Encoded Audio Synchronization

• US 20170098466A1
• Filed: 10/02/2015
• Published: 04/06/2017
• Est. Priority Date: 10/02/2015
• Status: Active Grant

• Current Assignee: Bose Corporation
• Original Assignee: Bose Corporation
• Inventors: Elliot, Michael W., Banerjee, Debasmit, Sundaresan, Rameshwar
• Granted Patent: US 10,454,604 B2
• Time in Patent Office: Days
• CPC Class Codes: H04J 3/0641 Change of the master or reference, e.g. take-over or failure of the master
• CPC Class Codes: H04J 3/0661 using timestamps
• 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

Abstract

A method of synchronizing playback of audio over a plurality of wireless speaker packages that are each adapted to play audio, where the audio comprises a plurality of frames of encoded audio data. The method includes determining an offset time of a frame of encoded audio data, where the offset time corresponds to the time when the frame playback is to begin, and inserting the determined offset time into the frame of encoded audio data.

Claims

1. A method of synchronizing playback of audio over a plurality of wireless speaker packages that are each adapted to play audio, where the audio comprises a plurality of frames of encoded audio data, and wherein one of the plurality of wireless speaker packages is a master playback device that receives encoded audio data from an audio source and distributes the encoded audio data to the rest of the plurality of wireless speaker packages, which function as slave playback devices, the method comprising:

determining an offset time of a frame of encoded audio data, where the offset time corresponds to the time when the frame playback is to begin; and

inserting the determined offset time into the frame of encoded audio data.

2. The method of claim 1 wherein the offset times of a plurality of frames of encoded audio data is determined.

3. The method of claim 1 wherein each of the wireless speaker packages comprises an encoded data buffer that stores frames of encoded audio data.

4. The method of claim 3 wherein at least some of the frames stored in the encoded data buffer of the master playback device further comprise the inserted determined offset times of the respective frames.

5. The method of claim 4 wherein at least some of the frames stored in the encoded data buffer of the master playback device comprise frame headers, and the determined offset times of the respective frames are inserted into the frame headers.

6. The method of claim 4 wherein at least some of the frames that are stored in the encoded data buffer of the master playback device with the inserted determined offset times of the respective frames are distributed by the master playback device to the slave playback devices.

7. The method of claim 6 further comprising synchronizing the playback of audio among the master playback device and a synchronized slave playback device, and wherein after the synchronizing, the frames that are distributed by the master playback device to the synchronized slave playback device do not include frame offset times.

8. The method of claim 6 wherein each of the wireless speaker packages comprises a decoder that decodes encoded data that is stored in the encoded data buffer of the respective wireless speaker package, and a decoded data, buffer that stores frames of decoded audio data.

9. The method of claim 8 wherein the decoded data buffers of each of the wireless speaker packages store offset times along with the frames of decoded audio data.

10. The method of claim 8 wherein the decoder of the master playback device determines the offset time for each frame of encoded audio data stored in the encoded data buffer of the master playback device.

11. The method of claim 10 wherein the decoder of the master playback device further determines information about the content of decoded audio samples in each frame of encoded audio data stored in the encoded data buffer of the master playback device.

12. The method of claim 11 wherein the determined information about the content of decoded audio samples is stored in the master encoded data buffer along with each respective frame, before the frames are distributed to the slave playback devices.

13. The method of claim 12 wherein the slave playback devices also determine the same information about the content of decoded audio samples in frames of encoded audio data they receive from the master playback device.

14. The method of claim 13 wherein a slave playback device synchronizes playback of audio with a master playback device based at least in part on a match between the information determined by the master about the content of decoded audio samples in a frame that was stored in the master encoded data buffer along with the respective frame, and the same information about the content of decoded audio samples in the same frame as determined by the slave playback device.

15. The method of claim 14 wherein the master playback device determines and provides to at least one slave playback device a play at time for audio received from an audio source, where the offset time defines the time when a frame begins playback after the play at time, and wherein the master playback device and the slave playback device have clocks that are both synchronized to a common reference clock, and wherein the slave playback device synchronizes playback of audio with the master playback device beginning by playing a first frame when the play at time plus the offset for that first frame equals the current synchronized clock time.

16. The method of claim 8 wherein at least one of the slave devices uses the offset time that it determines for its playback of the corresponding frame, and the master device uses the offset time as determined by the master device for its playback of the corresponding audio frame.

17. A method of synchronizing playback of audio over a master wireless speaker package and a slave wireless speaker package that are each adapted to play audio, where the audio comprises a plurality of frames of encoded audio data, where the master wireless speaker package plays frames of decoded audio data that each comprise a frame header that includes information about the content of decoded audio samples in the frame, and where the slave wireless speaker package receives from the master wireless speaker package encoded frames that include in the frame header the information about the content of decoded audio samples that are present in the frame, the method comprising:

the slave wireless speaker package determining the information about the content of decoded audio samples in a frame that it received from the master wireless speaker package; and

the slave wireless speaker package beginning playback based at least in part on the slave wireless speaker package determining that the information it determined about the content of decoded audio samples in a frame that it received from the master wireless speaker package matches the information about the content of decoded audio samples in the header of the same frame.

18. The method of claim 17 wherein the master wireless speaker package determines and provides to at least one slave wireless speaker package a play at time for audio received from an audio source, where the offset time corresponds to the time when a frame begins playback after the play at time, and wherein the master wireless speaker package and the slave wireless speaker package have clocks that are both synchronized to a common reference clock, and wherein the slave wireless speaker package synchronizes playback of audio with the master wireless speaker package beginning by playing a first frame when the play at time plus the offset for that first frame equals the current synchronized clock time.

19. A wireless speaker package, comprising:

an electro-acoustic transducer;

a processor; and

memory comprising instructions which when executed by the processor cause the wireless speaker package to;

determine an offset time of a frame of encoded audio data, where the offset time corresponds to the time when the frame playback is to begin; and

insert the determined offset time into the frame of encoded audio data.

20. A method of synchronizing playback of audio over a plurality of wireless speaker packages that are each adapted to play audio, where the audio comprises a plurality of frames of encoded audio data, the method comprising:

synchronizing respective clocks on the plurality of wireless speaker packages;

obtaining the plurality of frames of encoded audio data at each of the plurality of wireless speaker packages; and

at each playback device,

decoding the plurality of frames of encoded audio data to provide a plurality of frames of decoded audio data;

determining a corresponding offset time for each of the plurality of frames of decoded audio data, wherein the offset time corresponds to the time when playback of the associated frame is to begin;

storing the decoded audio frames and the corresponding offset times in a decoded audio buffer; and

rendering the decoded audio data based on a play at time and the offset times, wherein the play at time represents a time to begin rendering a first frame of the decoded audio data.

21. The method of claim 20, wherein one of the plurality of wireless speaker packages is a master playback device that receives encoded audio data from an audio source, arranges the encoded audio data into a plurality of frames to obtain the plurality of frames of encoded audio data, and distributes the plurality of frames of encoded audio data to the rest of the plurality of wireless speaker packages, which function as slave playback devices.

22. The method of claim 21, wherein the master device also distributes the play at time to the slave playback devices.

23. The method of claim 21, wherein at least the master playback device updates respective headers of the plurality of frames of encoded audio to include corresponding ones of the offset times.

24. The method of claim 23, further comprising distributing one or more of the frames of encoded audio with the corresponding offset time to one or more additional slave playback devices to enable the one or more additional slave playback devices to synchronize playback of the audio with the master playback device after the master playback device has already begun rendering the decoded audio data.

25. The method of claim 21, wherein synchronizing respective clocks on the plurality of wireless speaker packages, comprises synchronizing the respective clocks to a common reference clock.