HDMI Boosts 8K Support With Version 2.2
HDMI Licensing was at CES 2025 to announce a significant boost to the HDMI standard, a new HDMI 2.2 version that uses existing connectors and, together with new cables, can enable formats up to 8K at 240 fps as well as resolutions up to 12K at lower frame rates. Of course, as usual, it will take some time for chip and system makers to incorporate the standard into devices as the full specification has not yet been released, and even cable makers are unlikely to have new products before the second half of the year. The full specification is due in the first half of 2025. Experience tells us that wide adoption by TVs and other devices is likely to take a couple of years.
The key change from the video point of view is a doubling of the maximum bit rate from 48Gbps (the maximum with HDMI 2.1) to 96Gbps, which is higher even than the 80Gbps of DisplayPort 2.1a. In the past, DisplayPort has tended to lead HDMI in terms of the maximum bit rate, but DisplayPort 2.1a (at 80 Gbps) is not widely adopted in January 2025. As with DisplayPort, the new HDMI 2.2 version can provide different levels of capability depending on
- whether compression is used,
- the bit depth,
- whether there is chroma subsampling for video and on
- the cable.
HDMI Licensing provided a table of capabilities.
DSC Compression is Used
The compression technology used is the DisplayStream Compression (DSC) specification developed by VESA and used in DisplayPort. DSC is ‘perceptually lossless’ – which is to say that viewers of compressed streams are unable to detect any differences, although instruments can.
As with previous versions of HDMI, there will be no simple way for consumers and users to know if devices support compression, so care will need to be taken by buyers to check the capabilities of sending and receiving devices. HDMI has implementors with very different use cases and cost models, so it has been up to the buyer for some years to work out what combinations of devices will work together with all the features supported. (The editor has a personal view that HDMI should specify subsets particular use cases for sets of features, but HDMI has explained in the past that its members prefer maximum flexibility.)
In recent years, HDMI Licensing has certified cables and the HDMI 2.2 specification specifies a new Ultra96 HDMI cable to get the full bandwidth and like previously certified cables, they will be sold with a QR code to guarantee that designs have been tested.
Why is HDMI 2.2 Needed?
Higher refresh rates are important not only for gamers, but for VR and XR applications in headsets. As we have previously reported, the ITU is looking eventually to 32K for 360 degree content. The high immersiveness of 8K content on large displays also benefits a lot from higher frame rates and higher frame rates should enable a wider range of production styles.
Given the time it takes for new standards to be implemented and for costs to come down to high volume levels, standards have to be several years ‘ahead of the curve’. It is good to see HDMI pushing the limits of the technology.
Another feature included in HDMI 2.2 is the HDMI Latency Indication Protocol (LIP). As frame rates get higher and audio systems get more sophisticated, issues of poor lip sync can become more bothersome to consumers, so the LIP protocol will allow better negotiation between source and sink devices to minimize any issues.
