Methods for transporting digital media

• US 10,461,872 B2
• Filed: 08/31/2018
• Issued: 10/29/2019
• Est. Priority Date: 04/22/2005
• Status: Active Grant

• Current Assignee: Audinate Holdings Pty Limited
• Original Assignee: Audinate Pty Ltd (Audinate Group Ltd.)
• Inventors: Williams, Aidan, Witana, Varuni
• Primary Examiner(s): Chery, Dady
• Application Number:
  US16/119,595
• Publication Number:
  US 20190058539A1
• Time in Patent Office: 424 Days
• 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 data network suitable for transporting at least one of audio and video packets, the network comprising:

a master clock device to generate a system time signal for the network;

a plurality of network devices interconnected such that the network devices can send at least one of audio and video packets to other network devices, and to receive at least one of audio and video packets from other network devices;

wherein at least one network device is configured to receive at least one of audio and video signals from a media device and to transmit at least one of audio and video signals to a media device; and

wherein, the network devices are coupled to the master clock device and use the system time signal and a network time protocol to generate a local clock signal synchronised to the system time signal for both rate and offset, the local clock signal governing both the rate and offset of the received or transmitted at least one of audio and video signals.

2. A data network according to claim 1 wherein, in use, the network devices that receive media signals from a media device use its local clock signal to packetise the at least one of audio and video signals, and to timestamp the at least one of audio and video packets with system time before transmitting them to another network device.

3. A data network according to claim 2 wherein the timestamp of an at least one of audio and video packet includes the earliest system time at which the at least one of audio and video signal contained within the at least one of audio and video packet was generated.

4. A data network according to claim 1 wherein the network devices that receive at least one of audio and video packets use the packet timestamps to reorder at least one of audio and video packets as required, and in addition to perform at least one of (1) to align and combine at least one of audio and video signals received from different network devices, and (2) to determine the appropriate playout time for at least one of audio and video signals contained in the at least one of audio and video packets.

5. A data network according to claim 4 wherein the appropriate playout time for at least one of audio and video signals contained in the at least one of audio and video packets is different for two network devices that receive the at least one of audio and video packets.

6. A data network according to claim 1 wherein the media packets contain both audio and video media signals.

7. A data network according to claim 1 wherein the network comprises an Ethernet network.

8. A data network according to claim 1 wherein a media clock signal is synthesized from at least the local clock signal, such that the media clock signal directly governs the rate and offset at which at least one of audio and video signals are received or transmitted.

9. A data network according to claim 1 wherein the rate of the local clock signal of a network device is different from the rate of a local clock signal of another network device.

10. A data network according to claim 8 wherein the rate of the media clock signal of a network device is different from the rate of a media clock signal of another network device.

11. A data network according to claim 8 wherein the media clock signal is used for conversion between analogue and digital media signals.

12. A data network according to claim 8 wherein the media clock signal is synthesized by one of pulse width modulated clock synthesis involving a pulse width modulated counter, direct digital synthesis, a digitally controlled oscillator, a voltage controlled oscillator controlled by a digital to analogue converter, and a software timer caused to track a synchronized local clock signal.

13. A data network according to claim 1 wherein at least one media device is connected to a network device for carrying out at least one of (1) to generate and deliver at least one of audio and video signals, (2) to receive, to process and to deliver at least one of audio and video signals, and (3) to receive and playout at least one of audio and video signals.

14. A data network according to claim 1 wherein a quality of service scheme of the data network operates to prioritize the transmission of packets that contain network time information.

15. A data network device for connection to other network devices to transport at least one of audio and video packets between them, the network device comprising:

a media port for receiving at least one of audio and video signals from a media device and transmitting at least one of audio and video signals to a media device;

a clock port coupled to receive a system time signal; and

a local clock generator coupled to use the system time signal and 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 governing both the rate and offset of the received or transmitted media at least one of audio and video signals.

16. A method of operating a data network device to transport at least one of audio and video packets, comprising the steps of:

generating or receiving a system time signal for the network;

configuring a plurality of the network devices such that the plurality of network devices are able to perform at least one of (1) sending packets to other network devices, and (2) receiving packets from other network devices;

configuring at least one of the network devices to receive at least one of audio and video signals from a media device, and transmit at least one of audio and video signals to a media device;

connecting the network devices to receive the system time signal; and

,

operating the network devices to use the system time signal and 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 governing the rate and offset of the received or transmitted at least one of audio and video signals.