1. A playback device comprising: one or more processors; and tangible, non-transitory computer-readable memory, the memory storing instructions, wherein the instructions, when executed by the one or more processors, cause the playback device to perform a method comprising: receiving a plurality of frames from a source device over a network, wherein individual frames of the plurality of frames comprise (i) one or more portions of audio information and (ii) a playback time indicating when to play the one or more portions of audio information, wherein the playback time is based on a clock of the source device, which is independent of a clock of the playback device; receiving over the network, a message transmitted from the source device, the message comprising clock information of the source device; computing a time differential between the clock of the source device and the clock of the playback device based on the clock information of the message; determining an output time for each of the one or more portions of audio information based on both the playback time for the one or more portions of audio information and the computed time differential; and outputting each of the one or more portions of audio information at its determined output time in synchrony with the source device.