Measuring end-to-end delay in real-time auralisation systems
Regular paper
Centro Algoritmi, University of Minho
Tuesday 2 june, 2015, 11:00 - 11:20
0.3 Copenhagen (49)
Abstract:
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.