Patent ID: 7463688
Filing Date: 2008-12-09
Classification: H04N

Abstract:
1. A method for processing video image signals to remove blocking artifacts resulting from block-based transform coding in a frame of pixels representing an image, comprising the steps of: (a) for each pixel in the frame, determining if the pixel is proximate a block boundary resulting from block-based transform coding; and (b) if the pixel is proximate a block boundary, then determining an image feature direction across the block boundary relative to the pixel, and modifying the pixel characteristic value substantially along the image feature direction to create a natural transition across the block boundary to essentially remove blocking artifacts resulting from said block-based transform coding, wherein determining an image feature direction includes determining an image feature direction based on a least central variance direction that is a function of multiple 1-D central variances in multiple directions, respectively, wherein step (b) further includes the steps of: determining the least central variance direction across the block boundary relative to the pixel as a function of said multiple 1-D central variances, wherein each 1-D central variance in a direction is a function of absolute differences between the pixel and its neighboring pixels along that direction, and then modifying the pixel characteristic value using characteristic values of neighboring pixels substantially along the least central variance direction, to create a natural transition across the block boundary to essentially remove blocking artifacts resulting from said block-based transform coding, wherein the step of determining the least central variance direction across the block boundary relative to the current pixel, further comprises the steps of: if the horizontal direction is across the block boundary relative to the current pixel, then determining a 1-D central variance in the horizontal direction across the block boundary, using neighboring pixels substantially along a horizontal line centered at the current pixel; if the vertical direction is across the block boundary relative to the current pixel, then determining a 1-D central variance in the vertical direction across the block boundary, using neighboring pixels substantially along a vertical line centered at the current pixel; determining 1-D central variances relative to the current pixel in two diagonal directions across the block boundary, using neighboring pixels substantially along two diagonal lines centered at the current pixel, respectively; selecting the least central variance direction by finding the direction which has minimal 1-D central variance among the 1-D central variances that correspond to the directions across the block boundary; and then modifying the current pixel characteristic value as a function of the characteristic values of the neighboring pixels along the selected least central variance direction, to create a natural transition across the block boundary to essentially remove blocking artifacts resulting from said block-based transform coding, wherein: a characteristic value of the current pixel is denoted by f(m,n), wherein m and n are the row and column indices for the current pixel in the frame; the horizontal 1-D central variance V the vertical 1-D central variance V the diagonal 1-D central variance V the other diagonal 1-D central variance V