Pv. Rangan et al., FEEDBACK TECHNIQUES FOR CONTINUITY AND SYNCHRONIZATION IN MULTIMEDIA INFORMATION-RETRIEVAL, ACM transactions on information systems, 13(2), 1995, pp. 145-176
Citations number
31
Categorie Soggetti
Information Science & Library Science","Computer Science Information Systems
Future advances in storage and networking technologies will make it fe
asible to build multimedia on-demand information servers capable of pr
oviding services similar to those of a neighborhood videotape rental s
tore over metropolitan area networks, Such multimedia information serv
ers must not only support retrieval of continuous media units (such as
video frames and audio samples), but also preserve synchrony among pl
ayback of the different media components constituting a multimedia obj
ect. We develop techniques for supporting continuous and synchronous r
etrieval from multimedia servers. We present feedback techniques by wh
ich, during retrieval of multimedia objects from a multimedia server t
o mediaphones, the multimedia server uses lightweight messages called
feedback units transmitted periodically back to it (by mediaphones) to
detect impending discontinuities as well as asynchronies at mediaphon
es. The multimedia server then preventively readjusts media transmissi
on so as to avoid either anomaly, and steers the mediaphones back to s
ynchrony. Given the available buffer sizes at mediaphones and the maxi
mum tolerable asynchrony, we present methods to determine the minimum
rate at which feedback units must be transmitted so as to maintain bot
h continuity and synchronization. These feedback techniques remain rob
ust even in the presence of playback rate mismatches and network delay
jitter, and their initial simulation for video-audio playback yields
a feedback rate of one per 1,000 media units to keep the asynchrony wi
thin 250ms, showing that the overhead due to feedback transmission is
very small. The constant rate feedback techniques developed in this ar
ticle form the basis of a prototype on-demand information server being
developed at the UCSD Multimedia Laboratory.