While display interface standards are slow to move, at the same time their movement is inexorable: monitor resolutions continue to increase, as do refresh rates and color depths, requiring more and more bandwidth to carry signals for the next generation of monitors. Keeping pace with the demand for bandwidth, the DisplayPort standard, the cornerstone of PC display standards, has now been through several revisions since it was first launched over a decade ago. And now this morning the standard is taking its biggest leap yet with the release of the DisplayPort 2.0 specification. Set to offer nearly triple the available bandwidth of DisplayPort 1.4, the new revision of DisplayPort is almost moving a number of previously optional features into the core standard, creating what's in many ways a new baseline for the interface.
The big news here, of course, is raw bandwidth. The current versions of DisplayPort – 1.3 & 1.4 – offer up to 32.4 Gbps of bandwidth – or 25.9 Gbps after overhead – which is enough for a standard 16.7 million color (24-bit) monitor at up to 120Hz, or up to 98Hz for 1 billion+ (30-bit) monitors. This is a lot of bandwidth, but it still isn't enough for the coming generation of monitors, including the likes of Apple's new 6K Pro Display XDR monitor, and of course, 8K monitors. As a result, the need for more display interface bandwidth continues to grow, with these next-generation monitors set to be the tipping point. And all of this is something that the rival HDMI Forum has already prepared for with their own HDMI 2.1 standard.
DisplayPort 2.0, in turn, is shooting for 8K and above. Introducing not just one but a few different bitrate modes, the fastest mode in DisplayPort 2.0 will top out at 80 Gbps of raw bandwidth, about 2.5 times that of DisplayPort 1.3/1.4. Layered on that, DisplayPort 2.0 also introduces a more efficient coding scheme, resulting in much less coding overhead. As a result, the effective bandwidth of the new standard will peak at 77.4 Gbps, with at 2.98x the bandwidth of the previous standard is just a hair under a full trebling of available bandwidth.
The HDMI Forum on Wednesday announced key specifications of the HDMI 2.1 standard, which will be published in the second quarter. The new standard will increase link bandwidth to 48 Gbps and will enable support for up to 10K resolutions without compression, new color spaces with up to 16 bits per component, dynamic HDR, variable refresh rates for gaming applications as well as new audio formats
The most important feature that the HDMI 2.1 specification brings is massively increased bandwidth over predecessors. That additional bandwidth (48 Gbps over 18 Gbps, a bit more than what a USB-C cable is rated for) will enable longer-term evolution of displays and TVs, but will require the industry to adopt the new 48G cable, which will keep using the existing connectors (Type A, C and D) and will retain backwards compatibility with existing equipment (which probably means 8b/10b encoding and effective bandwidth of around 38 Gbps). The standard-length 48G cables (up to two meters) will use copper wires, but it remains to be seen what happens to long cables. It is noteworthy that while some of the new features that the HDMI 2.1 spec brings to the table require the new cable, others do not. As a result, some of the new features might be supported on some devices, whereas others might be not.
The increased bandwidth of HDMI 2.1's 48G cables will enable support of new UHD resolutions, including 4Kp120, 8Kp100/120, 10Kp100/120, and increased frame rates. It is no less important that increased bandwidth will enable support of the latest and upcoming color spaces, such as BT.2020 (Rec. 2020) with 10, 12, or even more advanced with 16 bits per color component and without compression. HDMI Forum does not say it explicitly, but the version 2.1 of their standard will also likely support the BT.2100 (Rec. 2100), which has a number of important enhancements to the BT.2020 when it comes to HDR. While HDMI 2.0 already supports BT.2020 and HDMI 2.0b adds support for HDR10 (through support for Hybrid Log-Gamma (HLG)), it only can transmit 10 and 12 bits per sample at 4Kp60 resolution. To support HDR at 8K, one will need HDMI 2.1.
10K resolution (5760p)? 16-bits per channel color (281,474,976,710,656 shades of grey)? It's necessary!
LinuxGizmos has an interesting article on how an Intel Engineer fixed up Linux's DisplayPort compliance, and got the kernel patch moved upstream.
At ELC 2017, Intel's Manasi Navare described how she patched Linux 4.12 for true DisplayPort compliance, and offered tips on pushing patches upstream.
If you've ever hooked up a Linux computer to a DisplayPort monitor and encountered only a flickering or blank screen, we've got good news for you. A graphics kernel developer at Intel's Open Source Technology Center has solved the problem with a patch that will go into Linux Kernel 4.12. Manasi Navare's patch modifies Atomic Kernel Mode Setting (KMS) technology to gracefully drop down to a lower resolution to display the image.
"Someone had to fix this problem, so I said okay, I have the knowledge and I have the community to help me," said Navare at the recent Embedded Linux Conference.
The High-Definition Multimedia Interface 2.1 specification has been released. The total transmission bandwidth has been increased to 48 Gb/s from the 18 Gb/s of HDMI 2.0 (or a maximum data rate of 42.6̅ Gb/s from 14.4 Gb/s). The new data rate is effectively tripled to 128 Gb/s when using Display Stream Compression (DSC).
Using DSC, HDMI 2.1 cables can transmit 4K (3840×2160) @ 240 Hz, and 8K (7680×4320) as well as UW10K (10240×4320) at 120 Hz. Without DSC, you will be able to transmit 4K @ 120 Hz, 5K (5120×2880) @ 120 Hz, 8K @ 60 Hz, and UW10K @ 30 Hz. Keep in mind that color depth and chroma subsampling also affect the necessary data rate.
The specification also adds new features such as dynamic high-dynamic-range support (you read that right - the first "dynamic" refers to "dynamic metadata that allows for changes on a scene-by-scene or frame-by-frame basis"), Variable Refresh Rate, Quick Frame Transport, Quick Media Switching, and Auto Low-Latency Mode:
This new version of the HDMI specification also introduces an enhanced refresh rate that gamers will appreciate. VRR, or Variable Refresh Rate, reduces, or in some cases eliminates, lag for smoother gameplay, while Quick Frame Transport (QFT) reduces latency. Quick Media Switching, or QMS, reduces the amount of blank-screen wait time while switching media. HDMI 2.1 also includes Auto Low Latency Mode (ALLM), which automatically sets the ideal latency for the smoothest viewing experience.
- Here is the HDMI Forum's PPT PDF explaining HDMI 2.1.
- Here are the data rates and cables required for various resolutions/bit depths/chroma. Resolutions requiring Display Stream Compression are indicated.
- Here is another table showing the various color depths and chroma subsampling levels.
Previously: HDMI 2.1 Announced
Future generations of virtual reality headsets for PCs could use a single USB Type-C cable for both power and data. That's thanks to a new standardized spec from the VirtualLink Consortium, a group made up of GPU vendors AMD and Nvidia and virtual reality rivals Valve, Microsoft, and Facebook-owned Oculus.
The spec uses the USB Type-C connector's "Alternate Mode" capability to implement different data protocols—such as Thunderbolt 3 data or DisplayPort and HDMI video—over the increasingly common cables, combined with Type-C's support for power delivery. The new headset spec combines four lanes of HBR3 ("high bitrate 3") DisplayPort video (for a total of 32.4 gigabits per second of video data), along with a USB 3.1 generation 2 (10 gigabit per second) data channel for sensors and on-headset cameras, along with 27W of electrical power.
That much video data is sufficient for two 3840×2160 streams at 60 frames per second, or even higher frame rates if Display Stream Compression is also used. Drop the resolution to 2560×1440, and two uncompressed 120 frame per second streams would be possible.
Framerate is too low, and it's not wireless. Lame.
As the tech industry gears up for the launch of the new USB4 standard, a few more parts first need to fall into place. Along with the core specification itself, there is the matter of alternate modes, which add further functionality to USB Type-C host ports by allowing the data pins to be used to carry other types of signals. Keeping pace with the updates to USB4, some of the alt modes are being updated as well, and this process is starting with the granddaddy of them all: DisplayPort Alt Mode.
The very first USB-C alt mode, DisplayPort Alt Mode was introduced in 2014. By remapping the USB-C high speed data pins from USB data to DisplayPort data, it became possible to use a USB-C port as a DisplayPort video output, and in some cases even mix the two to get both USB 3.x signaling and DisplayPort signaling over the same cable. As a result of DisplayPort Alt Mode's release, the number of devices with video output has exploded, and in laptops especially, this has become the preferred mode for driving video outputs when a laptop doesn't include a dedicated HDMI port.
If you're willing to accept Display Stream Compression... New DisplayPort spec enables 16K video over USB-C
Previously: Forget USB 3.2: Thunderbolt 3 Will Become the Basis of USB 4
DisplayPort 2.0 Announced, Triples Bandwidth to ~77.4 Gbps for 8K Displays
Speed-Doubling USB4 is Ready -- Now We Just Have to Wait for Devices