An improved method for coding video is provided that includes Virtual Reality (VR) sequences that enables more efficient encoding by organizing the VR sequence as a single 2D block structure. In the method, reference picture and subpicture lists are created and extended to account for coding of the VR sequence. To further improve coding efficiency, reference indexing can be provided for the temporal and spatial difference between a current VR picture block and the reference pictures and subpictures for the VR sequence. Further, because the reference subpictures for the VR sequence may not have the proper orientation once the VR sequence subpictures are organized into the VR sequence, reorientation of the reference subpictures is made so that the reference subpicture orientations match the current VR subpicture orientations.

Described herein are systems, methods, and instrumentalities associated with video coding. The signaling of certain syntax elements may be moved from a slice header to a picture header and/or a layer access unit delimiter (AUD). The dependency between AUD and one or more parameter sets may be explored. Syntax elements may be signaled to enable wrap-around motion compensation for certain sub-picture(s) and specify wrap-around motion compensation offsets for the sub-picture(s).

A method for decoding a video according to the present invention may comprise: deriving a spatial merge candidate for a current block, generating a merge candidate list for the current block based on the spatial merge candidate, obtaining motion information for the current block based on the merge candidate list, and performing motion compensation for the current block using the motion information. Herein, if the current block does not have a pre-defined shape or does not have a size equal to or greater than a pre-defined size, the spatial merge candidate of the current block is derived based on a block having the pre-defined shape or having a size equal to or greater than the pre-defined size, the block comprising the current block.

A method for decoding a video according to the present invention may comprise: deriving a spatial merge candidate for a current block, generating a merge candidate list for the current block based on the spatial merge candidate, obtaining motion information for the current block based on the merge candidate list, and performing motion compensation for the current block using the motion information. Herein, if the current block does not have a pre-defined shape or does not have a size equal to or greater than a pre-defined size, the spatial merge candidate of the current block is derived based on a block having the pre-defined shape or having a size equal to or greater than the pre-defined size, the block comprising the current block.

Disclosed is a method and apparatus for encoding/decoding a video. According to an embodiment, provided is a method of setting a level for each of one or more regions, including decoding a definition syntax element related to level definition and a designation syntax element related to target designation from a bitstream; defining one or more levels based on the definition syntax element; and setting a target level designated by the designation syntax element among the defined levels for a target region designated by the designation syntax element.

Systems, methods and apparatus for video processing are described. The video processing may include video encoding, video decoding, or video transcoding. One example method of video processing includes performing a conversion between a video including one or more video regions and a bitstream of the video according to a format rule. The format rule specifies that a variable X indicates whether B slice is allowed or used in a video region. The format rule further specifies that the variable X is based on values of a reference picture list information present flag and/or a field indicating a number of entries in a reference picture list syntax structure.

A system for storing and providing video pixel data for video encoding is disclosed. The system comprises a memory storage and a cache storage. The system further comprises a controller. The controller is configured to receive a request that causes transferring of a reference pixel block of a video, wherein the video is being encoded using the reference pixel block. The controller is configured to determine whether the reference pixel block has at least a portion that is outside a frame of the video. In response to the determination of the reference pixel block having at least a portion outside the frame of the video, the controller is configured to cause a portion of the reference pixel block of the video inside the frame of the video to be fetched from a memory storage and stored in a cache storage, pad a remaining missing portion of the reference pixel block of the video outside the frame of the video with padding pixel data to form the reference pixel block, and transfer the reference pixel block in response to the request.

A video coder is configured to determine a reference block of a reference picture for prediction of a current block of a current picture using motion information and to generate a set of reference samples for the current block of the current picture. To generate the set of reference samples, the video coder is configured to perform reference sample clipping on the reference block of the reference picture based on a size of the reference picture. The video coder is further configured to generate a prediction block for the current block of the current picture based on the set of reference samples.

A method for decoding a video according to the present invention may comprise: deriving a spatial merge candidate for a current block, generating a merge candidate list for the current block based on the spatial merge candidate, obtaining motion information for the current block based on the merge candidate list, and performing motion compensation for the current block using the motion information. Herein, if the current block does not have a pre-defined shape or does not have a size equal to or greater than a pre-defined size, the spatial merge candidate of the current block is derived based on a block having the pre-defined shape or having a size equal to or greater than the pre-defined size, the block comprising the current block.

A method for decoding a video according to the present invention may comprise: deriving a spatial merge candidate for a current block, generating a merge candidate list for the current block based on the spatial merge candidate, obtaining motion information for the current block based on the merge candidate list, and performing motion compensation for the current block using the motion information. Herein, if the current block does not have a pre-defined shape or does not have a size equal to or greater than a pre-defined size, the spatial merge candidate of the current block is derived based on a block having the pre-defined shape or having a size equal to or greater than the pre-defined size, the block comprising the current block.