Method for transporting digital media

• US 8,005,939 B2
• Filed: 05/14/2010
• Issued: 08/23/2011
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Audinate Holdings Pty Limited
• Original Assignee: Audinate Pty Ltd (Audinate Group Ltd.)
• Inventors: Witana, Varuni, Williams, Aidan
• Primary Examiner(s): Jacobs; Lashonda T
• Application Number:
  US12/662,994
• Publication Number:
  US 20100228881A1
• Time in Patent Office: 466 Days
• Field of Search: 709/223, 709/224, 709/203, 709/217, 709/248, 709/231, 709/209, 370/503
• US Class Current: 709/223
• CPC Class Codes: H04J 3/0632 Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES] queuing arrangements in packet switching elements H04L49/90; synchronising systems for the synchronous transmission of a pulse code modulated video signal with one or more other pulse code modulated signals H04N7/56
• CPC Class Codes: H04J 3/0661 using timestamps
• 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 43/106 using time related information in packets, e.g. by adding timestamps
• CPC Class Codes: H04L 65/1101 Session protocols
• CPC Class Codes: H04L 65/60 Network streaming of media packets
• CPC Class Codes: H04L 65/762 at the source reformatting of additional data in video distribution servers H04N21/2355
• CPC Class Codes: H04L 65/80 Responding to QoS
• CPC Class Codes: H04L 67/1095 Replication or mirroring of data, e.g. scheduling or transport for data synchronisation between network nodes
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• CPC Class Codes: H04L 9/12 Transmitting and receiving encryption devices synchronised or initially set up in a particular manner
• CPC Class Codes: H04N 21/2381 Adapting the multiplex stream to a specific network, e.g. an Internet Protocol [IP] network transmission of MPEG streams over ATM H04L12/5601
• 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

Abstract

A networked system is provided for transporting digital media packets, such as audio and video. The network includes network devices interconnected to send and receive packets. Each network device can receive and transmit media signals from media devices. A master clock generates a system time signal that the network devices use, together with a network time protocol to generate a local clock signal synchronized to the system time signal for both rate and offset. The local clock signal governs both the rate and offset of the received or transmitted media signals. The system, which can be implemented using conventional network equipment enables media signals to be transported to meet quality and timing requirements for high quality audio and video reproduction.

Claims

1. A computer-implemented method for transporting a media signal over a network comprising the steps of:

receiving a master clock signal at a network device via a network;

synchronizing a local clock at the network device with the master clock signal;

deriving a media clock from the local clock, wherein the media clock is a software timer;

receiving a packetized media signal at the network device via the network;

decoding the packetized media signal, wherein the media clock directly governs a rate and an offset at which the packetized media signal is decoded; and

communicating the decoded media signal to a media device or software application.

2. The computer-implemented method of claim 1 wherein the network device is a general purpose computer system.

3. The computer-implemented method of claim 1 wherein the packetized media signal includes a timestamp.

4. The computer-implemented method of claim 3 further comprising determining a playout time for the packetized media signal based on the timestamp.

5. The computer-implemented method of claim 1 wherein the packetized media signal is audio.

6. The computer-implemented method of claim 1 wherein the packetized media signal is video.

7. The computer-implemented method of claim 1 wherein the network is an Ethernet network.

8. A computer-implemented method for transporting a media signal over a network comprising the steps of:

receiving a master clock signal at a network device via a network;

synchronizing a local clock at the network device with the master clock signal;

deriving a media clock from the local clock, wherein the media clock is a software timer;

receiving a media signal at the network device from a media device or software application;

packetizing the media signal, wherein the media clock directly governs a rate and an offset at which the media signal is packetized; and

transmitting the packetized media signal over the network.

9. The computer-implemented method of claim 8 wherein the network device is a general purpose computer system.

10. The computer-implemented method of claim 8 further comprising adding a timestamp to the packetized media signal.

11. The computer-implemented method of claim 8 wherein the packetized media signal is audio.

12. The computer-implemented method of claim 8 wherein the packetized media signal is video.

13. The computer-implemented method of claim 8 wherein the network is an Ethernet network.

14. A, non-transitory, computer readable storage medium having computer program instructions adapted to cause a processing system to perform the steps of:

receiving a master clock signal at a network device via a network;

synchronizing a local clock at the network device with the master clock signal;

deriving a media clock from the local clock, wherein the media clock is a software timer;

receiving a packetized media signal at the network device via the network;

decoding the packetized media signal, wherein the media clock directly governs a rate and an offset at which the packetized media signal is decoded; and

communicating the decoded media signal to a media device or software application.

15. The non-transitory computer readable storage medium of claim 14 wherein the network device is a general purpose computer system.

16. The non-transitory computer readable storage medium of claim 14 wherein the packetized media signal includes a timestamp.

17. The non-transitory computer readable storage medium of claim 14, further comprising determining a playout time for the packetized media signal based on the time stamp.

18. The non-transitory computer readable storage medium of claim 14 wherein the packetized media signal is audio.

19. The non-transitory computer readable storage medium of claim 14 wherein the packetized media signal is video.

20. The non-transitory computer readable storage medium of claim 14 wherein the network is an Ethernet network.

21. A, non-transitory, computer readable storage medium having computer program instructions adapted to cause a processing system to perform the steps of:

receiving a master clock signal at a network device via a network;

synchronizing a local clock at the network device with the master clock signal;

deriving a media clock from the local clock, wherein the media clock is a software timer;

receiving a media signal at the network device from a media device or software application;

packetizing the media signal, wherein the media clock directly governs a rate and an offset at which the media signal is packetized; and

transmitting the packetized media signal over the network.

22. The non-transitory computer readable storage medium of claim 21 wherein the network device is a general purpose computer system.

23. The non-transitory computer readable storage medium of claim 21 further comprising adding a timestamp to the packetized media signal.

24. The non-transitory computer readable storage medium of claim 21 wherein the packetized media signal is audio.

25. The non-transitory computer readable storage medium of claim 21 wherein the packetized media signal is video.

26. The non-transitory computer readable storage medium of claim 21 wherein the network is an Ethernet network.