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Sound and Vision: HDMI 2.1 has become too convoluted

OPINION: Back in 2017 when the HDMI 2.1 standard was finalised, there was much promise and intrigue about it. The new connection aimed to elevate the current standard of home cinema connectivity, and cast an eye towards the future. So how has it been allowed to become so confusing?

Every big change in the HDMI standard is something of a fresh start, but can also open the door to new handshake, lip-sync issues and other such problems to raise their head. Who knew trying to get devices to talk to each could be so complicated?

Nevertheless, the introduction of HDMI 2.1 marked a push forward, an attempt to incorporate the various new technologies (HDR, 8K), as well as automate features that required human input with the introduction of Auto Low Latency Mode and Variable Refresh Rate.

But the launch of HDMI 2.1 has brought about a string of complications and awkward implementations. And news of the HDMI 2.1a update appears not to simplify things but make them more convoluted instead.

The HDMI 2.1a update introduces a new feature called Source-Based Tone Mapping (SBTM). The source device sends a video signal to a display, and SBTM would take into account the screen’s HDR capability and adapt the performance accordingly. Not all HDR displays operate at the same level, so this would be a useful addition to the spec.

The problem is that like ALLM, VRR, Quick Frame Transport (QFT), Quick Media Switching (QMS) and eARC, this feature is not mandatory. You could be sold a device certified to the HDMI 2.1 standard but, depending on the manufacturer’s discretion, may not have access to the features listed above.

It’s a problem further compounded by the HDMI Forum and HDMI Licensing Administrator recent decree that the HDMI 2.1 standard completely replaces the HDMI 2.0 spec (eating it whole, as it were). You could purchase a cable that says it supports HDMI 2.1 but could instead be a HDMI 2.0 cable with none of advanced features the v2.1 spec promises. That’s rather irritating as a number of these advanced features do require a new cable that’s actually HDMI 2.1.

It’s a convoluted state of affairs founded on an already confusing situation. Some TVs have flopped between full support for maximum bitrate HDMI 2.1 offers (48GBps) to a restricted bitrate (40GBps). Others have taken an age to support HDMI 2.1 features – for instance Sony on their PS5 console and Bravia TVs – promising updates that still haven’t arrived. Some HDMI 2.0 ports support HDMI 2.1 features but aren’t labelled as HDMI 2.1 certified, and if you’ve been following the palaver surrounding AV receivers’ HDMI 2.1 support, that’s been a mess across the board with faulty chips and capped bitrates affecting performance.

The HDMI 2.1 standard was meant to bring uniformity and consistency, but appears to have allowed for more leeway that has caused more confusion. The recent updates add up to HDMI 2.1 in name but not in practice.

A stricter implementation would have avoided this, and the current rules aren’t customer friendly, especially for those who are less tech savvy. Those who decide the spec and those who implement it need to get their act together otherwise these problems will keep causing more unnecessary grief instead of the simplicity and ease of mind they should be offering.

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