the system can use separate tone-mapping for a windowed game, a browser window, and a text editor. Furthermore, this can all happen without user intervention or fiddling with sliders.

As the HDMI LA states, SBTM "doesn't replace existing HDR technologies," but that should probably be obvious if you read the above. While SBTM is technically an HDMI 2.1a feature, it's purely a protocol change and doesn't require physical or electrical modifications, so the HDMI LA says that devices could gain SBTM in a firmware update. While firmware updates for high-end televisions are fairly common, lower-end devices and PC monitors very rarely get such niceties. Hopefully as these connections continue to get smarter, that becomes more commonplace.

hdmi feature table maybe
HDMI feature table from HDMI LA. Edit by our own inimitable Marco.

Of course, while SBTM is coming with HDMI 2.1a, it will—like the rest of the HDMI 2.1 features—be completely optional. That means that any display which says HDMI 2.1a may or may not support SBTM, and it's up to the purchaser to investigate whether the display in question actually supports SBTM, or VRR, or FRL, or any of the newer HDMI features. Manufacturers are supposed to enumerate support for these features themselves (and in fact are explicitly not supposed to label their devices with the HDMI version anymore) but we all know how that goes. Keep your eyes here on HotHardware for the full HDMI 2.1a announcement soon.
Tags:  HDMI, HDR, hdmi 2.1, hdmi 2.1a