Methods, devices and systems for video coding and encoding, which include conforming to constraints on collocated pictures, are described. One example method of video processing includes performing a conversion between a video including a current picture and a bitstream of the video, wherein the bitstream conforms to a format rule, and wherein the format rule specifies that the bitstream includes a flag for disabling a use of a temporal motion vector prediction tool for the current picture based on whether a reference picture in a decoded picture buffer has a spatial resolution and a scaling window offset that are identical to that of the current picture.

A video decoding method, a video encoding method, related devices, and a storage medium are provided. The video decoding method includes: determining a current string to be decoded from a current coding unit of a current image; based on the current string being a unit vector string and the current string including a first pixel, determining a reference pixel of the first pixel from a historical decoding unit in the current image, the historical decoding unit being a decoded coding unit adjacent to the current coding unit in the current image, the reference pixel of the first pixel being adjacent to the first pixel in the current image; and acquiring a predicted value of the first pixel based on a reconstructed value of the reference pixel of the first pixel to obtain a decoded image. may

A video decoding method, a video encoding method, related devices, and a storage medium are provided. The video decoding method includes: determining a current string to be decoded from a current coding unit of a current image; based on the current string being a unit vector string and the current string including a first pixel, determining a reference pixel of the first pixel from a historical decoding unit in the current image, the historical decoding unit being a decoded coding unit adjacent to the current coding unit in the current image, the reference pixel of the first pixel being adjacent to the first pixel in the current image; and acquiring a predicted value of the first pixel based on a reconstructed value of the reference pixel of the first pixel to obtain a decoded image. may

For each prediction candidate of a set of one or more prediction candidates of the current block, a video coder computes a matching cost between a set of reference pixels of the prediction candidate in a reference picture and a set of neighboring pixels of a current block in a current picture. The video coder identifies a subset of the reference pictures as major reference pictures based on a distribution of the prediction candidates among the reference pictures of the current picture. A bounding block is defined for each major reference picture, the bounding block encompassing at least portions of multiple sets of reference pixels for multiple prediction candidates. The video coder assigns an index to each prediction candidate based on the computed matching cost of the set of prediction candidates. A selection of a prediction candidate is signaled by using the assigned index of the selected prediction candidate.

For each prediction candidate of a set of one or more prediction candidates of the current block, a video coder computes a matching cost between a set of reference pixels of the prediction candidate in a reference picture and a set of neighboring pixels of a current block in a current picture. The video coder identifies a subset of the reference pictures as major reference pictures based on a distribution of the prediction candidates among the reference pictures of the current picture. A bounding block is defined for each major reference picture, the bounding block encompassing at least portions of multiple sets of reference pixels for multiple prediction candidates. The video coder assigns an index to each prediction candidate based on the computed matching cost of the set of prediction candidates. A selection of a prediction candidate is signaled by using the assigned index of the selected prediction candidate.

Provided is a video decoding method including determining a displacement vector per unit time of pixels of a current block in a horizontal direction or a vertical direction, the pixels including a pixel adjacent to an inside of a boundary of the current block, by using values about reference pixels included in a first reference block and a second reference block, without using a stored value about a pixel located outside boundaries of the first reference block and the second reference block; and obtaining a prediction block of the current block by performing block-unit motion compensation and pixel group unit motion compensation on the current block by using a gradient value in the horizontal direction or the vertical direction of a first corresponding reference pixel in the first reference block which corresponds to a current pixel included in a current pixel group in the current block, a gradient value in the horizontal direction or the vertical direction of a second corresponding reference pixel in the second reference block which corresponds to the current pixel, a pixel value of the first corresponding reference pixel, a pixel value of the second corresponding reference pixel, and a displacement vector per unit time of the current pixel in the horizontal direction or the vertical direction. In this regard, the current pixel group may include at least one pixel.

Provided is a video decoding method including determining a displacement vector per unit time of pixels of a current block in a horizontal direction or a vertical direction, the pixels including a pixel adjacent to an inside of a boundary of the current block, by using values about reference pixels included in a first reference block and a second reference block, without using a stored value about a pixel located outside boundaries of the first reference block and the second reference block; and obtaining a prediction block of the current block by performing block-unit motion compensation and pixel group unit motion compensation on the current block by using a gradient value in the horizontal direction or the vertical direction of a first corresponding reference pixel in the first reference block which corresponds to a current pixel included in a current pixel group in the current block, a gradient value in the horizontal direction or the vertical direction of a second corresponding reference pixel in the second reference block which corresponds to the current pixel, a pixel value of the first corresponding reference pixel, a pixel value of the second corresponding reference pixel, and a displacement vector per unit time of the current pixel in the horizontal direction or the vertical direction. In this regard, the current pixel group may include at least one pixel.

Various concepts which further improve multi-view/layer coding concepts, are described.

Various concepts which further improve multi-view/layer coding concepts, are described.

Aspects of the present disclosure provide techniques for derive one or more intra prediction modes (IPMs) from a subset of IPM candidates in order to determine a predictor to use for decoding a block of an image. In some aspects, the subset of IPM candidates may include IPMs that are less than the number of IPMs in a full set of all available IPM candidates (e.g., 67 IPMs in VVC or 35 in HEVC). In some aspects, the subset of IPM candidates may be based on a most probable mode (MPM) list that can be used to determine or signal an IPM based on IPMs previously used in decoding other blocks.