New HDMI SBTM functionality combines devices and displays to optimize HDR
The HDMI organization presented a review of HDMI 2.1, allowing Source-based tone mapping (SBTM). Implemented in the new HDMI 2.1a standard, SBTM is not a new HDR format; on the contrary, it makes it easier to match existing HDR content with the screen you are using. Notably, the HDMI organization states that many devices can be updated by firmware to support SBTM; however, both devices must be aware of and conform to the standard for them to work.
HDR technology is gaining ground and it is welcome for the sometimes greatly enhanced, vivid and immersive visuals it can offer. However, if there is an obvious problem with HDR content as it is, it is often due to the proliferation of HDR standards (for example, HDR10, HDR10 +, HLG or Dolby Vision), as well as SDR content. older.
When SBTM is useful
SBTM solves some of the problems described above by allowing a source device to tailor its HDR output to match the capabilities of a connected monitor or TV. Modern displays can accommodate single HDR sources that use different HDR standards by mapping the signal sent to the available brightness, contrast, and gamut. However, the HDMI organization says SBTM will come into play when a source device “needs to combine different types of content (HDR, SDR, dynamic HDR, graphics) at the same time.”
Mixing of HDR standards can happen more than you might think on modern systems. For example, a video streaming service may seek to load thumbnails from various HDR and SDR content, as well as from the menu user interface. At this point, a processor should boot to render and optimize the thumbnails and menu for output. Another time when you might welcome SBTM, especially on PCs, might be when working in a multi-window environment with various multimedia contents.
These multiple HDR standard inputs result in less format friction with HDMI 2.1a, because SBTM “allows the source to send a video signal that takes full advantage of the HDR capability of a specific display by adjusting its output to best take advantage of it. of the potential of each screen “.
The HDMI organization goes on to mention that the new, smarter device-display linkage technology “can also be used by PCs and gaming devices to eliminate the user’s manual optimization for HDR.” Thus, this new smarter source-device link standard does not offer any manual mode.
It should be noted that the HDMI organization believes that many existing devices, including TVs, will be able to use SBTM if the manufacturer releases a firmware update. For STBM to work, both device and display must support it. No specific HDMI cable is required to use STBM, but quality high speed cables are recommended. As HDMI 2.1a proliferates, expect to see devices sporting a sticker or mention in the specs that they support HDMI with STBM.
Always check the specifications and the fine print
Last week we reported the confusion, which will likely ensue shortly due to the dropping of HDMI 2.0 certification. Technically unsupported devices are already relabeled with the HDMI 2.1 logo, as they qualify by supporting a subset of the enhanced standard. Beware of this unintuitive change, and also watch out for goodies like HDMI 2.1a with SBTM.