An electronic apparatus performs a method of coding video data. The method includes receiving, from a bitstream of the video data, a first syntax that indicates an affine motion model enabled for a current coding block, estimating parameters of the affine motion model using gradients of motion vectors of multiple spatial neighboring blocks of the current coding block, and constructing motion vectors of the affine motion model for the current coding block by using the estimated parameters. In some embodiments, constructing motion vectors further includes converting the estimated parameters into control point motion vectors (CPMVs), and adding the CPMVs into a current affine merge candidate list. In some embodiments, constructing motion vectors further includes deriving a motion vector predictor for an affine mode.

Methods, systems, and non-transitory computer readable storage media are disclosed for two-phase encoding a digital video based on downsampling distortion of the digital video and a constant rate factor transition threshold. For example, the disclosed system can determine a downsampling distortion indicating a measure of distortion resulting from downsampling an input digital video. The disclosed systems can utilize the downsampling distortion to determine a constant rate factor transition threshold for selecting sets of encoding parameters. For example, the disclosed systems can select a first set of encoding parameters below the constant rate factor transition threshold and a second set of encoding parameters at or above the constant rate factor transition threshold. Additionally, the disclosed systems can generate first and second sets of digital video encodings of the input digital video by utilizing the first and second sets of encoding parameters, respectively.

A decoder may determine reference signals of a chroma block. The decoder may decode a decision rule in a bitstream. The decoder may determine a chroma prediction model among one or more linear models and one or more non-linear models based on the decision rule. The decoder may generate a prediction of the chroma block based on the reference signals of the chroma block and the chroma prediction model. The decoder may determine a reconstruction of the chroma block based on the prediction of the chroma block and a decoded residual of the chroma block.

A decoder may determine reference signals of a chroma block. The decoder may decode a decision rule in a bitstream. The decoder may determine a chroma prediction model among one or more linear models and one or more non-linear models based on the decision rule. The decoder may generate a prediction of the chroma block based on the reference signals of the chroma block and the chroma prediction model. The decoder may determine a reconstruction of the chroma block based on the prediction of the chroma block and a decoded residual of the chroma block.

A device for decoding video data includes a memory configured to store video data; and one or more processors implemented in circuitry and configured to: determine that a current block of the video data is to be predicted using an angular intra-prediction mode; determine neighboring samples to the current block that will be used to generate a prediction block for the current block according to an angle of the angular intra-prediction mode and that are to be upsampled; calculate predicted samples of the prediction block according to formulas that jointly upsample the neighboring samples that will be used to generate the prediction block and that generate the values for the predicted samples; and decode the current block using the prediction block.

A method, computer program, and computer system is provided for coding video data. Video data including one or more blocks is received. A current block coded in intra block copy mode or string matching mode is predicted from among the one or more blocks based on a coded block vector or a string offset vector corresponding to one or more spatial neighboring or non-neighboring blocks from among the one or more blocks. The video data is decoded based on the predicted current block.

This application provides a chroma block prediction method and apparatus. The method includes: obtaining a maximum luma value and a minimum luma value based on luma samples corresponding to neighboring samples of a target chroma block, and calculating a first difference between the maximum luma value and the minimum luma value; if the first difference is not equal to 0, processing the first difference based on a quantity of significant bits of the first difference and a first preset bit depth to obtain a second difference; and determining, based on a first chroma value, a second chroma value, and the second difference, an intra prediction model parameter corresponding to the target chroma block, and determining prediction information of the target chroma block based on the intra prediction model parameter and luma reconstruction information corresponding to the target chroma block.

This application provides a chroma block prediction method and apparatus. The method includes: obtaining a maximum luma value and a minimum luma value based on luma samples corresponding to neighboring samples of a target chroma block, and calculating a first difference between the maximum luma value and the minimum luma value; if the first difference is not equal to 0, processing the first difference based on a quantity of significant bits of the first difference and a first preset bit depth to obtain a second difference; and determining, based on a first chroma value, a second chroma value, and the second difference, an intra prediction model parameter corresponding to the target chroma block, and determining prediction information of the target chroma block based on the intra prediction model parameter and luma reconstruction information corresponding to the target chroma block.

Embodiments of the present invention relate to methods and systems for ordering, communicating and applying pixel intra-prediction modes.

A variable length coding method is comprised of: a coefficient value scanning step in which an RL sequence generation unit, a reordering unit, and a binarization unit scan coefficient values within a block in a predetermined scanning order starting at a higher-frequency component toward a lower-frequency component; and an arithmetic coding step in which an arithmetic coding unit and a table storage unit perform arithmetic coding on the absolute values of the coefficient values according to the scanning order used in the coefficient value scanning step, by switching between probability tables for use, wherein, in the arithmetic coding step, a probability table to be used is switched to another probability table in one direction, when the arithmetic-coded absolute values of the coefficient values include an absolute value exceeding a predetermined threshold value.