Providing synchronized audio to multiple devices

• US 20050288805A1
• Filed: 06/25/2004
• Published: 12/29/2005
• Est. Priority Date: 06/25/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Stewart, William G., Moore, Jeffrey C., Lengeling, Gerhard H.
• Granted Patent: US 7,631,119 B2
• Time in Patent Office: Days
• US Class Current: 700/94
• CPC Class Codes: G06F 3/00 Input arrangements for transferring data to be processed into a form capable of being handled by the computer; Output arrangements for transferring data from processing unit to output unit, e.g. interface arrangements
• 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: G11B 20/10527 Audio or video recording; Data buffering arrangements G11B20/12 - G11B20/18 take precedence
• CPC Class Codes: H04L 67/10 in which an application is distributed across nodes in the network software deployment G06F8/60; multiprogramming arrangements G06F9/46
• 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: H04N 21/4143 embedded in a Personal Computer [PC]
• 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 21/44004 involving video buffer management, e.g. video decoder buffer or video display buffer
• CPC Class Codes: H04N 21/8106 involving special audio data, e.g. different tracks for different languages

Abstract

An audio system communicates with an aggregate device that includes multiple audio devices. When providing audio data for playback, the system compensates for presentation latency differences between the various audio devices. In addition, the system adjusts for device clock drift by selecting a master device and resampling the audio data provided to the other devices based on the difference between the device clock of the master device and the device clocks of the other devices.

Claims

1. A method of handling to-be-communicated information, the method comprising:

placing audio data into each of a plurality of buffers for synchronized consumption by a plurality of audio devices;

wherein each device of the plurality of devices consumes to-be-communicated information from a corresponding buffer of the plurality of buffers; and

determining where to place to-be-communicated information within a particular buffer of the plurality of buffers based, at least in part, on presentation latency of a device that corresponds to a different buffer of the plurality of buffers.

49. The method of claim 1 wherein the to-be-communicated information is audio data.

53. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 1.

2. The method of claim 2 further comprising:

allocating the plurality of ring buffers for the plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

the first device currently reading to-be-communicated information from a first current position in the first ring buffer;

the second device currently reading to-be-communicated information from a second current position in the second ring buffer; and

wherein writing the to-be-communicated information includes selecting how far ahead of the first current position to write to-be-communicated information in the first ring buffer based, at least in part, on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

3. The method of claim 2 further comprising:

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first ring buffer; and

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second ring buffer.

4. The method of claim 2 wherein selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer includes:

receiving first latency information from said first device; and

receiving second latency information from said second device.

5. The method of claim 2, further comprising:

receiving first safety offset information from said first device, wherein said first safety offset information identifies a minimum amount ahead of said first current position to write to-be-communicated information in said first ring buffer; and

,

receiving second safety offset information from said second device, wherein said second safety offset information identifies a minimum amount ahead of said second current position to write to-be-communicated information in said second ring buffer

based on said first safety offset information and said second safety offset information, selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer based on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

6. A computer-readable medium comprising one or more sequences of instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

allocating a plurality of ring buffers for a plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

the first device currently reading to-be-communicated information from a first current position in the first ring buffer;

the second device currently reading to-be-communicated information from a second current position in the second ring buffer; and

wherein writing the to-be-communicated information includes selecting how far ahead of the first current position to write to-be-communicated information in the first ring buffer based, at least in part, on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

7. The computer readable medium of claim 6 further comprising instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first ring buffer; and

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second ring buffer.

8. The computer readable medium of claim 6 wherein selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer includes:

receiving first latency information from said first device; and

receiving second latency information from said second device.

9. The computer readable medium of claim 6, further comprising instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

receiving first safety offset information from said first device, wherein said first safety offset information identifies a minimum amount ahead of said first current position to write to-be-communicated information in said first ring buffer;

receiving second safety offset information from said second device, wherein said second safety offset information identifies a minimum amount ahead of said second current position to write to-be-communicated information in said second ring buffer; and

,

based on said first safety offset information and said second safety offset information, selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer based on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

10. A computer apparatus comprising:

a memory; and

one or more processors coupled to the memory and configured to execute one or more sequence of instructions for providing to-be-communicated information to multiple devices, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of;

allocating a plurality of ring buffers for a plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

the first device currently reading to-be-communicated information from a first current position in the first ring buffer;

the second device currently reading to-be-communicated information from a second current position in the second ring buffer; and

wherein writing the to-be-communicated information includes selecting how far ahead of the first current position to write to-be-communicated information in the first ring buffer based, at least in part, on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

11. The computer apparatus of claim 10 further comprising the steps of:

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first ring buffer; and

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second ring buffer.

12. The computer apparatus of claim 10 wherein selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer includes:

receiving first latency information from said first device;

receiving second latency information from said second device;

13. The computer apparatus of claim 10, further comprising instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

receiving first safety offset information from said first device, wherein said first safety offset information identifies a minimum amount ahead of said first current position to write to-be-communicated information in said first ring buffer;

receiving second safety offset information from said second device, wherein said second safety offset information identifies a minimum amount ahead of said second current position to write to-be-communicated information in said second ring buffer; and

,

based on said first safety offset information and said second safety offset information, selecting how far ahead of said first current position to write to-be-communicated information in said first ring buffer based on latency between when the second device reads data from the second ring buffer and when the second device plays the to-be-communicated information.

14. A method of handling audio data, the method comprising:

placing to-be-communicated information into each of a plurality of buffers for synchronized consumption by a plurality of audio devices;

wherein each to-be-communicated information device of the plurality of devices consumes to-be-communicated information from a corresponding buffer of the plurality of buffers; and

resampling the to-be-communicated information placed into a particular buffer of the plurality of buffers based, at least in part, on device clock rate difference between the audio device that corresponds to the buffer and one or device clock rates of one or more other devices of the plurality of devices.

15. The method of claim 14, further comprising:

allocating the plurality of ring buffers for the plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

the first device currently reading to-be-communicated information from a first current position in the first ring buffer;

the second device currently reading to-be-communicated information from a second current position in the second ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

determining a timing difference between the first device and the second device based, at least in part, on the first timestamp information and the second timestamp information; and

resampling the to-be-communicated information to be written to the second ring buffer based on the timing difference.

16. The method of claim 15, further comprising:

selecting one of said first and second devices as a master device based, at least in part, on latency information received from said first and second devices

determining a timing difference between said master device and any device of said plurality of devices

wherein resampling the to-be-communicated information to be written to any buffer of said plurality of buffers for a plurality of devices is based on said timing difference.

17. The method of claim 15, wherein resampling the to-be-communicated information to be written to said second ring buffer based on said timing difference further comprises increasing the rate at which to-be-communicated information is written to said second ring buffer.

18. The method of claim 15, wherein resampling the to-be-communicated information to be written to said second ring buffer based on said timing difference further comprises decreasing the rate at which to-be-communicated information is written to said second ring buffer.

50. The method of claim 14 wherein the to-be-communicated information is audio data.

54. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 14.

19. A computer-readable medium comprising one or more sequences of instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

allocating a plurality of ring buffers for a plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

the first device currently reading to-be-communicated information from a first current position in the first ring buffer;

the second device currently reading to-be-communicated information from a second current position in the second ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

determining a timing difference between the first device and the second device based, at least in part, on the first timestamp information and the second timestamp information; and

resampling the to-be-communicated information to be written to the second ring buffer based on the timing difference.

20. The computer readable medium of claim 19, further comprising:

selecting one of said first and second devices as a master device based, at least in part, on latency information received from said first and second devices;

determining a timing difference between said master device and any device of said plurality of devices; and

,

wherein resampling the to-be-communicated information to be written to any buffer of said plurality of buffers for a plurality of devices is based on said timing difference.

21. The computer readable medium of claim 19, wherein resampling the to-be-communicated information to be written to said second ring buffer based on said timing difference further comprises increasing the rate at which to-be-communicated information is written to said second ring buffer.

22. The computer readable medium of claim 19, wherein resampling the to-be-communicated information to be written to said second ring buffer based on said timing difference further comprises decreasing the rate at which to-be-communicated information is written to said second ring buffer.

23. A method of handling to-be-communicated information, the method comprising:

using a single thread of execution to place to-be-communicated information into each of a plurality of ring buffers for synchronized consumption by a plurality of devices; and

wherein each device of the plurality of devices consumes to-be-communicated information from a corresponding buffer of the plurality of buffer.

24. The method of claim 23 further comprising:

allocating the plurality of ring buffers for the plurality of to-be-communicated information, including a first ring buffer for a first device and a second ring buffer for a second device;

within a single thread of execution, writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

within the single thread of execution, determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

within the single thread of execution, determining where to insert to-be-communicated information into the second ring buffer based on the second timestamp information.

25. The method of claim 24 wherein:

the single thread of execution is executing in a computer system that has a CPU clock;

the step of storing first timestamp information includes storing data that indicates;

(a) current time of the CPU clock; and

(b) which samples of to-be-communicated information have been read by the first device.

26. The method of claim 24 wherein:

the step of determining where to insert to-be-communicated information into the first ring buffer includes;

based on the first timestamp information, estimating a first rate at which the first device consumes to-be-communicated information from the first ring buffer;

estimating a current position of the first device based on the first rate, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the first ring buffer based on the current position of the first device; and

the step of determining where to insert to-be-communicated information into the second ring buffer includes;

based on the second timestamp information, estimating a second rate at which the second device consumes to-be-communicated information from the second ring buffer;

estimating a current position of the second device based on the second rate, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the second ring buffer based on the current position of the second device.

27. The method of claim 24 wherein:

the single thread of execution is one of a plurality of threads of execution that are writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers; and

each thread of the plurality of threads of execution performs the steps of;

determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

determining where to insert to-be-communicated information into the second ring buffer based on the second timestamp information.

28. The method of claim 24 wherein:

the plurality of ring buffers into which the single thread of execution is writing to-be-communicated information does not include a third ring buffer associated with a third device; and

concurrent with the single thread of execution writing to-be-communicated information into each of the plurality of ring buffers, a second thread of execution is writing to-be-communicated information, for synchronized playback, into the third ring buffer and at least one of the plurality of ring buffers.

29. The method of claim 24 further comprising:

estimating a current position of the first device based on said first timestamp information, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the first device to write to-be-communicated information in said first ring buffer; and

,

estimating a current position of the second device based on said second timestamp information, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the second device to write to-be-communicated information in said second ring buffer.

37. The method of claim 24 wherein:

the single thread of execution is executing in a computer system that has a CPU clock;

the step of storing first timestamp information includes storing data that indicates;

(a) current time of the CPU clock; and

(b) which samples of to-be-communicated information have been read by the first device.

38. The method of claim 24 wherein:

the step of determining where to insert to-be-communicated information into the first ring buffer includes;

based on the first timestamp information, estimating a first rate at which the first device consumes to-be-communicated information from the first ring buffer;

estimating a current position of the first device based on the first rate, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the first ring buffer based on the current position of the first device; and

the step of determining where to insert to-be-communicated information into the second ring buffer includes;

based on the second timestamp information, estimating a second rate at which the second device consumes to-be-communicated information from the second ring buffer;

estimating a current position of the second device based on the second rate, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the second ring buffer based on the current position of the second device.

39. The method of claim 24 wherein:

the single thread of execution is one of a plurality of threads of execution that are writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers; and

each thread of the plurality of threads of execution performs the steps of;

determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

determining where to insert to-be-communicated information into the second ring buffer based on the second timestamp information.

40. The method of claim 24 wherein:

the plurality of ring buffers into which the single thread of execution is writing to-be-communicated information does not include a third ring buffer associated with a third device; and

concurrent with the single thread of execution writing to-be-communicated information into each of the plurality of ring buffers, a second thread of execution is writing to-be-communicated information, for synchronized playback, into the third ring buffer and at least one of the plurality of ring buffers.

41. The method of claim 24 further comprising:

estimating a current position of the first device based on said first timestamp information, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the first device to write to-be-communicated information in said first ring buffer; and

,

estimating a current position of the second device based on said second timestamp information, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the second device to write to-be-communicated information in said second ring buffer.

51. The method of claim 23 wherein the to-be-communicated information is audio data.

55. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 23.

30. A computer-readable medium comprising one or more sequences of instructions for providing to-be-communicated information to multiple devices, which instructions, when executed by one or more processors, cause the one or more processors to carry out the steps of:

allocating a plurality of ring buffers for a plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

within a single thread of execution, writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

within the single thread of execution, determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

within the single thread of execution, determining where to insert to-be-communicated information into the second ring buffer based on the second timestamp information.

31. The computer readable medium of claim 30 wherein:

the single thread of execution is executing in a computer system that has a CPU clock;

the step of storing first timestamp information includes storing data that indicates;

(a) current time of the CPU clock; and

(b) which samples of to-be-communicated information have been read by the first device.

32. The computer readable medium of claim 30 wherein:

the step of determining where to insert to-be-communicated information into the first ring buffer includes;

based on the first timestamp information, estimating a first rate at which the first device consumes to-be-communicated information from the first ring buffer;

estimating a current position of the first device based on the first rate, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the first ring buffer based on the current position of the first device; and

the step of determining where to insert to-be-communicated information into the second ring buffer includes;

based on the second timestamp information, estimating a second rate at which the second device consumes to-be-communicated information from the second ring buffer;

estimating a current position of the second device based on the second rate, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

determining where to insert to-be-communicated information into the second ring buffer based on the current position of the second device.

33. The computer readable medium of claim 30 wherein:

the single thread of execution is one of a plurality of threads of execution that are writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers; and

each thread of the plurality of threads of execution performs the steps of;

determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

determining where to insert audio data into the second ring buffer based on the second timestamp information.

34. The computer readable medium of claim 30 wherein:

the plurality of ring buffers into which the single thread of execution is writing to-be-communicated information does not include a third ring buffer associated with a third device; and

concurrent with the single thread of execution writing to-be-communicated information into each of the plurality of ring buffers, a second thread of execution is writing to-be-communicated information, for synchronized playback, into the third ring buffer and at least one of the plurality of ring buffers.

35. The computer readable medium of claim 30 further comprising:

estimating a current position of the first device based on said first timestamp information, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the first device to write to-be-communicated information in said first ring buffer; and

,

estimating a current position of the second device based on said second timestamp information, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

,

within said single thread of execution, identifying a minimum amount ahead of said current position of the second device to write to-be-communicated information in said second ring buffer.

36. A computer apparatus comprising:

a memory; and

one or more processors coupled to the memory and configured to execute one or more sequence of instructions for providing to-be-communicated information to multiple devices, wherein execution of the one or more sequences of instructions by one or more processors causes the one or more processors to perform the steps of;

allocating a plurality of ring buffers for a plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

within a single thread of execution, writing to-be-communicated information, for synchronized playback on each of the plurality of devices, into each of the plurality of ring buffers;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, the corresponding device performing a wrap-around operation to continue reading the to-be-communicated information beginning at the start of the ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

within the single thread of execution, determining where to insert to-be-communicated information into the first ring buffer based on the first timestamp information; and

within the single thread of execution, determining where to insert to-be-communicated information into the second ring buffer based on the second timestamp information.

42. A method of handling to-be-communicated information, the method comprising:

within a single thread of execution receiving to-be-communicated information from each of a plurality of buffers for synchronized production by a plurality of audio devices; and

wherein each audio device of the plurality of audio devices stores to-be-communicated information into a corresponding buffer of the plurality of buffers.

43. The method of claim 42, further comprising:

allocating the plurality of ring buffers for the plurality of devices, including a first ring buffer for a first device and a second ring buffer for a second device;

within the single thread of execution, reading to-be-communicated information, for synchronized receipt from each of the plurality of devices, from each of the plurality of ring buffers;

upon reaching the end of any ring buffer while reading to-be-communicated information from the ring buffer, performing a wrap-around operation to continue reading the audio data beginning at the start of the ring buffer;

upon reaching the end of any ring buffer while writing to-be-communicated information to the ring buffer, the corresponding device performing a wrap-around operation to continue writing the to-be-communicated information beginning at the start of the ring buffer;

storing first timestamp information when the first device performs a wrap-around operation while reading to-be-communicated information from the first buffer;

storing second timestamp information when the second device performs a wrap-around operation while reading to-be-communicated information from the second buffer;

within the single thread of execution, determining where to read to-be-communicated information from the first ring buffer based on the first timestamp information; and

within the single thread of execution, determining where to read to-be-communicated information from the second ring buffer based on the second timestamp information.

44. The method of claim 43 wherein:

the single thread of execution is executing in a computer system that has a CPU clock;

the step of storing first timestamp information includes storing data that indicates;

(a) current time of the CPU clock; and

(b) which samples of to-be-communicated information have been read by the first device.

45. The method of claim 43 wherein:

the step of determining where to read to-be-communicated information from the first ring buffer includes;

based on the first timestamp information, estimating a first rate at which the first device writes to-be-communicated information from the first ring buffer;

estimating a current position of the first device based on the first rate, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently writing to-be-communicated information; and

determining where to insert to-be-communicated information into the first ring buffer based on the current position of the first device; and

the step of determining where to read to-be-communicated information from the second ring buffer includes;

based on the second timestamp information, estimating a second rate at which the second device writes to-be-communicated information from the second ring buffer;

estimating a current position of the second device based on the second rate, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently writing to-be-communicated information; and

determining where to read to-be-communicated information from the second ring buffer based on the current position of the second device.

46. The method of claim 43 wherein:

the single thread of execution is one of a plurality of threads of execution that are reading to-be-communicated information, for synchronized playback on each of the plurality of devices, from each of the plurality of ring buffers; and

each thread of the plurality of threads of execution performs the steps of;

determining where to read to-be-communicated information from the first ring buffer based on the first timestamp information; and

determining where to read to-be-communicated information from the second ring buffer based on the second timestamp information.

47. The method of claim 43 wherein:

the plurality of ring buffers into which the single thread of execution is reading to-be-communicated information from does not include a third ring buffer associated with a third device; and

concurrent with the single thread of execution reading to-be-communicated information from each of the plurality of ring buffers, a second thread of execution is reading to-be-communicated information, for synchronized playback, into the third ring buffer and at least one of the plurality of ring buffers.

48. The method of claim 43 further comprising:

estimating a current position of the first device based on said first timestamp information, wherein the current position of the first device is a position within the first ring buffer from which the first device is currently reading to-be-communicated information; and

within said single thread of execution, identifying a minimum amount ahead of said current position of the first device to read to-be-communicated information from said first ring buffer;

estimating a current position of the second device based on said second timestamp information, wherein the current position of the second device is a position within the second ring buffer from which the second device is currently reading to-be-communicated information; and

within said single thread of execution, identifying a minimum amount ahead of said current position of the second device to read to-be-communicated information from said second ring buffer.

52. The method of claim 42 wherein the to-be-communicated information is audio data.

56. A computer-readable medium carrying one or more sequences of instructions which, when executed by one or more processors, causes the one or more processors to perform the method recited in claim 42.