Adding voice to distributed games on the Internet

Much of the work on distributed virtual environments (DVEs) has focused on efficient schemes and algorithms for the description and visual rendering of such environments. However, there has been comparatively little effort on senses other than sight, and in particular on live voice. This is surprising because adding voice to DVEs enhances the sense of immersion in the environment, and can in fact completely change the way entities interact. For example, adding voice in a distributed game impacts tactics, team building, cheating, etc. We examine issues related to adding voice between participants in DVEs. We consider in particular a special kind of DVE, namely distributed games over the Internet. We consider all stages of voice manipulation, including voice generation (with emphasis on echo cancellation), voice transmission (with emphasis on RTP and packetization), and voice restitution (with emphasis on spatial rendition and on synchronization between voice and visual cues). We also consider implementation issues, and illustrate these with the MiMaze game and the FreePhone audio tool, both developed at INRIA