ENCODER AND DECODER

To achieve a further improvement in an encoder and a decoder.SOLUTION: There is provided an encoder in which luminance filter processing is performed on a first boundary between a first luminance block and a second luminance block, and color difference filter processing is performed on a second boundary between a first color difference block and a second color difference block. In the luminance filter processing, values of a plurality of luminance samples are changed using clip processing such that change amounts of the plurality of luminance samples do not exceed respective first thresholds, the luminance samples being included in the first luminance block and the second luminance block and being lined up in a direction perpendicular to the first boundary. The respective first thresholds are determined based on quantization parameters, and set to be asymmetrical with respect to the first boundary. In the color difference filter processing, values of a plurality of color difference samples are changed using clip processing such that change amounts of the plurality of color difference samples do not exceed respective second thresholds, the color difference samples being included in the first color difference block and the second color difference block and being lined up in a direction perpendicular to the second boundary.SELECTED DRAWING: Figure 13 【課題】さらなる改善を実現する。【解決手段】符号化装置は、第１輝度ブロックと第２輝度ブロックとの第１境界に対して輝度フィルタ処理を行い、第１色差ブロックと第２色差ブロックとの第２境界に対して色差フィルタ処理を行い、輝度フィルタ処理において、第１境界に直交する方向に並んだ、第１輝度ブロック及び第２輝度ブロックに含まれる複数の輝度サンプルの値の変化量が各第１閾値を超えないようなクリップ処理を用いて、複数の輝度サンプルの値を変更し、各第１閾値は、量子化パラメータに基づいて決定され、かつ、第１境界を基準に非対称に設定され、色差フィルタ処理において、第２境界に直交する方向に並んだ、第１色差ブロック及び第２色差ブロックに含まれる複数の色差サンプルの値の変化量が各第２閾値を超えないようなクリップ処理を用いて、複数の色差サンプルの値を変更する。【選択図】図１３