Time synchronization of multiple time-based data streams with independent clocks

• US 8,694,670 B2
• Filed: 10/12/2012
• Issued: 04/08/2014
• Est. Priority Date: 01/08/2007
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Batson, James D., Bushell, John S., Chapman, Gregory R., Flick, Christopher L.
• Primary Examiner(s): Doan, Duyen
• Application Number:
  US13/651,175
• Publication Number:
  US 20130117597A1
• Time in Patent Office: 543 Days
• Field of Search: 709/231, 709/248, 713502-503, 713/601
• US Class Current: 709/231
• CPC Class Codes: G06F 1/12 Synchronisation of different clock signals provided by a plurality of clock generators
• CPC Class Codes: H04N 21/2368 Multiplexing of audio and video streams
• CPC Class Codes: H04N 21/4341 Demultiplexing of audio and video streams
• CPC Class Codes: H04N 21/8547 involving timestamps for synchronizing content

Abstract

Techniques are described for synchronizing multiple time-based data streams with independent clocks wherein relationships between clock rates of timing devices associated with the time-based data streams are determined, and based on these relationships, times in at least one of the time-based data streams may be translated to times in any of the other time-based data streams despite the data streams having independent clocks.

Claims

1. An apparatus for playing multi-media data, comprising:

a first multi-media data rendering timing device;

a second multi-media data rendering timing device;

a reference timing device; and

a processor that determines a first relationship between a clock rate of the first multi-media data rendering timing device and a clock rate of the reference timing device,

wherein the processor determines a second relationship between a clock rate of the second multi-media data rendering timing device and the clock rate of the same reference timing device,

wherein, based at least partially upon the first relationship and the second relationship, the processor determines a timing relationship between (a) a first time base that is based on the first multi-media data rendering timing device and (b) a second time base that is based on the second multi-media data rendering timing device,

wherein the apparatus plays multi-media data based upon the determined timing relationship, and

wherein the first multi-media data rendering timing device and the second multi-media data rendering timing device are separate timing devices having clock rates that are independent of and different from each other.

2. The apparatus of claim 1, wherein the multi-media data comprise a plurality of multi-media data streams.

3. The apparatus of claim 1, wherein the multi-media data comprises at least one of video data, audio data, and closed captioning data.

4. The apparatus of claim 1, wherein the apparatus is a movie playing device.

5. The apparatus of claim 1, wherein each of the first multi-media data rendering timing device, the second multi-media data rendering timing device, and the reference timing device comprises:

timing information generated based upon one of;

video timing, Musical Instrument Digital Interface (MIDI) sequencer timing information, Society of Motion Picture and Television Engineers (SMPTE) time code, timing information delivered via radio signals, and atomic clock timing information.

6. The apparatus of claim 1, further comprising a communication interface that receives the multi-media data.

7. The apparatus of claim 6, wherein the communication interface comprises at least one of a local area network (LAN) interface, an Integrated Services Digital Network (ISDN) interface, a telephone modem, an optical link, and a wireless link.

8. A method of playing multi-media data in an apparatus, comprising:

determining, by a processor, a first relationship between a clock rate of a first multi- media data rendering timing device in the apparatus and a clock rate of a reference timing device in the apparatus,

wherein the processor determines a second relationship between a clock rate of a second multi-media data rendering timing device in the apparatus and the clock rate of the same reference timing device in the apparatus,

wherein, based at least partially upon the first relationship and the second relationship, the processor determines a timing relationship between (a) a first time base that is based on the first multi-media data rendering timing device and (b) a second time base that is based on the second multi-media data rendering timing device,

wherein the apparatus plays multi-media data based upon the determined timing relationship, and

wherein the first multi-media data rendering timing device and the second multi-media data rendering timing device are separate timing devices having clock rates that are independent of and different from each other.

9. The method of claim 8, wherein the multi-media data comprise a plurality of multi-media data streams.

10. The method of claim 8, wherein the multi-media data comprises at least one of video data, audio data, and closed captioning data.

11. The method of claim 8, wherein the apparatus is a movie playing device.

12. The method of claim 8, wherein each of the first multi-media data rendering timing device, the second multi-media data rendering timing device, and the reference timing device comprises:

timing information generated based upon one of;

video timing, Musical Instrument Digital Interface (MIDI) sequencer timing information, Society of Motion Picture and Television Engineers (SMPTE) time code, timing information delivered via radio signals, and atomic clock timing information.

13. The method of claim 8, further comprising a communication interface that receives the multi-media data.

14. The method of claim 13, wherein the communication interface comprises at least one of a local area network (LAN) interface, an Integrated Services Digital Network (ISDN) interface, a telephone modem, an optical link, and a wireless link.

15. A non-transitory computer readable medium storing program codes executable by a process to play multi-media data in an apparatus by performing:

determining, by the processor, a first relationship between a clock rate of a first multi-media data rendering timing device in the apparatus and a clock rate of a reference timing device in the apparatus,

wherein the processor determines a second relationship between a clock rate of a second multi-media data rendering timing device in the apparatus and the clock rate of the same reference timing device in the apparatus,

wherein, based at least partially upon the first relationship and the second relationship, the processor determines a timing relationship between (a) a first time base that is based on the first multi-media data rendering timing device and (b) a second time base that is based on the second multi-media data rendering timing device,

wherein the apparatus plays multi-media data based upon the determined timing relationship, and

wherein the first multi-media data rendering timing device and the second multi-media data rendering timing device are separate timing devices having clock rates that are independent of and different from each other.

16. The non-transitory computer readable medium of claim 15, wherein the multi-media data comprise a plurality of multi-media data streams.

17. The non-transitory computer readable medium of claim 15, wherein the multi-media data comprises at least one of video data, audio data, and closed captioning data.

18. The non-transitory computer readable medium of claim 15, wherein the apparatus is a movie playing device.

19. The non-transitory computer readable medium of claim 15, wherein each of the first multi-media data rendering timing device, the second multi-media data rendering timing device, and the reference timing device comprises:

timing information generated based upon one of;

video timing, Musical Instrument Digital Interface (MIDI) sequencer timing information, Society of Motion Picture and Television Engineers (SMPTE) time code, timing information delivered via radio signals, and atomic clock timing information.

20. The non-transitory computer readable medium of claim 15, further comprising a communication interface that receives the multi-media data, wherein the communication interface comprises at least one of a local area network (LAN) interface, an Integrated Services Digital Network (ISDN) interface, a telephone modem, an optical link, and a wireless link.