System and method for synchronizing operations among a plurality of independently clocked digital data processing devices

A non-transitory computer readable medium comprising instructions for synchronizing audio playback of a plurality of separate audio playing devices with one another, the instructions, when executed by a processor, cause the processor to perform the following:

• receiving, by a playback device, a multicast stream including a plurality of frames from a source device over a local network, wherein each frame of the plurality of frames is associated with audio information and a time indicating when to play the audio information of the respective frame, wherein the time is based on a clock of the source device, which is independent of a clock of the playback device;
• periodically receiving, by the playback device, a unicast message transmitted from the source device, the unicast message separate from the multicast stream and including clock information of the source device;
• computing, by the playback device, a time differential between the clock of the source device and the clock of the playback device based on a most recently received unicast message;
• converting, by the playback device and for each frame of the plurality of frames, a computed output time of the audio information for each respective frame, the converting based on both the time associated with each respective frame and a most recent computation of the time differential;
• outputting, by the playback device, audio information based on the plurality of frames by playing audio information for each respective frame based on a clock of the playback device, wherein the playback device is configured to output the audio information in synchrony with the source device;
• and
• adjusting a speed at which the playback device outputs the audio information, wherein the speed is adjusted based on a comparison between an expected output time of audio information for a particular frame and the computed output time of the particular frame.