Systems and methods are described for reducing the complexity of using bi-directional optical flow (BIO) in video coding. In some embodiments, bit-width reduction steps are introduced in the BIO motion refinement process to reduce the maximum bit-width used for BIO calculations. In some embodiments, simplified interpolation filters are used to generate predicted samples in an extended region around a current coding unit. In some embodiments, different interpolation filters are used for vertical versus horizontal interpolation. In some embodiments, BIO is disabled for coding units with small heights and/or for coding units that are predicted using a sub-block level inter prediction technique, such as advanced temporal motion vector prediction (ATMVP) or affine prediction.

Methods and systems for providing a bitstream comprising video data encoded by an encoder apparatus are described, wherein the method may include: a processor of the encoder apparatus determining a current motion vector of a current block of a current video frame of a sequence of video frames comprising video data, the current motion vector defining a spatial offset of the current block relative to a prediction block of a previously encoded reference video frame stored in a memory of the encoder apparatus; the processor determining or receiving motion information associated with the current video frame, the motion information signaling the processor whether at least part of the offset defined by the current motion vector is associated with non-uniform motion in the video data of the current video frame; the processor determining a motion vector predictor candidate based on the motion information, at least a first motion vector predicator algorithm and a second motion vector predictor algorithm; and, the processor determining a motion vector difference based on the selected motion vector predictor candidate and the current motion vector; and, the processor using an encoding process to encode a residual block, the motion vector difference, an indication of the selected motion vector predictor candidate, and at least part of the motion information into a bitstream, wherein the residual block defines a difference between the current block and the prediction block.

The inter prediction method comprises: determining a prediction mode parameter of a current block; determining a GPM parameter of the current block in response to that the prediction mode parameter indicates that a GPM is used to determine inter prediction of the current block; determining a first prediction value of a first partition of the current block and a second prediction value of a second partition of the current block; determining a weight index of a sample in the current block based on the GPM parameter of the current block; determining a first weight value and a second weight value of the sample in the current block based on the weight index of the sample in the current block; performing weighted combination of the first prediction value and the second prediction value to obtain the inter prediction of the current block.

A method of video processing includes determining, for a conversion between a current video block of a video and a bitstream of the video, that the current video block is coded with a geometric partitioning mode. The method further includes deriving at least one refined motion vector (MV) for the current video block by adding at least one motion vector difference (MVD) of multiple MVDs signaled or derived for the current video block to a MV derived from a merge candidate associated with the current video block. The MV being associated with an offset distance and/or an offset direction. The method further includes performing the conversion based on the refined MV.

A method of video processing includes determining, for a conversion between a current video block of a video and a bitstream of the video, that the current video block is coded with a geometric partitioning mode. The method further includes deriving at least one refined motion vector (MV) for the current video block by adding at least one motion vector difference (MVD) of multiple MVDs signaled or derived for the current video block to a MV derived from a merge candidate associated with the current video block. The MV being associated with an offset distance and/or an offset direction. The method further includes performing the conversion based on the refined MV.

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.

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.

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.

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

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