METHOD AND APPARATUS FOR LOW JITTER CLOCK RECOVERY IN WIRELESS DISPLAY EXTENSIONS

• US 20150382035A1
• Filed: 12/21/2011
• Published: 12/31/2015
• Est. Priority Date: 12/21/2011
• Status: Active Grant

• Current Assignee: Intel Corporation
• Original Assignee: Intel Corporation
• Inventors: Li, Guoqing, Bennett, Joseph A., Prat, Gideon, Trainin, Solomon B., Lee, Sang-Hee, Somayazulu, Vallabhajosyula Z., Hayek, George R., Brouillette, Pat, Loukianov, Dmitrii A.
• Granted Patent: US 9,723,342 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/242 Synchronization processes, e.g. processing of PCR [Program Clock References] arrangements for synchronising broadcast or distribution via plural systems in broadcast distribution systems H04H20/18
• CPC Class Codes: H04N 21/4305 Synchronising client clock from received content stream, e.g. locking decoder clock with encoder clock, extraction of the PCR packets arrangements for synchronising receiver with transmitter by comparing receiver clock with transmitter clock H04L7/0012; arrangements for synchronising receiver with transmitter wherein the receiver takes measures against momentary loss of synchronisation H04L7/0083
• CPC Class Codes: H04N 21/6131 involving transmission via a mobile phone network wireless downlink channel access H04W74/006

Abstract

An approach is provided for determining a program clock reference (PCR) value validity, for avoiding inaccurate variable delay reference (VDR) values, and for avoiding a mismatch in a data packet between a sequence number and a packet number for a wireless display extension. The approach involves determining to generate a data packet carrier having an optional PCR value, a VDR) value, and a validity indicator. The approach may further involve processing the data packet carrier to determine whether the data packet carrier has the optional PCR value. The approach may also involve causing, at least in part, a surrogate PCR value to be generated based, at least in part, on a determined absence of the optional PCR value from the data packet carrier.

Claims

1. A method comprising:

determining to generate a data packet carrier comprising an optional program clock reference (PCR) value, a variable delay reference (VDR) value, and a validity indicator.

2. A method of claim 1, further comprising:

processing the data packet carrier to determine whether the data packet carrier comprises the optional PCR value; and

causing, at least in part, a surrogate PCR value to be generated based, at least in part, on a determined absence of the optional PCR value from the data packet carrier.

3. A method of claim 2, further comprising:

determining a value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is valid;

determining a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is invalid;

causing, at least in part, the value of the validity indicator to change to indicate one of the optional PCR value and the surrogate PCR value is invalid; and

causing, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the changed value of the validity indicator.

4. A method of claim 3, wherein the value of the validity indicator is caused to change by a media access control layer.

5. A method of claim 2, further comprising:

determining a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is valid;

determining a value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is invalid; and

causing, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the value of the validity indicator.

6. A method of claim 2, further comprising:

determining a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is invalid;

causing, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the value of at least the media access control retry bit value.

7. A method of claim 2, further comprising:

determining a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is valid;

determining a value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is valid; and

causing, at least in part, the data packet carrier to be communicated based, at least in part, on the media access control retry bit value and the value of the validity indicator.

8. A method of claim 2, wherein the VDR value is based, at least in part, on one of the optional PCR value and the surrogate PCR value.

9. A method of claim 2, wherein the surrogate PCR value is generated remotely from a graphics processing unit.

10. A method of claim 9, further comprising:

causing, at least in part, a phase-locked loop to lock the surrogate PCR value to a clock of the graphics processing unit.

11. An apparatus comprising:

at least one processor; and

at least one memory including computer program code for one or more programs,

the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to perform at least the following,

determine to generate a data packet carrier comprising an optional program clock reference (PCR) value, a variable delay reference (VDR) value, and a validity indicator.

12. An apparatus of claim 11, wherein the apparatus is further caused to:

process the data packet carrier to determine whether the data packet carrier comprises the optional PCR value; and

cause, at least in part, a surrogate PCR value to be generated based, at least in part, on a determined absence of the optional PCR value from the data packet carrier.

13. An apparatus of claim 12, wherein the apparatus is further caused to:

determine value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is valid;

determine a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is invalid;

cause, at least in part, the value of the validity indicator to change to indicate one of the optional PCR value and the surrogate PCR value is invalid; and

causing, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the changed value of the validity indicator.

14. An apparatus of claim 12, wherein the apparatus is further caused to:

determine a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is valid;

determine a value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is invalid; and

cause, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the value of the validity indicator.

15. An apparatus of claim 12, wherein the apparatus is further caused to:

determine a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is invalid;

cause, at least in part, one of the optional PCR value and the surrogate PCR value to be discarded based, at least in part, on the value of at least the media access control retry bit value.

16. An apparatus of claim 12, wherein the apparatus is further caused to:

determine a media access control retry bit value indicates one of the optional PCR value and the surrogate PCR value is valid;

determine a value of the validity indicator indicates one of the optional PCR value and the surrogate PCR value is valid; and

cause, at least in part, the data packet carrier to be communicated based, at least in part, on the media access control retry bit value and the value of the validity indicator.

17. An apparatus of claim 12, wherein the VDR value is based, at least in part, on one of the optional PCR value and the surrogate PCR value.

18. An apparatus of claim 17, wherein the apparatus is further caused to:

cause, at least in part, a phase-locked loop to lock the surrogate PCR value to a clock of the graphics processing unit.

19. A computer-readable storage medium carrying one or more sequences of one or more instructions which, when executed by one or more processors, cause an apparatus to at least perform the following:

determine to generate a data packet carrier comprising an optional program clock reference (PCR) value, a variable delay reference (VDR) value, and a validity indicator.

20. A computer-readable storage medium of claim 19, wherein the apparatus is caused to:

process the data packet carrier to determine whether the data packet carrier comprises the optional PCR value; and

cause, at least in part, a surrogate PCR value to be generated based, at least in part, on a determined absence of the optional PCR value from the data packet carrier.