# US 2021/0344951 A1 · Method and device for encoding or decoding image on basis of inter mode > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2021/0344951 A1 - Document ID: US20210344951A1 - Status: Published application - Kind: A1 - Application number: 17/280,099 - Filed: 2019-09-25 - Published: 2021-11-04 - Earliest claimed: 2018-09-25 - Assignees: Digitalinsights Inc. - Applicants: Digitalinsights Inc. - Inventors: Yong Jo AHN - Web page: https://patentgrep.com/patent/US20210344951A1 ## CPC - H04N 19/577: Motion compensation with bidirectional frame interpolation, i.e. using B-pictures - H04N 19/105: Selection of the reference unit for prediction within a chosen coding or prediction mode, e.g. adaptive choice of position and number of pixels used for prediction - H04N 19/119: Adaptive subdivision aspects, e.g. subdivision of a picture into rectangular or non-rectangular coding blocks - H04N 19/159: Prediction type, e.g. intra-frame, inter-frame or bidirectional frame prediction - H04N 19/176: the region being a block, e.g. a macroblock - H04N 19/513: Processing of motion vectors - H04N 19/52: by predictive encoding - H04N 19/30: using hierarchical techniques, e.g. scalability (H04N19/63 takes precedence) - H04N 19/426: using memory downsizing methods - H04N 19/436: using parallelised computational arrangements - H04N 19/54: using feature points or meshes - H04N 19/70: characterised by syntax aspects related to video coding, e.g. related to compression standards - H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION ## Abstract 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. ## Claims ### Claim 1 A method of decoding an image, the method comprising: deriving motion information for bidirectional prediction of a current block, based on an inter mode pre-defined in an image decoding apparatus; and performing inter prediction on the current block based on the motion information, wherein, according to the pre-defined inter mode, the motion information for the bidirectional prediction is adjusted to motion information for unidirectional prediction. ### Claim 2 (depends on 1) The method of claim 1, wherein, when the pre-defined inter mode is a merge mode, the motion information for the bidirectional prediction is adjusted to motion information for unidirectional prediction, and wherein, when the pre-defined inter mode is an affine mode, the motion information for the bidirectional prediction is not adjusted to motion information for unidirectional prediction. ### Claim 3 (depends on 2) The method of claim 2, wherein, when the pre-defined inter mode is a merge mode, the motion information for the bidirectional prediction is adjusted to motion information for unidirectional prediction in consideration of a size of the current block. ### Claim 4 (depends on 1) The method of claim 1, wherein, when the pre-defined inter mode is a merge mode, the deriving of the motion information comprises: constructing a merge candidate list of the current block; and deriving motion information of the current block from the merge candidate list, and wherein the merge candidate list includes at least one of a spatial merge candidate, a temporal merge candidate, or a combined merge candidate. ### Claim 5 (depends on 1) The method of claim 1, wherein, when the pre-defined inter mode is an affine mode, the deriving of the motion information comprises: generating a candidate list consisting of affine candidates of the current block; deriving a control point vector of the current block based on the candidate list and a candidate index; and deriving a motion vector of the current block based on the control point vector of the current block. ### Claim 6 (depends on 5) The method of claim 5, wherein the affine candidates include at least one of a spatial candidate, a temporal candidate, or a configured candidate. ### Claim 7 (depends on 5) The method of claim 5, wherein, in consideration of a size of a predetermined reference region, a motion vector of the current block is derived, and wherein the reference region includes a reference block specified by motion vectors of n sub-blocks and a pixel used to interpolate a fractional pel of the reference block. ### Claim 8 (depends on 7) The method of claim 7, wherein, when the size of the reference region is less than or equal to a threshold value, the motion vector of the current block is derived for each sub-block, and wherein, when the size of the reference region is greater than the threshold value, one motion vector is derived for the current block. ### Claim 9 (depends on 8) The method of claim 8, wherein the motion vector of the current block is derived based on an affine motion parameter, and wherein the affine motion parameter is calculated based on the control point vector of the current block. ### Claim 10 (depends on 1) The method of claim 1, wherein the current block belongs to a predetermined sub-picture, and wherein the sub-picture is defined as a group of grids having the same index among a plurality of grids constituting one picture.