Encoding apparatus and encoding method as well as decoding apparatus and decoding method

An encoding method, comprising:

• performing a filter process for a first image to generate a second image, the performing a filter process including
• selecting, from within the first image that is obtained by addition of a residual of prediction encoding and a prediction image, pixels that become a prediction tap to be used for prediction arithmetic operation for determining a pixel value of a corresponding pixel of the second image, which corresponds to a processing target pixel that is a processing target in the first image and is to be used for prediction of the prediction image,
• classifying the processing target pixel to one of a plurality of classes,
• acquiring tap coefficients of the class of the processing target pixel from among tap coefficients obtained using reduction filter information that reduces the tap coefficients for individual ones of the plurality of classes determined by learning that uses a student image corresponding to the first image and a teacher image equivalent to an original image corresponding to the first image, and
• determining a pixel value of the corresponding pixel by performing the prediction arithmetic operation using the tap coefficients of the class of the processing target pixel and the prediction tap of the processing target pixel;
• and
• transmitting the reduction filter information.

A decoding apparatus, comprising:

• an acceptance section configured to accept reduction filter information that reduces tap coefficients for individual ones of a plurality of classes determined by learning that uses a student image equivalent to a first image obtained by adding a residual of prediction encoding and a prediction image and a teacher image equivalent to an original image corresponding to the first image;
• and
• a filter processing section that includes
• a prediction tap selection section configured to select, from within the first image, pixels that become a prediction tap to be used for prediction arithmetic operation for determining a pixel value of a corresponding pixel of a second image, which is used for prediction of the prediction image, corresponding to a processing target pixel that is a processing target from within the first image,
• a classification section configured to classify the processing target pixel to one of the plurality of classes,
• a tap coefficient acquisition section configured to acquire a tap coefficient of the class of the processing target pixel from the tap coefficients obtained using the reduction filter information, and
• an arithmetic operation section configured to determine a pixel value of the corresponding pixel by performing the prediction arithmetic operation using the tap coefficient of the class of the processing target pixel and the prediction tap of the processing target pixel, the filter processing section performing a filter process for the first image to generate the second image.

A decoding method, comprising:

• accepting reduction filter information that reduces tap coefficients for individual ones of a plurality of classes determined by learning that uses a student image equivalent to a first image obtained by adding a residual of prediction encoding and a prediction image and a teacher image equivalent to an original image corresponding to the first image;
• and
• performing a filter process for the first image to generate a second image, the performing a filter process including
• selecting, from within the first image, pixels that become a prediction tap to be used for prediction arithmetic operation for determining a pixel value of a corresponding pixel of a second image, which is used for prediction of the prediction image, corresponding to a processing target pixel that is a processing target from within the first image,
• classifying the processing target pixel to one of the plurality of classes,
• acquiring a tap coefficient of the class of the processing target pixel from the tap coefficients obtained using the reduction filter information, and
• determining a pixel value of the corresponding pixel by performing the prediction arithmetic operation using the tap coefficient of the class of the processing target pixel and the prediction tap of the processing target pixel.