DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

On June 26, the VESA standards organization officially announced the new DisplayPort 2.0 data transmission standard specification, which is closely integrated with Thunderbolt 3 and USB-C to meet the Display output requirements of 8K and even higher levels. This is the first major update after the DisplayPort 1.4 protocol.

On June 26, the VESA standards organization officially announced the new DisplayPort 2.0 data transmission standard specification, which is closely integrated with Thunderbolt 3 and USB-C to meet the Display output requirements of 8K and even higher levels. This is the first major update after the DisplayPort 1.4 protocol.

Prior to this, the theoretical total bandwidths of DP 1.1, 1.2, 1.3/1.4 were 10.8Gbps, 21.6Gbps, and 32.4Gbps respectively, but the effective efficiency was only 80% (8/10b encoding), which was difficult to meet the requirements of 6K, 8K high resolution and The demand for high color depth and high refresh rate.

DP 2.0 increases the theoretical bandwidth to 80Gbps in one fell swoop, and adopts a new encoding mechanism 128/132b, which increases the efficiency to 97%. The actual usable rate is as high as 77.4Gbps, which is equivalent to three times that of DP 1.3/1.4 and far exceeds HDMI 2.1. The theoretical bandwidth is 48Gbps.

In this way, DP 2.0 can easily support 8K/60Hz HDR, >8K/60Hz SDR, 4K/144Hz HDR, 2×5K/60Hz and other output formats. Not only can it support any 8K display without compression, it can also support up to 30 -bit color depth (more than 1 billion colors) to achieve 8K HDR.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

VESA will use the physical layer of Thunderbolt 3 to achieve ultra-high bandwidth. DisplayPort 2.0 can support two 8K resolution screens at a refresh rate of 60Hz, and achieve full-color 4:4:4 resolution and HDR-10 support.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

DisplayPort 2.0 is very fast, not only can support 8K displays without any compression (including chroma subsampling), but it is enough to perform in 30-bit color, and it can support HDR even at high resolutions. Similarly, it is now possible to display 10K monitors in 24-bit color without compression, and use 16K monitors when compressed. In general, the applications are as diverse as the manufacturers want, and the options include ensuring sufficient bandwidth for the next generation of VR, enabling new daisy chain settings, and some more interesting settings, such as combining USB data with high Resolution DisplayPort monitors are mixed.

DisplayPort 2.0: Thunderbolt 3, UHBR and passive data cable

Next, let’s talk about the DisplayPort 2.0 physical layer. In the past five years or so, VESA members have discussed the future development direction of the standard and the direction the physical port will take. The development of the next generation of high-bandwidth external interfaces will only make each generation of products more difficult and expensive, which has increasingly caused various standards organizations to merge around a few physical layers and data transmission technologies. At the same time, the physical display port was designed more than ten years ago, and the original design was not to expand to the bandwidth that 2.0 will promote. Therefore, each option is public to some extent, including disregarding most DisplayPort standards, DisplayPort, and all options.

The end result is an interesting compromise, and importantly, it provides more bandwidth while retaining backward compatibility with existing display port devices. DisplayPort itself still exists: it and the USB-C connector (via DP alt mode) are both official ports of the new DisplayPort 2.0 standard. Because of this, the number of pins and the resulting high-speed data channels remain unchanged, and DisplayPort continues to run on 4 channels. Finally, the DisplayPort 2.0 standard also retains the technology’s packet-based communication method, which means that image data will continue to be sent in the form of packets over a fixed bandwidth link, rather than a pixel-centric pixel clock method.

As for the data line, DP 2.0 actually introduces three different mechanisms. The bandwidth of each channel is set at 10Gbps, 13.5Gbps, and 20Gbps. VESA calls it “UHBR/Ultra High Bit Rate” (UHBR/Ultra High Bit Rate). They are called UHBR 10, UHBR 13.5, and UHBR 20.

The original bandwidth of UHBR 10 is 40Gbps, and the effective bandwidth is 38.69Gbps. Passive copper wire is sufficient. The previous DP 8K wire certification project actually included it, that is, the DP data cable that has passed the 8K certification meets the signal integrity of UHBR 10 Require.

UHBR 13.5 and UHBR 20 are different. The original bandwidth is 54Gbps and 80Gbps, and the effective bandwidth is 52.22Gbps and 77.37Gbps. Passive cables can only be used for extremely short-distance transmission. Into the corresponding control and amplification chip.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

So, what makes DisplayPort 2.0 so powerful? The answer is: Thunderbolt 3 (Thunderbolt 3), although the nominal display port itself is retained, but the rest of the physical layer is almost completely replaced by Thunderbolt 3.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

For DisplayPort 2.0, VESA directly utilizes Intel’s existing Thunderbolt 3 technology, which has reached the data rate VESA seeks. Although originally an Intel proprietary technology, Intel released the technology as a royalty-free standard to the wider industry earlier this year. This allows third parties not only to create pure Thunderbolt 3 devices without paying Intel, but also allows Thunderbolt 3 technology to be reused for other standards. Therefore, while USB4 is a more direct rebranding of Thunderbolt 3, DisplayPort 2.0 takes it in a different direction by essentially creating a one-way Thunderbolt 3 connection.

The operation of Thunderbolt 3 is very similar to DisplayPort. Each channel has 4 high-speed transmission 20 Gbps packets. However, although TB3 is a true two-way full-duplex link with 2 channels allocated in each direction, DisplayPort focuses on sending large amounts of data in one direction: out. Therefore, DisplayPort 2.0 reverses two inbound channels into outbound channels, allowing four total channels to be combined into an 80 Gbps link.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

Speaking of the link itself, the switch to Thunderbolt 3 technology also means that DisplayPort inherits the signal encoding scheme of Thunderbolt 3. Although DisplayPort 1.x has been using relatively inefficient 8/10b encoding-resulting in 20% overhead-DisplayPort 2.0 will provide 128/132b encoding with an overhead of only 3%. This is why the actual bandwidth gain of DisplayPort 2.0 is not just the original bandwidth gain; the standard is not just to get more bandwidth, but to use it more efficiently. Therefore, at the highest data rate, DisplayPort 2.0 will be able to provide 77.37 Gbps of bandwidth.

DisplayPort 2.0 function: mandatory DSC, branch device and panel replay

In addition to the important physical layer changes introduced in DisplayPort 2.0, the standard also introduces some more modest feature improvements.

First, for DisplayPort 2.0 devices, display stream compression must now be supported. Prior to this, DSC was introduced as part of DisplayPort 1.4, but it was not fully developed until a few years later. DSC is the organization’s “visually lossless” image compression standard. DSC runs on a smaller pixel group and provides a moderate compression ratio of about 3:1. Its goal is to compress images to save power and bandwidth without introducing visual artifacts or adding significant delays.

DisplayPort 2.0 is officially released: Raiden 3 is blessed, the bandwidth is increased by 3 times, and the image lossless compression transmission is officially introduced

In any case, starting with DisplayPort 2.0, DSC is now a core part of the DisplayPort standard. What needs to be clear is that 2.0 devices do not need to use DSC when bandwidth permits, and uncompressed images are preferred. But 2.0 devices must be able to encode, transmit and decode DSC compressed data. Over time, this will lay the foundation for manufacturers to develop and release displays that require DSC (at least in some modes), because they will be able to sell displays that know that all 2.0 devices can drive them.

Speaking of efficiency, the DisplayPort 2.0 standard also introduces another vendor-optional feature that focuses on power efficiency, which is Panel Replay. Panel Replay is derived from the early Panel Self Refresh technology and is part of the embedded DisplayPort standard. It is a partial self-update mechanism that allows the system to transmit and update only the part of the image that has changed since the last video frame. Like PSR in eDP, this feature is mainly used for notebook computers and other mobile devices, where power consumption and the impact on battery runtime are crucial. Transmission of less data not only reduces the energy consumption during transmission, but also reduces the amount of processing required by the display controller.

Last but not least, DisplayPort 2.0 has also updated the way “branch devices” work in the standard. It is basically a splitter in a multi-stream transmission setting. DisplayPort 1.x requires the branch device to be able to decode the DisplayPort bitstream, which is not an easy task for data above 20Gbps. Therefore, in version 2.0, branch devices have made some simplifications, and now they can only forward data without having to decode data. This will make MST (and daisy chain) easier to implement, because branch devices don’t need to be so complicated.

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