System for determining noise content of a video signal in the disclosure

• US 5,329,311 A
• Filed: 05/11/1993
• Issued: 07/12/1994
• Est. Priority Date: 05/11/1993
• Status: Expired due to Term

• Current Assignee: Beckett Mining LLC (Intellectual Ventures LLC)
• Original Assignee: University of British Columbia
• Inventors: Zhang, Qin, Ward, Rabab K.
• Primary Examiner(s): Groody, James J.
• Assistant Examiner(s): GRANT, CHRISTOPHER C
• Application Number:
  US08/059,378
• Time in Patent Office: 427 Days
• Field of Search: 358/139, 358/10, 358/133, 358/167, 382/57, 455/226.3, 348/192, 348/193, 348/180
• US Class Current: 348/180
• CPC Class Codes: H04N 17/00 Diagnosis, testing or measuring for television systems or their details

Abstract

A method of determining the noise content of a video signal by digitizing a frame based on the video signal to provide a digitized signal which is then filtered via a high pass filter. The filtered image is then divided into a plurality of subimages and the noise signal in each of the subimages is determined from a selected number of subimages having the lowest noise signal are further processed to determine the average noise in the selected subimages and the signal-to-noise ratio determined. The carrier-to-noise ratio may also be determined if desired.

Claims

1. A method of determining the noise content of a video signal comprising digitizing a frame of said video signal to provide a digitized signal, subjecting said digitized signal to a high pass filter to remove the majority of said signal representing picture information in said frame and provide a filtered image, subdividing said filtered image into a plurality of subimages, determining noise signal in each of said subimages, selecting a selected number of subimages having the lowest noise signals, determining the signal-to-noise ratio based on the average noise in said selected number of subimages.

2. A method as defined in claim 1 wherein said signal-to-noise ratio is further used to determine the carrier-to-noise ratio.

3. A method as defined in claim 1 wherein said filtering comprises convolving said digitized frame with the following filter:

##EQU14##

4. A method as defined in claim 3 wherein said high pass filter in the spectrum domain will be as follows:

##EQU15## I,J=0,1,2 . . . ,N-1

5. A method as defined in claim 4 wherein said noise will have an average value calculated (based on each sub image being 32×

32 pixels) in accordance with the following equation;

##EQU16## wherein y is the average noise pixel value and

y_ij is the pixel value after high pass filtering.

6. A method as defined in claim 5 wherein the signal-to-noise ratio is calculated using the following model:

##EQU17## wherein √

x² is defined as ##EQU18##

7. A method as defined in claim 6 wherein a carrier-to-noise ratio is determined in accordance with ##EQU19## wherein √

x² is defined as ##EQU20##

8. A method as defined in claim 6 wherein a carrier-to-noise ratio is determined in accordance with the formula

9. A method as defined in claim 1 wherein said selected number is between two and five.

10. A method as defined in claim 3 wherein said selected number is between two and five.

11. A method as defined in claim 4 wherein said selected number is between two and five.

12. A method as defined in claim 5 wherein said selected number is between two and five.

13. A method as defined in claim 6 wherein said selected number is between two and five.

14. A method as defined in claim 7 wherein said selected number is between two and five.

15. A method as defined in claim 8 wherein said selected number is between two and five.