Aspects of the disclosure provide methods and apparatuses for video encoding/decoding. In some examples, an apparatus for video decoding includes receiving circuitry and processing circuitry. In some embodiments, the processing circuitry decodes prediction information of a current block in a current coding from a coded video bitstream. The prediction information is indicative of an intra block copy mode. Then, the processing circuitry determines a block vector that points to a reference block in a same picture as the current block. The reference block is restricted within a coding region with reconstructed samples buffered in a reference sample memory. The coding region is one of multiple predefined regions of a coding tree unit (CTU). Then, the processing circuitry reconstructs at least a sample of the current block based on the reconstructed samples of the reference block that are retrieved from the reference sample memory.

Devices, systems and methods for sub-block based prediction are described. In a representative aspect, a method for video processing includes partitioning a first component of a current video block into a first set of sub-blocks and partitioning a second component of the current video block into a second set of sub-blocks. A sub-block of the second component corresponds to one or more sub-blocks of the first component. The method also includes deriving, based on a color format of the current video block, motion vectors for a sub-block of the second component based on motion vectors for one or more corresponding sub-blocks of the first color component.

Devices, systems and methods for sub-block based prediction are described. In a representative aspect, a method for video processing includes partitioning a first component of a current video block into a first set of sub-blocks and partitioning a second component of the current video block into a second set of sub-blocks. A sub-block of the second component corresponds to one or more sub-blocks of the first component. The method also includes deriving, based on a color format of the current video block, motion vectors for a sub-block of the second component based on motion vectors for one or more corresponding sub-blocks of the first color component.

Devices, systems and methods for sub-block based prediction are described. In a representative aspect, a method for video processing comprises determining a block size constrain, making a determination, based on the block size constrain, about whether or not a merge affine mode and a non-merge affine mode are allowed for a video block in a video frame, and generating a bitstream representation of the video block based on the making the determination.

Disclosed is an image data encoding/decoding method and apparatus. A method for decoding a 360-degree image comprises the steps of: receiving a bitstream obtained by encoding a 360-degree image; generating a prediction image by making reference to syntax information obtained from the received bitstream; combining the generated prediction image with a residual image obtained by dequantizing and inverse-transforming the bitstream, so as to obtain a decoded image; and reconstructing the decoded image into a 360-degree image according to a projection format.

Method, apparatus and systems are disclosed. In one embodiment, a method of decoding includes obtaining a sub-block based motion prediction signal for a current block of the video; obtaining one or more spatial gradients of the sub-block based motion prediction signal or one or more motion vector difference values; obtaining a refinement signal for the current block based on the one or more obtained spatial gradients or the one or more obtained motion vector difference values; obtaining a refined motion prediction signal for the current block based on the sub-block based motion prediction signal and the refinement signal; and decoding the current block based on the refined motion prediction signal.

Method, apparatus and systems are disclosed. In one embodiment, a method of decoding includes obtaining a sub-block based motion prediction signal for a current block of the video; obtaining one or more spatial gradients of the sub-block based motion prediction signal or one or more motion vector difference values; obtaining a refinement signal for the current block based on the one or more obtained spatial gradients or the one or more obtained motion vector difference values; obtaining a refined motion prediction signal for the current block based on the sub-block based motion prediction signal and the refinement signal; and decoding the current block based on the refined motion prediction signal.

Different implementations are described, particularly implementations for video encoding and decoding are presented. According to an implementation, in a method for encoding or decoding a part of an image, an inter-prediction refinement of the image block using optical flow based on boundary smoothed motion compensation is performed. The inter-prediction refinement of the image block further comprises obtaining a motion information for the block, a motion information for the top neighboring block, a motion information for the left neighboring block; and applying an optical flow based on a weighted sum of the obtained motion information to refine the prediction for the block. Advantageously, the refined inter-prediction is applied on boundary sub-blocks of the causal border of the image block or on any sub-block of the image block at a sub-block level if the image block has sub-block motion field.

Different implementations are described, particularly implementations for video encoding and decoding are presented. According to an implementation, in a method for encoding or decoding a part of an image, an inter-prediction refinement of the image block using optical flow based on boundary smoothed motion compensation is performed. The inter-prediction refinement of the image block further comprises obtaining a motion information for the block, a motion information for the top neighboring block, a motion information for the left neighboring block; and applying an optical flow based on a weighted sum of the obtained motion information to refine the prediction for the block. Advantageously, the refined inter-prediction is applied on boundary sub-blocks of the causal border of the image block or on any sub-block of the image block at a sub-block level if the image block has sub-block motion field.

Reconstructing a video signal based on low-complexity DST7 design including obtaining a transform index of a current block from the video signal and deriving a transform combination corresponding to the transform index. The transform index corresponds to any one of a plurality of transform combinations including a combination of DST7 and/or DCT8, and the transform combination includes horizontal and vertical transforms that correspond to at least one of the DST7 or the DCT8. The reconstruction also includes performing an inverse transform in a vertical direction by using the DST7, performing an inverse transform in a horizontal direction by using the DCT8, and reconstructing the video signal by using the current block on which the inverse transform is performed. The DST7 includes Discrete Fourier Transform (DFT) and has a different type of DFT structure based on a size of the current block.