An image decoding method performed by a decoding apparatus according to the present disclosure comprises the steps of: decoding, on the basis of a bitstream, an affine flag that indicates whether affine prediction is applicable to a current block and a sub-block TMVP flag that indicates whether a temporal motion vector predictor based on a sub-block of the current block is usable; determining whether to decode a predetermined merge mode flag that indicates whether to apply a predetermined merge mode to the current block, on the basis of the decoded affine flag and the decoded sub-block TMVP flag; deriving prediction samples of the current block on the basis of the determining of whether to decode the predetermined merge mode flag; and generating reconstructed samples of the current block based on the prediction samples of the current block.

Methods and apparatuses are provided for estimating motion vectors of a dense motion field based on subsampled sparse motion field. The sparse motion field includes two or more motion vectors with their respective start positions. For each of the motion vectors, a transformation is derived which transforms the motion vector from its start point into a target point. The transformed motion vectors then contribute to the estimated motion vector on the target position. The contribution of each motion vector is weighted. Such motion estimation may be readily used for video encoding and decoding.

An image decoding method and apparatus according to an embodiment may extract, from a bitstream, a quantization coefficient generated through core transformation, secondary transformation, and quantization; generate an inverse-quantization coefficient by performing inverse quantization on the quantization coefficient; generate a secondary inverse-transformation coefficient by performing secondary inverse-transformation on a low frequency component of the inverse-quantization coefficient, the secondary inverse-transformation corresponding to the secondary transformation; and perform core inverse-transformation on the secondary inverse-transformation coefficient, the core inverse-transformation corresponding to the core transformation.

An image decoding method and apparatus according to an embodiment may extract, from a bitstream, a quantization coefficient generated through core transformation, secondary transformation, and quantization; generate an inverse-quantization coefficient by performing inverse quantization on the quantization coefficient; generate a secondary inverse-transformation coefficient by performing secondary inverse-transformation on a low frequency component of the inverse-quantization coefficient, the secondary inverse-transformation corresponding to the secondary transformation; and perform core inverse-transformation on the secondary inverse-transformation coefficient, the core inverse-transformation corresponding to the core transformation.

Systems and techniques are described for encoding and/or decoding data based on motion estimation that applies variable-scale warping. An encoding device can receive an input frame and a reference frame that depict a scene at different times. The encoding device can generate an optical flow identifying movements in the scene between the two frames. The encoding device can generate a weight map identifying how finely or coarsely the reference frame can be warped for input frame prediction. The encoding device can generate encoded video data based on the optical flow and the weight map. A decoding device can generate a reconstructed optical flow and a reconstructed weight map from the encoded data. A decoding device can generate a prediction frame by warping the reference frame based on the reconstructed optical flow and the reconstructed weight map. The decoding device can generate a reconstructed input frame based on the prediction frame.

An encoder includes circuitry and memory coupled to the circuitry. In operation, the circuitry switches between storing and not storing of a decoded picture buffer (DPB) parameter related to a DPB in a common header shared between layers in layer groups each including at least one output layer, according to whether or not all the layer groups in a bitstream each include only one layer.

Provide are an inter prediction method, encoder, decoder, and storage medium. Said method comprises: determining a prediction mode parameter of the current block; when the prediction mode parameter indicates a geometrical partitioning prediction mode is used for determining inter prediction of the current block, determining a geometrical partitioning prediction mode parameter of the current block; according to the geometrical partitioning prediction mode parameter, determining a first and a second prediction value and a weight index corresponding to the sample in the current block; clipping the weight index corresponding to the sample in the current block to obtain absolute information of the weight index; determining a first and a second weight value based on absolute information of the weight index; and determining an inter prediction of the sample of the current block according to weighted combination of the first prediction value, first weight value, second prediction value and second weight value.

An encoder includes memory, and circuitry accessible to the memory. The circuitry accessible to the memory: determines whether OBMC is applicable to generation of a prediction image of a current block, according to whether BIO is to be applied to the generation of the prediction image of the current block; when BIO is to be applied to the generation of the prediction image of the current block, determines that OBMC is not applicable to the generation of the prediction image of the current block, and applies BIO to the generation of the prediction image of the current block without applying OBMC.

A point cloud data processing method, according to embodiments, enables encoding and transmitting point cloud data. A point cloud data processing method, according to embodiments, enables receiving and decoding point cloud data.

An image coding method includes selecting two or more transform components from among a plurality of transform components that include a translation component and non-translation components, the two or more transform components serving as reference information that represents a reference destination of a current block; coding selection information that identifies the two or more transform components that have been selected from among the plurality of transform components; and coding the reference information of the current block by using reference information of a coded block different from the current block.