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Mini-review: HDMI 2.1 QMS in Apple TV 4K is great, but not perfect

07 Jun 2023 | Rasmus Larsen |

QMS (Quick Media Switching) aims to eliminate the black screen when your playback device matches frame rates. It does what it says but there are still hurdles to overcome. Europeans may want to change settings.

Frame rate matching – and dynamic range matching – is at the core of good signal and picture quality, but without HDMI 2.1's QMS it involves a brief black screen between switches.

Apple TV 4K (2022) is the first playback device to support QMS while LG's 2023 OLED models are the first TVs to support it. To work, QMS must be supported in both player and TV.

 Also read: Guide: What is HDMI 2.1 QMS and which TV models support it?

FlatpanelsHD is currently reviewing LG's C3 and G3 OLED TVs, so naturally we examined QMS. Here's our mini-review.


QMS Apple TV 4K

QMS in action on Apple TV 4K (2022) and LG C3. Photo: FlatpanelsHD

An important step

QMS promises to eliminate the black screen (HDMI Bonk) only when the frame rate changes – not when changing between SDR/HDR, chroma, and other video parameters. It does what it says. Nothing more, nothing less. QMS is a clear improvement that greatly enhances the experience of using Apple TV 4K's already-excellent frame rate matching system which works with the majority of apps and even supports both integer (i.e. 24.000fps) and fractional frame rates (i.e. 23.976fps). It is a more seamless experience when using Netflix, Apple TV+, Disney+, and other streaming apps. See for yourself in our video where we have pulled up LG's HDMI information box. Notice how QMS seamlessly changes the frequency (Hz) depending on the source content. Also notice how it doesn't when changing between SDR / HDR10 / Dolby Vision.

60Hz for Europeans?

With QMS enabled, Europeans (or users in other 50Hz PAL regions) may consider changing their default video output on Apple TV 4K to 60Hz rather than 50Hz, as long as your favorite apps support frame rate matching. Changing the default video output to 60Hz will first and foremost ensure a smoother homescreen and app experience, and screensavers without judder (they are shot in 30fps). It will also noticeably improve gameplay in some games, as not all games currently employ dynamic range / frame rate matching (some do). For example, we have noticed that some games on Apple TV continue to run at 30/60fps even when the HDMI output is 50Hz. This mismatch leads to gameplay judder. A third benefit of setting 60Hz as the default video output is that videos shot on your iPhone, which are typically 60fps or 30fps, play without judder on Apple TV 4K, as AirPlay is not matching the frame rate.

Room for improvement

However, LG has some further work to do on its side. When switching between, for example, SDR and Dolby Vision an LG 2023 OLED TV will push a notification to say that QMS is now active, as seen in the video. LG should simply allow the user to disable this annoying notification. Also read: Report: Faulty HDMI 2.1 chip in receivers also prevents QMS from working The next step is obviously to develop something similar for SDR/HDR switching and other changes to the HDMI mode that involve a black screen. To get there, other challenges must be solved but we hope to eventually see QMS 2.0. An alternative is to let Apple TV 4K output everything in, for example, Dolby Vision by disabling the match dynamic range funciton, but you will then sacrifice some accuracy in color and luminance. This is not an approach we recommend.

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