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VESA Publishes Embedded DisplayPort Standard 1.4a, Includes Adaptive Sync

To maintain pace with ever-increasing resolutions, color bit-depth and refresh rates, the Video Electronics Standards Association (VESA) has announced the latest version of the Embedded DisplayPort (eDP) specification – 1.4a. This supersedes version 1.4, which was first introduced in February of 2013.

The principal upgrades include a new Display Stream Compression (DSC) standard (1.1) and an enhanced segmented display panel capability. Both features allow for greater data rates and lower power usage, especially in integrated graphics systems such as smartphones, tablets, laptops and all-in-ones.

We first learned of DisplayPort's segmented panel architecture when the first-generation Ultra HD monitors hit the market. Users had a choice of connecting their PC using two HDMI cables or a single DisplayPort supporting Multi-Stream Transport (MST). The dual-HDMI solution was so quickly rejected by the market that it's seen on few products today. Because the majority of newer graphics boards support DisplayPort 1.2 with MST, it's far easier to use the single-cable solution to take advantage of a UHD monitor's native 3840 x 2160 pixel resolution.

The name of the game in today's rapidly changing video display market is bandwidth. With new standards such as Rec.2020 demanding the rendering of more colors and more pixels at higher refresh rates, connection interfaces must be able to keep up. The resolution evolution is moving fastest in the portable device realm. Products such as the iPhone and iPad boast pixel densities of over 300 ppi, and computer monitors are now topping 200 ppi. And with 5K monitors already shipping, it seems like we'll always need more bandwidth.

The new eDP 1.4a standard can move bits at 8.1 Gbps per lane. The GPU-to-display interface can be divided into two or four screen segments, allowing for a theoretical limit of 32.4 Gbps. Coupled with DSC 1.1 compression, data packet size can be reduced at up to a 3:1 ratio. Not only does this allow for more of all the good stuff – pixels, colors and framerate – it does so with lower power consumption.

Although the signal chain does not yet exist, eDP 1.4a can support 8K (7680 x 4320) resolution at 60 Hz, and Ultra HD is supported at 120 Hz with 10-bit color.

Refinements to previous technologies in eDP 1.4 include Panel Self-Refresh (PSR). By only updating changed pixels from frame to frame, the amount of data in the pipeline is reduced. Any pixels that remain the same between frames are not updated, further saving power and bandwidth.

Finally, for those wondering about Adaptive Sync (or FreeSync as AMD calls it), it is indeed part of both the eDP 1.4 and 1.4a specs. Why aren't we seeing it yet in shipping products? As it turns out, it's part of the optional section of the standard. It seems that all that's needed are monitors that support it. AMD has stated that as many as 11 new displays will be shipping in Q1 with the feature enabled. Coupled with an appropriate AMD graphics board and a driver update, frame-tearing could quickly become a thing of the past.

Because we're only just now seeing products based on DisplayPorts 1.3 and 1.4, it's logical to conclude that version 1.4a will begin to emerge by 2016, first in portable devices and eventually in desktop systems. For hardware developers, the standard is available to VESA members immediately.

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