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When using media players such as the Apple TV 4K, many users notice a brief blanking of the picture when starting a film or TV series. This is caused by the TV changing its refresh rate to match the content's frame rate. The solution to this problem is HDMI 2.1 QMS, or Quick Media Switching, which allows switching between different refresh rates without a momentary loss of picture.
What is HDMI 2.1 QMS and how does this technology work?
Quick Media Switching, or QMS for short, is an optional feature of the HDMI 2.1a standard designed to eliminate the brief black screen that appears when the frame rate changes. This phenomenon occurs, for example, when a player automatically adjusts the refresh rate to match the material being watched. Films are most often shown at 24 frames per second, while television broadcasts may use 25, 30, 50 or 60 frames. The television then has to change its refresh rate, which causes a momentary blackout. QMS uses a mechanism known from VRR, but it is a separate feature intended solely for video playback rather than for gaming. Using Video Timing Extended Metadata, the source device informs the television of an upcoming change before it happens. This allows the refresh rate to switch almost instantly and without the annoying black screen. The feature works with any HDMI cable and does not require buying special cables. However, to use it both the television and the player must support QMS.
Which devices and TVs support HDMI 2.1 QMS?
The first media player to support HDMI QMS was the 2022 Apple TV 4K. The feature makes most sense in devices that offer automatic frame-rate matching to the source material. On the TV side, LG was the first to announce support, and the technology later started appearing in models from other manufacturers. Currently, the list of compatible devices consists mainly of LG, Samsung and TCL TVs from the 2023, 2024, 2025 and 2026 model years. Supported models include, among others, the LG C3, C4, C5 and C6 series; LG G3, G4, G5 and G6; Samsung S90C, S90D, S90F and S90H; Samsung S95C, S95D, S95F and S95H; and numerous TCL models from the C, QM and X series. In the past Sony stated it did not plan to implement QMS, while Philips said it would analyse the possibility of adding the feature in the future. It is worth remembering that simply having HDMI 2.1 or VRR support does not automatically mean compatibility with QMS. It is a separate feature whose implementation depends entirely on the TV manufacturer.
HDMI 2.1 QMS eliminates the brief blackout that occurs when the refresh rate changes while watching films and TV series. To use it, both the TV and the playback device must support it, and the number of compatible models is steadily increasing.
source: flatpanelshd
