John MacCormick

John MacCormick

The dominant paradigm for video chat employs a single camera at each end of the conversation, but some conversations can be greatly enhanced by using multiple cameras at one or both ends. This paper provides the first rigorous investigation of multi-camera video chat, concentrating especially on the ability of users to switch between views at either end of the conversation. A user study of 23 individuals analyzes the advantages and disadvantages of permitting a user to switch between views at a remote location. Benchmark experiments employing up to four webcams simultaneously demonstrate that multi-camera video chat is feasible on consumer hardware. The paper also presents the design of MultiCam, a software package permitting multi-camera video chat. Some important trade-offs in the design of MultiCam are discussed, and typical usage scenarios are analyzed.

Aleksandr Simma, Moises Goldszmidt, John MacCormick et al.

We present a generative model for representing and reasoning about the relationships among events in continuous time. We apply the model to the domain of networked and distributed computing environments where we fit the parameters of the model from timestamp observations, and then use hypothesis testing to discover dependencies between the events and changes in behavior for monitoring and diagnosis. After introducing the model, we present an EM algorithm for fitting the parameters and then present the hypothesis testing approach for both dependence discovery and change-point detection. We validate the approach for both tasks using real data from a trace of network events at Microsoft Research Cambridge. Finally, we formalize the relationship between the proposed model and the noisy-or gate for cases when time can be discretized.