Synchronization Of A Split Audio, Video, Or Other Data Stream With Separate Sinks

• US 20080291891A1
• Filed: 05/23/2007
• Published: 11/27/2008
• Est. Priority Date: 05/23/2007
• Status: Active Grant

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Jerlhagen, Sven, Agren, Mattias Per, Krithikaivasan, Sathiyanarayanan
• Granted Patent: US 8,102,836 B2
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04L 43/0864 Round trip delays
• CPC Class Codes: H04L 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/25 with rate being modified by the source upon detecting a change of network conditions
• CPC Class Codes: H04L 47/38 by adapting coding or compression rate
• CPC Class Codes: H04W 28/02 Traffic management, e.g. flow control or congestion control
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

Methods, systems, and apparatuses for synchronizing one or more output/sink devices are described. In each sink device, a communication packet is received from a source device. The communication packet includes data and a source clock timestamp. A local clock signal is generated that is synchronized with a source clock signal of the source device. The data is decoded using a codec. At least one delay and the source clock timestamp are subtracted from a current value of the local clock signal to generate a local latency value. A difference between a desired latency value and the local latency value is determined. A rate of a clock signal of the codec is adjusted according to the determined difference. Because each sink device adjusts its latency to a common desired latency value, the sink devices are thereby synchronized.

Claims

1. An output system, comprising:

a plurality of output devices that each include

a radio frequency (RF) communication module configured to receive a communication packet from a source device, wherein the communication packet includes data and a source clock timestamp;

a local clock signal generator configured to generate a local clock signal synchronized with a source clock signal of the source device;

a codec configured to decode the data; and

a latency calculator configured to determine a difference between a desired latency value and a local latency value of the output device, wherein a rate the codec is adjusted according to the determined difference;

whereby the plurality of output devices produce substantially synchronized output streams.

2. The output system of claim 1, wherein the codec is configured to decode the data and to convert the decoded data to an analog signal according to a codec clock signal;

wherein a rate of the codec clock signal is adjusted according to the determined difference to adjust the rate of the codec.

3. The output system of claim 2, wherein each output device of the plurality of output devices further includes:

an output element that receives the analog signal and generates an output signal.

4. The output system of claim 1, wherein the latency calculator is configured to subtract at least one delay and the source clock timestamp from a current value of the local clock signal to generate the local latency value.

5. The output system of claim 1, wherein a first output device is a first earphone and a second output device is a second earphone.

6. The output system of claim 5, wherein the source device, the first earphone, and the second earphone are configured to form a piconet having the source device as a master device, the first earphone as a first slave device, and a the second earphone as a second slave device.

7. The output system of claim 3, wherein the output element is a speaker, and wherein the output signal is an audio stream.

8. The output system of claim 1, wherein a first output device is a display device, and wherein the output signal is a video image stream.

9. The output system of claim 1, wherein the RF communication module is configured to receive communication signals configured according to a BLUETOOTH protocol, wherein the source clock signal is a master BLUETOOTH clock.

10. The output system of claim 1, wherein the local clock signal generator is configured to synchronize the local clock signal with the source clock signal upon receipt of a synchronization packet by the RF communication module from the source device.

11. The output system of claim 4, wherein the at least one delay includes a current delay time for data to be processed by the codec.

12. The output system of claim 4, wherein the at least one delay includes a current delay time for data to be buffered.

13. The output system of claim 1, wherein each output device of the plurality of output devices further includes:

an output element that receives the decoded data and generates a digital output signal.

14. The output system of claim 13, wherein a first output device is a first video display and a second output device is a second video display.

15. The output system of claim 14, wherein the source device, the first video display, and the second video display are configured to form a piconet having the source device as a master device, the first video display as a first slave device, and a the second video display as a second slave device.

16. The output system of claim 13, wherein the output device is a display device, and wherein the output signal is a digital video image stream.

17. A source device, comprising;

a source clock generator;

a radio frequency (RF) communication module configured to generate a plurality of communication packets that each include data of a data stream and a respective timestamp generated by the source clock generator, wherein each communication packet of the plurality of communication packets is configured to be received by a designated output device of a plurality of output devices; and

an antenna configured to transmit the plurality of communication packets;

wherein each output device of the plurality of output devices receives a designated portion of the transmitted communication packets, whereby the output devices generate substantially synchronized output streams.

18. The source device of claim 17, wherein the RF communications module is further configured to generate a plurality of synchronization packets configured to synchronize local clock generators of the output devices with the source clock generator.

19. The source device of claim 18, wherein the RF communication module is configured to transmit communication signals configured according to a BLUETOOTH protocol, wherein the source clock generator is a BLUETOOTH master piconet clock generator, and wherein the local clock generators are BLUETOOTH slave piconet clock generators.

20. The source device of claim 17, wherein the data stream is a stream of audio data or video data.

21. A method for synchronizing data output by a plurality of output devices, comprising:

performing steps (a)-(f) in each output device of the plurality of output devices to produce substantially synchronized output streams,

(a) receiving a communication packet from a source device, wherein the communication packet includes data and a source clock timestamp;

(b) generating a local clock signal synchronized with a source clock signal of the source device;

(c) decoding the data using a codec;

(d) subtracting at least one delay and the source clock timestamp from a current value of the local clock signal to generate a local latency value;

(e) determining a difference between a desired latency value and the local latency value; and

(f) adjusting a rate of a clock signal of the codec according to the determined difference.

22. The method of claim 21, further comprising performing steps (g) and (h) in each output device:

(g) converting the decoded data to an analog signal according to a codec clock signal; and

(h) generating an output signal from the analog signal.

23. The method of claim 21, wherein a first output device is a first earphone and a second output device is a second earphone, the method further comprising:

(g) forming a piconet having the source device as a master device, the first earphone as a first slave device, and the second earphone as a second slave device.

24. The method of claim 22, wherein each output device includes a speaker, wherein step (h) comprises:

generating an audio stream from the speaker.

25. The method of claim 21, wherein a first output device is a first display device and a second output device is a second display device, the method further comprising:

(g) forming a piconet having the source device as a master device, the first display device as a first slave device, and the second display device as a second slave device.

26. The method of claim 21, wherein a first output device is a display device, wherein said generating an output signal comprises:

generating a video image stream by the display device.

27. The method of claim 21, wherein said receiving comprises:

receiving the communication packet according to a BLUETOOTH protocol.

28. The method of claim 21, further comprising performing steps (g) and (h) in each output device:

(g) receiving a synchronization packet from the source device that provides information regarding the source clock signal; and

(h) synchronizing the local clock signal with the source clock signal according to the provided information.

29. A method in a source device for synchronizing output devices, comprising;

generating a plurality of communication packets that each include data of a data stream and a respective timestamp generated by a source clock generator, wherein each communication packet of the plurality of communication packets is configured to be received by a designated output device of a plurality of output devices; and

transmitting the plurality of communication packets;

wherein each output device of the plurality of output devices receives a designated portion of the transmitted communication packets, whereby the output devices generate substantially synchronized output streams.

30. The method of claim 29, further comprising:

prior to said transmitting the plurality of communication packets,

generating a plurality of synchronization packets configured to synchronize local clock generators of the output devices with the source clock generator, and

transmitting the plurality of synchronization packets.

31. The method of claim 29, wherein said generating a plurality of communication packets comprises:

configuring the plurality of communication packets according to a BLUETOOTH protocol.