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

Patent metadata

Field	Value
Publication number	US-11272465-B2
Application number	US-202016866403-A
Country	US
Kind code	B2
Filing date	May 4, 2020
Priority date	Nov 19, 2014
Publication date	Mar 8, 2022
Grant date	Mar 8, 2022

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 method for asynchronous sample rate conversion of media data transmitted within a network, the method comprising:
initiating capture of one or more observed timelines associated with the media data;
identifying an anchor pair associated with the media data, the anchor pair being indicative that a first time reference corresponding to a network time matches a second time reference corresponding to first one or more media samples received from the network;
for one or more media samples received subsequent to the first one or more media samples, and based at least in part on the identifying of the anchor pair, determining a difference between an ideal timeline and an observed timeline;
adjusting a rate scalar parameter of the media data based at least on the determined difference; and
scheduling playback of the media data.

2. The method of claim 1 , wherein the second time reference comprises a time value associated with the first one or more media samples received from the network, the time value being obtained prior to a rate conversion by a signal converter.

3. The method of claim 1 , wherein the captured one or more observed timelines associated with the media data comprises two timelines, the two timelines comprising a hardware sample time and a time associated with a local device, the hardware sample time corresponding to a time value obtained subsequent to a rate conversion by a signal converter.

4. The method of claim 3 , wherein the time associated with the local device comprises a time value generated from a counter associated with the local device.

5. The method of claim 1 , further comprising independently tracking a local timeline, the local timeline comprising: (i) a time value generated from a counter common to all devices of the network, and (ii) a time associated with the local device.

6. The method of claim 5 , wherein the adjusting of the rate scalar parameter of the media data is further based at least on a drift of: (i) the time value generated from a counter common to all devices of the network, relative to (ii) the second time reference.

7. The method of claim 1 , wherein:
the scheduling of the playback of the media data comprises causing the playback at the first time reference corresponding to the network time; and
the method further comprises causing synchronization of the playback of the media data across a plurality of devices on the network based at least on the playback at the first time reference and the adjusting of the rate scalar parameter.

8. The method of claim 7 , wherein the adjusting of the rate scalar parameter comprises adjusting the rate scalar parameter via a plurality of instances, such that the plurality of devices on the network remain rate locked and phase locked, the rate locking comprising maintaining a rate of the playback consistent with the first time reference, the phase lock comprising an establishment of a desired phase between the first and second time references.

9. A computerized media apparatus configured to receive media, the computerized media apparatus comprising:
a first processor apparatus;
a data interface in data communication with the first processor apparatus and configured to receive media data;
an asynchronous sample rate converter; and
a non-transitory computer-readable apparatus comprising a memory subsystem, the memory subsystem comprising a plurality of computer-executable instructions configured to, when executed by the first processor apparatus, cause the media apparatus to:
receive data indicative of one or more observed timelines associated with the media data;
determine an anchor point associated with the media data, the anchor point comprising a first time reference corresponding to a network time and a second time reference corresponding to one or more first media samples of the media data;
determine an error between an ideal timeline and an observed timeline for one or more second media samples based at least on the determination of the anchor point; and

adjust a rate associated with the media data based at least on the determined error.

10. The computerized media apparatus of claim 9 , wherein the anchor point represents an absence of a phase difference between the one or more first media samples and the network time.

11. The computerized media apparatus of claim 9 , wherein the adjustment of the rate comprises an adjustment of a rate scalar parameter associated with the asynchronous sample rate converter.

12. The computerized media apparatus of claim 11 , wherein the asynchronous sample rate converter is configured to resample a signal having a first sample rate, and output a resampled signal at a second sample rate, the rate scalar parameter comprising a ratio of the first and second sample rates.

13. The computerized media apparatus of claim 9 , wherein the second time reference comprises a time value associated with the one or more first media samples, the time value being obtained prior to a rate conversion by the asynchronous sample rate converter.

14. The computerized media apparatus of claim 9 , wherein the received one or more observed timelines associated with the media data comprises a plurality of timelines, the plurality of timelines comprising a hardware sample time, and a time associated with the computerized media apparatus.

15. The computerized media apparatus of claim 14 , wherein:
the computerized media apparatus further comprises an oscillator apparatus configured to oscillate at one or more selected frequencies;
the hardware sample time corresponds to a time value obtained subsequent to a rate conversion by the asynchronous sample rate converter; and
the time associated with the computerized media apparatus comprises a time value generated from a counter associated with the oscillator apparatus.

16. The computerized media apparatus of claim 9 , further comprising a second processor apparatus configured for data communication with the first processor apparatus, wherein the second processor apparatus comprises a wireless modem configured for data communication with a wireless network via the data interface.

17. 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, enable a computerized apparatus to:
responsive to initiation of audio playback, capture a plurality of observed time values associated with audio data;
identify anchor data associated with the audio data, the anchor data comprising a network time reference and a sample time associated with the audio data;
determine a difference between an ideal time value and a given one of the plurality of observed time values; and
adjust a rate associated with the audio data based on the determined difference; schedule playback of the audio data based on the adjusted rate.

18. The non-transitory computer-readable apparatus of claim 17 , wherein the determination of the difference is responsive to an update of the network time reference.

19. The non-transitory computer-readable apparatus of claim 17 , wherein the adjustment of the rate associated with the audio data comprises an adjustment of a rate scalar parameter associated with a sample rate converter of the computerized apparatus.

20. The non-transitory computer-readable apparatus of claim 19 , wherein:
the sample time associated with the audio data comprises a first time value obtained prior to a rate conversion by th

Assignees

• Apple Inc

Inventors

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

Classifications

• H04W56/00 Primary

  Synchronisation arrangements · CPC title

• H04R2420/07

  Applications of wireless loudspeakers or wireless microphones · CPC title

• H04W84/12

  WLAN [Wireless Local Area Networks] · CPC title