The Ethernet Speaker System

If we wish to distribute audio in a large room, building, or even a campus, we need multiple speakers. These speakers must be jointly managed and synchronized. The Ethernet Speaker (ES) system presented in this paper can be thought of as a distributed audio amplifier and speakers, it does not ``play'' any particular format, but rather relies on off-the-shelf audio applications (mpg123 player, Real Audio player) to act as the audio source. The Ethernet Speaker, consists of three elements: (a) a system that converts the audio output of the unmodified audio application to a network stream containing configuration and timing information (rebroadcaster), (b) the devices that generate sound from the audio stream (Ethernet Speakers), and (c) the protocol that ensures that all the speakers in a LAN play the same sounds.

This paper covers all three elements, discussing design considerations, experiences from the prototype implementations, and our plans for extending the system to provide additional features such as automatic volume control, local user interfaces, and security.