With next-gen consoles arriving by the end of 2020 and NVIDIA’s RTX 30 series of graphics cards cresting the horizon, HDMI 2.1 is looking 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 displays on the market currently support the HDMI 2.0 standard, which has a bandwidth cap of 18 Gbits per second. That’s enough to carry an uncompressed 4K signal at 60 frames per second at up to eight-bit color. This is adequate 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 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 push a 10K signal at 120 frames per second in 12 bit.
Some implementations of HDMI 2.1 use ports that only reach around 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-grade TVs.
High-end PC gamers tempted by NVIDIA’s new 30 series cards will be pleased to learn that the company has confirmed 10-bit support moving forward. This means it won’t matter if your TV lacks the full 48 Gbits per second specification.
Currently, HDMI 2.1 is aimed mostly at gamers hopping on the next-generation console or graphics card train. Both the Xbox Series X and PlayStation 5 will support 4K resolution at 120 frames per second. This will require that the HDMI 2.1 standard be implemented.
If your TV doesn’t support HDMI 2.1, you’ll have to make do with a 4K signal running at only(!) 60 frames per second. The majority of titles for the last 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 series cards aren’t HDMI 2.1 compatible. Many TV manufacturers, including Sony, have yet to include HDMI 2.1 in their top-tier 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 budget displays.
Support for Dynamic HDR
With so much bandwidth available, there’s more room in the pipes for raw data, too. HDR stands for High Dynamic Range, and it enables a broader range of colors in content like movies and games. Older HDR standards, like HDR10, only support static metadata. However, the newer HDR10+ and Dolby Vision formats allow for dynamic metadata on a per-scene or -frame basis.
Dynamic HDR provides a TV with more information about what to do with the signal it’s receiving. Rather than reading a single set of instructions for an entire movie, dynamic metadata gives the TV constant updates about how to tweak the image on-screen so it looks its best.
While every HDR-capable TV supports HDR10 with its static metadata, dynamic HDR is another beast altogether. The most widely supported format is Dolby Vision. It’s favored by hardware manufacturers including LG, Sony, Panasonic, and Philips. Samsung is going all-in on the less prevalent HDR10+, which also happens to be an open format (Dolby Vision, as its name suggests, is proprietary).
It’s important to note that you don’t need an HDMI 2.1 device to display 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.
Moving forward, though, the HDMI 2.1 standard ensures plenty of bandwidth will be available for both 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’ll likely be the main proving ground for dynamic HDR over HDMI over the next few years.
Variable Refresh Rate (VRR)
A TV’s refresh rate is how many times the panel refreshes per second. This is measured in hertz, and it’s closely tied to the frame rate. When the two are out of sync, you get an effect called “screen tearing.” It’s caused by the display trying to show more than one frame simultaneously when the console or PC isn’t ready.
If you adjust the refresh rate of the display to match the frame rate of your console or PC, you can effectively eliminate screen tearing with no performance penalties. Companies like NVIDIA and AMD have their own methods of dealing with screen tearing, known as 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 the Xbox Series X will support this feature, and the PlayStation 5 is expected to, as well, since it will require HDMI 2.1 to deliver 4K at 120 Hz.
For the best possible next-generation console experience, HDMI VRR is a must. If you’re a PC gamer, it’s unlikely NVIDIA and AMD will ditch their existing technologies in favor of HDMI VRR. This means you’ll still need to match your graphics card with your monitor.
Auto Low Latency Mode (ALLM)
Another perk for next-gen console gamers is auto low latency mode (ALLM). Most TVs now include all kinds of additional processing to smooth out motion, improve picture quality, and even boost 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 this whenever you want the fastest possible response times from your TV. This is particularly handy for games that require fast, precise reflexes. The only problem is many TVs require that you turn Game mode on and off manually.
ALLM removes the need to do this. When your HDMI 2.1-compliant TV understands that you’re using a supported console, ALLM will disable any extra processing that might introduce lag. You don’t have to do anything at all to enable it—it’s baked 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 gamers that works in conjunction with ALLM to deliver a more responsive gaming experience. The feature prioritizes video frames in a bid to keep latency as low as possible.
If you want to take advantage of this feature, make sure any intermediary devices, like a surround sound receiver, are also compatible. This will ensure all of your devices work together to deliver a smooth, responsive experience. If you’re routing your console via a receiver that’s only rated for HDMI 2.0, you won’t get the benefit of QFT, even if your TV and console support it.
Quick Media Switching (QMS)
Have you ever noticed that your screen goes black shortly before you watch a video or trailer? This is because the display is adjusting its refresh rate to suit the content you’re about to watch. As different content uses different frame rates, your display has to sync to it, hence, the short blackout.
Sometimes, this might cause you to miss the first few seconds of a video. However, some content providers delay playback to account for the change. Assuming the resolution of whatever you’re watching remains the same, Quick Media Switching (QMS) eliminates the blackout caused by refresh rate changes.
This allows you to watch content with differing frame rates back-to-back, without a blackout. The feature uses HDMI VRR to smoothly transition from one refresh rate to another.
Enhanced Audio Return Channel (eARC)
ARC stands for Audio Return Channel. It allows you to send audio over 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 ensures 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-rate or object-based audio at up to 192 kHz in 24-bit resolution. It does this with an audio bandwidth of 37 Mbits per second, compared with under 1 Mbit per second via regular ARC.
If you want to carry a Dolby Atmos signal over HDMI, you’ll need eARC. There are also a few other enhancements, like proper lip-synch 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 throughput, you’ll need HDMI 2.1-compliant cables to take advantage of its new features. The HDMI Licensing Administrator has approved a new “Ultra High Speed” label for these cables.
Any device that uses HDMI 2.1, like a game console or Blu-ray player, should include a cable in the box. Also, whenever you buy an HDMI cable, you can avoid the overpriced “premium” kind.
HDMI 2.1 Is Mostly for Gamers (for Now)
Most people don’t need HDMI 2.1 at this stage. The improved standard mostly benefits gamers buying next-generation consoles or graphics cards, who want features like HDMI VRR and ALLM. Outside of eARC, the new standard offers few benefits to home theater enthusiasts.
Microsoft has announced the multiplayer portion of Halo Infinite will ruin in native 4K at 120 frames per second, but the game has been delayed until 2021. We’ll have to wait and see whether any console titles will hit that lofty target.
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