PRECISION TIMING FOR BROADCAST NETWORK

• US 20160301831A1
• Filed: 04/08/2016
• Published: 10/13/2016
• Est. Priority Date: 04/10/2015
• Status: Active Grant

• Current Assignee: Grass Valley Canada (Belden Inc.)
• Original Assignee: Gvbb Holdings SARL (Vislink Technologies, Inc.)
• Inventors: Meyer, Charles S.
• Granted Patent: US 9,838,571 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04L 7/033 using the transitions of the received signal to control the phase of the synchronising-signal-generating means, e.g. using a phase-locked loop
• 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 5/04 Synchronising for television systems using pulse code modulation H04N7/56

Abstract

The present aspects relate to techniques of timing synchronization of audio and video (AV) data in a network. In particular, the techniques for a AV master to distribute AV data encoded with one or more time markers to a plurality of processing nodes. The one or more time markers may be indexed to a precision time protocol (PTP) time stamp used as a time reference. In one technique, the nodes extract the time markers to determine an offset value that is applied to a PLL to synchronize AV data packets at a distribution node or a processing node. In another technique the distribution node or the processing node determines the worst case path, which corresponds to a system offset value. The distribution node then reports the system offset value to the AV master, which in turn adjusts the phase based on the report.

Claims

1. A method for timing synchronization of audio video (AV) data, comprising:

receiving the AV data encoded with one or more time markers, wherein the one or more time markers are indexed to a precision time protocol (PTP) time stamp used as a time reference for a network; and

locking phase of the AV data to align phase of the AV data based on the one or more time markers.

2. The method of claim 1, further comprising determining one or more frequencies of the AV data based on the one or more time markers.

3. The method of claim 2, further comprising detecting one or more phase offset values of the AV data based on absolute reference values of the one more time markers.

4. The method of claim 2, further comprising detecting one or more phase offset values for each particular media type of the AV data based on absolute reference values of the one or more time markers.

5. The method of claim 1, further comprising:

determining a system offset value based on a worst case absolute phase offset value; and

setting a media buffer to prevent overflow based on the system offset value.

6. The method of claim 5, wherein the system offset value is based on a number of video lines.

7. A node for timing synchronization of audio video (AV) data, comprising:

a receiver configured to receive the AV data encoded with one or more time markers, wherein the one or more time markers are indexed to a precision time protocol (PTP) time stamp used as a time reference for a network

a timing module configured to lock phase of the AV data based on the one or more time markers.

8. The node of claim 7, further comprising a processor configured to determine one or more frequencies of the AV data based on the one or more time markers.

9. The node of claim 8, wherein the processor is further configured to detect one or more phase offset values of the AV data based on absolute reference values of the one more time markers.

10. The node of claim 8, wherein the processor is further configured to detect one or more phase offset values for each particular media type of the AV data based on absolute reference values of the one more time markers.

11. The node of claim 7, further comprising a processor configured to:

determine a system offset value based on a worst case absolute phase offset value; and

set a media buffer to prevent overflow based on the system offset value.

12. The node of claim 11, wherein the system offset value is based on a number of video lines.

13. A computer-readable medium storing computer executable code for timing synchronization of received audio video (AV) data encoded with one or more time markers, the one or more time markers are indexed to a precision time protocol (PTP) time stamp used as a time reference for a network, the computer readable media comprising code to:

lock phase of the AV data to align phase of the AV based on the one or more time markers.

14. The computer-readable medium of claim 13, further comprising code to determine one or more frequencies of the AV data corresponding to the transmitter based on the one or more time markers.

15. The computer-readable medium of claim 14, further comprising code to detect one or more phase offset values of the AV data based on absolute reference values of the one more time markers.

16. The computer-readable medium of claim 14, further comprising code to detect one or more phase offset values for each particular media type of the AV data based on absolute reference values of the one or more time markers.

17. The computer-readable medium of claim 13, further comprising code to:

determine a system offset value based on a worst case absolute phase offset value; and

set a media buffer to prevent overflow based on the system offset value.

18. The computer-readable medium of claim 17, wherein the system offset value is based on a number of video lines.