| CPC H04N 19/154 (2014.11) [H04N 19/117 (2014.11); H04N 19/14 (2014.11); H04N 19/159 (2014.11); H04N 19/176 (2014.11); H04N 19/186 (2014.11); H04N 19/593 (2014.11); H04N 19/61 (2014.11); H04N 19/82 (2014.11); H04N 19/865 (2014.11); H04N 19/46 (2014.11)] | 2 Claims |

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1. An image decoding device that carries out a decoding process on a coded data obtained by performing a block based coding process on an image, the image decoding device comprising:
a coded data decoder to decode the coded data to acquire compressed data of a difference image associated with each of coding blocks, and an offset;
a loop filter to carry out a filtering process on a decoded image obtained by inverse-quantizing the compressed data of the difference image and adding a prediction image to the difference image obtained by inverse-quantizing the compressed data, the loop filter carrying out the filtering process to remove a block distortion at a boundary between adjacent transform blocks of the decoded image, the transform block being for transforming the difference image and corresponding to the coding block hierarchically divided from a maximum size of a coding block; and a memory to store decoded pixel values for outputting the decoded image on which the filtering process has been carried out,
wherein the filtering process carried out by the loop filter includes determining whether a vertical edge or a horizontal edge of the coding block expressed by K*K pixel grid overlaps the boundary, and deriving, in a case that the vertical edge or the horizontal edge overlaps the boundary, a parameter of the coding block specifying filtering strength as a default value for the offset according to a set of conditions including whether a non-zero transform coefficient is included in at least one of the adjacent transform blocks to which the filtering process is to be applied, and the offset is added to a value of the parameter by the loop filter in a process of selecting from different filtering processes.
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