HDMI 2.1: What’s New, and Do You Need to Upgrade?

An HDMI connector with blue lines indicating the speed.Negro Elkha / Shutterstock

With new generation consoles arriving by the end of 2020 and NVIDIA RTX 30 Series graphics cards on the horizon, HDMI 2.1 seems more critical than ever. Does that mean you need to upgrade your TV to take advantage of the new features?

Higher bandwidth, more pixels

An HDMI 1.4, 2.0 and 2.1 bandwidth comparison chart.HDMI licensing authority

Most displays on the market currently support the HDMI 2.0 standard, which has a bandwidth limit of 18 Gbits per second. This is enough to carry a 4K 60 frames per second signal with up to eight bit color. This is suitable for the vast majority of uses, including watching UHD Blu-rays or playing games on an Xbox One X.

HDMI 2.1 is the next step forward for the standard, adding support for a 8K signal at 60 frames per second in 12-bit color. It does this with a bandwidth of 48 Gbits per second. Using Display Stream Compression (DSC), HDMI 2.1 can push a 10K signal at 120 frames per second in 12 bits.

Some implementations of HDMI 2.1 use ports that only reach about 40 Gbits per second. This is enough to handle a 4K signal at 120fps in 10-bit color, which is also enough to take full advantage of 10-bit panels on consumer TVs.

High-end PC gamers tempted by NVIDIA’s new 30 Series cards will be happy to hear that the company has 10-bit support confirmed moving forward. This means it doesn’t matter if your TV doesn’t have the full 48 Gbps specification.

Ultra high speed HDMI.HDMI license administrator

Currently, HDMI 2.1 is primarily intended for gamers who use the console or the next-gen graphics card train. The Xbox Series X and PlayStation 5 will support 4K resolution at 120 frames per second. This will require the implementation of the HDMI 2.1 standard.

If your TV does not support HDMI 2.1, you will have to settle for a 4K signal operating at just (!) 60 frames per second. The majority of titles in the latest console generation were running at 30fps, so it remains to be seen how much of a deal this will be.

HDMI 2.1 is so new that NVIDIA only has three new 30 Series cards in the pipeline that support the standard. Their previous RTX 2000 and GTX 1000 series cards are not HDMI 2.1 compatible. Many TV manufacturers, including Sony, have yet to include HDMI 2.1 in their high-end displays.

We expect the HDMI 2.1 standard to really take off in 2021. However, it will be a few years before we see widespread adoption in low budget displays.

Dynamic HDR support

With so much bandwidth available, there is also more room in the pipes for raw data. HDR stands for High Dynamic Range and allows for a wider color gamut in content such as movies and games. Old HDR standards, like HDR10, only supports static metadata. however, newest HDR10 + and Dolby Vision formats allow dynamic metadata on a per scene or per frame basis.

Dynamic HDR gives the TV more information on what to do with the signal it receives. Rather than reading a single set of instructions for an entire movie, dynamic metadata provides the TV with constant updates on how to change the image on the screen to look its best.

The same image of a campfire displayed in SDR, Static HDR and Dynamic HDR.HDMI license administrator

While every HDR-enabled TV supports HDR10 with its static metadata, dynamic HDR is another beast. The most widely supported format is Dolby Vision. It is popular with hardware manufacturers such as LG, Sony, Panasonic and Philips. Samsung is pushing hard on the less popular HDR10 +, which also happens to be an open format (Dolby Vision, as the name suggests, owns it).

It’s important to note that you don’t need an HDMI 2.1 device to view HDR10 + and Dolby Vision, at least not at current 4K resolutions. If your TV supports it, it will stream Netflix Dolby Vision content just fine.

In the future, however, the HDMI 2.1 standard ensures that high bandwidth will be available for metadata and high-resolution signals at high frame rates.

We don’t yet know how the PlayStation 5 or Xbox Series X will implement HDR, but they will likely be the primary testing ground for dynamic HDR over HDMI over the next few years.

Variable refresh rate (VRR)

A TV’s refresh rate is the number of panel refreshes per second. This is measured in hertz, and it is closely related to the frame rate. When the two are not in sync, you get an effect called “screen tearing”. This is because the screen tries to display more than one image simultaneously when the console or PC is not ready.

If you adjust the display refresh rate to match the frame rate of your console or PC, you can effectively eliminate screen tearing without performance penalties. Companies like NVIDIA and AMD have their own methods of dealing with screen tearing, called G-Sync and FreeSync, respectively.

However, the HDMI 2.1 standard also has its own independent solution, called HDMI Variable Refresh Rate (VRR). Microsoft has confirmed that the Xbox Series X will support this feature, and the PlayStation 5 is expected to do so too, as it will require HDMI 2.1 to deliver 4K at 120Hz.

A scene from a game at HDMI VRR frame rate, compared to low, mid, and high frame rates.HDMI license administrator

For the best possible next-gen console experience, HDMI VRR is a must. If you are a PC gamer, NVIDIA and AMD are unlikely to abandon their existing technologies in favor of HDMI VRR. This means that you will always have to pair your graphics card with your monitor.

Low Latency Automatic Mode (ALLM)

Another benefit for next-gen console gamers is the Low Latency Automatic Mode (ALLM). Most TVs now include all kinds of additional treatments to smooth movement, improve picture quality, and even increase audio clarity. While some of this is appreciated when watching TV and movies, for gamers it introduces latency (lag).

This is what Game Mode is for – you can switch to it anytime you want to get the fastest response times from your TV. This is especially handy for games that require quick and precise reflexes. The only problem is that many TVs require you to manually turn Game Mode on and off.

ALLM removes the need to do this. When your HDMI 2.1 compatible TV understands that you are using a supported console, ALLM will disable any additional processing that may cause lag. You don’t have to do anything to activate it – it’s built into the HDMI standard.

Microsoft has confirmed ALLM support for the Xbox Series X, but no word from Sony at this time.

Fast frame transport (QFT)

Quick Frame Transport is another feature for gamers that works in conjunction with ALLM to provide a more responsive gaming experience. The feature prioritizes video images in an effort to keep latency as low as possible.

If you want to take advantage of this feature, make sure that any intermediate devices, like a surround sound receiver, are also compatible. This will ensure that all of your devices work together to provide a smooth and responsive experience. If you route your console through a receiver designed only for HDMI 2.0, you will not benefit from QFT, even if your TV and console support it.

Quick media change (QMS)

Have you ever noticed that your screen goes black shortly before watching a video or trailer? This is because the screen adjusts its refresh rate according to the content you are about to watch. Since different content uses different frame rates, your screen must sync with it, hence the short blackout.

Sometimes it can cause you to miss the first few seconds of a video. However, some content providers are delaying playback to accommodate the change. Assuming that the resolution of everything you watch stays the same, Quick Media Switching (QMS) eliminates the crash caused by refresh rate changes.

This allows you to watch content with different frame rates back to back without power cut. The function uses HDMI VRR to smoothly switch from one refresh rate to another.

Enhanced Audio Return Channel (eARC)

ARC stands for Audio Return Channel. It allows you to send audio via HDMI to your sound bar or surround receiver without additional optical audio cables. Whether you’re watching Netflix, playing a game on a console, or watching a Blu-ray, ARC ensures that the sound is delivered to the right output.

A table comparing the quality of functions using TOSLINK, HDMI-ARC and HDMI-eARC.HDMI license administrator

Enhanced Audio Return Channel (eARC) is part of the HDMI 2.1 standard. The additional bandwidth available in HDMI 2.1 allows the eARC to carry uncompressed 5.1, 7.1, and high bitrate or object-based audio up to 192 kHz in 24-bit resolution. It does so with an audio bandwidth of 37 Mbps per second, compared to less than 1 Mbps per second via normal ARC.

If you want to carry a Dolby Atmos signal over HDMI, you will need eARC. There are a few other improvements as well, like proper lip sync correction as standard, better device discovery, and a dedicated eARC data channel.

Do HDMI 2.1 devices require special cables?

Since HDMI 2.1 has a higher bandwidth rate, you will need HDMI 2.1 compatible cables to take advantage of its new features. The HDMI licensing administrator has approved a new “Ultra High Speed” label for these cables.

HDMI license administrator

Any device that uses HDMI 2.1, such as a game console or Blu-ray player, must include a cable in the box. Moreover, every time you buy an HDMI cable, you can avoid the overpriced Type “premium”.

HDMI 2.1 is primarily for gamers (for now)

Most people don’t need HDMI 2.1 at this point. The improved standard mainly benefits gamers buy new generation consoles or graphics cards, which want features like HDMI VRR and ALLM. Outside of eARC, the new standard offers little benefit to home theater enthusiasts.

Microsoft has announced that the multiplayer portion of Halo Infinite will wreak havoc in native 4K at 120fps, but the game has been delayed until 2021. We’ll have to wait and see if any console titles reach that ambitious goal.

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