Zero Perceived Latency (ZPL) for Virtual Reality (VR)

//Zero Perceived Latency (ZPL) for Virtual Reality (VR)
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Zero Perceived Latency (ZPL) for Virtual Reality (VR)

Products being released for the consumer market next year from companies such as Oculus, HTC and FOVE have pushed developers and technology forward immensely in the past 24 months.

As a testament to the volume of users expected to adopt the VR experience for themselves, Facebook have reportedly said they will be trying to connect over 1 billion people through HMDs (head mounted displays) such as the Oculus Rift in the coming few years.

This technology is therefore set to play a huge part in everyone’s lives, and for this reason, I wanted to spend some time talking about a recently coined term “Zero Perceived Latency” or ZPL and what it has to do with Virtual Reality.

One of the criticisms of VR from the current state of the art, is the problem of the user feeling sick when using the HMDs. The reasons for “Simulator Sickness” are attributed in a big way to the framerate and the latency.   The latency we are talking about is the time it takes for the user’s eyes to see a scene change after they have performed some kind of interaction with the world.  For example, when the user moves their head, the system must track this movement, the GPU and software alter the way the scene is displayed, this data must be fed from the PC through the HDMI or other transport medium, the data must be received and decoded by the HMD and then displayed on the screen to the user.   This complete system pipeline must happen as quick as possible, and if the time that is takes to complete this is too long, then the user will experience an un-natural feeling and typically results in sickness.

Zero Perceived Latency (or ZPL) is the minimum latency time for the system as described above whereby the user experiences a completely immersive experience (no noticeable delays) which can greatly increase the chances of not having any adverse effects such as simulator sickness whilst interacting in the virtual world.  It has been postulated in the literature and industry that the ZPLtime should be less than 20ms, so the challenge for developers is to develop complete systems from capturing users movements all the way through to what is displayed on the HMD to the user in less than 20ms.

Companies developing parts of the complete system (for example our company,Immersive Robotics that has developed a VR Wireless link) must ensure that their additions to the latency of the system are well below this Zero Perceived Latency (ZPL) level, otherwise there is no advantage to their technology for the VR community.   This is why the link we are developing is targeting ultra-low latency and is specific to the VR community – something that is yet to be done – supporting both ultra-high resolutions and ultra-low latencies.

For more information about our technology please see:


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By | 2016-12-20T23:30:11+00:00 December 11th, 2015|Design|Comments Off on Zero Perceived Latency (ZPL) for Virtual Reality (VR)