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The HDMI Fourm is responsible for standardizing HDMI functions. At CES 2022, HDMI Forum will launch HDMI 2.1a, a new standard that will offer a new feature: Source-Based Tone Mapping (SBTM).
The HDMI Forum, in charge of standardizing HDMI standards, will showcase HDMI 2.1a at CES 2022. The new standard brings Source-Based Tone Mapping (SBTM). According to The Verge, “SBTM is a new HDR feature that offloads some of the HDR tone mapping to the content source (such as your computer or set-top box) along with the tone mapping that your TV or monitor is doing.”
What is HDMI 2.1a and Source Based Tone Mapping (SBTM)?
HDMI 2.1a is the new standard announced by the HDMI Forum. The unique thing about this new HDMI standard is source-based tone mapping. Source-based tone mapping or SBTM, in short, downloads the HDR tone mapping from the TV to the player or rather to the source of the HDR content. For example, if you have a Blu-ray player or laptop connected to the TV and you are consuming HDR content, the tone mapping can be handled by the player instead of the TV.
This ability of the player to handle tone mapping instead of the TV is nothing new and we’ve seen it in action with Dolby Vision content. You can watch the video below to understand the difference between Dolby Vision LED from TV and Dolby Vision LED from player (or rather source-based).
In the video above, it’s clear that the TV’s Dolby Vision LED had a more accurate output when it comes to colors, brightness, and overall color strength for the content being consumed. The same goes for Dolby Vision IQ content. According to the video, the light sensor is on the TV to determine the amount of ambient light in the room, which is what Dolby Vision IQ is based on. Therefore, the Dolby Vision IQ content will appear inaccurate with the player-driven Dolby Vision implementation as there is no way for the TV to tell the player that data is being collected through the light sensor for mapping. the colors and the brightness.
What remains to be seen is whether these issues are somehow addressed by the HDMI 2.1a standard. According to Verge, SBTM is “intended to help existing HDR setups work better by allowing the content source to better optimize the content that passes to the screen or by eliminating the need for the user to manually calibrate their displays for HDR when have the source device configure content for the specific screen. Other use cases could be for when there is a mix of content types, such as for streamers (which could have an HDR game next to a black and white text window), displaying each content area. “
This will be interesting to see, as calibrating a TV for HDR involves modifying the backlight, contrast, sharpness, tone mapping, color temperature, and so on. to get the best result. Some TVs like the Sony A80J (review) and even the LG G1 (review) / C1 (review) offer some fantastic picture presets for the best HDR experience.
Speaking of self-calibration, Sony has released an update that automatically calibrates the PS5’s brightness settings (revision) eliminating the need for the user to manually calibrate the maximum brightness and black level when the console is connected to the TV for the first time. . You can see this setup in action in our video review of the Sony A80J below.
As for HDMI 2.1a, it’s another addition to the confusion the HDMI Forum is creating with the HDMI standard. In the future, a TV may call itself HDMI 2.1 enabled without offering features like 4K 120Hz, VRR, ALLM, and more. This is because HDMI 2.0 and 1.4 are now a subset of the HDMI 2.1 standard. You can understand more about the current state of HDMI 2.1 here.