Image coding apparatus, image coding method, image decoding apparatus, image decoding method, and storage medium

An image coding apparatus comprising:

• an acquisition unit configured to acquire a difference value between elements included in a quantization matrix of n rows×n columns (n is an integer equal to or greater than 4) that is used for encoding image data to be coded and that can be expressed in a two-dimensional array;
• and
• a coding unit configured to code the image data by using the quantization matrix,
• wherein the acquisition unit acquires a difference value between a first element and 8, wherein the first element corresponds to a first row and a first column of the quantization matrix, and
• wherein the acquisition unit acquires a difference value between an element corresponding to a (p+1)-th row (p is an integer equal to or greater than 2 and smaller than n) and the first column of the quantization matrix and an element corresponding to the first row and a p-th column of the quantization matrix.

An image decoding method for decoding a bit stream, the image decoding method comprising:

• acquiring, from the bit stream, a difference value between elements included in a quantization matrix of n rows×n columns (n is an integer equal to or greater than 4);
• deriving a first element by adding a first difference value and 8, and deriving an (r-th)-element (r is an integer equal to or greater than 2) by adding an r-th difference value and an (r−1)-th element, so as to derive a plurality of elements, wherein the first difference value and the r-th difference value are difference values acquired for the quantization matrix;
• and
• associating the plurality of elements derived with elements in the quantization matrix that can be expressed in a two-dimensional array,
• wherein in a case where a predetermined element of the plurality of elements derived is associated with an element corresponding to a first row and a p-th column (p is an integer equal to or greater than 2 and smaller than n) of the quantization matrix, associates an element next to the predetermined element derived with an element corresponding to a (p+1)-th row and a first column of the quantization matrix.

A non-transitory computer-readable storage medium storing a program for causing a computer to execute an image decoding method for decoding a bit stream, the image decoding method comprising:

• acquiring, from the bit stream, a difference value between elements included in a quantization matrix of n rows×n columns (n is an integer equal to or greater than 4);
• deriving a first element by adding a first difference value and 8, and deriving an (r-th)-element (r is an integer equal to or greater than 2) by adding an r-th difference value and an (r−1)-th element, so as to derive a plurality of elements, wherein the first difference value and the r-th difference value are difference values acquired for the quantization matrix;
• and
• associating the plurality of elements derived with elements in the quantization matrix that can be expressed in a two-dimensional array,
• wherein in a case where a predetermined element of the plurality of elements derived is associated with an element corresponding to a first row and a p-th column (p is an integer equal to or greater than 2 and smaller than n) of the quantization matrix, associates an element next to the predetermined element derived with an element corresponding to a (p+1)-th row and a first column of the quantization matrix.

An image coding method comprising:

• acquiring a difference value between elements included in a quantization matrix of n rows×n columns (n is an integer equal to or greater than 4) that is used for encoding image data to be coded and that can be expressed in a two-dimensional array;
• and
• coding the image data by using the quantization matrix,
• wherein a difference value between a first element and 8 is acquired for the quantization matrix, wherein the first element corresponds to a first row and a first column of the quantization matrix, and
• wherein a difference value between an element corresponding to a (p+1)-th row (p is an integer equal to or greater than 2 and smaller than n) and the first column of the quantization matrix and an element corresponding to the first row and a p-th column of the quantization matrix is acquired.

A non-transitory computer-readable storage medium storing a program for causing a computer to execute an image coding method comprising:

• acquiring a difference value between elements included in a quantization matrix of n rows×n columns (n is an integer equal to or greater than 4) that is used for encoding image data to be coded and that can be expressed in a two-dimensional array;
• and
• coding the image data by using the quantization matrix,
• wherein a difference value between a first element and 8 is acquired for the quantization matrix, wherein the first element corresponds to a first row and a first column of the quantization matrix, and
• wherein a difference value between an element corresponding to a (p+1)-th row (p is an integer equal to or greater than 2 and smaller than n) and the first column of the quantization matrix and an element corresponding to the first row and a p-th column of the quantization matrix is acquired.