In a method and a device for encoding or decoding an image according to the present invention, motion information for bidirectional prediction of a current block may be derived on the basis of an inter mode previously defined in the device for encoding or decoding an image, and inter prediction may be performed on the current block on the basis of the motion information, wherein the motion information for bidirectional prediction is adjusted to be motion information for unidirectional prediction according to the predefined inter mode.

The present disclosure provides a method and an apparatus for determining an intra-frame prediction mode of a current video block. The method includes determining, in an image area including a to-be-coded current video block, reference modes of the current video block based on a plurality of intra-frame prediction modes of a plurality of second video blocks, the image area being in an area defined by an adjacent coding unit (CU) and a father CU corresponding to the current video block in a video frame or slice including the current video block; determining an alternative prediction mode set from preset intra-frame prediction modes, the alternative prediction mode set comprising a plurality of alternative prediction modes, including the reference modes; and determining, in the alternative prediction mode set, a prediction mode having optimal intra-frame prediction coding performance on the current video block as an intra-frame prediction mode of the current video block.

The present disclosure provides a method and an apparatus for determining an intra-frame prediction mode of a current video block. The method includes determining, in an image area including a to-be-coded current video block, reference modes of the current video block based on a plurality of intra-frame prediction modes of a plurality of second video blocks, the image area being in an area defined by an adjacent coding unit (CU) and a father CU corresponding to the current video block in a video frame or slice including the current video block; determining an alternative prediction mode set from preset intra-frame prediction modes, the alternative prediction mode set comprising a plurality of alternative prediction modes, including the reference modes; and determining, in the alternative prediction mode set, a prediction mode having optimal intra-frame prediction coding performance on the current video block as an intra-frame prediction mode of the current video block.

A video decoding method includes determining, based on an area of a current block, whether a multi-prediction combination mode for predicting the current block by combining prediction results obtained according to a plurality of prediction modes is applied to the current block, when the multi-prediction combination mode is applied to the current block, determining the plurality of prediction modes to be applied to the current block, generating a plurality of prediction blocks of the current block, according to the plurality of prediction modes, and determining a combined prediction block of the current block, by combining the plurality of prediction blocks according to respective weights.

A video decoding method includes determining, based on an area of a current block, whether a multi-prediction combination mode for predicting the current block by combining prediction results obtained according to a plurality of prediction modes is applied to the current block, when the multi-prediction combination mode is applied to the current block, determining the plurality of prediction modes to be applied to the current block, generating a plurality of prediction blocks of the current block, according to the plurality of prediction modes, and determining a combined prediction block of the current block, by combining the plurality of prediction blocks according to respective weights.

Provided is a video decoding method of applying a deblocking filter to neighboring pixels adjacent to a boundary of a current block, the video decoding method including selecting a deblocking filter to be applied to the neighboring pixels from among a plurality of deblocking filters according to pixel values of the neighboring pixels and a size of the current block, and applying the selected deblocking filter to the neighboring pixels, wherein the plurality of deblocking filters include three or more deblocking filters having different ranges of neighboring pixels to which deblocking filtering is applied.

Provided is a video decoding method of applying a deblocking filter to neighboring pixels adjacent to a boundary of a current block, the video decoding method including selecting a deblocking filter to be applied to the neighboring pixels from among a plurality of deblocking filters according to pixel values of the neighboring pixels and a size of the current block, and applying the selected deblocking filter to the neighboring pixels, wherein the plurality of deblocking filters include three or more deblocking filters having different ranges of neighboring pixels to which deblocking filtering is applied.

According to the disclosure of the present document, on the basis of NAL unit type-associated information on whether a picture has mixed NAL unit types, NAL unit types for slices within the picture can be determined, and for the picture having the mixed NAL unit types, not only IRAP but also a form mixed with NAL units of other types can be provided.

According to the disclosure of the present document, on the basis of NAL unit type-associated information on whether a picture has mixed NAL unit types, NAL unit types for slices within the picture can be determined, and for the picture having the mixed NAL unit types, not only IRAP but also a form mixed with NAL units of other types can be provided.

An image decoding method according to the present disclosure presents indication information related to whether deblocking parameters for a deblocking filtering procedure exist in a picture header or a slice header.