Aspects of the disclosure provide a method and an apparatus for video decoding. The apparatus includes processing circuitry receiving prediction information of a plurality of blocks in a current picture from a coded video bitstream. The processing circuitry determines, based on the prediction information, whether at least one of a decoder-side motion vector refinement (DMVR) mode or a bi-directional optical flow (BDOF) mode is allowed for the plurality of blocks. If the DMVR mode or the BDOF mode is allowed for the plurality of blocks, the processing circuitry determines that a plurality of merge with motion vector difference (MMVD) merge flags indicating whether a MMVD mode is applied to the plurality of blocks, respectively, is inferred as false for the plurality of blocks. If the plurality of MMVD merge flags is inferred as false, the processing circuitry reconstructs each block in the plurality of blocks without applying the MMVD mode.

Aspects of the disclosure provide a method and an apparatus for video decoding. The apparatus includes processing circuitry receiving prediction information of a plurality of blocks in a current picture from a coded video bitstream. The processing circuitry determines, based on the prediction information, whether at least one of a decoder-side motion vector refinement (DMVR) mode or a bi-directional optical flow (BDOF) mode is allowed for the plurality of blocks. If the DMVR mode or the BDOF mode is allowed for the plurality of blocks, the processing circuitry determines that a plurality of merge with motion vector difference (MMVD) merge flags indicating whether a MMVD mode is applied to the plurality of blocks, respectively, is inferred as false for the plurality of blocks. If the plurality of MMVD merge flags is inferred as false, the processing circuitry reconstructs each block in the plurality of blocks without applying the MMVD mode.

A method includes acquiring a current picture segmented into a plurality of units and divided into a plurality of tiles, each unit divided into a plurality of blocks, the plurality of blocks in each unit being arranged as a first grid, and the plurality of units being arranged as a second grid in each tile. The method includes decoding, for one of the units in a first tile, a first current block from the plurality of blocks using an entry from a first HMVP buffer associated with the first tile. The method includes updating the first HMVP buffer with a motion vector of the decoded first current block. The method includes in response to determining that the first current block is located in a first column and a first row of a first unit of a row in the second grid of the first tile, resetting the first HMVP buffer.

A method includes acquiring a current picture segmented into a plurality of units and divided into a plurality of tiles, each unit divided into a plurality of blocks, the plurality of blocks in each unit being arranged as a first grid, and the plurality of units being arranged as a second grid in each tile. The method includes decoding, for one of the units in a first tile, a first current block from the plurality of blocks using an entry from a first HMVP buffer associated with the first tile. The method includes updating the first HMVP buffer with a motion vector of the decoded first current block. The method includes in response to determining that the first current block is located in a first column and a first row of a first unit of a row in the second grid of the first tile, resetting the first HMVP buffer.

Processing circuitry decodes information of a coding block in a current picture from a bitstream. The information indicates a bi-prediction mode without weight signaling. Weights associated with the bi-prediction mode are not signaled in the bitstream. Further, the processing circuitry determines a first motion vector associated with a first reference picture and a second motion vector associated with a second reference picture, and determine a first reference template in the first reference picture based on a current template of the coding block and the first motion vector and a second reference template in the second reference picture based on the current template and the second motion vector. The processing circuitry also calculates a weight for use in the bi-prediction mode based on the first reference template, the second reference template and the current template, and reconstructs the coding block using the bi-prediction with the calculated weight.

Processing circuitry decodes information of a coding block in a current picture from a bitstream. The information indicates a bi-prediction mode without weight signaling. Weights associated with the bi-prediction mode are not signaled in the bitstream. Further, the processing circuitry determines a first motion vector associated with a first reference picture and a second motion vector associated with a second reference picture, and determine a first reference template in the first reference picture based on a current template of the coding block and the first motion vector and a second reference template in the second reference picture based on the current template and the second motion vector. The processing circuitry also calculates a weight for use in the bi-prediction mode based on the first reference template, the second reference template and the current template, and reconstructs the coding block using the bi-prediction with the calculated weight.

A method of video decoding performed in a video decoder includes receiving a coded video bitstream including a current block that is divided into a plurality of sub-blocks. Sub-block based affine motion compensation is performed on the current block to generate a sub-block prediction for each pixel in each sub-block of the current block. One or more spatial gradients are determined for each sub-block prediction. For each sub-block prediction, prediction refinement with optical flow process is performed using the respective determined one or more spatial gradients and at least one constraint included in the coded video bitstream. For each sub-block prediction, an output of the respective prediction refinement is added to the respective sub-block prediction to generate a final prediction for each pixel in each sub-block of the current block.

The present disclosure provides systems and methods for performing adaptive resolution change during video encoding and decoding. The methods include: comparing resolutions of a target picture and a first reference picture; in response to the target picture and the first reference picture having different resolutions, resampling the first reference picture to generate a second reference picture; and encoding or decoding the target picture using the second reference picture.

A decoding method includes obtaining an identifier from a bitstream, where the identifier indicates a minimum decoding time interval k between library pictures that is allowed in the bitstream, obtaining, when parsing the bitstream, a decoding moment t.sub.i of a current decoded picture and a decoding moment t.sub.j of a first decoded picture that is closest to the current decoded picture and that references a new library picture when the current decoded picture is decoded by referencing a library picture, where the new library picture is a library picture that is not decoded or needs to be re-decoded when the first decoded picture is decoded, and determining a preset quantity of library pictures as candidate reference pictures of the current decoded picture based on a relationship between k and a difference between t.sub.i and t.sub.j.

Several improvements for use with Bidirectionally Predictive (B) pictures within a video sequence are provided. In certain improvements Direct Mode encoding and/or Motion Vector Prediction are enhanced using spatial prediction techniques. In other improvements Motion Vector prediction includes temporal distance and subblock information, for example, for more accurate prediction. Such improvements and other presented herein significantly improve the performance of any applicable video coding system/logic.