PRECISION TIMING FOR BROADCAST NETWORK

• US 20180054549A1
• Filed: 10/27/2017
• Published: 02/22/2018
• 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 10,455,126 B2
• Time in Patent Office: Days
• 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 system for synchronizing transmission of audio/video (AV) data in a media distribution network, the system comprising:

a media transmission controller configured to transmit a plurality of data streams having packetized AV data across a plurality of network paths to a plurality of receiving nodes;

a network delay determiner configured to determine a network delay of each of the plurality of network paths based on a delay calculation generated by each of the plurality of receiving nodes having received at least one of the plurality of data streams transmitted across the plurality of network path;

a network delay calculator configured to calculate a system offset value for the media distribution network by comparing the determined network delay of each of the plurality of network paths to determine the system offset value based on a worst network path of the plurality of network paths that experiences a longest network delay for receiving the respective data stream; and

a media stream synchronizer configured to synchronize the plurality of data streams processed by one or more of the plurality of receiving nodes by adjusting at least one media buffer at the one or more of the plurality of receiving nodes based on the calculated system offset value to accommodate delayed packetized AV data in the plurality of data streams to prevent overflow during media playout of the packetized AV data.

2. The system according to claim 1, further comprising a data encoder configured to encode the packetized AV data of the plurality of data streams to each have one or more timestamps.

3. The system according to claim 2, wherein the one or more timestamps are indexed to a precision time protocol (PTP) used as a time reference for the media distribution network.

4. The system according to claim 3, wherein the network delay determiner determines the network delay of each of the plurality of network paths based on the PTP indexed to the one or more timestamps in the packetized AV data of the plurality of data streams.

5. The system according to claim 2, further comprising:

a phase lock loop at each of the plurality of receiving nodes configured to lock a phase of the packetized AV data of the data streams received at the respective receiving node to align the received data streams based on the respective one or more timestamps of the packetized AV data; and

a frequency determiner configured to determine one or more frequencies of the packetized AV data of the data streams received at the respective receiving node.

6. The system according to claim 5, wherein the network delay determiner is further configured to calculate the delay calculation based on the locked phase and determined one or more frequencies of the packetized AV data.

7. A system for synchronizing audio/video (AV) data in a media distribution network, the system comprising:

a media transmission controller configured to transmit a plurality of data streams having packetized AV data across a plurality of network paths to at least one receiving node;

a network delay determiner configured to determine a network delay of at least one of the plurality of network paths based on a delay calculation generated by the at least one receiving node for the respective data stream transmitted across the at least one network path; and

a media stream synchronizer configured to synchronize the plurality of data streams processed by the at least one receiving node based on a system offset value calculated from the determined network delay.

8. The system according to claim 7, further comprising a network delay calculator configured to calculate the system offset value for the media distribution network by comparing the determined network delay of each of the plurality of network paths to determine the system offset value based on a worst network path of the plurality of network paths that experiences a longest network delay for receiving the respective data stream.

9. The system according to claim 8, wherein the media stream synchronizer synchronizes the plurality of data streams processed by the at least one receiving node by adjusting at least one media buffer at the at least one receiving node based on the calculated system offset value to accommodate delayed packetized AV data in the plurality of data streams to prevent overflow during media playout of the packetized AV data.

10. The system according to claim 7, further comprising a data encoder configured to encode the packetized AV data of the plurality of data streams to each have one or more timestamps.

11. The system according to claim 10, wherein the one or more timestamps are indexed to a precision time protocol (PTP) used as a time reference for the media distribution network;

and

wherein the network delay determiner determines the network delay of each of the plurality of network paths based on the PTP indexed to the one or more timestamps in the packetized AV data of the plurality of data streams.

12. The system according to claim 10, further comprising:

a phase lock loop at each of the plurality of receiving nodes configured to lock a phase of the packetized AV data of the data streams received at the respective receiving node to align the data streams based on the respective one or more timestamps of the packetized AV data; and

a frequency determiner configured to determine one or more frequencies of the packetized AV data of the data streams received at the respective receiving node.

13. The system according to claim 12, wherein the network delay determiner is further configured to calculate the delay calculation based on the locked phase and determined one or more frequencies of the packetized AV data.

14. A media distribution system for synchronizing audio/video (AV) data for media playout, the system comprising:

a network delay determiner configured to determine a network delay of a plurality of data streams with AV data transmitted across a plurality of network paths in a media distribution network to at least one receiving node; and

a media stream synchronizer configured to prevent overflow during media playout of the AV data by synchronizing the plurality of data streams processed by the at least one receiving node based on a system offset value calculated from the determined network delay of the plurality of data streams.

15. The media distribution system according to claim 14, further comprising:

a media transmission controller configured to transmit the plurality of data streams having the AV data across the plurality of network paths to the at least one receiving node; and

a network delay calculator configured to calculate the system offset value for the media distribution network by comparing the determined network delay of each of the plurality of network paths to determine the system offset value based on a worst network path of the plurality of network paths that experiences a longest network delay for receiving the respective data stream.

16. The media distribution system according to claim 15, wherein the media stream synchronizer synchronizes the plurality of data streams processed by the at least one receiving node by adjusting at least one media buffer at the at least one receiving node based on the calculated system offset value to accommodate delayed AV data in the plurality of data streams to prevent overflow during media playout of the AV data.

17. The media distribution system according to claim 15, further comprising a data encoder configured to encode the AV data of the plurality of data streams to each have one or more timestamps.

18. The media distribution system according to claim 17,

wherein the one or more timestamps are indexed to a precision time protocol (PTP) used as a time reference for the media distribution network;

and

wherein the network delay determiner determines the network delay of each of the plurality of network paths based on the PTP indexed to the one or more timestamps in the AV data of the plurality of data streams.

19. The media distribution system according to claim 17, further comprising:

a phase lock loop at each of the plurality of receiving nodes configured to lock a phase of the AV data of the data streams received at the respective receiving node to align the data streams based on the respective one or more timestamps of the AV data; and

a frequency determiner configured to determine one or more frequencies of the AV data of the data streams received at the respective receiving node.

20. The media distribution system according to claim 19, wherein the network delay determiner is further configured to calculate the delay calculation based on the locked phase and determined one or more frequencies of the AV data.