Post-processing method and apparatus for removing a blocking effect in a decoded image signal

An apparatus, for use in an image signal decoding system, for post-processing, on a pixel-by-pixel basis, decoded image data of a current frame provided from an image signal decoder included in the image signal decoding system, which comprises:

• means for storing the decoded image data of the current frame and generating target pixel data from the stored decoded image data, wherein the target pixel data represents the value of a pixel to be filtered;
• means for filtering the target pixel data to produce filtered target pixel data;
• means for calculating an absolute difference value between original target pixel data and the filtered target pixel data, wherein the original target pixel data denotes non-filtered target pixel data contained in the stored decoded image data;
• means for comparing the calculated absolute difference value with a predetermined threshold value;
• means for updating the stored target pixel data with the filtered target pixel data if the absolute difference value is smaller than a predetermined threshold value;
• and
• means for updating the stored target pixel data with compensated target pixel data if the absolute difference value is equal to or larger than the predetermined threshold value, wherein the compensated target pixel data is derived by adding the original target pixel data and the predetermined threshold value if the original target pixel data is smaller than the filtered target pixel data and by subtracting the predetermined threshold value from the original target pixel data if the original target pixel data is greater than the filtered target pixel data.

An apparatus, for use in an image signal decoding system, for post-processing, on a pixel-by-pixel basis, decoded image data of a current frame provided from an image signal decoder included in the image signal decoding system, which comprises:

• memory means for storing the decoded image data;
• means for filtering target pixel data stored in the memory means to provide filtered target pixel data, wherein the target pixel data represents a pixel value of a pixel to be filtered;
• means for comparing the filtered target pixel data with original target pixel data, wherein the original target pixel data represents non-filtered target pixel data included in the stored decoded image data;
• and
• means for updating the stored target pixel data with the filtered target pixel data if an absolute difference value is smaller than a predetermined threshold value and updating the stored target pixel data with compensated target pixel data if the absolute difference value is equal to or larger than the predetermined threshold value, wherein the absolute difference value represents an absolute difference between the original target pixel data and the filtered target pixel data and the compensated target pixel data is provided by adding the original target pixel data and the predetermined threshold value if the original target pixel data is smaller than the filtered target pixel data and by subtracting the predetermined threshold value from the original target pixel data if the original target pixel data is greater than the filtered target pixel data.