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

• US 9,164,531 B2
• Filed: 01/27/2012
• Issued: 10/20/2015
• Est. Priority Date: 07/28/2003
• Status: Active Grant

• Current Assignee: Sonos, Inc.
• Original Assignee: Sonos, Inc.
• Inventors: Millington, Nicholas A. J.
• Primary Examiner(s): Survillo, Oleg
• Application Number:
  US13/359,976
• Publication Number:
  US 20120185072A1
• Time in Patent Office: 1,362 Days
• Field of Search: 709/219, 709/220, 709/231
• US Class Current: 1/1
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: G06F 1/00 Details not covered by groups G06F3/00 - G06F13/00 and G06F21/00 architectures of general purpose stored program computers G06F15/76
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators
• CPC Class Codes: G06F 16/2322 using timestamps
• CPC Class Codes: G06F 16/60 of audio data
• CPC Class Codes: G06F 16/63 Querying
• CPC Class Codes: G06F 16/635 Filtering based on additional data, e.g. user or group profiles
• CPC Class Codes: G06F 16/638 Presentation of query results
• CPC Class Codes: G06F 16/639 using playlists
• CPC Class Codes: G06F 16/68 Retrieval characterised by using metadata, e.g. metadata not derived from the content or metadata generated manually
• CPC Class Codes: G06F 17/00 Digital computing or data processing equipment or methods, specially adapted for specific functions information retrieval, database structures or file system structures therefor G06F16/00
• CPC Class Codes: G06F 3/048 Interaction techniques based on graphical user interfaces [GUI]
• CPC Class Codes: G06F 3/0482 Interaction with lists of selectable items, e.g. menus
• CPC Class Codes: G06F 3/0484 for the control of specific functions or operations, e.g. selecting or manipulating an object, an image or a displayed text element, setting a parameter value or selecting a range
• CPC Class Codes: G06F 3/04842 Selection of displayed objects or displayed text elements G06F3/0482 takes precedence
• CPC Class Codes: G06F 3/04847 Interaction techniques to control parameter settings, e.g. interaction with sliders or dials
• CPC Class Codes: G06F 3/16 Sound input; Sound output speech processing G10L
• CPC Class Codes: G06F 3/162 Interface to dedicated audio devices, e.g. audio drivers, interface to CODECs
• CPC Class Codes: G06F 3/165 Management of the audio stream, e.g. setting of volume, audio stream path
• CPC Class Codes: G06F 3/167 Audio in a user interface, e.g. using voice commands for navigating, audio feedback
• CPC Class Codes: G11B 20/10527 : Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: G11B 2020/10592 : specifically adapted for recording or reproducing multichannel signals
• CPC Class Codes: H03G 3/00 : Gain control in amplifiers or frequency changers
• CPC Class Codes: H03G 3/20 : Automatic control H03G3/005 takes precedence; combined with volume compression or expansion H03G7/00
• CPC Class Codes: H04H 20/103 : Transmitter-side switching
• CPC Class Codes: H04H 20/26 : Arrangements for switching distribution systems
• CPC Class Codes: H04H 2201/20 : digital audio broadcasting [DAB]
• CPC Class Codes: H04J 3/0644 : External master-clock
• CPC Class Codes: H04J 3/0664 : unidirectional timestamps
• CPC Class Codes: H04L 12/2854 : Wide area networks, e.g. public data networks
• CPC Class Codes: H04L 65/1069 : Session establishment or de-establishment
• CPC Class Codes: H04L 65/1094 : Inter-user-equipment sessions transfer or sharing
• CPC Class Codes: H04L 65/60 : Network streaming of media packets
• CPC Class Codes: H04L 65/61 : for supporting one-way streaming services, e.g. Internet radio
• CPC Class Codes: H04L 65/611 : for multicast or broadcast systems for broadcast or conference H04L12/18; arrangements for broadcast or distribution combined with broadcast H04H20/00; arrangements for broadcast applications with a direct linkage to broadcast information or to broadcast space-time H04H60/00; selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS], H04W4/06
• CPC Class Codes: H04L 65/612 : for unicast
• CPC Class Codes: H04L 65/613 : for the control of the source by the destination control signals issued by the client directed to the server or network components specially adapted for selective content distribution H04N21/637
• CPC Class Codes: H04L 65/75 : Media network packet handling
• CPC Class Codes: H04L 65/80 : Responding to QoS
• CPC Class Codes: H04L 67/1095 : Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 67/12 : specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks
• CPC Class Codes: H04L 67/55 : Push-based network services
• CPC Class Codes: H04L 69/28 : Timers or timing mechanisms used in protocols
• CPC Class Codes: H04N 21/4307 : Synchronising the rendering of multiple content streams or additional data on devices, e.g. synchronisation of audio on a mobile phone with the video output on the TV screen
• CPC Class Codes: H04N 21/43076 : of the same content streams on multiple devices, e.g. when family members are watching the same movie on different devices
• CPC Class Codes: H04N 21/43615 : Interfacing a Home Network, e.g. for connecting the client to a plurality of peripherals home Audio Video Interoperability [HAVI] data switching networks H04L12/2805
• CPC Class Codes: H04N 5/04 : Synchronising for television systems using pulse code modulation H04N7/56
• CPC Class Codes: H04N 9/7904 : using intermediate digital signal processing
• CPC Class Codes: H04R 2227/003 : Digital PA systems using, e.g. LAN or internet
• CPC Class Codes: H04R 2227/005 : Audio distribution systems for home, i.e. multi-room use
• CPC Class Codes: H04R 27/00 : Public address systems circuits for preventing acoustic reaction H04R3/02; circuits for distributing signals to loudspeakers H04R3/12; monitoring or testing arrangements for public address systems H04R29/007; amplifiers H03F
• CPC Class Codes: H04R 3/12 : for distributing signals to two or more loudspeakers specially adapted for hearing aids H04R25/407
• CPC Class Codes: H04W 56/0015 : one node acting as a reference for the others
• CPC Class Codes: H04W 84/20 : Master-slave selection or change arrangements

Abstract

A system is described for maintaining synchrony of operations among a plurality of devices having independent clocking arrangements. A task distribution device is to distribute tasks to a synchrony group comprising a plurality of devices to perform tasks distributed by the task distribution device in synchrony. The task distribution device distributes each task to synchrony group members over a network. Each task is associated with a time stamp that indicates a time, relative to a clock maintained by the task distribution device, at which synchrony group members are to execute the task. Each synchrony group member periodically obtains from the task distribution device an indication of current time indicated by its clock, determines a time differential between the task distribution device'"'"'s clock and its respective clock and determines therefrom a time at which, according to its respective clock, the time stamp indicates that it is to execute the task.

Claims

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.

2. The playback device of claim 1, wherein the output time for each of the one or more portions of audio information is determined by adding the time differential to the playback time for the one or more portions of audio information when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the playback time for the one or more portions of audio information when the clock of the playback device is behind the clock of the source device.

3. The playback device of claim 1, wherein outputting each of the one or more portions of audio information at its determined output time in synchrony with the source device comprises playing the one or more portions of audio information from one or more speakers of the playback device.

4. The playback device of claim 1, wherein the playback device is configured to receive the plurality of frames via a group multicast transmission methodology, and wherein the playback device is configured to receive the message comprising clock information of the source device via a unicast transmission methodology.

5. The playback device of claim 1, wherein the source device is another playback device.

6. The playback device of claim 1, wherein the step of computing a time differential is performed periodically.

7. Tangible, non-transitory computer-readable media having instructions encoded thereon, wherein the instructions, when executed by one or more processors, cause a 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.

8. The computer-readable media of claim 7, wherein the output time for each of the one or more portions of audio information is determined by adding the time differential to the playback time for the one or more portions of audio information when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the playback time for the one or more portions of audio information when the clock of the playback device is behind the clock of the source device.

9. The computer-readable media of claim 7, wherein the step of receiving the plurality of frames from the source device comprises receiving the plurality of frames via a group multicast transmission methodology, and wherein the step of receiving the message from the source device including clock information of the source device comprises receiving the message via a unicast transmission methodology.

10. The computer-readable media of claim 7, wherein the source device is another playback device.

11. The computer-readable media of claim 7, wherein the step of computing a time differential is performed periodically.

12. A playback device comprising:

one or more processors; and

tangible, non-transitory computer-readable memory, the memory comprising instructions, wherein the instructions, when executed by the one or more processors, cause the playback device to perform a method comprising;

receiving an audio stream comprising a plurality of frames from a source device over a local network, wherein an individual frame of the plurality of frames comprises audio information and a time indicating when to play the audio information of the individual frame, wherein the time is based on a clock of the source device, which is independent of a clock of the playback device;

receiving over the local network, a message transmitted from the source device, the message separate from the audio stream and including 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 message;

determining for the individual frame, an output time of the audio information of the individual frame based on both the time indicating when to play the audio information of the individual frame and the computed time differential; and

outputting the audio information of the individual frame at the determined output time in synchrony with the source device.

13. The playback device of claim 12, wherein the method further comprises:

adjusting when the playback device outputs the audio information of the individual frame based on a comparison between an expected output time of the audio information of the individual frame and the determined output time of the audio information of the individual frame.

14. The playback device of claim 13, wherein adjusting when the playback device outputs the audio information comprises adjusting the clock of the playback device.

15. The playback device of claim 12, wherein the step of computing a time differential occurs periodically.

16. The playback device of claim 15, wherein the step of determining the output time of the individual frame is based on a most recent computation of the time differential.

17. The playback device of claim 15, wherein the step of computing a time differential is performed in response to receiving the message from the source device.

18. The playback device of claim 12, wherein the output time of the audio information for the individual frame is determined by adding the time differential to the time indicating when to play the audio information of the individual frame when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the time indicating when to play the audio information of the individual frame when the clock of the playback device is behind the clock of the source device.

19. The playback device of claim 12, wherein the method further comprises:

buffering the audio information along with the output time prior to outputting the audio information.

20. The playback device of claim 12, wherein the method further comprises:

prior to receiving the plurality of frames, receiving an address that the source device will use to send the plurality of frames.

21. The playback device of claim 12, wherein receiving the audio stream comprising the plurality of frames from the source device comprises the playback device receiving the plurality of frames from the source device according to a group multicast transmission methodology.

22. The playback device of claim 12, wherein the source device is a second playback device.

23. The playback device of claim 12, wherein the playback device is one of a plurality of playback devices in a synchrony group.

24. The playback device of claim 23, wherein the synchrony group is dynamically configurable, such that a number of the plurality of playback devices in the synchrony group is adjustable.

25. The playback device of claim 12, wherein the playback device is configured to receive the plurality of frames from the source device over a wireless network.

26. The playback device of claim 12, wherein the message comprises a Simple Network Time Protocol message.

27. Tangible, non-transitory computer-readable media having instructions encoded thereon, wherein the instructions, when executed by one or more processors, cause a playback device to perform a method comprising:

receiving an audio stream comprising a plurality of frames from a source device over a local network, wherein an individual frame of the plurality of frames comprises audio information and a time indicating when to play the audio information of the individual frame, wherein the time is based on a clock of the source device, which is independent of a clock of the playback device;

receiving over the local network, a message transmitted from the source device, the message separate from the audio stream and including 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 message;

determining for the individual frame, an output time of the audio information of the individual frame based on both the time indicating when to play the audio information of the individual frame and the computed time differential; and

outputting the audio information of the individual frame at the determined output time in synchrony with the source device.

28. The computer-readable media of claim 27, wherein the output time of the audio information for the individual frame is determined by adding the time differential to the time indicating when to play the audio information of the individual frame when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the time indicating when to play the audio information of the individual frame when the clock of the playback device is behind the clock of the source device.

29. The computer-readable media of claim 27, wherein the step of receiving the audio stream comprising the plurality of frames from the source device comprises receiving the plurality of frames via a group multicast transmission methodology, and wherein the step of receiving the message from the source device including clock information of the source device comprises receiving the message via a unicast transmission methodology.

30. The computer-readable media of claim 27, wherein the source device is another playback device.

31. The computer-readable media of claim 27, wherein the step of computing a time differential is performed periodically.

32. A playback device comprising:

one or more processors; and

tangible, non-transitory computer-readable memory with instructions stored thereon, wherein the instructions, when executed by the one or more processors, cause the playback device to perform a method comprising;

receiving an audio stream comprising a plurality of frames from a source device over a local network, wherein each frame of the plurality of frames with comprises 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 over the local network, a message transmitted from the source device, the message separate from the audio stream and including 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 message;

determining for each frame of the plurality of frames, an output time of the audio information of each respective frame based on both the time indicating when to play the audio information of each respective frame and the computed time differential; and

outputting the audio information of each respective frame at the respective frame'"'"'s determined output time in synchrony with the source device.

33. The playback device of claim 32, wherein the method further comprises:

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 determined output time of the particular frame.

34. The playback device of claim 33, wherein adjusting the speed at which the playback device outputs the audio information comprises adjusting the clock of the playback device.

35. The playback device of claim 32, wherein the step of computing a time differential is performed periodically.

36. The playback device of claim 35, wherein each determined output time for each frame is based on a most recent computation of the time differential.

37. The playback device of claim 36, wherein the step of computing a time differential is performed in response to receiving the message from the source device.

38. The playback device of claim 32, wherein the output time of the audio information for each respective frame is determined by adding the time differential to the time indicating when to play the audio information of each respective frame when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the time indicating when to play the audio information of each respective frame when the clock of the playback device is behind the clock of the source device.

39. The playback device of claim 32, wherein the method further comprises:

buffering the audio information along with the output time prior to outputting the audio information.

40. The playback device of claim 32, wherein the method further comprises:

prior to receiving the plurality of frames, receiving an address that the source device will use to send the plurality of frames.

41. The playback device of claim 32, wherein the plurality of frames received from the source device is received from the source device according to a group multicast transmission methodology.

42. The playback device of claim 32, wherein the source device is a second playback device.

43. The playback device of claim 32, wherein the playback device is one of a plurality of playback devices in a synchrony group.

44. The playback device of claim 43, wherein the synchrony group is dynamically configurable, such that a number of the plurality of playback devices in the synchrony group is adjustable by adding one or more playback devices to the synchrony group and/or removing one or more playback devices from the synchrony group.

45. The playback device of claim 32, wherein the playback device is configured to receive the plurality of frames from the source device over a wireless network.

46. The playback device of claim 32, wherein the message comprises a Simple Network Time Protocol message.

47. Tangible, non-transitory computer-readable media having instructions encoded thereon, wherein the instructions, when executed by one or more processors, cause a playback device to perform a method comprising:

receiving an audio stream comprising a plurality of frames from a source device over a local network, wherein each frame of the plurality of frames comprises 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 a message transmitted from the source device, the message separate from the audio stream and including 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 message;

determining an output time of the audio information of each respective frame based on both the time indicating when to play the audio information of each respective frame and the computed time differential; and

outputting the audio information of each respective frame at the respective frame'"'"'s determined output time in synchrony with the source device.

48. The computer-readable media of claim 47, wherein the output time of the audio information for each respective frame is determined by adding the time differential to the time indicating when to play the audio information of the respective frame when the clock of the playback device is ahead of the clock of the source device and by subtracting the time differential from the time indicating when to play the audio information of the respective frame when the clock of the playback device is behind the clock of the source device.

49. The computer-readable media of claim 47, wherein the step of receiving the audio stream comprising the plurality of frames from the source device comprises receiving the plurality of frames via a group multicast transmission methodology, and wherein the step of periodically receiving the message including clock information of the source device comprises receiving the message via a unicast transmission methodology.

50. The computer-readable media of claim 47, wherein the source device is another playback device.

51. The computer-readable media of claim 47, wherein the step of computing a time differential is performed periodically.