The debate was launched after our test of the Panasonic TX-55HZ1000, a 2020 television set which does not have HDMI 2.1 inputs and which borrows only a few functionalities (eARC, ALLM) from the latest HDMI standard. Why is HDMI 2.1 so rare?
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In 2019, TVs with an HDMI 2.1 input could be counted on the fingers of one hand: the LG Oled C9, E9, W9 and even the B9 the most affordable (with a limitation to the 4K 120 Hz definition without HDR all the same), the Sony 8K KD-85ZG9 and the Samsung Q950R of 2019 (only the HDMI 4 port). In 2020, the situation improves somewhat since in addition to the new LG Oled (CX, EX, GX, WX, ZX (8K) and RX (roll-up)), the majority of Qled Samsung televisions will adopt HDMI 2.1 (Samsung Q70T (from 55 “), Samsung Q80T (from 55”), Samsung Q90T, Samsung Q95T, Samsung Q800T, Samsung Q900T and Samsung Q950TS). But all manufacturers are far from taking the plunge. This is the case of Panasonic which does not provide HDMI 2.1 compatibility, just like Sony which reserves full HDMI 2.1 compatibility for only a few models, including the Sony XH90 and the Sony 8K ZH8.
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What is HDMI 2.1?
For an input to be certified HDMI 2.1, it must support all the features of HDMI 2.1. It must first be compatible with all the functionalities of the previous HDMI standards (1.0, 1.1, 1.2, 1.3, 1.4 and 2.0 / 2.0b) in order to ensure backward compatibility with the CEC, DSD, Audio lip-Sync, 3D functions. Video, Ethernet 100 Mb / s, ARC, HLG, HDR, for example. Then the HDMI 2.1 input must be compatible with thetogether the following new features:
- Dynamic HDR: Dynamic HDR like HDR10 + or Dolby Vision.
- eARC: audio return via an HDMI port with an increased bandwidth supposed to support all formats.
- VRR (Variable Refresh Rate): standardized variable refresh rate identical to FreeSync and GSync.
- QMS (Quick Media Switching): Reduces the duration of display of black screens when loading source or format.
- QFT (Quick Frame Transport): reduces the transmission time of images so as to reduce the delay in display.
- ALLM (Auto Low Latency Mode): automatically reduces the delay in the display depending on the source (especially for consoles).
- DSC (Display Stream Compression): lossless compression of the video signal.
- 4K 120 fps for an Ultra HD television and 8K 60 fps for an 8K television.
If only one of these features is missing, the HDMI input cannot inherit the HDMI 2.1 label. However, this does not prevent manufacturers from using an HDMI 2.0b connector and adding certain features of HDMI 2.1. This is the case of the Panasonic 55HZ1000 TV that we tested and which supports eARC and ALLM, features introduced by HDMI 2.1.
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With the exception of the Socionext 8K Player sold for around € 20,000 that we used in the test of the Sony KD 8K TV.85ZG9, there is today no source using HDMI 2.1 output. PCs – which are currently the only sources capable of producing 4K content at 120 Hz and 8K at 60 Hz – are also not equipped since to date no graphics card has an HDMI 2.1 output. Even the most expensive graphics cards, GeForce RTX 2080 Ti, RTX 2080 Super or Radeon RX 5700 XT are content with an HDMI 2.0b output.
HDMI 2.1 is slated to launch with the release of next-generation consoles, Microsoft’s Xbox Series X and Sony’s PS5 planned for the end of the year. These consoles should support ALLM and VRR. This is already the case for the Xbox One S / X, but it should be something new for the PlayStation, although we are still awaiting confirmation of VRR support for Sony. Finally, theoretically, these consoles should be able to display 120 frames per second in Ultra HD and 60 frames per second in 8K. These frame rates at these image definitions already pose serious problems for the most powerful PC graphics cards and there is very little chance that the consoles can exploit these native definitions at these display frequencies. On the other hand, console developers have many optimization levers to increase the pace without necessarily increasing the definition. One of the commonly used techniques is to use a lower definition, for example Quad HD (2560 x 1440 px) and then to use a very efficient scaling algorithm (Checkerboard Rendering, Temporal Injection, etc.) in order to display a native image in Ultra HD (3840 x 2160 px). For a quick game like Fortnite, developers will be able to use Quad HD rendering, for example to reach 90 or even 120 frames per second and thus exploit the 4K 120 Hz output of HDMI 2.1 while limiting the impact on image quality.
Some games should be able to run at 120 frames per second, but the vast majority will be content with 60 frames per second. In practice, it is especially native video games in Ultra HD (4K) at 60 frames per second (60 Hz) which should become more popular with the new generations of consoles. There will therefore be no real need for the famous HDMI 2.1 connector, except in a few special cases.
As with each new generation of connector (USB Type-C, Thunderbolt, HDMI, etc.), manufacturers expect each other. TV manufacturers are not really inclined to integrate an expensive HDMI 2.1 connector when no source is available, when on the other side, console manufacturers did not want to adopt this new connector for lack compatible TVs. The release of new consoles should force TV manufacturers to review their copy and the 2021 models should be – for the most part – HDMI 2.1 compatible, although as we have seen, it is possible to opt for the most more important than VRR, ALLM or eARC without necessarily using HDMI 2.1.
Is it absolutely necessary to buy an HDMI 2.1 compatible TV?
The reason would be that when you spend several hundred euros, even several thousand euros on a TV, it should be HDMI 2.1 compatible. This is an undeniable plus, but for us, it is better to move towards a TV offering a good quality / price ratio, rather than absolutely wanting HDMI 2.1. Like any new standard, its implementation is quite variable and as with each first generation of connector, it is not impossible to end up with some incompatibilities. Our colleagues of Rtings who have already tested the new Samsung Q70T point out that it does not accept a 4K 120 Hz signal from a PC while the same procedure works on the Samsung Q90T …
If you’re looking for a TV that is perfectly compatible with next-generation consoles, the easiest way is to wait for the consoles to come out and for the first feedback from users. Be aware that we will not hesitate to conduct tests to confirm the compatibility of different televisions, but for now, it is still too early to say.
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