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USB4/DisplayPort/Thunderbolt Changes Boost 8K Support

By Bob Raikes

There have been a number of announcements about changes to USB4 (to Version 2), DisplayPort to Version 2.1 and Thunderbolt to Thunderbolt 5 that are really going to help support for 8K in the future.

These were announcements that are intended for equipment makers and it will take around a year or so for the changes to get into products (so around the end of 2023 – perhaps at CES in 2024).

The key change is a new encoding scheme for USB4 which will double the throughput of data while keeping the same cables and signal speeds. We explain it on the 8KAssociation website here. However the key changes are:

  • Double the output from 20Gbps per lane to 40Gbps per lane. Two lanes in USB4 are usually used in each direction so the interface can support 80Gbps in each direction
  • A new mode that allows three of the four lanes to be used for output, so providing 120Gbps for display applications, which will allow the support of dual 8K monitors or 8K monitors with up to 120Hz (and Intel said that future Macs would support dual 8K displays using Thunderbolt 5)
  • There is a new active cable specification for USB4 that will standardise active cables for long lengths
  • DisplayPort 2.1 will include DisplayStream Compression as standard for even higher resolutions and frame rates

All in all, these changes are great news for the development of 8K displays in a whole range of applications. Many believe that 8K really benefits from higher frame rates of 120Hz more than lower resolutions, but up to now there hasn’t been a way to connect displays to host systems to support this.

This is how USB cables will be identified as supporting the higher bandwidth of USB4 Version 2.

HDMI?

So, the question for consumers is when will HDMI catch up? Arguably, it doesn’t need to as DisplayPort and USB4/USB Type-C are mainly computer specifications and computer graphics need 4:4:4 video sampling, whereas consumer 8K video will use 4:2:0 sub-sampling. This isn’t the article for a deep dive into sub-sampling (for that, look here), but suffice it to say that 4:2:0 video uses much less bandwidth than the 4:4:4 needed for computer graphics. Further, for viewing on a single screen, HDMI 2.1a can support 8K60P video already.