When the next generation of consoles arrives by the end of 2020 and NVIDIA̵7;s RTX 30 series graphics cards hit the horizon, HDMI 2.1 looks more critical than ever. Does this mean you have to upgrade your TV to take advantage of the new features?
Higher bandwidth, more pixels
Most monitors on the market currently support the HDMI 2.0 standard, which has a bandwidth of 18 Gbit per second. It’s enough to carry an uncompressed 4K signal at 60 frames per second in up to eight bits of color. This is enough for most 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 by adding support for an uncompressed 8K signal at 60 frames per second in 12-bit color. It achieves this with a bandwidth throughput of 48 Gbits per second. Using display stream compression (DSC), HDMI 2.1 can shoot a 10K signal at 120 frames per second at 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 120 frames per second in 10-bit color, which is also enough to take full advantage of the 10-bit panels on consumer TVs.
Advanced PC gamers who are tempted by NVIDIA’s new 30-series cards will be happy to know that the company has confirmed 10-bit support going forward. This means that it does not matter if your TV lacks a full 48 Gbits per second.
At present, HDMI 2.1 is primarily aimed at gamers who are jumping on the next generation console or graphics card train. Both Xbox Series X and PlayStation 5 support 4K resolution at 120 frames per second. This requires the HDMI 2.1 standard to be implemented.
If your TV does not support HDMI 2.1, you have to settle for a 4K signal running at only (!) 60 frames per second. The majority of the titles for the latest console generation ran at 30 frames per second, so it remains to be seen how much of a deal-breaker this will be.
HDMI 2.1 is so new, NVIDIA has only three new 30-series cards in the pipeline that support the standard. Their previous RTX 2000 and GTX 1000 cards are not HDMI 2.1 compatible. Many TV manufacturers, including Sony, have not yet included HDMI 2.1 in their top screens.
We expect the HDMI 2.1 standard to really pick up speed in 2021. However, it will be a few years before we see extensive use in budget displays.
Dynamic HDR support
With so much bandwidth available, there is more room in the raw data tubes as well. HDR stands for High Dynamic Range, and it enables a wider range of colors in content such as movies and games. Older HDR standards, such as HDR10, only support static metadata. However, the newer HDR10 + and Dolby Vision formats enable dynamic metadata per scene or frame.
Dynamic HDR gives a TV more information about what to do with the signal it is receiving. Instead of reading a single set of instructions for an entire movie, dynamic metadata provides the TV with constant updates on how to adjust the image on the screen to look its best.
While every HDR-compatible TV supports HDR10 with its static metadata, dynamic HDR is completely different. The most supported format is Dolby Vision. It benefits hardware manufacturers including LG, Sony, Panasonic and Philips. Samsung goes all-in on the less common HDR10 +, which also happens to be an open format (Dolby Vision, as the name suggests, is proprietary).
It’s important to note that you do not 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 Dolby Vision content from Netflix just fine.
But going forward, the HDMI 2.1 standard ensures that a lot of bandwidth will be available for both metadata and high-resolution signals at high frame rates.
We do not yet know how PlayStation 5 or Xbox Series X will implement HDR, but they will probably be the main evidence base for dynamic HDR over HDMI in the coming years.
Variable refresh rate (VRR)
A TV’s refresh rate is how many times the panel is updated per second. This is measured in hertz, and it is closely related to the frame rate. When the two are out of sync, you get an effect called “screen tearing”. This is because the screen tries to display more than one frame at a time when the console or computer is not ready.
If you adjust the refresh rate of your screen to match the frame rate of your console or computer, you can effectively eliminate screen tearing without a performance penalty. Companies such as NVIDIA and AMD have their own methods for handling screen tearing, so-called G-Sync and FreeSync respectively.
However, the HDMI 2.1 standard also has its own independent solution, called the HDMI Variable Refresh Rate (VRR). Microsoft has confirmed that the Xbox Series X will support this feature, and PlayStation 5 is also expected, as it requires HDMI 2.1 to deliver 4K at 120 Hz.
For the best possible next-generation console experience, the HDMI VRR is a must. If you’re a PC gamer, it’s unlikely that NVIDIA and AMD will kill their existing technology in favor of HDMI VRR. This means that you still have to match your graphics card with your monitor.
Automatic low latency mode (ALLM)
Another benefit for the next generation of console players is auto low latency mode (ALLM). Most TVs now include all types of additional processing to smooth out motion, improve picture quality and even increase sound clarity. While some of this is appreciated when watching TV and movies, in front of players, it introduces latency (law).
This is what the game mode is for – you can switch to this when you want the fastest possible response time from your TV. This is especially handy for games that require fast, accurate reflexes. The only problem is that many TVs require you to turn the game mode on and off manually.
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 result in a delay. You do not need to do anything to enable it – it is built into the HDMI standard.
Microsoft has confirmed ALLM support for the Xbox Series X, but no word from Sony yet.
Quick Frame Transport (QFT)
Quick Frame Transport is another feature aimed at players working with ALLM to deliver a more responsive gaming experience. The feature prioritizes video frames in a bid to keep latency as low as possible.
To take advantage of this feature, make sure that all intermediate devices, such as a surround sound receiver, are also compatible. This will ensure that all your devices work together to provide a smooth, responsive experience. If you direct your console via a receiver that is only rated for HDMI 2.0, you will not benefit from QFT, even if your TV and console support it.
Quick Media Switching (QMS)
Have you ever noticed that your screen turns black just before watching a video or trailer? This is because the screen adjusts the refresh rate to suit the content you are viewing. Because different content uses different frame rates, your screen needs to be synchronized with it, hence the short blackout.
Sometimes this can cause you to miss the first few seconds of a video. However, some content providers delay playback to account for the change. Provided that the resolution of what you are watching remains the same, Quick Media Switching (QMS) eliminates blackouts caused by changes in refresh rate.
This allows you to view content at different frame rates back to back without blackout. 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 soundbar or surround receiver without an additional optical audio cable. Whether you’re watching Netflix, playing a game on a console or watching a Blu-ray, ARC makes sure the audio is delivered to the right output.
Enhanced Audio Return Channel (eARC) is part of the HDMI 2.1 standard. Additional bandwidth available in HDMI 2.1 allows eARC to carry uncompressed 5.1, 7.1 and high-bit or object-based audio at up to 192 kHz in 24-bit resolution. It does so with an audio bandwidth of 37 Mbits per second, compared to less than 1 Mbit per second via standard ARC.
If you want a Dolby Atmos signal over HDMI, you need eARC. There are also some other improvements, such as correct lip-sync correction by default, better device detection, and a dedicated eARC data channel.
Do HDMI 2.1 devices require special cables?
Because HDMI 2.1 has a higher bandwidth, you need HDMI 2.1 compatible cables to take advantage of its new features. The HDMI License Administrator has approved a new “Ultra High Speed” label for these cables.
All devices that use HDMI 2.1, such as a game console or Blu-ray player, should include a cable in the box. When buying an HDMI cable, you can also avoid the overpriced “premium” type.
HDMI 2.1 is primarily for gamers (for now)
Most people do not need HDMI 2.1 at this stage. The improved standard mainly benefits players who buy next-generation consoles or graphics cards, who want features such as HDMI VRR and ALLM. Outside of eARC, the new standard offers few benefits for home theater enthusiasts.
Microsoft has announced the multiplayer part of Halo Infinite will destroy in native 4K at 120 frames per second, but the game has been delayed until 2021. We will have to wait and see if any console titles will reach the high goal.