HDMI 2.1b Specification Technology Overview

The HDMI 2.1b Specification supersedes 2.0b and 2.1b continues to make reference to, and rely upon, HDMI 1.4b Specification.

• Ultra High Speed HDMI Cable
• Auto Low Latency Mode (ALLM)
• Enhanced Audio Return Channel (eARC)
• Quick Frame Transport (QFT)
• Quick Media Switching (QMS)
• Variable Refresh Rate (VRR)

The uncompressed/compressed feature name designations include: A= uncompressed, B=compressed, AB=Both

• 4K100_A
• 4K100_AB
• 4K100_B
• 4K120_A
• 4K120_AB
• 4K120_B
• 8K50_A
• 8K50_AB
• 8K50_B
• 8K60_A
• 8K60_AB
• 8K60_B

Please note that in order to use the feature names adopters must follow the HDMI 2.1b specification requirements for those features.

You can only use version numbers when clearly associating the version number with a feature or function as defined in that version of the HDMI Specification. You cannot use version numbers by themselves to define your product or component capabilities or the functionality of the HDMI interface.

And please note that NO use of version numbers is allowed in the labeling, packaging, or promotion of any cable product.

Please check the Adopted Trademark and Logo Usage Guideline for a complete explanation of the policy, available on the Adopter extranet and the ATLUG document.

Yes, in order to ensure performance and compatibility the Ultra High Speed HDMI Cable is required.

• 4K50/60
• 4K100/120
• 5K50/60
• 5K100/120
• 8K50/60
• 8K100/120
• 10K50/60
• 10K100/120

The specification supports both uncompressed and compressed modes. Manufacturers can implement either or both modes. The designations are:

• 4K100_A    - supports uncompressed mode
• 4K100_B    - supports compressed mode
• 4K100_AB   - supports both
• 4K120_A    - supports uncompressed mode
• 4K120_B    - supports compressed mode
• 4K120_AB   - supports both
• 8K50_A      - supports uncompressed mode
• 8K50_B      - supports compressed mode
• 8K50_AB    - supports both
• 8K60_A      - supports uncompressed mode
• 8K60_B      - supports compressed mode

Manufacturers may use the designations indicated above (e.g. 8K60_A, 8K60_B, 8K60_AB) in their product marketing, advertising, user guides, packaging, website, and on-product.

The specification incorporates VESA DSC 1.2a link compression, which is a visually lossless compression scheme. VESA DSC 1.2a also can be used to obtain higher resolutions than 8K60/4:2:0/10-bit color, such as 8K60 RGB, 8K120 and even 10K120. VESA DSC 1.2a also supports 4Kp50/60 with the benefit of enabling operation at much lower link rates.

HDMI 2.1b Specification supports the latest color spaces including BT.2020 with 10, 12, and 16 bits per color component.

FRL stands for Fixed Rate Link and it’s a signaling technology supported in the HDMI 2.1b Specification. FRL is necessary to achieve the higher uncompressed resolutions such as those above 4k60 as well as the ultra high speed bandwidths up to 48Gbps. It’s also required for compressed video transport which in turn enables operation at lower data rates for example 4k60 and ultra-high pixel rate video such as 10Kp120.

Yes, it replaces TMDS. Note that the HDMI 2.1b specification still requires support for TMDS for backwards compatibility and still seamlessly supports the billions of HDMI devices that utilize TMDS.

Upgradeability needs to be designed into the silicon and that is up to the manufacturers, although implementing FRL is most likely going to require new hardware.

The Ultra High Speed HDMI Cable is the first cable defined by the HDMI Forum. Ultra High Speed HDMI Cables comply with stringent specifications designed to ensure support for high resolution video modes such as 4Kp50/60/100/120 and 8Kp50/60 as well as new features such as eARC and VRR. Ultra High Speed HDMI Cables exceed the requirements of the latest international EMI standards to significantly reduce the probability of interference with wireless services such as Wi-Fi.

Yes

Yes

The cable is the best way to ensure that high-bandwidth dependent features are delivered, including the enhanced video and audio performance, while ensuring the new EMI requirements are met.

Yes. Ultra High Speed HDMI cables support all HDMI 2.1b and 1.4b features.

Installations with 1080p or 4K displays can benefit by using the new Ultra High Speed HDMI cables. The new cable is tested to ensure low EMI to reduce the possibility of interference with wireless networks, streaming media players, Bluetooth devices and mobile phones. Also, for those who install the cables in inaccessible locations such as inside walls, the new cable provides a future-proof solution.

Ultra High Speed HDMI Cables are designed to support the new eARC feature in addition to the highest resolution video modes. The Standard HDMI Cable with Ethernet and the High Speed HDMI Cable with Ethernet will also support eARC.

Existing HDMI High Speed Cables with Ethernet can only deliver some of the new features, and the new Ultra High Speed HDMI Cable is the best way to connect HDMI 2.1b enabled devices to ensure delivery of all the features with improved EMI characteristics.

The Ultra High Speed HDMI cable specification covers connectors Types A, C and D. The initial Ultra High Speed HDMI Cable Certification Program is for cables with Type A connectors.

The cable is backwards compatible and can be used with all existing HDMI devices.

The specification does not indicate a cable length. Cable length depends on many factors including cable type and construction.  Based on early testing in the UHS Cable program, it is expected that passive cables of 5 meters will be achievable.

The specification permits wire, passive, active, and converter Category 3 cable assemblies.

In order for cables to be marketed and sold as compliant to the HDMI 2.1b Specification and use the official Ultra High Speed HDMI Cable designation they must past all certification tests and, in addition, affix the Ultra High Speed HDMI Certification Label on their packaging. The label has the Ultra High Speed HDMI Cable name and logo on it. The cables are also required to have the cable name printed on the cable jacket itself.

It has two main functions. First, it prevents counterfeiting and protects the manufacturers, enables each package to be traceable back to its source, and enables consumers and the industry to scan the QR code and security hologram to verify the brand name, model number, length and that it is a certified cable registered in the HDMI LA verification system. Secondly, it cuts through the confusion sometimes found in resellers’ marketing that might include variations on the cable name or claims about supporting certain bandwidths or features, by ensuring consumers and end-users that all they need to do is look for the label to know the cable is an official Ultra High Speed HDMI Cable.

Yes, the Cable Name Logo is on the Ultra High Speed HDMI Certification Label. Also the logo is not allowed to be printed on cable packages and must only be displayed on products by affixing the Ultra High Speed HDMI Certification Label to the package.

No, but it will be necessary to enable 4K120 and 8K60 video with HDR due to the high bandwidth required by these resolutions and refresh rates.

It supports various static and dynamic HDR solutions.

Static and Dynamic HDR-enabled devices that implement the HDMI 2.1b Specification transmit both Static and Dynamic HDR metadata over the HDMI interface in a standardized way; and also go through the same mandatory HDMI compliance testing to ensure they can properly send/receive Static and Dynamic HDR metadata over the HDMI interface regardless of product manufacturer. This ensures consumers can get all the benefits of Dynamic HDR without possible compatibility issues.

Manufacturers may or may not be able to enable Dynamic HDR with a firmware upgrade. Contact the manufacturer of your product to see if this is possible.

This works with HDMI High Speed Cables with Ethernet and the new Ultra High Speed HDMI Cable.

Generally speaking, no. Check with the manufacturer of your product to confirm.

The latest high-bitrate audio formats are supported including DTS Master, DTS:X, Dolby TrueHD, Dolby Atmos and more.

Maybe. Manufacturers can produce products that are compatible with both eARC and ARC. However, eARC is not defined to be backwards compatible with ARC.

HDMI 2.1b has the following features:

• Auto Low-Latency Mode (ALLM)
• Variable Refresh Rate (VRR)
• Quick Frame Transport (QFT)

This feature lets a game console, PC or other device send a signal to the display which will cause it to automatically switch to a low-latency, low-lag mode for gaming. This could benefit other uses, such as karaoke and video conferencing. When the source no longer requires this mode—for example, when switching to a movie stream—the source disables the signal and the display reverts back to its previous mode.

VRR lets a gaming source deliver video frames as fast as it can, which in many cases is slower than the normal static refresh rate. Graphics processors require different absolute periods to render each frame, and this time is dependent upon the complexity of the scene, the horsepower of the GPU, the resolution selected and the frame rate. When the GPU is taxed by the other three factors and does not finish rendering the next frame by the time it needs to be displayed, the source must either repeat the current frame or display the partially-rendered next frame, which causes judder and tearing. By waiting until the next frame is ready to transport it, a smoother gaming experience can be provided to the user.

QFT transports each frame at a higher rate to decrease “display latency”, which is the amount of time between a frame being ready for transport in the GPU and that frame being completely displayed. This latency is the sum of the transport time through the source’s output circuits, the transport time across the interface, the processing of the video data in the display, and the painting of the screen with the new data. This overall latency affects the responsiveness of games: how long it appears between a button is pressed to the time at which the resultant action is observed on the screen.

While there are a lot of variables in this equation, not many are adjustable from an HDMI specification perspective. QFT operates on the transport portion of this equation by reducing the time it takes to send only the active video across the cable. This results in reduced display latency and increased responsiveness.

QMS is all about presenting the best media playback experience. There are no reaction times involved, so latency is not an issue (ALLM and QFT should not be used). ALLM should not be enabled with QMS because ALLM disables the extensive video processing your TV does. The frame rates are static within a video stream, so VRR is not necessary. And as described previously, QMS and VRR use the same technology under the hood, so they cannot operate together. (QMS has a constant frame rate, VRR has a varying frame rate.)

On the other hand, adding ALLM to VRR and QFT is encouraged for the best gaming experience.

Your gaming box will take care of these choices for you. If you are streaming video or playing a Blu-ray, it would only enable QMS; if you fire up a game, it would enable ALLM, VRR, and QFT, depending on what your system supports.

Ask the manufacturers of your devices. More details are available in the HDMI 2.1b Gaming and Media Features white paper available to HDMI 2.1b Adopters on the Adopter Extranet.

An HDMI Cable with Cable Power will work with any HDMI device, but if the HDMI Source Device does not support HDMI Cable Power, a separate power connection must be attached to the cable.

Please check the source device’s Specifications or feature labeling to determine whether HDMI Cable Power is supported.

Yes, all categories of HDMI Cable, including Standard, High Speed, Premium High Speed and Ultra High Speed, may incorporate the HDMI Cable Power feature.

An HDMI Cable with Cable Power that uses one of the following labels will support ARC and eARC:

• Ultra High Speed HDMI Cable
• Premium High Speed HDMI Cable with Ethernet
• High Speed HDMI Cable with Ethernet
• Standard HDMI Cable with Ethernet

Using HDMI Cable Power, the cable can draw up to 300 mA from the 5V supply of the source.

Active HDMI Cables can require more than the minimum power supplied by HDMI source devices. A source device that supports HDMI Cable Power can provide higher power and can indicate this capability to the cable.