Automatic Verification of a Lip-Synchronisation Protocol Using Uppaal

Abstract

Abstract. We present the formal specification and verification of a lip-synchronisation protocol using the real-time model checker Uppaal. A number of specifications of this protocol can be found in the literature, but this is the first automatic verification. We take a published specification of the protocol, code it up in the Uppaal timed automata notation and then verify whether the protocol satisfies the key properties of jitter and skew. The verification reveals some aws in the protocol. In particular, it shows that for certain sound and video streams the protocol can time-lock before reaching a prescribed error state. We also discuss our experience with Uppaal, with particular reference to modelling timeouts and to deadlock analysis.

A Symbolic Algorithm for the Analysis of Robust Timed Automata

“…The last model we have used is a lip synchronisation protocol described in [6]. Specifically we have used the model which assumes an ideal video stream.…”

Modelling Timeouts without Timelocks

“…transition is not urgent, i.e. the good transition is never forced to happen 6 . In the terminology of 3], such transitions are called lazy.…”

“…This represents the timeout performing its good escape transition. However, con- 6 We prefer to enforce the urgency of good in the timeout because in some of our case studies, e.g. 6], there are situations in which enforcing the urgency of good on the system side can cause problems, since nothing ensures that the timeout is ready to synchronise on the good exactly when it is o ered.…”

An Automatic Test Framework for Interactive Music Systems

“…Some tools exists for automating the test of IMS, like for instance the max-test package [18] Other work has addressed the formal verification of multimedia systems based on Timed Automata models, such as for instance the verification of a lip-synchronisation protocol (synchronization of audio and video streams) in [7]. Timed Automata Networks, Uppaal, as well as timed Petri nets, are used in iScore [5], a framework for composition, verification and real-time performance of Multimedia Interactive Scenarios.…”