Methods and apparatus of video coding using sub-block based affine mode are disclosed. According to this method, control-point motion vectors (MVs) associated with the affine mode are determined for a block. A sub-block MV is derived for a target sub-block of the block from the control- point MVs for the block. A prediction offset is determined for a target pixel of the target sub-block using information comprising a pixel MV offset from the sub-block MV for the target pixel according to Prediction Refinement with Optical Flow (PROF). The target pixel of the target sub-block is encoded or decoded using a modified predictor. The modified prediction is generated by clipping the prediction offset to a target range and combining the clipped prediction offset with an original predictor.

An image encoding/decoding method and apparatus are provided. An image decoding method according to the present disclosure is performed by an image decoding apparatus. The image decoding method comprises deriving a prediction sample of a current block based on motion information of the current block, deriving a reference picture resampling (RPR) condition for the current block, determining whether prediction refinement with optical flow (PROF) applies to the current block based on the RPR condition, and deriving a refined prediction sample for the current block by applying PROF to the current block.

A method and apparatus for video coding. In some examples, an apparatus includes receiving circuitry and processing circuitry. The processing circuitry decodes prediction information of a block in a current picture from a coded video bitstream. The prediction information includes an index for prediction offset associated with an affine model in an inter prediction mode. The affine model is used to transform between the block and a reference block in a reference picture that has been reconstructed. Further, the processing circuitry determines parameters of the affine model based on the index and a pre-defined mapping of indexes and offset values, and reconstructs at least a sample of the block according to the affine model.

A method for video decoding includes decoding prediction information of a current block, the prediction information being indicative of a symmetric motion vector difference mode for bi-prediction from a pair of forward and backward reference pictures. The method also includes assigning, to a reference picture marked as a long term reference picture (LTRP), a calculated picture order count with a default POC distance to the current picture, and excluding a reference picture from being in the pair of forward and backward reference pictures without a check based on a picture order count (POC) of the reference picture. The method further includes determining a first reference block for the current block in the forward reference picture and a second reference block for the current block in the backward reference picture, and reconstructing at least a sample of the current block according to the first reference block and the second reference block.

The present disclosure provides a video picture coding method, a video picture decoding method, a coding device, and a decoding device. The method includes: determining a distance between control points for an affine picture block; determining a motion vector difference for the affine picture block, motion vectors of the control points being used to determine the motion vector difference; and performing coding processing on the affine picture block over a size that includes a horizontal length and a vertical length, wherein the horizontal length and the vertical length vary based on the distance between the control points, the motion vector difference, and a motion vector precision.

The present disclosure provides a video picture coding method, a video picture decoding method, a coding device, and a decoding device. The method includes: determining a distance between control points for an affine picture block; determining a motion vector difference for the affine picture block, motion vectors of the control points being used to determine the motion vector difference; and performing coding processing on the affine picture block over a size that includes a horizontal length and a vertical length, wherein the horizontal length and the vertical length vary based on the distance between the control points, the motion vector difference, and a motion vector precision.

Systems and methods are disclosed for compressing a target video. A computer-implemented method may use a computer system that include one or more physical computer processors and non-transient electronic storage. The computer-implemented method may include: obtaining the target video, extracting one or more frames from the target video, and generating an estimated optical flow based on a displacement of pixels between the one or more frames. The one or more frames may include one or more of a key frame and a target frame.

Systems and methods are disclosed for compressing a target video. A computer-implemented method may use a computer system that include one or more physical computer processors and non-transient electronic storage. The computer-implemented method may include: obtaining the target video, extracting one or more frames from the target video, and generating an estimated optical flow based on a displacement of pixels between the one or more frames. The one or more frames may include one or more of a key frame and a target frame.

A decoder includes circuitry configured to receive a bitstream; construct, for a current block, a motion vector candidate list including adding a single global motion vector candidate to the motion vector candidate list, the single global motion vector candidate selected based on a global motion model utilized by the current block; and reconstruct pixel data of the current block and using the motion vector candidate list. Related apparatus, systems, techniques and articles are also described.

Systems, methods, and instrumentalities are disclosed for motion vector clipping when affine motion mode is enabled for a video block. A video coding device may determine that an affine mode for a video block is enabled. The video coding device may determine a plurality of control point affine motion vectors associated with the video block. The video coding device may store the plurality of clipped control point affine motion vectors for motion vector prediction of a neighboring control point affine motion vector. The video coding device may derive a sub-block motion vector associated with a sub-block of the video block, clip the derived sub-block motion vector, and store it for spatial motion vector prediction or temporal motion vector prediction. For example, the video coding device may clip the derived sub-block motion vector based on a motion field range that may be based on a bit depth value.