Luminance deblock filtering encoding device, decoding device, and program

A decoding device which decodes encoded data of an input image comprising:

• an entropy decoder configured to decode the encoded data and obtain a quantization coefficient generated by quantizing a transform coefficient;
• an image decoder configured to restore a transform coefficient from the quantization coefficient based on a quantization parameter and generate a pre-filtering image by adding a predicted image to a residual image restored by performing inverse transformation on the transform coefficient;
• and
• a deblocking filter configured to perform a filtering process on the pre-filtering image, wherein
• the deblocking filter is configured to control a filtering strength depending on a result of comparison between a luminance signal level of the pre-filtering image and a luminance threshold value,
• the deblocking filter is configured to calculate the luminance signal level of the pre-filtering image by averaging pixel values of a plurality of pixels in a boundary area of a pair of neighboring blocks corresponding to the pre-filtering image, and
• the deblocking filter is configured to determine the luminance threshold value for each picture or each sequence.

An image encoding method for encoding an input image, the image encoding method comprising:

• calculating a transform coefficient by performing a transformation process on a residual image indicating a difference between the input image and a predicted image of the input image;
• generating quantization coefficient by quantizing the transform coefficient based on a quantization parameter;
• generating encoded data by encoding the quantization coefficient;
• restoring a transform coefficient from the quantization coefficient based on the quantization parameter and generate a pre-filtering image by adding the predicted image to a residual image restored by performing inverse transformation on the transform coefficient;
• performing a filtering process on the pre-filtering image, wherein
• the performing the filtering process comprises:
• calculating a luminance signal level of the pre-filtering image by averaging pixel values of a plurality of pixels in a boundary area of a pair of neighboring blocks corresponding to the pre-filtering image, and
• controlling a filtering strength depending on a result of comparison between the luminance signal level of the pre-filtering image and a luminance threshold value, wherein
• the luminance threshold value is determined for each picture or each sequence.

An image decoding method for decoding encoded data of an input image, the image decoding method comprising:

• decoding the encoded data and obtain a quantization coefficient generated by quantizing a transform coefficient;
• restoring a transform coefficient from the quantization coefficient based on a quantization parameter and generate a pre-filtering image by adding a predicted image to a residual image restored by performing inverse transformation on the transform coefficient;
• and
• performing a filtering process on the pre-filtering image, wherein
• the filtering process comprises
• controlling a filtering strength depending on a result of comparison between a luminance signal level of the pre-filtering image and a luminance threshold value, and
• calculating the luminance signal level of the pre-filtering image by averaging pixel values of a plurality of pixels in a boundary area of a pair of neighboring blocks corresponding to the pre-filtering image, wherein
• the luminance threshold value is determined for each picture or each sequence.