Video encoding and decoding method and device

A video encoding method for encoding a sequence of pictures which are partitioned into a plurality of subpictures including a plurality of coding tree blocks into a bitstream, the method comprising:

• encoding, into the bitstream, information on a coding tree block size and layout information about the subpictures which are partitioned from the pictures included in the sequence;
• splitting, in a tree structure, a to-be-encoded coding tree block among the coding tree blocks which have the coding tree block size in any one of the subpictures, and determining a target block;
• encoding, into the bitstream, prediction information for predicting the target block;
• generating a prediction block based on the prediction information;
• generating a residual block based on the target block and the prediction block;
• and
• encoding the residual block into the bitstream,
• wherein, loop filtering is performed on a target pixel to be filtered in the target block by applying filter coefficients to the target pixel and neighboring pixels of the target pixel,
• wherein, when at least one of the neighboring pixels is outside the boundary of a subpicture including the target block, loop filtering is performed on the target pixel based on an alternative pixel in place of the at least one of the neighboring pixels,
• wherein, the alternative pixel is a pixel in the subpicture which is adjacent to the boundary of the subpicture,
• wherein, the layout information includes a number of the subpictures, identification information for identifying a position of a first coding tree block in a raster scan order within each of the subpictures, and information about subpicture sizes,
• wherein, the identification information is information for identifying a position of a coding tree block located at a top left in each of the subpictures,
• wherein, the information about the subpicture sizes includes a width of each of the subpictures in units of coding tree block size, which is determined by the information on the coding tree block size, and a height of each of the subpictures in units of coding tree block size, wherein, the information on the coding tree block size and the width of each of the subpictures in units of coding tree block size is encoded to identify widths of the subpictures,
• wherein, the information on the coding tree block size and the height of each of the subpictures in units of coding tree block size is encoded to identify heights of the subpictures;
• wherein ID information indicating a parameter set related to the loop filtering is encoded into a header of a slice containing the target block positioned therein,
• wherein one or more filter coefficient sets for the loop filtering of blocks in the slice are contained in the parameter set corresponding to the ID information encoded into the header of the slice,
• wherein a filter coefficient set to be used for the to-be-encoded coding tree block including the target block is selected either from the one or more filter coefficient sets contained in the parameter set or from pre-defined filter coefficient sets, based on information about filter sets applied to coding tree block, and
• wherein the loop filtering on the target pixel is performed using the filter coefficients in the selected filter coefficient set for the to-be-encoded coding tree block.

A method for storing a bitstream associated with video data, the method comprising:

• generating the bitstream by encoding the video data;
• and
• storing the bitstream in a non-transitory computer-readable medium,
• wherein generating the bitstream comprises:
• encoding, into the bitstream, information on a coding tree block size and layout information about subpictures which are partitioned from pictures included in a sequence;
• splitting, in a tree structure, a to-be-encoded coding tree block among a plurality of coding tree blocks which have the coding tree block size in any one of the subpictures, and determining a target block;
• encoding, into the bitstream, prediction information for predicting the target block;
• generating a prediction block based on the prediction information;
• generating a residual block based on the target block and the prediction block;
• and
• encoding the residual block into the bitstream,
• wherein, loop filtering is performed on a target pixel to be filtered in the target block by applying filter coefficients to the target pixel and neighboring pixels of the target pixel,
• wherein, when at least one of the neighboring pixels is outside the boundary of a subpicture including the target block, loop filtering is performed on the target pixel based on an alternative pixel in place of the at least one of the neighboring pixels,
• wherein, the alternative pixel is a pixel in the subpicture which is adjacent to the boundary of the subpicture,
• wherein, the layout information includes a number of the subpictures, identification information for identifying a position of a first coding tree block in a raster scan order within each of the subpictures, and information about subpicture sizes,
• wherein, the identification information is information for identifying a position of a coding tree block located at a top left in each of the subpictures,
• wherein, the information about the subpicture sizes includes a width of each of the subpictures in units of coding tree block size which is determined by the information on the coding tree block size and a height of each of the subpictures in units of coding tree block size, wherein, the information on the coding tree block size and the width of each of the subpictures in units of coding tree block size is encoded to identify widths of the subpictures,
• wherein, the information on the coding tree block size and the height of each of the subpictures in units of coding tree block size is encoded to identify heights of the subpictures;
• wherein ID information indicating a parameter set related to the loop filtering is encoded into a header of a slice containing the target block positioned therein,
• wherein one or more filter coefficient sets for the loop filtering of blocks in the slice are contained in the parameter set corresponding to the ID information encoded into the header of the slice,
• wherein a filter coefficient set to be used for the to-be-encoded coding tree block including the target block is selected either from the one or more filter coefficient sets contained in the parameter set or from pre-defined filter coefficient sets, based on information about filter sets applied to coding tree block, and
• wherein the loop filtering on the target pixel is performed using the filter coefficients in the selected filter coefficient set for the to-be-encoded coding tree block.