Home » HDMI 2.1: all features explained and everything you need to know
Tips and advice

HDMI 2.1: all features explained and everything you need to know

HDMI 2.1
HDMI 2.1: all features explained and everything you need to know
4 - 1 review

The introduction of the HDMI 2.1 specifications has been behind us for some time now. But not every TV model is equipped with all new features. A question we often hear is: why don't they have HDMI 2.1? That is why we go through all the features in this article so that you have a good idea of ​​what you may or may not need.

HDMI 2.1 in a nutshell

The announcement of HDMI 2.1 emphasized the higher bandwidth of the new version. It increases from 18 Gbps (HDMI2.0) to 48 Gbps (HDMI2.1).

Those higher bandwidths are necessary for future resolutions (8K and higher) and frame rates (100fps and higher). The figure below shows which resolutions are possible with HDMI 2.1. Any resolution / fps combo that you find in the “Speed” column Standard, High Speed, or Premium is still possible with HDMI 2.0. If the “Speed” column says Ultra or Ultra #, it means that you need an HDMI 2.1 connection. Full HD / 120 fps is not shown in the table, but you can also realize that with HDMI 2.0.

In addition, HDMI 2.1 brings a number of new features, such as dynamic metadata for HDR, VRR (Variable Refresh Rate), ALLM (Auto Low Latency mode), eARC (Enhanced ARC), QFT (Quick Frame Transport), QMS (Quick Media Switching) and DSC (Display Stream Compression).

HDMI 2.1 – Confusing?

Unfortunately the designation HDMI 2.1 is not unambiguously. After all, the HDMI specification does not oblige manufacturers to offer all features on a connection. That has always been the case, even with previous versions. As a simple example: not every port offers ARC.

Manufacturers are also free to provide only as much bandwidth as they deem necessary. That means that as a consumer you have to stay alert when you want certain features. It is certainly not enough to just look at the HDMI version.

With this in mind, which features are really important?

More bandwidth in general

As can be seen from the table at the start of this article, the extra bandwidth of HDMI 2.1 is mainly required in the following scenarios:

  • 4K / 120fps
  • Everything with 8K (we leave out 5K, that is not a usual resolution for televisions)

The extra bandwidth of HDMI 2.1 is really a necessity on 8K models, so you are ready for any 8K sources. Although we must say that they are not really at the door. For 4K TVs, that extra bandwidth is only relevant for HFR sources. That's about PC gamers using a very powerful GPU. The Xbox One supports HFR but only in 1080p or 1440p. The latest generation of consoles (PS5, XboX Series X) will probably offer 4K / 120fps.

HFR: High Frame Rate

High Frame Rates we discuss in our article about HFR and what you get from it [19659018]. Specifically, this is not an HDMI 2.1 feature, but in some cases (4K HFR) there is a need for the higher bandwidth that HDMI 2.1 offers. But the presence of HDMI 2.1 does not in itself guarantee that the TV in question also supports HFR. Again, it is therefore best to specifically check whether the model in question supports HFR or not. Full HD HFR is often referred to as 2K HFR.

Is HFR support important? For traditional content? To a limited extent. In the film industry, we speak of HFR as soon as more than 24fps are used (think of the Hobbit versions at 48fps). Frame rates up to 60fps are already possible on (Ultra HD) Blu-ray, and on your TV. So they are not a problem. In terms of the required bandwidth, we really speak of HFR at frame rates above that. For example, live TV would benefit from 100 or 120fps for sports. But that is not to a large extent.

Gamers can offer HFR (via console or PC). Certainly for Full HD, that is simple enough with the current graphics cards, but 2K HFR fits within the HDMI 2.0 bandwidth. You only need more bandwidth from 4K HFR. In addition, gamers should not only look at “4K HFR”, but also what bit depth and chroma subsampling that are supported. For 4K HFR gaming that is also in HDR, you definitely need 10 bit 4: 4: 4. You will often only find such matters in the manual.

Dynamic metadata for HDR

The advantages of dynamic metadata compared to static metadata for HDR we explained earlier in our article about different HDR formats [19659018]. Anyone who wonders “Hey, we already have that, right?”, Is right. Both Dolby Vision and HDR10 + support dynamic metadata, and both are already available even on previous years models with HDMI 2.0.

In concrete terms, we see little importance for this feature at the moment. If you attach importance to HDR, it is better to check which HDR standards a TV supports. (HDR10 + and Dolby Vision use dynamic metadata, HDR10 static metadata, and HLG does not need metadata.)

ALLM: Auto Low Latency Mode

This feature allows you to automatically switch to game mode. For this, your source device must of course also support ALLM (the Xbox One for example). As soon as you start gaming, the console switches your TV to the Game picture mode, so that you have the lowest possible input lag.

ALLM is of course only important for gamers. Even if it is missing, you can still manually switch to game mode.

VRR: Variable Refresh Rate

This feature comes from the PC world and is similar to, but not the same as, AMD Freesync or Nvidia GSync . With this technology, the display can synchronize its refresh rate with the source (PC or console), instead of using a fixed refresh rate (such as 50 Hz). That is of course only important for gamers, because all regular content uses 24 or 50/60 fps and that has supported your TV for a long time. Why is that different for gamers?

A game console or PC creates its frames in real time, and depending on what is on the screen, the speed at which that happens will vary. So the TV does not get a fixed number of images per second, but maybe 15 at a time and then 55 images per second. There are then two options.

Either you fix the refresh rate based on the TV, for example 50fps. The TV will then show a new frame every 50th of a second and if your source cannot provide those images, it is therefore obliged to show some frames two or even three times. That causes stuttering images.

An alternative is to allow the source to deliver images as fast as it can, but then you risk the GPU delivering a new image while the TV is not yet fully on the previous image. the screen. In that case you see “tearing” a horizontal crack in the image.

The solution for all this is VRR. With VRR activated, the screen synchronizes with the source. The TV then draws a completely new picture every time the source signals that one is ready. The stuttering then largely disappears (low frame rates are of course never optimal), and tearing becomes impossible. All this leads to a much smoother experience.

VRR within HDMI 2.1 is available in three different flavors: HDMI VRR, AMD FreeSync, and Nvidia GSync. So make sure that the version you want is supported.

eARC: Enhanced ARC

You can read about eARC in our extensive HDMI eARC background article . We know Enhanced ARC mainly because it offers a larger bandwidth and can therefore also transport lossless formats such as Dolby True HD and DTS HD Master Audio. In addition, eARC also provides mandatory support for lip sync, but it remains to be seen how well it works.

However, the importance of eARC is less than you may suspect. After all, streaming services use lossy codecs such as Dolby Digital Plus, which fit into ARC. The only widely available source of lossless soundtracks is (Ultra HD) Blu-ray. And that is only possible through an external player. You can then connect that player directly to your AV receiver or soundbar, so you do not need eARC at all. For now, eARC is only important if you are in a situation where the following three things apply:

  1. You have a source that is internal to the TV (built-in media player, for example) or you MUST connect to your TV (any reason: too few HDMI connections on your soundbar, restrictions in your cabling …)
  2. The audio you listen to is in Dolby True HD, DTS HD Master Audio, or another audio format that does not fit within the bandwidth of ARC
  3. You send the audio via eARC to an external sound solution.

QFT, QMS and DSC

We don't find these three features mentioned anywhere for the time being.

  • QFT (Quick Frame Transport): lowers the display lag. This feature will only be important for gamers.
  • QMS (Quick Media Switching): eliminates the distracting black screen the moment you change frame rate. For example, you are watching trailers and some are in 24fps, others in 50fps or 60fps. With each switch, the HDMI connection has to adjust its video mode, which results in a temporary black screen. With QMS, the transition is seamless.
  • DSC (Display Stream Compression): This is a lossless compression technique that will only be needed for extremely high resolution / frame rate combinations. In the table at the top of this article you can see which they are (marked with Ultra # in red).

Conclusion

Do you really need an HDMI 2.1 connection? On an 8K TV, yes. Even though there are no abundance of 8K sources ahead, these TVs require a full bandwidth HDMI 2.1 connection for future sources.

On a 4K TV, however, things are different. There, the bandwidth of HDMI 2.0 is sufficient in the vast majority of cases. Only those who absolutely want 4K HFR must demand HDMI 2.1. For the time being, however, only gamers.

Also in terms of features, your use is very decisive. ALLM and VRR are only important for gamers. And eARC has a place, but only for people with a very specific setup.

More information

Do you want to know more about HDMI standards and the possibilities to connect equipment in your home cinema system? Then read our home cinema information guide .

Add Comment

Click here to post a comment