Method and apparatus for blocking artifact detection and measurement in block-coded video

A system comprising:

• a source of a video signal;
• a block grid detection circuit coupled to the source of the video signal;
• and
• a blocking artifact reduction circuit coupled to the source of the video signal and to the block grid detection circuit;
• the block grid detection circuit operative to:
• detect vertical edge pixels in an image;
• accumulate counts of the detected vertical edge pixels in said image;
• analyze said counts by horizontal location in said image to detect a spatial periodicity in said detected vertical edge pixels;
• detect horizontal edge pixels in said image;
• accumulate counts of the detected horizontal edge pixels in said image;
• and
• analyze said counts of horizontal edge pixels by vertical location in said image to detect a spatial periodicity in said detected horizontal edge pixels;
• wherein:
• said detecting vertical edge pixels includes, with respect to a target pixel:
• calculating a first difference Δ1 as an absolute value of a difference between a value of the target pixel and a value of a first pixel that is immediately to the left of the target pixel;
• calculating a second difference Δ0 as an absolute value of a difference between the value of said first pixel and a value of a second pixel that is immediately to the left of the first pixel;
• calculating a third difference Δ2 as an absolute value of a difference between the value of the target pixel and a value of a third pixel that is immediately to the right of the target pixel;
• and
• classifying the target pixel as an edge pixel if and only if all of the following conditions are met:
• (a) the first difference Δ1 is less than a threshold;
• (b) the first difference Δ1 is greater than the second difference Δ0 ;
• and
• (c) the first difference Δ1 is greater than the third difference Δ2.

A method comprising:

• receiving a video signal from a video signal source, the video signal source being a video tuner, a satellite earth station or a DVD player;
• detecting vertical edge pixels in an image in the video signal;
• accumulating counts of said detected vertical edge pixels in each of 32 groups of columns of pixels of the image, each of the groups of columns corresponding to an offset modulo 32 in a horizontal direction;
• determining a respective index for each of four groups of columns having larger counts of vertical edge pixels accumulated therein than any group of columns that is not one of the four groups;
• determining whether any two of the determined indices differ by 21 or 22;
• post-processing said image based on results of said determining steps;
• and
• displaying said post-processed image on a display device;
• wherein:
• said detecting vertical edge pixels includes, with respect to a target pixel:
• calculating a first difference Δ1 as an absolute value of a difference between a value of the target pixel and a value of a first pixel that is immediately to the left of the target pixel;
• calculating a second difference Δ0 as an absolute value of a difference between the value of said first pixel and a value of a second pixel that is immediately to the left of the first pixel;
• calculating a third difference Δ2 as an absolute value of a difference between the value of the target pixel and a value of a third pixel that is immediately to the right of the target pixel;
• and
• classifying the target pixel as an edge pixel if and only if all of the following conditions are met:
• (a) the first difference Δ1 is less than a threshold;
• (b) the first difference Δ1 is greater than the second difference Δ0 ;
• and
• (c) the first difference Δ1 is greater than the third difference Δ2.