Clock Synchronization for Audio Playback Devices

An audio system comprising:

• a time server;
• a synchronization agent;
• and
• a plurality of audio playback devices for providing synchronized playback of audio content, wherein each audio playback device of the plurality is configured to:
• receive a broadcast/multicast acknowledgement packet from a synchronization agent;
• record a first timestamp representing a time when the acknowledgement packet was received;
• receive a broadcast/multicast timestamp packet from the time server, wherein the timestamp packet includes a second timestamp representing a time when the time server received the acknowledgement packet from the synchronization agent;
• update a local clock time based on the first timestamp and the second timestamp, such that the local clock time corresponds to that of the other audio playback devices;
• and
• using the updated local clock time to render the audio content in synchrony with the other audio playback devices.

A non-transitory computer readable storage medium including a set of instructions for execution by a processor, the set of instructions, when executed, causes the processor to:

• receive a broadcast/multicast acknowledgement packet via the network interface from a synchronization agent;
• record a first timestamp representing a time when the acknowledgement packet was received;
• receive a broadcast/multicast timestamp packet from a time server, wherein the timestamp packet includes a second timestamp representing a time when the time server received the acknowledgement packet from the synchronization agent;
• update a local clock time based on the first timestamp and the second timestamp;
• and
• using the updated local clock time to enable synchronized playback of the audio content among a plurality of audio playback devices.

An audio playback device comprising:

• a digital-to-analog converter configured to receive an audio stream comprising a digital representation of audio content via a network and convert to analog form;
• an electro-acoustic transducer;
• a network interface;
• a processor coupled to the digital-to-analog converter, the electro-acoustic transducer, and the network interface;
• and
• instructions stored on a non-transitory computer-readable media that, when executed, cause the processor to:
• receive a broadcast/multicast acknowledgement packet via the network interface from a synchronization agent;
• record a first timestamp representing a time when the acknowledgement packet was received by the playback device;
• receive a broadcast/multicast timestamp packet via the network interface from a time server, wherein the timestamp packet includes a second timestamp representing a time when the time server received the acknowledgement packet from the synchronization agent;
• update a local clock time based on the first timestamp and the second timestamp, such that the local clock time corresponds to that of at least one other audio playback device on the network;
• and
• using the updated local clock time to render the audio content in synchrony with the at least one other audio playback devices.