Method and apparatus for removing noise in still and moving pictures

• US 6,360,024 B1
• Filed: 07/06/2000
• Issued: 03/19/2002
• Est. Priority Date: 02/07/1997
• Status: Expired due to Fees

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Shen, Sheng Mei, Tan, Thiow Keng
• Primary Examiner(s): Lee, Thomas D.
• Assistant Examiner(s): BRINICH, STEPHEN M
• Application Number:
  US09/610,996
• Time in Patent Office: 621 Days
• Field of Search: 382/260-269, 358/1.9, 358/1.15
• US Class Current: 382/260
• CPC Class Codes: H04N 19/86 involving reduction of coding artifacts, e.g. of blockiness

Abstract

A method for filtering a blocky noise, as well as ring and mosquito noise, from still and moving pictures is disclosed. The method has the steps for locating a block boundary in the picture and selecting pixels on one side of the block boundary as a first group and pixels on the other side of the block boundary as a second group, calculating mean values (m₁, m₂) and deviation (c₁, c₂) of the pixels in each of the first and second groups, detecting whether or not the deviations (c₁, c₂) are smaller than a predetermined threshold value (T₂), applying a first predetermined filtering (equations (5), (6)) when the deviations (c₁, c₂) are not smaller than a predetermined threshold value (T₂); and applying a second predetermined filtering (equations (7), (8)) when the deviations (c₁, c₂) are smaller than a predetermined threshold value (T₂).

Claims

1. An integrated method of blocky noise and ring and mosquito noise removal in still and moving pictures, said method comprising:

filtering the pictures in two passes, wherein the two passes comprise a pass in a vertical direction followed by a pass in the horizontal direction or vice versa;

wherein each pass comprises an application of a blocky noise removal filter followed by a ring and mosquito noise removal filter.

2. A method of block based ring and mosquito noise removal in still and moving pictures according to claim 1, said method comprising:

processing pixels as a two dimensional array so as to maintain the horizontal and vertical relationships of the pixels;

selecting a plurality of pixels in a block surrounding a current pixel to be filtered;

excluding pixels from the selected pixels according to a selection criteria;

calculating a mean value of the selected groups of pixels remaining after said excluding; and

using the calculated mean value as a new value of the current pixel.

3. A method of ring and mosquito noise removal in still and moving pictures according to claim 2, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

4. An integrated method of blocky noise and ring and mosquito noise removal in still and moving pictures, said method comprising:

filtering the pictures in two passes, wherein the two passes comprise a pass in a vertical direction followed a pass in the horizontal direction or vice versa;

wherein each pass comprises an application of a ring and mosquito noise removal filter followed by a blocky noise removal filter.

5. A method of block based ring and mosquito noise removal in still and moving pictures according to claim 4, said method comprising:

processing pixels as a two dimensional array so as to maintain the horizontal and vertical relationships of the pixels;

selecting a plurality of pixels in a block surrounding a current pixel to be filtered;

excluding pixels from the selected pixels according to a selection criteria;

calculating a mean value of the selected groups of pixels remaining after said excluding; and

using the calculated mean value as a new value of the current pixel.

6. A method of ring and mosquito noise removal in still and moving pictures according to claim 5, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

7. An integrated method of blocky noise and ring and mosquito noise removal in still and moving pictures, said method comprising:

filtering the pictures in three passes, wherein the three passes comprise;

a blocky noise removal first pass in a horizontal direction;

a block based ring and mosquito noise removal second pass; and

a blocky noise removal third pass in a vertical direction.

8. A method of one dimensional ring and mosquito noise removal in still and moving pictures according to claim 7, said method comprising:

processing pixels along the horizontal and vertical directions;

selecting a plurality of pixels in lexical order before and after a current pixel to be filtered;

excluding pixels from the selected pixels according to a selection criteria;

calculating a mean value of the selected groups of pixels remaining after said excluding; and

using the calculated mean value as a new value of the current pixel.

9. A method of ring and mosquito noise removal in still and moving pictures according to claim 8, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

10. An integrated method of blocky noise and ring and mosquito noise removal in still and moving pictures, said method comprising:

filtering the pictures in three passes, wherein the three passes comprise;

a blocky noise removal pass in a horizontal direction;

a blocky noise removal pass in a vertical direction; and

a block based ring and mosquito noise removal pass;

wherein the three passes may be applied in any given order.

11. A method of one dimensional ring and mosquito noise removal in still and moving pictures according to claim 10, said method comprising:

processing pixels along the horizontal and vertical directions;

selecting a plurality of pixels in lexical order before and after a current pixel to be filtered;

excluding pixels from the selected pixels according to a selection criteria;

calculating a mean value of the selected groups of pixels remaining after said excluding; and

using the calculated mean value as a new value of the current pixel.

12. A method of ring and mosquito noise removal in still and moving pictures according to claim 11, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

13. An apparatus for filtering a blocky noise and ring and mosquito noise from still and moving pictures, said apparatus comprising:

a blocky noise removal filter operable to remove blocky noise; and

a ring and mosquito noise removal filter operable to remove ring and mosquito noise;

wherein the pictures are filtered in two passes, wherein the two passes comprise a pass in a vertical direction followed by a pass in the horizontal direction or vice versa;

wherein each pass comprises an application of said blocky noise removal filter followed by said ring and mosquito noise removal filter.

14. An apparatus for block based ring and mosquito noise removal in still and moving pictures according to claim 13, said apparatus comprising:

a unit operable to process pixels as a two dimensional array so as to maintain the horizontal and vertical relationships of the pixels;

a unit operable to select a plurality of pixels in a block surrounding a current pixel to be filtered;

a unit operable to exclude pixels from the selected pixels according to a selection criteria;

a unit operable to calculate a mean value of the selected groups of pixels remaining after the excluding of pixels; and

a unit operable to use the calculated mean value as a new value of the current pixel.

15. An apparatus for ring and mosquito noise removal in still and moving pictures according to claim 14, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

16. An apparatus for filtering a blocky noise and ring and mosquito noise from still and moving pictures, said apparatus comprising:

a blocky noise removal filter operable to remove blocky noise; and

a ring and mosquito noise removal filter operable to remove ring and mosquito noise;

wherein the pictures are filtered in two passes, wherein the two passes comprise a pass in a vertical direction followed by a pass in the horizontal direction or vice versa;

wherein each pass comprises an application of said ring and mosquito noise removal filter followed by said blocky noise removal filter.

17. An apparatus for block based ring and mosquito noise removal in still and moving pictures according to claim 16, said apparatus comprising:

a unit operable to process pixels as a two dimensional array so as to maintain the horizontal and vertical relationships of the pixels;

a unit operable to select a plurality of pixels in a block surrounding a current pixel to be filtered;

a unit operable to exclude pixels from the selected pixels according to a selection criteria;

a unit operable to calculate a mean value of the selected groups of pixels remaining after the excluding of pixels; and

a unit operable to use the calculated mean value as a new value of the current pixel.

18. An apparatus for ring and mosquito noise removal in still and moving pictures according to claim 17, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

19. An apparatus for filtering a blocky noise and ring and mosquito noise from still and moving pictures, said apparatus comprising:

a horizontal deblocking filter operable to remove blocky noise in the horizontal direction;

a block based ring and mosquito noise filter operable to remove ring and mosquito noise;

a vertical deblocking filter operable to remove blocky noise in the vertical direction;

wherein the pictures are filtered in three passes, the three passes comprising;

a blocky noise removal first pass in the horizontal direction using said horizontal deblocking filter;

a block based ring and mosquito noise removal second pass using said block based ring and mosquito noise filter; and

a blocky noise removal third pass in the vertical direction using said vertical deblocking filter.

20. An apparatus for one dimensional ring and mosquito noise removal in still and moving pictures according to claim 19, said apparatus comprising:

a unit operable to process pixels along the horizontal and vertical directions;

a unit operable to select a plurality of pixels in lexical order before and after a current pixel to be filtered;

a unit operable to exclude pixels from the selected pixels according to a selection criteria;

a unit operable to calculate a mean value of the selected groups of pixels remaining after the excluding of pixels; and

a unit operable to use the calculated mean value as a new value of the current pixel.

21. An apparatus for ring and mosquito noise removal in still and moving pictures according to claim 20, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.

22. An apparatus for filtering a blocky noise and ring and mosquito noise from still and moving pictures, said apparatus comprising:

a horizontal deblocking filter operable to remove blocky noise in the horizontal direction;

a block based ring and mosquito noise filter operable to remove ring and mosquito noise;

a vertical deblocking filter operable to remove blocky noise in the vertical direction;

wherein the pictures are filtered in three passes, the three passes comprising;

a blocky noise removal pass in the horizontal direction using said horizontal deblocking filter;

a blocky noise removal pass in the vertical direction using said vertical deblocking filter; and

a block based ring and mosquito noise removal pass using said block based ring and mosquito noise filter;

wherein the three passes may be applied in any given order.

23. An apparatus for one dimensional ring and mosquito noise removal in still and moving pictures according to claim 22, said apparatus comprising:

a unit operable to process pixels along the horizontal and vertical directions;

a unit operable to select a plurality of pixels in lexical order before and after a current pixel to be filtered;

a unit operable to exclude pixels from the selected pixels according to a selection criteria;

a unit operable to calculate a mean value of the selected groups of pixels remaining after the excluding of pixels; and

a unit operable to use the calculated mean value as a new value of the current pixel.

24. An apparatus for ring and mosquito noise removal in still and moving pictures according to claim 23, wherein the selection criteria for excluding pixels from the selected pixels is performed by comparing the current pixel and the selected pixel, and excluding the pixel when an absolute difference is greater than a predefined threshold.