Image decoding device and image coding device
Even in a case in which a color format is a format other than 4:2:0, an image coding device and an image decoding device capable of accurately locating a reference pixel position in inter-layer image prediction are realized. A hierarchical moving image decoding device ( 1 ) includes a parameter set decoding section ( 12 ) that decodes a scaled reference layer offset syntax that is coded in a chroma pixel unit and a predicted image generation section ( 1442 ) that derives a scale based on a scaled reference layer offset which is a product of the scaled reference layer offset syntax and a luminance chroma size ratio of a target layer picture and generates a predicted image.
1. An image decoding device that decodes coded data that is hierarchically coded to reconstruct a decoded picture of a higher layer which is a target layer, the image decoding device comprising:
a parameter set decoding circuit that decodes a parameter set; and
a predicted image generation circuit that generates a predicted image by inter-layer prediction with reference to decoded pixels of a reference layer picture,
wherein the parameter set decoding circuit decodes a color format identifier and derives a luma chroma width ratio depending upon a chroma format, which is specified by the color format identifier,
wherein the parameter set decoding circuit decodes: (i) a scaled reference layer offset syntax which is decoded in a chroma pixel unit of the target layer picture, and (ii) a reference layer offset syntax which is decoded in a chroma pixel unit of the reference layer picture,
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture,
wherein the predicted image generation circuit derives a reference position by using a scaled reference layer offset, a reference layer offset, and a scale,
wherein the scaled reference layer offset is derived by multiplying a value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma width ratio of the target layer picture,
wherein the reference layer offset is derived by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture, and
wherein the scale is derived by using the scaled reference layer offset and the reference layer offset.
2. An image coding device that generates coded data of a higher layer which is a target layer from an input image, the image coding device comprising:
a parameter set coding circuit that codes a parameter set; and
a predicted image generation circuit that generates a predicted image by inter-layer prediction with reference to decoded pixels of a reference layer picture,
wherein the parameter set coding circuit codes a color format identifier and derives a luma chroma width ratio depending upon a chroma format, which is specified by the color format identifier,
wherein the parameter set coding circuit codes a scaled reference layer offset syntax which is coded in a chroma pixel unit of the target layer picture and a reference layer offset syntax which is coded in a chroma pixel unit of the reference layer picture,
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture,
wherein the predicted image generation circuit derives a reference position by using a scaled reference layer offset, a reference layer offset, and a scale,
wherein the scaled reference layer offset is derived by multiplying a value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma width ratio of the target layer picture,
wherein the reference layer offset is derived by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture, and
wherein the scale is derived by using the scaled reference layer offset and the reference layer offset.
3. An image decoding method for decoding coded data that is hierarchically coded to reconstruct a decoded picture of a higher layer which is a target layer, the image decoding method comprising:
decoding a color format identifier;
deriving a luma chroma width ratio depending upon a chroma format, which is specified by the color format identifier;
decoding a scaled reference layer offset syntax which is decoded in a chroma pixel unit of the target layer picture and a reference layer offset syntax which is decoded in a chroma pixel unit of a reference layer picture;
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture;
deriving a scaled reference layer offset by multiplying a value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma width ratio of the target layer picture;
deriving a reference layer offset by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture,
deriving a scale by using the scaled reference layer offset and the reference layer offset;
deriving a reference position by using the scaled reference layer offset, the reference layer offset, and the scale; and
generating a predicted image by inter-layer prediction.
4. An image coding method for generating coded data of a higher layer which is a target layer from an input image, the image coding method comprising:
coding a color format identifier;
deriving a luma chroma width ratio depending on a chroma format, which is specified by the color format identifier;
coding a scaled reference layer offset syntax which is coded in a chroma pixel unit of the target layer picture and a reference layer offset syntax which is coded in a chroma pixel unit of the reference layer picture;
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture;
deriving a scaled reference layer offset by multiplying a value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma width ratio of the target layer picture;
deriving a reference layer offset by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture;
deriving a scale by using the scaled reference layer offset and the reference layer offset;
deriving a reference position by using the scaled reference layer offset, the reference layer offset, and the scale; and
generating a predicted image by inter-layer prediction.
5. A non-transitory computer-readable recoding medium storing a program for making a computer decode coded data that is hierarchically coded to reconstruct a decoded picture of a higher layer which is a target layer, wherein the program making the computer:
decode a color format identifier;
derive a luma chroma width ratio depending upon a chroma format, which is specified by the color format identifier;
decode a scaled reference layer offset syntax which is decoded in a chroma pixel unit of the target layer picture and a reference layer offset syntax which is decoded in a chroma pixel unit of a reference layer picture;
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture;
derive a scaled reference layer offset by multiplying a value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma width ratio of the target layer picture;
derive a reference layer offset by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture,
derive a scale by using the scaled reference layer offset and the reference layer offset;
derive a reference position by using the scaled reference layer offset, the reference layer offset, and the scale; and
generate a predicted image by inter-layer prediction.
6. A non-transitory computer-readable recoding medium storing a program for making a computer generate coded data of a higher layer which is a target layer from an input image, wherein the program making the computer:
code a color format identifier;
derive luma chroma width ratio depending on a chroma format, which is specified by the color format identifier;
code a scaled reference layer offset syntax which is coded in a chroma pixel unit of the target layer picture and a reference layer offset syntax which is coded in a chroma pixel unit of the reference layer picture;
wherein the scaled reference layer offset syntax specifies an offset between a top-left sample of a reference region in the target layer picture and a top-left sample of the target layer picture, and the reference layer offset syntax specifies an offset between a top-left sample of the reference region in the reference layer picture and a top-left sample of the reference layer picture;
derive a scaled reference layer offset by multiplying value of the scaled reference layer offset syntax by a first luma chroma width ratio that is set to the luma chroma size ratio of the target layer picture;
derive a reference layer offset by multiplying a value of the reference layer offset syntax by a second luma chroma width ratio that is set to the luma chroma width ratio of the reference layer picture;
derive a scale by using the scaled reference layer offset and the reference layer offset;
derive a reference position by using the scaled reference layer offset, the reference layer offset, and the scale; and
generate a predicted image by inter-layer prediction.