Method and apparatus for receiving video signals from a plurality of video cameras

• US 7,065,140 B1
• Filed: 10/06/1999
• Issued: 06/20/2006
• Est. Priority Date: 10/06/1999
• Status: Expired due to Fees

• Current Assignee: Semiconductor Components Industries LLC (ON Semiconductor Corporation)
• Original Assignee: Fairchild Semiconductor Corporation (ON Semiconductor Corporation)
• Inventors: Bicakci, Ara, Ritter, David W.
• Primary Examiner(s): An, Shawn S.
• Application Number:
  US09/414,307
• Time in Patent Office: 2,449 Days
• Field of Search: 375/240.26, 375/240.25, 375/240, 375/240.01, 348/153, 348/154, 348/159, 348/246, 348/241, 348/143, 348/663, 348/705, 348/564, 348211-214, 348/156, 348/509, 348/563, 348/654, 348/662, 348/689, 348/558, 348/207.1, 382/233
• US Class Current: 375/240.25
• CPC Class Codes: H04N 7/181 for receiving images from a plurality of remote sources

Abstract

A method and apparatus for receiving video signals from a plurality of video cameras, such as in a video surveillance system. The video cameras are each coupled to provide a video signal to a respective input of a multiplexer. The multiplexer routes a selected one of the video signals to a video decoder. The video decoder receives the selected video signal and is conditioned according to the video signal. This includes synchronizing the video decoder to a frequency and phase of the video signal, controlling a gain level for the video signal and adjusting a dc clamping level for dc restoration of the video signal. Parameters representative of each of these quantities are stored in association with the identity of the corresponding video camera. The video decoder also places each video signal into a format suitable for storage in a storage device and for display by a display device. As the multiplexer is utilized to cycle through the cameras according to a sequence, the parameters for each camera are retrieved and utilized to initialize the video decoder for decoding the video signal received from the corresponding camera. As a result, the amount of time required to condition the video decoder according to the video signal received from each camera is significantly reduced. Accordingly, the present invention allows a surveillance system to cycle through a plurality of cameras in less time than prior systems having a single decoder, but without higher costs associated with prior systems which employ multiple video decoders.

Claims

1. A method of receiving video signals from a plurality of video cameras wherein the method comprises steps of:

a. selecting one of the plurality of video cameras for providing a video signal to a video decoder;

b. retrieving a parameter representative of the video signal from a memory store; and

c. conditioning the video decoder according to the parameter; and

d. updating the parameter according to the video signal thereby forming an updated parameter and a predicted value for the parameter,

wherein forming the predicted value for the parameter includes calculating a difference between prior value obtained for the parameter and a current value obtained for the parameter and combining the difference with the current value.

2. The method according to claim 1 further comprising a step of capturing a video frame from the selected one of the plurality of video cameras.

3. The method according to claim 2 further comprising a step of storing the captured video frame.

4. The method according to claim 2 further comprising a step of completing a cycle wherein the step of completing the cycle comprises performing the steps of selecting, retrieving, conditioning and capturing for each camera of the plurality.

5. The method according to claim 1 further comprising a step of storing the updated parameter in association with an identification of the selected one of the plurality of video cameras.

6. The method according to claim 5 further comprising a step of selecting a next one of the plurality of cameras according to a sequence.

7. The method according to claim 1 further comprising a step of storing the updated parameter in a storage location which is associated with the corresponding camera.

8. The method according to claim 7 further comprising a step of selecting a next one of the plurality of cameras according to a sequence.

9. The method according to claim 1 further comprising a step of initializing the apparatus upon start-up by obtaining an initial value for the parameter corresponding to each video signal during a first cycle through all of the cameras wherein a video frame is captured from each camera during the first cycle.

10. The method according to claim 1 further comprising a step of initializing the apparatus upon start-up by performing two or more cycles through all of the cameras and wherein a video frame is captured from each camera only upon completion of the two or more cycles.

11. The method according to claim 1 wherein the parameter is a horizontal frequency of the video signal.

12. The method according to claim 11 wherein the parameter is a horizontal phase of the video signal.

13. The method according to claim 12 wherein the parameter is a chrominance frequency of the video signal.

14. The method according to claim 13 wherein the parameter is a chrominance phase of the video signal.

15. The method according to claim 1 wherein the parameter is a gain level for the video signal.

16. The method according to claim 15 wherein the parameter is a dc clamping level for the video signal.