Method of generating timestamps for isochronous data

• US 6,895,009 B1
• Filed: 04/07/2000
• Issued: 05/17/2005
• Est. Priority Date: 04/07/2000
• Status: Expired due to Term

• Current Assignee: Harmonic Incorporated
• Original Assignee: Omneon Video Networks
• Inventors: Stallkamp, Richard Wissler
• Primary Examiner(s): Ton, Dang
• Assistant Examiner(s): HOM, SHICK C
• Application Number:
  US09/544,738
• Time in Patent Office: 1,866 Days
• Field of Search: 370/230.1, 370/252, 370/394, 370/395.62, 370/395.65, 370/503, 370/508, 370/509, 370/510, 370/512, 370/516, 370/517, 370/522, 375/354, 375/355
• US Class Current: 370/394
• CPC Class Codes: H04N 21/43632 involving a wired protocol, e.g. IEEE 1394 high-speed IEEE 1394 serial bus H04L12/40052
• CPC Class Codes: H04N 21/8547 involving timestamps for synchronizing content

Abstract

A method of generating timestamps for isochronous data includes locking a data stream time and an isochronous network time to a local clock signal such that a bi-directional mapping may be made between the two time domains. Timing information is extracted from both IEEE 1394 based data packets and a conventional house reference signal in order to obtain scale and offset factors that exist between the two signals. The scale and offset factors are applied to a generated video clock signal in order to predict a future video time in terms of IEEE 1394 time.

Claims

1. A method comprising;

receiving a first signal defining a reference time domain;

receiving a second signal defining a transport time domain asynchronous to the reference time domain;

generating an isochronous network packet including a first timestamp indicating a point in time measured with respect to the reference time domain and represented as a measure of the transport time domain;

determining an output signal based at least in part upon the first signal;

dynamically sampling the first signal and the second signal to determine a scale factor and an offset factor between the reference and transport time domains; and

modifying the output signal by at least one of the scale factor and the offset factor to represent the output signal in terms of the transport time domain.

2. The method of claim 1, wherein receiving the first signal comprises receiving a house reference signal.

3. The method of claim 1, wherein receiving the second signal comprises receiving at least on isochronous network packet including a second timestamp indicating an isochronous network cycle-time.

4. The method of claim 3, wherein the isochronous network cycle time is determined by an IEEE 1394 cycle master device.

5. The method of claim 1, wherein generating the isochronous network packet includes associating the timestamp with at least one frame of generated video data to be transmitted across an isochronous network.

6. The method of claim 1, wherein generating the isochronous network packet includes associating the timestamp with at least one frame of received video data to be transmitted across an isochronous network.

7. An article of manufacture comprising a machine readable medium having a plurality of machine readable instructions stored thereon, wherein when executed by a processor, the instructions cause the processor to:

receive a first signal defining a reference time domain;

receive a second signal defining a transport time domain asynchronous to the reference time domain;

generate an isochronous network packet including a first timestamp indicating a point in time measured with respect to the reference time domain and represented as a measure of the transport time domain;

determine an output signal based at least in part upon the first signal;

dynamically sample the first signal and the second signal to determine a scale factor and an offset factor between the reference and transport time domains; and

modify the output signal by at least one of the scale factor and the offset factor to represent the output signal in terms of the transport time domain.

8. The article of manufacture of claim 7, wherein the machine readable instructions that cause the processor to receive the first signal further cause the processor to receive a house reference signal.

9. The article of manufacture of claim 7, wherein the machine readable instructions that cause the processor to receive the second signal further cause the processor to receive at least one isochronous network packet including a second timestamp indicating an isochronous network cycle-time.

10. The article of manufacture of claim 9, wherein the isochronous network cycle time is determined by an IEEE 1394 cycle master device.

11. The article of manufacture of claim 7, wherein the machine readable instructions that cause the processor to generate the isochronous network packet further cause the processor to associate the timestamp with at least one frame of generated video data to be transmitted across an isochronous network.

12. The article of manufacture of claim 7, wherein the machine readable instructions that cause the processor to generate the isochronous network packet further cause the processor to associate the timestamp with at least one frame of received video data to be transmitted across an isochronous network.

13. An apparatus comprising:

means for receiving a first signal defining a reference time domain;

means for receiving a second signal defining a transport time domain asynchronous to the reference time domain;

means for generating an isochronous network packet including a timestamp indicating a point in time measured with respect to the reference time domain and represented as a measure of the transport time domain;

means for determining an output signal based at least in part upon the first signal;

means for dynamically sampling the first signal and the second signal to determine a scale factor and an offset factor between the reference and transport time domains; and

means for modifying the output signal by at least one of the scale factor and the offset factor to represent the output signal in terms of the transport time domain.

14. The apparatus of claim 13, wherein the means for receiving the first signal comprises means for receiving a house reference signal.

15. The apparatus of claim 13, wherein means for receiving the second signal comprises means for receiving at least one isochronous network packet including a timestamp indicating an isochronous network cycle-time.

16. The apparatus of claim 13, wherein the means for generating the isochronous network packet includes means for associating the generated timestamp with at least one frame of generated video data to be transmitted across an isochronous network.

17. The apparatus of claim 13, wherein the means for generating the isochronous network packet includes means for associating the generated timestamp with at least one frame of received video data to be transmitted across an isochronous network.

18. A system comprising:

a communications port to receive a first signal defining a reference time domain;

a network interface to receive a second signal defining a transport time domain asynchronous to the reference time domain, and to generate an isochronous network packet including a timestamp indicating a point in time measured with respect to the reference time domain and represented as a measure of the transport time domain; and

synchronization logic to;

determine an output signal based at least in part upon the first signal

dynamically sample the first signal and the second signal to determine a scale factor and an offset factor between the reference and transport time domains, and

modify the output signal by at least one of the scale factor and the offset factor to represent the output signal in terms of the transport time domain.

19. The system of claim 18, wherein the network interface comprises logic to receive at least one isochronous network packet including a timestamp indicating an isochronous network time.

20. The system of claim 18, wherein the synchronization logic further comprises logic to associate the generated timestamp with at least one frame of generated video data to be transmitted across an isochronous network.

21. The system of claim 18, wherein the synchronization logic further comprises logic to associate the generated timestamp with at least one frame of received video data to be transmitted across an isochronous network.