Abstract:

The Spline scalable platform for interactive environments makes it easy to build virtual worlds where multiple people interact with each other and with computer simulations in a 3D visual and audio environment. A key problem shared by Spline and many other systems is achieving accurate time synchronization of events and data streams. In Spline, synchronization is achieved through the use of timestamps. Given the nature of the audio and visual data supported by Spline, timestamps on the order of 64 bits are required to accurately specify the absolute position of individual pieces of data in time. Nevertheless, synchronization is achieved by using timestamps only 32 bits long, thereby saving bandwidth, storage and computation time. The use of 32-bit timestamps is made possible by reducing the precision and range of the timestamps required by the data. The precision is limited by grouping data that is sampled at high frequency into lower frequency chunks, and giving each chunk a low precision timestamp. The range is limited by using an efficient form of modular arithmetic for expressing timestamps.