Image encoding/decoding method and apparatus based on subpicture information aligned between layers, and recording medium storing bitstream

1. An image decoding method performed by an image decoding apparatus, the image decoding method comprising:

obtaining, by the image decoding apparatus, subpicture information from a bitstream;

deriving, by the image decoding apparatus, one or more subpictures in a current picture based on the subpicture information; and

decoding, by the image decoding apparatus, a current subpicture in the current picture based on the subpicture information,

wherein the subpicture information comprises a first flag specifying whether each of the one or more subpictures is treated as a picture,

wherein, based on the bitstream including at least one first layer referring to a current layer including the current picture, the first flag for a first subpicture included in the first layer, and the first flag for the current subpicture have the same value, and

wherein the first subpicture corresponds to the current subpicture.

2. The image decoding method of claim 1 , wherein a first picture including the first subpicture has the current picture as an entry in a reference picture list of the first picture.

3. The image decoding method of claim 1 , wherein, based on the number of the one or more subpictures being two or more and the current subpicture being treated as a picture, a first picture including the first subpicture and the current picture have the same width and the same height.

4. The image decoding method of claim 1 , wherein, based on the number of the one or more subpictures being two or more and the current subpicture being treated as a picture, a first picture including the first subpicture and the current picture include the same number of subpictures.

5. The image decoding method of claim 1 , wherein the current layer is included in an output layer set as an output layer.

6. The image decoding method of claim 1 , wherein the first flag has a predetermined value specifying the current subpicture being treated as a picture, based on boundaries of the current subpicture being treated as picture boundaries.

7. The image decoding method of claim 1 , wherein the subpicture information further comprises a second flag specifying whether in-loop filtering operation across a boundary of the current subpicture is capable of being performed, based on boundaries of the current subpicture being not treated as picture boundaries.

8. An image encoding method performed by an image encoding apparatus, the image encoding method comprising:

partitioning, by the image encoding apparatus, a current picture into one or more subpictures;

generating, by the image encoding apparatus, a subpicture information on the one or more subpictures; and

generating, by the image encoding apparatus, a bitstream by encoding image information including the subpicture information,

wherein the subpicture information comprises a first flag specifying whether each of the one or more subpictures is treated as a picture,

wherein, based on the bitstream including at least one first layer referring to a current layer including the current picture, the first flag for a first subpicture included in the first layer and the first flag for the current subpicture have the same value, and

wherein the first subpicture corresponds to the current subpicture.

9. The image encoding method of claim 8 , wherein a first picture including the first subpicture has the current picture as an entry in a reference picture list of the first picture.

10. The image encoding method of claim 8 , wherein, based on the number of the one or more subpictures being two or more and the current subpicture being treated as a picture, a first picture including the first subpicture and the current picture have the same width and the same height.

11. The image encoding method of claim 8 , wherein, based on the number of the one or more subpictures being two or more and the current subpicture being treated as a picture, a first picture including the first subpicture and the current picture include the same number of subpictures.

12. The image encoding method of claim 8 , wherein the current layer is included in an output layer set as an output layer.

13. The image encoding method of claim 8 , wherein the subpicture information further comprises a second flag specifying whether in-loop filtering operation across a boundary of the current subpicture is capable of being performed, based on boundaries of the current subpicture being not treated as picture boundaries.

14. A method for transmitting a bitstream, the method comprising:

obtaining, by an encoding apparatus, the bitstream generated by an image encoding method; and

transmitting, by an encoding apparatus, the bitstream,

wherein the image encoding method comprising:

partitioning a current picture into one or more subpictures;

generating a subpicture information on the one or more subpictures; and

generating a bitstream by encoding image information including the subpicture information,

wherein the subpicture information comprises a first flag specifying whether each of the one or more subpictures is treated as a picture,

wherein, based on the bitstream including at least one first layer referring to a current layer including the current picture, the first flag for a first subpicture included in the first layer and the first flag for the current subpicture have the same value, and

wherein the first subpicture corresponds to the current subpicture.