Remember the faulty HDMI 2.1 chip in the first HDMI 2.1 receivers from major brands such as Denon, Marantz and Yamaha? It also renders QMS unusable, according to Heise.de. In 2020, Denon, Marantz and Yamaha launched the first receivers with HDMI 2.1. Such HDMI 2.1 receivers are required if you want to pass-though PS5 or Xbox Series X's highest-quality video signals (4K120 with HDR, 8K60, 120Hz VRR etc.) through the receiver. Unfortunately, it turned out that the HDMI 2.1 chip for receivers made by Nuvoton was faulty. Manufacturers scrambled to find a solution but it ultimately required a new HDMI board which amended the situation but did not fully fix it.
HDMI 2.1 bug also affects QMSThe HDMI 2.1 bug is back with a vengeance, this time to wreak havoc on QMS (Quick Media Switching) which is finally emerging in Apple TV 4K (2022) and 2023 LG OLED TVs. Also read: Guide: What is HDMI 2.1 QMS and which TV models support it? German newspaper Heise.de, which was also first to report on the original HDMI 2.1 issue in receivers, reports that the changes in QMS from when it was originally announced as part of HDMI 2.1 to the QMS revision in HDMI 2.1a means that the two versions of QMS are incompatible. In practice it means that Apple TV 4K (2022) and 2023 LG OLED TV's correct and certified implementation of HDMI 2.1a QMS will not work when passed through the HDMI 2.1 receivers from Denon, Marantz and Yamaha. This was confirmed by Jeff Park, CTO at HDMI Licensing.
No solution in sightIt apparently boils down to how QMS was not clearly defined in the original HDMI 2.1 specification, according to Jeff Park, leading Nuvoton, which produces the HDMI 2.1 chips for most AV receivers, with a faulty QMS implementation in its chips. Nuvoton's implementation was not certified. - "There is probably no solution to this problem – in contrast to the HDMI 2.1 bug: According to our current knowledge, the QMS implementation of the current chips cannot be "bent" to fit with a firmware update. According to c't information, Nuvoton's roadmap also does not envisage the next revision of the HDMI chip until 2026. Until then, no processor with QMS according to HDMI 2.1a will come from the manufacturer," reports Heise.de's c't magazine. Denon, Marantz (link) and Yamaha (link) have all advertised QMS as an official feature of their HDMI 2.1 receivers, but it may never work in their current receiver models. Instead, you should connect Apple TV 4K (2022) and future media players with HDMI 2.1a QMS support directly to your 2023 LG OLED or future TV model with HDMI 2.1a QMS support, and pass back audio to your receiver with the TV's eARC port. What a mess... FlatpanelsHD is chasing more information. - Source: Heise
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