Methods and apparatus for synchronization of media playback within a wireless network

Patent metadata

Field	Value
Publication number	US-10645659-B2
Application number	US-201816140158-A
Country	US
Kind code	B2
Filing date	Sep 24, 2018
Priority date	Nov 19, 2014
Publication date	May 5, 2020
Grant date	May 5, 2020

Abstract

Methods and apparatus for synchronization of media playback within a wireless network. In one embodiment, the present disclosure is directed to precision synchronization over time, based on repeated measurements of a common time reference. In one exemplary embodiment, the common time reference is a Time Synchronization Function (TSF) of a Wireless Local Area Network (WLAN). In another exemplary embodiment of the present disclosure, the application processor and the modem processor measure a pulse width and the aforementioned common time reference in order to adjust media playback.

First claim

What is claimed is:

1. A non-transitory computer-readable apparatus comprising a storage medium, the storage medium comprising a computer program having a plurality of instructions configured to, when executed by a processor apparatus, cause a media device to:
determine a rate mismatch based on (i) a number of clock cycles of a first clock associated with the media device and (ii) a number of clock cycles of a second clock associated with the media device;
derive a parameter based on the determined rate mismatch, the derived parameter configured to modify a sample rate of one or more media samples; and
correct a rate of playback of the one or more media samples based on the determined rate mismatch and a dynamic adjustment of the derived parameter during the playback based on a condition associated with one or more of the first clock and the second clock.

2. The non-transitory computer-readable apparatus of claim 1 , wherein the first clock comprises a local clock associated with a first processor apparatus of the media device, and the second clock comprises a local clock associated with a second processor apparatus of the media device.

3. The non-transitory computer-readable apparatus of claim 2 , wherein the plurality of instructions are further configured to, when executed by the processor apparatus, exchange the number of clock cycles of the first clock associated with the media device with the second processor apparatus of the media device.

4. The non-transitory computer-readable apparatus of claim 1 , wherein the derived parameter is configured to be periodically adjusted during playback of the one or more media samples.

5. The non-transitory computer-readable apparatus of claim 1 , wherein the correction of the rate of playback of the one or more media samples comprises alignment of the one or more media samples to a network clock, the network clock being common to a plurality of media devices of a wireless network, the plurality of media devices comprising the media device and a second media device; and
wherein the plurality of instructions are further configured to, when executed by the processor apparatus, cause the media device to receive the one or more media samples from the second media device over the wireless network.

6. The non-transitory computer-readable apparatus of claim 5 , wherein the media device comprises an asynchronous sample rate converter configured to output one or more resampled media samples aligned to the network clock.

7. The non-transitory computer-readable apparatus of claim 6 , wherein the parameter comprises a rate scalar parameter that is based on a ratio of an input rate and an output rate of the one or more media samples;
wherein the input rate is correlated to a rate of the one or more media samples accepted into the asynchronous sample rate converter, and the output rate is correlated to a rate of the one or more media samples outputted from the asynchronous sample rate converter.

8. A wireless media device configured to receive media via a wireless network, the wireless media device comprising:
a first processor apparatus configured to process media;
a second processor apparatus configured to connect to the wireless network; and
a non-transitory computer-readable apparatus comprising a storage medium, the storage medium comprising a computer program having a plurality of instructions configured to, when executed by the first processor apparatus, cause the wireless media device to:
receive one or more media samples from the wireless network;
determine a rate scalar parameter based on an input rate and output rate associated with the one or more media samples; and
adjust a rate of playback of the one or more media samples based on the determined rate scalar parameter, wherein the rate scalar parameter is configured to be adjusted during playback of the one or more media samples.

9. The wireless media device of claim 8 , further comprising an asynchronous sample rate converter (ASRC), where the ASRC is configured to accept the one or more media samples at the input rate and output one or more resampled media samples at the output rate.

10. The wireless media device of claim 8 , wherein the adjustment of the rate of playback of the one or more media samples is further based on a comparison of an observed timeline based on observed events with an ideal timeline, the ideal timeline comprising a determined mathematical relationship between the observed events and a determined anchor point.

11. The wireless media device of claim 8 , wherein the rate scalar parameter is further configured to be adjusted periodically, the periodic adjustment enabling a dynamic adjustment of the input rate.

12. The wireless media device of claim 11 , wherein the periodic adjustment of the rate scalar parameter is based on bandwidth congestion of the wireless network.

13. The wireless media device of claim 8 , wherein the first processor apparatus comprises an application processor, and the second processor apparatus comprises a wireless modem.

14. The wireless media device of claim 8 , wherein the plurality of instructions are further configured to, when executed by the first processor apparatus, cause the wireless media device to generate a common event between the first processor apparatus and the second processor apparatus.

15. A method for interrupt driven time synchronization within a device, the method comprising:
generating a common event by a first processor apparatus;
observing the common event generated by the first processor apparatus by a second processor apparatus;
determining a rate mismatch based on the common event and respective clock cycles associated with the first processor apparatus and the second processor apparatus; and
based on the determined rate mismatch, resampling one or more media samples received by the second processor apparatus during playback of the one or more media samples, the resampling of the one or more media samples comprising applying a rate scalar parameter to the one or more media samples to adjust a rate of playback of the one or more media samples during the playback of the one or more media samples.

16. The method of claim 15 , further comprising receiving the one or more media samples from a wireless network.

17. The method of claim 16 , wherein the observing of the common event comprises observing a pulse width generated by the first processor apparatus setting a latch, and observing the second processor apparatus resetting the latch in response.

18. The method of claim 15 , further comprising:
weighting one or more previously gathered rate mismatches based on a size of each of the one or more previously gathered rate mismatches;
wherein the determining of the rate mismatch comprises determining the rate mismatch with respect to the one or more weighted previously gathered rate mismatches.

19. The method of claim 15 , further comprising: comparing an observed timeline of observed media samples to an ideal timeline, the ideal timeline being derived from the observed media samples; measuring an error from the comparing of the observed timeline to the ideal timeline; adjusting the rate scalar parameter based on the measured error; and adjusting the rate of playback of the one or more media samples during the playback via use of the adjusted rate scalar parameter.

Assignees

• Apple Inc

Inventors

• Powell Richard
• Naito Daniel
• Hollabaugh James
• Klingler Daniel

Classifications

• H04W84/12

  WLAN [Wireless Local Area Networks] · CPC title

• H04R2420/07

  Applications of wireless loudspeakers or wireless microphones · CPC title

• H04W56/00 Primary

  Synchronisation arrangements · CPC title