Recursive filter system for a video signal

• US 7,903,901 B2
• Filed: 06/01/2007
• Issued: 03/08/2011
• Est. Priority Date: 06/02/2006
• Status: Expired due to Fees

• Current Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
• Original Assignee: Ericsson AB (Telefonaktiebolaget LM Ericsson)
• Inventors: Mitchell, Arthur, Huggett, Anthony Richard
• Primary Examiner(s): Le; Brian Q
• Assistant Examiner(s): PATEL, JAYESH A
• Application Number:
  US11/809,658
• Publication Number:
  US 20080002903A1
• Time in Patent Office: 1,376 Days
• Field of Search: 382/265
• US Class Current: 382/265
• CPC Class Codes: G06T 2207/10016 Video; Image sequence
• CPC Class Codes: G06T 5/20 using local operators
• CPC Class Codes: G06T 5/70 Denoising; Smoothing
• CPC Class Codes: H04N 19/117 Filters, e.g. for pre-processing or post-processing sub-band filter banks H04N19/635
• CPC Class Codes: H04N 19/14 Coding unit complexity, e.g. amount of activity or edge presence estimation H04N19/146 takes precedence
• CPC Class Codes: H04N 19/182 the unit being a pixel
• CPC Class Codes: H04N 19/80 Details of filtering operations specially adapted for video compression, e.g. for pixel interpolation H04N19/635, H04N19/86 take precedence
• CPC Class Codes: H04N 19/85 using pre-processing or post-processing specially adapted for video compression

Abstract

A recursive filter system and method is provided. A weighted value of luminance and chrominance of a stored picture element is generated by summing weighted values of luminance and chrominance of a picture element and neighboring picture elements. A first proportional parameter for the stored picture element is generated with a sum of differences between the luminance and chrominance of the stored picture element and surrounding picture elements. A weighted picture element is generated from a proportion of the stored picture element and a complimentary proportion of the weighted value. Picture elements of the next image and a second proportional parameter are inputted. A filtered image is generated by combining a proportion of each input picture element of the next image with a complementary proportion of the weighted stored picture element of the first image. The filtered image is stored for corresponding combination with a succeeding image.

Claims

1. A recursive filter system for a video image comprising:

a. memory storage means arranged to store a first image of stored picture elements S(x,y);

b. weighting means arranged to generate weighted values W(x,y) of luminance and chrominance of a stored picture element S(x,y) by summing weighted values B(x,y)·

S(x,y) of luminance and chrominance of the picture element and neighbouring picture elements;

c. generating means arranged to generate a first proportional parameter A(x,y) for the stored picture element based on a modular sum of differences between luminance and chrominance of the stored picture element and of surrounding picture elements;

d. first combinatorial means arranged to use the first proportional parameter A(x,y) to generate a weighted picture element M(x,y) from a proportion of the stored picture element S(x,y) and a complementary proportion 1−

A(x,y) of the weighted value W(x,y);

e. inputting means arranged to input picture elements of a next image and a second proportional parameter K;

f. second combinatorial means arranged to use the second proportional parameter K to generate a filtered image R(x,y) by combining a proportion of each input picture element C(x,y) of the next image with a complementary proportion 1−

K of the weighted stored picture element M(x,y) of the first image and to store the filtered image in the storage means.

2. The recursive filter system as claimed in claim 1, wherein the weighting means is arranged to weight neighbouring picture elements using an array of weighting values.

3. The recursive filter system as claimed in claim 1, wherein the generating means comprises means for calculating a sum of absolute differences between chrominance and luminance of the picture element and surrounding picture elements.

4. The recursive filter system as claimed in claim 1, wherein the generating means comprises means for calculating a sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

5. The recursive filter system as claimed in claim 4, wherein the generating means comprises means for calculating a positive square root of the sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

6. The recursive filter system as claimed in claim 1, wherein the generating means comprises multiplication means for multiplying the modular sum of differences between luminance and chrominance of the stored picture element and of surrounding picture elements by the luminance and chrominance of the stored picture element respectively.

7. The recursive filter system as claimed in claim 1, wherein the generating means comprises scalar means for generating a normalised value of the proportional parameter A(x,y).

8. The recursive filter system as claimed in claim 1, further comprising programmable spatial low pass filter means and means for estimating spatial noise in the input image for controlling the low pass filter means, such that the input image is filtered proportionally to noise detected.

9. The recursive filter system as claimed in claim 8, wherein output from the means for estimating spatial noise is adjustable dependent upon a degree of detail detected in a region of an image being processed.

10. The recursive filter system as claimed in claim 8, further comprising a logic block controllable by a factor indicative of a degree of motion in an area of an image being processed such that a proportional factor applied to the combinatorial means is a function of the noise and a degree of motion in a vicinity of a picture element being processed.

11. A method of enhancing noise attenuation in recursive filtering of a video image comprising the steps of:

a. storing a first image to comprise stored picture elements S(x,y) in a memory;

b. generating a weighted value W(x,y) of luminance and chrominance of a stored picture element by summing weighted values B(x,y)·

S(x,y) of luminance and chrominance of the picture element and neighbouring picture elements;

c. generating a first proportional parameter A(x,y) for the stored picture element based on a modular sum of differences between the luminance and chrominance of the stored picture element and surrounding picture elements;

d. using the first proportional parameter A(x,y) to generate a weighted picture element M(x,y) from a proportion of the stored picture element S(x,y) and a complementary proportion 1−

A(x,y) of the weighted value W(x,y);

e. inputting picture elements C(x,y) of a next image and a second proportional parameter K;

f. using the second proportional parameter K to generate a filtered image by combining a proportion of each input picture element C(x,y) of the next image with a complementary proportion 1−

K of the weighted stored picture element M(x,y) of the first image; and

g. storing the filtered image for corresponding combination with a succeeding image.

12. The method as claimed in claim 11, wherein generating a weighted value comprises using an array of weighting values to weight neighbouring picture elements.

13. The method as claimed in claim 11, wherein generating a weighted value comprises calculating a sum of absolute differences between chrominance and luminance of the picture element and surrounding picture elements.

14. The method as claimed in claim 11, wherein generating a weighted value comprises calculating a sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

15. The method as claimed in claim 14, wherein generating a weighted value comprises calculating a positive square root of the sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

16. The method as claimed in claim 11, wherein generating a weighted value comprises multiplying the modular sum of differences between luminance and chrominance of the stored picture element and of surrounding picture elements by the luminance and chrominance of the stored picture element, respectively.

17. The method as claimed in claim 11, wherein generating a weighted value comprises generating a normalised value of the proportional parameter A(x,y).

18. The method as claimed in claim 11, further comprising filtering the input image with programmable spatial low pass filter means using means for estimating spatial noise in the input image for controlling the low pass filter means, such that the input image is filtered proportionally to noise detected.

19. The method as claimed in claim 18, wherein output from the means for estimating spatial noise is adjustable dependent upon a degree of detail detected in a region of an image being processed.

20. The method as claimed in claim 18, further comprising using a logic block controllable by a factor indicative of a degree of motion in an area of an image being processed such that a proportional factor applied to the combinatorial means is a functional of the noise and a degree of motion in a vicinity of a picture element being processed.

21. A computer executable software code stored on a non-transitory computer readable medium, the code being for enhancing noise attenuation in recursive filtering of a video image comprising the steps of:

a. storing a first image to comprise stored picture elements S(x,y) in a memory;

b. generating a weighted value W(x,y) of luminance and chrominance of a stored picture element by summing weighted values B(x,y)·

S(x,y) of luminance and chrominance of the picture element and neighbouring picture elements;

c. generating a first proportional parameter A(x,y) for the stored picture element based on a modular sum of differences between the luminance and chrominance of the stored picture element and surrounding picture elements;

d. using the first proportional parameter A(x,y) to generate a weighted picture element M(x,y) from a proportion of the stored picture element S(x,y) and a complementary proportion 1−

A(x,y) of the weighted value W(x,y);

e. inputting picture elements C(x,y) of a next image and a second proportional parameter K;

f. using the second proportional parameter K to generate a filtered image by combining a proportion of each input picture element C(x,y) of the next image with a complementary proportion 1−

K of the weighted stored picture element M(x,y) of the first image; and

g. storing the filtered image for corresponding combination with a succeeding image.

22. The computer executable software code as claimed in claim 21, wherein generating a weighted value comprises using an array of weighting values to weight neighbouring picture elements.

23. The computer executable software code as claimed in claim 21, wherein generating a weighted value comprises calculating a sum of absolute differences between chrominance and luminance of the picture element and surrounding picture elements.

24. The computer executable software code as claimed in claim 21, wherein generating a weighted value comprises calculating a sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

25. The computer executable software code as claimed in claim 24, wherein generating a weighted value comprises calculating a positive square root of the sum of squares of the differences between chrominance and luminance of the picture element and surrounding picture elements.

26. The computer executable software code as claimed in claim 21, wherein generating a weighted value comprises multiplying the modular sum of differences between luminance and chrominance of the stored picture element and of surrounding picture elements by the luminance and chrominance of the stored picture element respectively.

27. The computer executable software code as claimed in claim 21, wherein generating a weighted value comprises generating a normalised value of the proportional parameter A(x,y).

28. The computer executable software code as claimed in claim 21, further comprising filtering the input image with programmable spatial low pass filter means using means for estimating spatial noise in the input image for controlling the low pass filter means, such that the input image is filtered proportionally to noise detected.

29. The computer executable software code as claimed in claim 28, wherein output from the means for estimating spatial noise is adjustable dependent upon a degree of detail detected in a region of an image being processed.

30. The computer executable software code as claimed in claim 28, further comprising using a logic block controllable by a factor indicative of a degree of motion in an area of an image being processed such that a proportional factor applied to the combinatorial means is a functional of the noise and a degree of motion in a vicinity of a picture element being processed.