New VR interface simplifies future designs

on July 19, 2018
Reading Time: 4 minutes

One of the biggest hassles of getting up and running with a high performance, desktop-class VR configuration is the setup. Despite the ease of use associated with phone-based designs that simply click into a headset and allow you to interact in an untethered fashion, PC-based systems require cables going between the user and the system. The virtual reality headsets also require the setup of cameras or tracking sensors in the room and then routing cables from the headset to the notebook or PC in a way that won’t entangle the user.

Ideally we would be moving to a wireless video and data transmission state for VR, but that is something that has and is being attempted by several in the industry. Intel, as well as partners of HTC and Oculus, having options, but nothing I would call perfected. It also doesn’t solve the issue of power delivery for situations where batteries aren’t ideal.

A new consortium representing all the major players in the PC VR space created a standard connection based around USB Type-C. On board are NVIDIA, AMD, Oculus, Valve, and Microsoft – essentially anyone that matters to this market. Called VirtualLink, the group claims that it was “developed to meet the connectivity requirements of current and next-generation virtual reality (VR) headsets.”

As an “Alternate Mode” for Type-C, VirtualLink can utilize a lot of the capability from the USB consortiums previous work while augmenting it for the VR space. The purpose of this connection is to create an environment for VR users that is simplified, condensing the cable management requirements and leaving headroom for future products and bandwidth needs.

A single VirtualLink connection will offer four lanes of DisplayPort HBR3 (high bitrate) which in total are capable of 32.4 Gbit/s of bandwidth, 25.92 Gbit/s of which is dedicated for video. That allows VR headsets to receive as high as 120Hz refresh rate at 4K resolution or stretch to 8K with a 60Hz. Though the group says that this interface is scalable for future designs, I don’t know if that means the DP integration will scale higher than what we see today or that VR devices will scale up into the 4K/8K resolutions.

VirtualLink includes a USB 3.1 data channel for sensor data transmissions to and from the headset. Any cameras or telemetry data that the headset is reading or generating can be passed back to the PC in a way that melds with the current software infrastructure, but in the simplicity of a single cable.

Power delivery is something that USB Type-C and Thunderbolt have added that greatly improves the usability of new interfaces. VirtualLink does this as well, pushing out as much as 27 watts to the HMD (head mounted display) to power the display, cameras, sensors, etc.

With current implementations from Oculus (the Rift) and HTC (Vive and Vive Pro) requiring 2-3 cables each, with a breakout box in the middle of the critical path, there is no doubt VirtualLink will make things easier for consumers and for vendors. VirtualLink cables will need to be hardwired into the headsets (or use a different, proprietary connector at the HMD) due to slight alterations to the USB Type-C standard (making existing Type-C cables unusable), dropping the chances of disconnection or failed setup and configuration.

No timeline is given for the integration of VirtualLink in PCs or HMDs, though there have been rumors circulating that NVIDIA was including a “VR port” on its upcoming GeForce family update coming late in the summer. It seems likely that this is what those rumors were referring to – now with the background info on VirtualLink we can connect the dots. We don’t know anything about AMD’s plans but its name as part of this consortium indicates that the next generation of Radeon GPUs will also integrate support for VirtualLink.

There is no roadmap for new PC-based VR headsets currently, with the Vive Pro being the most recent release, still using the standard integration methods from previous generations. I assume that the follow on to that, and the next Rift device from Oculus, will integrate VirtualLink to start the process of simplified VR. In the interim, the consortium details converter boxes from companies like Bizlink that can output full-size DisplayPort, USB2 and USB3, and power, from a single input VirtualLink connection.

One tidbit of information I am still trying to hunt down is how VirtualLink ports on next-generation graphics cards will process the USB 3.1 data channel and integrate the 27 watts of power distribution required. Pushing out 27 watts through VirtualLink is simple enough for high-performance graphics cards in the GTX 1080-class, though staying within the PCIe-standards for power consumption will be critical. Lower performance cards, that might not even require external power connections inside a PC, might struggle more.

Graphics cards would have to emulate a USB 3.1 hub, or pass a virtual USB channel back to the host PC for the software infrastructure to detect and utilize the sensor data provided to and from the HMD itself. I haven’t seen anything like this done before, but it shouldn’t be hard for NVIDIA and AMD to integrate with the consortium unifying development.

Those details aside, the creation of a new standard interface and connection for virtual reality on the PC will improve on a comically complex situation that exists today. Will that be enough to accelerate the VR space on the PC? No, but it does mean the next generation of options from Oculus, HTC, or any other newcomer that integrates VirtualLink will have a better chance of convincing consumers it’s worth trying.