Method and apparatus for removing noise in still and moving pictures

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

• at least one filter for filtering the pictures in a vertical direction and a horizontal direction, each of said at least one filter comprising:
• unit 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;
• unit for calculating mean values (m1, m2) and deviation (c1, c2) of the pixels in each of the first and second groups;
• unit for detecting whether or not the deviations (c1, c2) are smaller than a predetermined threshold value (T2),
• unit for applying a first predetermined filtering (equations (5), (6)) when the deviations (c1, c2) are not smaller than a predetermined threshold value (T2);
• and
• unit for applying a second predetermined filtering (equations (7), (8)) when the deviations (c1, c2) are smaller than a predetermined threshold value (T2).

A noise removal method for removing blocky noise as well as ring and mosquito noise in still and moving pictures, said noise removal method comprising:

• locating a next block boundary in the picture and separating the pixels on either side of the block boundary into two groups;
• determining a type and length of a filter to be used based on the pixel values on either side of the block boundary;
• and
• applying an appropriate method of filtering to the groups of pixels;
• wherein block boundaries in the picture are located at intervals of a plurality of pixels equal to the dimension of a block transform and each group of pixels consists of up to one half of the number of pixels.

A noise removal method for removing blocky noise as well as ring and mosquito noise in still and moving pictures, said noise removal method comprising:

• locating a next block boundary in the picture and separating the pixels on either side of the block boundary into two groups;
• determining a type and length of a filter to be used based on the pixel values on either side of the block boundary;
• and
• applying an appropriate method of filtering to the groups of pixels;
• wherein said determining the type and length of filter to use comprises:
• calculating a mean value of the group of pixels, given by a mathematical sum of the pixels value divided by the total number of pixels in the group, and a deviation of the group of pixels, given by a mathematical sum of an absolute difference of the pixel value and the mean value of the group;
• checking that the absolute difference of the mean values at the block boundary is less than a first predefined threshold, proceeding with the filtering operation if the criteria is satisfied and otherwise the filtering operation ends;
• checking that the deviation of the group of pixels is less than a second predefined threshold and applying a first method of filtering if the criteria is satisfied;
• and
• applying a second of filtering, otherwise.