The present invention relates to a technique for encoding and decoding video data, and more particularly, to a method for performing inter-prediction in an effective manner. The present invention combines an inter-prediction method using an AMVP mode and an inter-prediction method using a merge mode so as to propose a method for using the same candidate. The method for encoding video data proposed by the present invention comprises the following steps: receiving mode information on an inter-prediction method of a current block; determining, on the basis of the received mode information, whether the interprediction method to be applied to the current block is an AMVP mode or a merge mode; and selecting a candidate to derive motion information of the current block, wherein the candidate is selected in a left region, top region and corner region of the current block and in the same position block as the current block, and the AMVP mode and the merge mode are applied on the basis of the selected candidate.

The present invention relates to a technique for encoding and decoding video data, and more particularly, to a method for performing inter-prediction in an effective manner. The present invention combines an inter-prediction method using an AMVP mode and an inter-prediction method using a merge mode so as to propose a method for using the same candidate. The method for encoding video data proposed by the present invention comprises the following steps: receiving mode information on an inter-prediction method of a current block; determining, on the basis of the received mode information, whether the interprediction method to be applied to the current block is an AMVP mode or a merge mode; and selecting a candidate to derive motion information of the current block, wherein the candidate is selected in a left region, top region and corner region of the current block and in the same position block as the current block, and the AMVP mode and the merge mode are applied on the basis of the selected candidate.

An image decoding method includes: dividing a current block into sub-blocks; deriving, for each sub-block, one or more prediction information candidates; obtaining an index; and decoding the current block using the prediction information candidate selected by the index. The deriving includes: determining whether a neighboring block neighboring each sub-block is included in the current block, and when not included in the current block, determining the neighboring block to be a reference block available to the sub-block, and when included in the current block, determining the neighboring block not to be the reference block; and deriving a prediction information candidate of the sub-block from prediction information of the reference block; and when the number of prediction information candidates is smaller than a predetermined number, generating one or more new candidates without using the prediction information of the reference block till the number of prediction information candidates reaches the predetermined number.

An image decoding method includes: dividing a current block into sub-blocks; deriving, for each sub-block, one or more prediction information candidates; obtaining an index; and decoding the current block using the prediction information candidate selected by the index. The deriving includes: determining whether a neighboring block neighboring each sub-block is included in the current block, and when not included in the current block, determining the neighboring block to be a reference block available to the sub-block, and when included in the current block, determining the neighboring block not to be the reference block; and deriving a prediction information candidate of the sub-block from prediction information of the reference block; and when the number of prediction information candidates is smaller than a predetermined number, generating one or more new candidates without using the prediction information of the reference block till the number of prediction information candidates reaches the predetermined number.

Innovations in encoder-side search ranges having horizontal bias or vertical bias are described herein. For example, a video encoder determines a block vector (“BV”) for a current block of a picture, performs intra prediction for the current block using the BV, and encodes the BV. The BV indicates a displacement to a region within the picture. When determining the BV, the encoder checks a constraint that the region is within a BV search range having a horizontal bias or vertical bias. The encoder can select the BV search range from among multiple available BV search ranges, e.g., depending at least in part on BV values of one or more previous blocks, which can be tracked in a histogram data structure.

Innovations in encoder-side search ranges having horizontal bias or vertical bias are described herein. For example, a video encoder determines a block vector (“BV”) for a current block of a picture, performs intra prediction for the current block using the BV, and encodes the BV. The BV indicates a displacement to a region within the picture. When determining the BV, the encoder checks a constraint that the region is within a BV search range having a horizontal bias or vertical bias. The encoder can select the BV search range from among multiple available BV search ranges, e.g., depending at least in part on BV values of one or more previous blocks, which can be tracked in a histogram data structure.

An image coding device is provided with a determination unit which determines whether to apply an orthogonal transform to a transform block obtained by dividing a prediction difference signal indicating a difference between an input image and a predicted image or perform a transform skip by which the orthogonal transform is not applied, and an orthogonal transform unit which performs processing selected on the basis of the determination, the image coding device comprising a quantization unit which, when the transform skip is selected on the basis of the determination, quantizes the transform block using a first quantization matrix in which the quantization roughnesses of all elements previously shared with a decoding side are equal, and when the orthogonal transform is applied to the transform block on the basis of the determination, quantizes the transform block using the first quantization matrix or a second quantization matrix that is transmitted to the decoding side.

An image coding device is provided with a determination unit which determines whether to apply an orthogonal transform to a transform block obtained by dividing a prediction difference signal indicating a difference between an input image and a predicted image or perform a transform skip by which the orthogonal transform is not applied, and an orthogonal transform unit which performs processing selected on the basis of the determination, the image coding device comprising a quantization unit which, when the transform skip is selected on the basis of the determination, quantizes the transform block using a first quantization matrix in which the quantization roughnesses of all elements previously shared with a decoding side are equal, and when the orthogonal transform is applied to the transform block on the basis of the determination, quantizes the transform block using the first quantization matrix or a second quantization matrix that is transmitted to the decoding side.

The present disclosure relates to motion vector refinement. As a first step, an initial motion vector and a template for the block are obtained. Then, the refinement of the initial motion vector is determined by template matching with said template in a search space. The search space is located on a position given by the initial motion vector and includes one or more fractional sample positions, wherein each of the fractional sample positions belonging to the search space is obtained by interpolation filtering with a filter of a predefined tap-size assessing integer samples only within a window, said window being formed by integer samples accessible for the template matching in said search space.

An image decoding method performed by a decoding device according to the present disclosure comprises: a step of deriving reference picture list 0 (L0) and reference picture list 1 (L1); a step of deriving two motion vectors (MV) for a current block, the two MVs including MVL0 for the L0 and MVL1 for the L1; a step of determining whether to apply bi-prediction optical flow (BIO) prediction for deriving refined motion vectors by sub-blocks to the current block; a step of deriving a refined motion vector for a sub-block of the current block based on the MVL0 and MVL1, if the BIO prediction is applied to the current block; and a step of deriving a prediction sample based on the refined motion vector.