Using a plurality of buffers to provide audio for synchronized playback to multiple audio devices having separate device clocks

• US 8,904,066 B2
• Filed: 05/22/2012
• Issued: 12/02/2014
• Est. Priority Date: 06/25/2004
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Moore, Jeffrey C., Stewart, William G., Lengeling, Gerhard
• Primary Examiner(s): PEYTON, TAMMARA R
• Application Number:
  US13/477,681
• Publication Number:
  US 20120232682A1
• Time in Patent Office: 924 Days
• Field of Search: 710 8- 10, 710 52- 54, 700/94, 348/400, 348/500, 381/94.4
• US Class Current: 710/52
• 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

According to one embodiment, a media system communicates with an aggregate device that includes multiple media output devices. When providing media data for presentation, the system adjusts for device clock drift by resampling the media data provided to a media output device based at least in part on a device clock rate difference between a device clock of one of the media output devices and a device clock of another of the media output devices.

Claims

1. A method for providing audio data to multiple audio output devices, the method comprising:

writing audio data into a plurality of buffers associated with a plurality of audio output devices, the plurality of audio output devices having separate device clocks;

determining a difference between a device clock rate of a first audio output device of the plurality of audio output devices and a device clock rate of a second audio output device of the plurality of audio output devices;

resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference;

wherein the method is performed by a computing device.

2. The method of claim 1, wherein the plurality of buffers comprise a ring buffer.

3. The method of claim 1, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises reducing audio data for a segment of audio.

4. The method of claim 1, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises increasing audio data for a segment of audio.

5. The method of claim 1, wherein determining the difference between the device clock rate of the first audio output device and the device clock rate of the second audio output device is based on a first timestamp information generated by the first audio output device and a second timestamp information generated by the second audio output device.

6. The method of claim 5, wherein the first timestamp information includes a clock time of the device clock of the first audio output device and an indication of which audio samples have been processed by the first audio output device.

7. A system comprising:

one or more processors;

a plurality of buffers corresponding to a plurality of audio devices, the plurality of audio devices having separate device clocks; and

a system-side handling input/output unit configured to;

write audio data into the plurality of buffers, determine a difference between a device clock rate of a first audio device of the plurality of audio devices and a device clock rate of a second audio device of the plurality of audio devices, and resample audio data to be written into a buffer of the plurality of buffers based at least in part on said difference.

8. The system of claim 7, wherein the plurality of buffers comprise a ring buffer.

9. The system of claim 7, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises reducing audio data for a segment of audio.

10. The system of claim 7, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises increasing audio data for a segment of audio.

11. The system of claim 7, wherein determining the difference between the device clock rate of the first audio output device and the device clock rate of the second audio output device is based on a first timestamp information generated by the first audio output device and a second timestamp information generated by the second audio output device.

12. The system of claim 11, wherein the first timestamp information includes a clock time of the device clock of the first audio output device and an indication of which audio samples have been processed by the first audio output device.

13. One or more non-transitory computer-readable media storing instructions which, when executed by one or more processors, cause performance of operations including:

writing audio data into a plurality of buffers associated with a plurality of audio output devices, the plurality of audio output devices having separate device clocks;

determining a difference between a device clock rate of a first audio output device of the plurality of audio output devices and a device clock rate of a second audio output device of the plurality of audio output devices;

resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference.

14. The non-transitory computer-readable media of claim 13, wherein the plurality of buffers comprise a ring buffer.

15. The non-transitory computer-readable media of claim 13, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises reducing audio data for a segment of audio.

16. The non-transitory computer-readable media of claim 13, wherein resampling audio data to be written into a buffer of the plurality of buffers based at least in part on said difference comprises increasing audio data for a segment of audio.

17. The non-transitory computer-readable media of claim 13, wherein determining the difference between the device clock rate of the first audio output device and the device clock rate of the second audio output device is based on a first timestamp information generated by the first audio output device and a second timestamp information generated by the second audio output device.

18. The non-transitory computer-readable media of claim 17, wherein the first timestamp information includes a clock time of the device clock of the first audio output device and an indication of which audio samples have been processed by the first audio output device.