Synchronization of Content Between Networked Devices

• US 20170181113A1
• Filed: 12/16/2015
• Published: 06/22/2017
• Est. Priority Date: 12/16/2015
• Status: Active Grant

• Current Assignee: Sonos, Inc.
• Original Assignee: Sonos, Inc.
• Inventors: Keyser-Allen, Lee, Higdon, Thomas, Vega-Zayas, Luis, Lin, Ted, Sarkic, Andrej
• Granted Patent: US 10,098,082 B2
• Time in Patent Office: Days
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 65/60 Network streaming of media packets
• 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 21/4392 involving audio buffer management
• CPC Class Codes: H04N 21/8113 comprising music, e.g. song in MP3 format
• 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 2420/07 Applications of wireless loudspeakers or wireless microphones
• 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: H04W 56/0015 one node acting as a reference for the others

Abstract

Networked devices are arranged to play content such as audio and video content in synchronization. A synching device receives a packet from an initiating device over a network. The packet may include an identifier of content to play, such as a URI, and an indication of when to play the content. A local clock time to play the content is determined based on a time of a local clock of the first device and the indication of when to play the content. The synching device obtains from a server the content based on the received identifier, and plays the content in synchronization with the initiating device based on a time on the local clock and the local clock time to play the content. In some embodiments, the synching device also adjusts a clock speed of the local clock reference to control rate of playback of the content.

Claims

1. A first device comprising:

a network interface configured to communicate with a second device and a third device over a network;

a processor comprising instructions, which when executed, cause the processor to;

receive, by the first device from the second device over the network, an identifier of content to play and an indication of when to play the content;

determine, by the first device, a local clock time to play the content, the local clock time to play the content based on a time of a local clock of the first device and the indication of when to play the content;

obtain, by the first device from the third device over the network, the content to play based on the received identifier of content to play; and

play, by the first device, the obtained content based on the time of the local clock and the local clock time to play the content.

2. The first device of claim 1, wherein the indication of when to play the content is associated with a network latency.

3. The first device of claim 1, wherein the network latency is based on a mean of a round trip packet delay between the first device and the second device.

4. The first device of claim 1, wherein the identifier of content to play is a uniform resource indicator (URI) which facilitates access to the content on the third device via the network.

5. The first device of claim 1, wherein receiving, by the first device from the second device over the network, the identifier of content to play further comprises receiving a presentation timestamp which indicates a location in the content to start playback.

6. The first device of claim 1, wherein the indication of when to play the content is a length of time until playback starts, and wherein determining, by the first device, a local clock time to play the content comprises adding the length of time until playback starts to the time of the local clock.

7. The first device of claim 1, wherein the content comprises a plurality of frames, and wherein the indication of when to play the content is a length of time until playback of a frame, the first device further comprising instructions to receive a synchronization packet comprising a new length of time until playback of the frame, determine an expected length of time until playback of the frame based on a presentation timestamp embedded in the content, wherein the presentation timestamp indicates a timing of playback for the content, and adjust a clock speed of the local clock based on the expected length of time until playback of the frame and the new length of time until playback of the frame.

8. The first device of claim 7 wherein adjusting the clock speed comprises calculating the following expression:

(Delta E−

DeltaR)/(Delta_R) where Delta_E is the expected length of time until playback of the frame and Delta_R is the new length of time until playback of the frame.

9. The first device of claim 1, further comprising instructions to play, by the first device, the content in synchronization with the second device based on presentation timestamps embedded in the content, the presentation timestamps indicating timing of playback for the content.

10. The first device of claim 1, wherein receiving, by the first device from the second device over the network, the identifier of content to play comprises receiving a packet with a sequence number.

11. The first device of claim 10, further comprising instructions to send, by the first device, an acknowledgement packet from the first device to the second device, the acknowledgment packet including the sequence number of the packet.

12. The first device of claim 1, wherein a network latency is subtracted from the indication of when to play the content.

13. A method for synchronizing playback between a first device and a second device, the method comprising:

receiving, by the first device from the second device over a network, an identifier of content to play and an indication of when to play the content;

determining, by the first device, a local clock time to play the content, the local clock time to play the content based on a time of a local clock of the first device and the indication of when to play the content;

obtaining, by the first device from a third device over the network, the content to play based on the received identifier of content to play; and

playing, by the first device, the obtained content based on the time of the local clock and the local clock time to play the content.

14. The method of claim 13, wherein determining, by the first device, a local clock time to play the content comprising subtracting, by the first device, a network latency from the indication of when to play the content.

15. The method of claim 13, wherein the first device is an audio playback device, wherein the content comprises audio content and video content, and wherein playing, by the first device, the content comprises dropping, by the first device, the video content and playing the audio content.

16. The method of claim 13, further comprising receiving a synchronization packet which defines at least one of a new presentation timestamp, a new length of time until playback of a frame, and a new clock generation number.

17. The method of claim 13, wherein the content comprises a plurality of frames, and wherein the indication of when to play the content is a length of time until playback of a frame, the method further comprising receiving a synchronization packet comprising a new length of time until playback of the frame, determining an expected length of time until playback of the frame based on a presentation timestamp embedded in the content, wherein the presentation timestamp indicates a timing of playback for the content, and adjusting a clock speed of the local clock based on the expected length of time until playback of the frame and the new length of time until playback of the frame.

18. The method of claim 13, further comprising playing, by the synchronizing device, the content in synchronization with the second device based on presentation timestamps embedded in the content, the presentation timestamps being indicative of a timing of playback for the content.

19. A computer readable storage medium including instructions for execution by a processor, the instructions, when executed, cause the processor to implement a method comprising:

receiving, by the first device from the second device over a network, an identifier of content to play and an indication of when to play the content;

determining, by the first device, a local clock time to play the content based on a time of a local clock of the first device and the indication of when to play the content;

obtaining, by the first device from a third device over the network, the content to play based on the received identifier of content to play; and

playing, by the first device, the obtained content based on the time of the local clock and the local clock time to play the content.

20. A computer readable storage medium of claim 19, wherein the content comprises a plurality of frames, and wherein the indication of when to play the content is a length of time until playback of a frame, the method further comprising instructions to receive a synchronization packet which defines a new length of time until playback of the frame;

determine an expected length of time until playback of the frame based on a presentation timestamp embedded in the content, wherein the presentation timestamp indicates a timing of playback for the content; and

adjust a clock speed of the local clock based on the expected length of time until playback of the frame and the new length of time until playback of the frame.