  Distributed Virtual Reality systems enable globally dispersed users to
interact with each other in a shared virtual environment. In such systems,
different types of latencies occur. For a good VR experience, they need to be
controlled. The time delay between the user's head motion and the corresponding
display output of the VR system might lead to adverse effects such as a reduced
sense of presence or motion sickness. Additionally, high network latency among
worldwide locations makes collaboration between users more difficult and leads
to misunderstandings. To evaluate the performance and optimize dispersed VR
solutions it is therefore important to measure those delays. In this work, a
novel, easy to set up, and inexpensive method to measure local and remote
system latency will be described. The measuring setup consists of a
microcontroller, a microphone, a piezo buzzer, a photosensor, and a
potentiometer. With these components, it is possible to measure
motion-to-photon and mouth-to-ear latency of various VR systems. By using
GPS-receivers for timecode-synchronization it is also possible to obtain the
end-to-end delays between different worldwide locations. The described system
was used to measure local and remote latencies of two HMD based distributed VR
systems.
