Interactive TV/arcade games have been entertaining people for over 50 years. Nowadays a large number of legacy TV/arcade games have been ported to new platforms such as PCs by emulation. However, they generally require that the players be co-located to interact with one computer that emulates the game. This paper proposes a novel approach to turning those single-computer games into multicomputer games such that multiple players can play their favorite legacy games in real time over a computer network. The main challenge in this work is how to synchronize multiple replicas of a game without semantic knowledge about or modifications to the game. We present the approach, especially the synchronization algorithm, and evaluate its effectiveness under a variety of network conditions. In future research we will extend this work on mobile devices.

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This paper presents a collaboration transparency system that allows for distributed sharing of legacy collocated video games in real time without modifying the original games. Our system has attracted two million registered players since it was launched in late 2008. As the system went beyond a research prototype and reached a large number of real users, we observed performance issues that were mainly caused by unpredicted networking latencies over the public Internet and opportunistic distinction of roles such as active players and passive observers. To address these issues, we propose a novel hybrid consistency control approach that combines the merits of optimistic methods, which help achieve interactivity, and pessimistic methods, which guarantee consistency. As a result, the system can tolerate network round-trip time up to 230 ms, improving the latest work by 43.7%. In addition, the system can support over 1,000 simultaneous observers when a video game is played over the Internet.