Image encoding apparatus, image decoding apparatus, control methods and non-transitory computer-readable storage medium

An image encoding apparatus for encoding an image, the apparatus comprising;

• a dividing unit configured to divide the image into a plurality of blocks;
• a quantizing unit configured to perform quantizing processing on an object block using a quantization matrix;
• and
• an encoding unit configured to encode data for indicating a plurality of values corresponding to at least a part of elements in the quantization matrix,
• wherein, in a case where a width of the object block is 16 samples and a height of the object block is 8 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element adjacent to the first element on a right side of the first element and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the first element and is below the first element, the fourth element is adjacent to the second element and is below the second element, and
• wherein, in a case where a width of the object block is 8 samples and a height of the object block is 16 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element which is adjacent to the first element and is below the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the second element and is below the second element, and the fourth element is adjacent to the third element and is below the third element.

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

• decoding data for indicating a plurality of difference values for a quantization matrix used for inverse quantizing processing which derives transform coefficients from quantized transform coefficients;
• deriving a plurality of values corresponding to at least a part of elements in the quantization matrix by using the data, and deriving the quantization matrix based on the plurality of values;
• and
• performing the inverse quantizing processing on an object block using the quantization matrix,
• wherein, in a case where a width of the object block is 16 samples and a height of the object block is 8 samples, the deriving unit derives the quantization matrix by:
• setting a first value among the plurality of values as a first element corresponding to DC component in the quantization matrix, wherein the first value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the first value is derived by using difference from a predetermined initial value;
• setting a second value among the plurality of values as a second element adjacent to the first element on a right side of the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the second value is derived by using difference from the first value;
• and
• setting a third value among the plurality of values as a third element and a fourth element, wherein the third element is adjacent to the first element and is below the first element, the fourth element is adjacent to the second element and is below the second element, and the third value is derived by using difference from the second value, and
• wherein, in a case where a width of the object block is 8 samples and a height of the object block is 16 samples, the deriving unit derives the quantization matrix by:
• setting a first value among the plurality of values as a first element corresponding to DC component in the quantization matrix, wherein the first value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the first value is derived by using difference from a predetermined initial value;
• setting a second value among the plurality of values as a second element which is adjacent to the first element and is below the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the second value is derived by using difference from the first value;
• and
• setting a third value among the plurality of values as a third element and a fourth element, wherein the third element is adjacent to the second element and is below the second element, the fourth element is adjacent to the third element and is below the third element, and the third value is derived by using difference from the second value.

An image encoding method for encoding an image, the method comprising;

• dividing the image into a plurality of blocks;
• performing quantizing processing on an object block using a quantization matrix;
• and
• encoding data for indicating a plurality of values corresponding to at least a part of elements in the quantization matrix,
• wherein, in a case where a width of the object block is 16 samples and a height of the object block is 8 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element adjacent to the first element on a right side of the first element and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the first element and is below the first element, the fourth element is adjacent to the second element and is below the second element, and
• wherein, in a case where a width of the object block is 8 samples and a height of the object block is 16 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element which is adjacent to the first element and is below the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the second element and is below the second element, and the fourth element is adjacent to the third element and is below the third element.

A non-transitory computer-readable storage medium which stores a program for executing an image decoding method for decoding an image from encoded data, the method comprising:

• decoding data for indicating a plurality of difference values for a quantization matrix used for inverse quantizing processing which derives transform coefficients from quantized transform coefficients;
• deriving a plurality of values corresponding to at least a part of elements in the quantization matrix by using the data, and deriving the quantization matrix based on the plurality of values;
• and
• performing the inverse quantizing processing on an object block using the quantization matrix,
• wherein, in a case where a width of the object block is 16 samples and a height of the object block is 8 samples, the deriving unit derives the quantization matrix by:
• setting a first value among the plurality of values as a first element corresponding to DC component in the quantization matrix, wherein the first value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the first value is derived by using difference from a predetermined initial value;
• setting a second value among the plurality of values as a second element adjacent to the first element on a right side of the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the second value is derived by using difference from the first value;
• and
• setting a third value among the plurality of values as a third element and a fourth element, wherein the third element is adjacent to the first element and is below the first element, the fourth element is adjacent to the second element and is below the second element, and the third value is derived by using difference from the second value, and
• wherein, in a case where a width of the object block is 8 samples and a height of the object block is 16 samples, the deriving unit derives the quantization matrix by:
• setting a first value among the plurality of values as a first element corresponding to DC component in the quantization matrix, wherein the first value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the first value is derived by using difference from a predetermined initial value;
• setting a second value among the plurality of values as a second element which is adjacent to the first element and is below the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the inverse quantizing processing, and the second value is derived by using difference from the first value;
• and
• setting a third value among the plurality of values as a third element and a fourth element, wherein the third element is adjacent to the second element and is below the second element, the fourth element is adjacent to the third element and is below the third element, and the third value is derived by using difference from the second value.

A non-transitory computer-readable storage medium which stores a program for executing an image encoding method for encoding an image, the method comprising;

• dividing the image into a plurality of blocks;
• performing quantizing processing on an object block using a quantization matrix;
• and
• encoding data for indicating a plurality of values corresponding to at least a part of elements in the quantization matrix,
• wherein, in a case where a width of the object block is 16 samples and a height of the object block is 8 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element adjacent to the first element on a right side of the first element and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the first element and is below the first element, the fourth element is adjacent to the second element and is below the second element, and
• wherein, in a case where a width of the object block is 8 samples and a height of the object block is 16 samples, the data includes:
• data indicating difference between a predetermined initial value and a first value which is set as a first element corresponding to DC component in the quantization matrix and is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• data indicating difference between the first value and a second value which is set as a second element which is adjacent to the first element and is below the first element, wherein the second value is not set for a plurality of elements in the quantization matrix used for the quantizing processing;
• and
• data indicating difference between the second value and a third value which is set as a third element and a fourth element, wherein the third element is adjacent to the second element and is below the second element, and the fourth element is adjacent to the third element and is below the third element.