Decoding apparatus including a filtering unit configured to filter an image using a selected filtering mask and threshold comparison operation

Abstract

A method and apparatus to remove a block effect and a ring effect appearing in a compression-coded image is disclosed. The present invention is especially applicable to an image compression-coded at a low bit rate. In particular, the present invention includes a variety of masks for the removal of the block/ring effect. Thus, one mask is select for a pixel to be filtered. Moreover, candidate pixels to be averaged with the pixel to be filtered is selected from the pixels of the selected mask to better maintain the details of the image, and a weight is applied to improve the calculation speed of the averaging operation. More particularly, the masks according to the present invention have longer tabs toward adjacent blocks at boundaries of the given block to remove the block and ring effect. In an embodiment, the filtering unit is configured to select a filtering mask based on a position of a pixel to be filtered. The filtering mask includes the pixel to be filtered and at least one candidate pixel. The filtering unit is configured to perform at least one comparison, and the comparison compares a determined value and a threshold. The determined value is based on the pixel to be filtered and the at least one candidate pixel, and the threshold is based on quantization information of at least a portion of the image including the pixel to be filtered.

Dependencies are inferred from the claim text.