Upcoming HDMI 2.1a specification to add source-based tone mapping to HDR content

HDMI Forum, the entity responsible for issuing and licensing HDMI standards, will announce HDMI 2.1a at CES 2022. This is the next version of the latest HDMI 2.1 standard currently available and will bring source-based tonemapping or SBTM.

According to The edge, SBTM enables tone mapping of HDR content on the source device instead of the monitor. This means that if you have a Blu-ray player connected to a TV and play HDR content, the tone assignment of the HDR content will be performed on the Blu-ray player instead of the TV.

Upcoming HDMI 2.1a specification to add source-based tone mapping to HDR content

Although the article does not provide further details, SBTM sounds remarkably similar to the TV-led or Player-led tone mapping supported by Dolby Vision. TV-led tone mapping is usually the default setting, as it allows the TV or screen to map the incoming signal to the characteristics of the display, resulting in the best picture quality.

However, some devices and TV models, especially the Xbox Series consoles and older Sony TVs, support player-controlled tone mapping for Dolby Vision, which performs the tone mapping on the source device in an attempt to reduce latency and input layers, but generally results in poorer picture quality.

It seems that SBTM in HDMI 2.1a will work in the same way and is likely to have a similar result. By being made part of the HDMI specification, it should be available for all HDR standards, including HDR10 and HDR10 + without having to rely on Dolby Vision’s proprietary implementation. However, it remains to be seen whether the feature has any notable advantages over existing display-based tone mapping technology.

To learn more about HDR, click here.

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