Video encoding method using offset adjustments according to pixel classification and apparatus therefor, video decoding method and apparatus therefor

A video decoding method comprising:

• parsing, from a bitstream, offset merge information indicating whether a sample offset parameter of a current block is derived from a sample offset parameter of a neighboring block;
• when the offset merge information indicates that the sample offset parameter of the current block is derived from the sample offset parameter of the neighboring block, determining the sample offset parameter of the current block using the sample offset parameter of the neighboring block;
• when the offset merge information indicates that the sample offset parameter of the current block is not derived from the sample offset parameter of the neighboring block, obtaining, from the bitstream, a plurality of offset values and information about an offset type of the current block;
• and
• compensating for a sample value of a current sample among samples of the current block, by using an offset value for the current sample among the plurality of offset values of the current block,
• wherein:
• when the information about an offset type indicates an edge offset type, the obtaining a plurality of offset values comprises further obtaining, from the bitstream, information about a particular edge direction of the current block among a plurality of edge directions,
• the plurality of offset values of the current block correspond to a plurality of edge classes,
• two neighboring samples, among samples adjacent to the current sample, are determined corresponding to the particular edge direction of the current block,
• an edge class for the current sample, among the plurality of edge classes, is determined according to whether the current sample is larger than the two neighboring samples, and
• the offset value for the current sample is determined, among the plurality of offset values of the current block, according to the edge class for the current sample, and
• wherein, when the information about an offset type indicates a band offset type, the obtaining a plurality of offset values comprises:
• obtaining, from the bitstream, a plurality of absolute values of the offset values;
• and
• when the absolute values of the offset values are not zero, obtaining, from the bitstream, a plurality of signs of the offset values.