Measuring end-to-end delay in real-time auralisation systems

Regular paper

João Lamas

Centro Algoritmi, University of Minho

Tuesday 2 june, 2015, 11:00 - 11:20

0.3 Copenhagen (49)

One of the major challenges in the development of an immersive system is handling the delay between the tracking of the user’s head position and the according projection of a 3D image or auralised sound, also called end-to-end delay (Di Luca, 2011). Excessive end-to-end delay can result in the general decrement of the “feeling of presence” (Machover & Tice, 1992) and in the occurrence of motion sickness and poor performance in perception-action tasks (Di Luca, 2011). No present system is exempt of end-to-end latencies. Nevertheless these latencies must be known to provide insights on the technological (hardware/software optimization) or psychophysical (recalibration sessions) strategies to deal with them. Our goal was to develop a new measurement method of end-to-end delay that is both precise and easily replicated. We used a Head and Torso simulator (H&T) as an auditory signal sensor, a fast response photo-sensor to detect a visual stimulus response from a Motion Capture System, and a voltage input trigger as real-time event. The Brüel & Kjær Pulse Platform was used as the data acquisition system for all the signals. The H&T simulator was mounted in a turntable which allowed us to precisely change the 3D sound relative to the head position. When the virtual sound source was at 90o azimuth, the correspondent HRTF would set all the intensity values to zero, at the same time a trigger would register the real-time event of turning the H&T 90o azimuth. Furthermore, with the H&T turned 90o to the left, the motion capture marker visualization would fell exactly in the photo-sensor receptor. This method allowed us to precisely measure the delay from tracking to displaying. Moreover, our results show that the method of tracking, its time sampling, and the rendering of the sound reflections are the main predictors of end-to-end delay.

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