Method for encoding/decoding image and device thereof

An image decoding method by a decoding apparatus, comprising:

• obtaining prediction information, residual information, and offset information for a sample adaptive offset (SAO) process from a bitstream;
• deriving prediction samples based on the prediction information;
• deriving residual samples based on the residual information;
• generating a reconstructed picture based on the prediction samples and the residual samples;
• and
• applying an in-loop filtering process to the reconstructed picture,
• wherein applying the in-loop filtering process includes applying a deblocking filtering process to the reconstructed picture, and applying the SAO process to a sample in the reconstructed picture to which the deblocking filtering process is completed,
• wherein the offset information includes offset type information representing that a band offset type is applied to the sample,
• wherein the offset information includes information on n offset values, and
• wherein the offset information includes explicit band information indicating one of 32 bands as a starting band of a band group consisting of n bands, and an offset value related to a band among the n bands is applied to the sample, wherein n is an integer.

An image encoding method by an encoding apparatus, comprising:

• deriving prediction samples in a current picture based on inter prediction or intra prediction;
• deriving residual samples in the current picture based on the prediction sample;
• generating a reconstructed picture of the current picture based on the prediction samples and the residual samples;
• applying an in-loop filtering process to the reconstructed picture, wherein applying the in-loop filtering process includes applying a deblocking filtering process to the reconstructed picture, and applying a sample adaptive offset (SAO) process to a sample in the reconstructed picture to which the deblocking filtering process is completed;
• and
• encoding prediction information on the prediction samples, residual information on the residual samples, and offset information for the SAO process,
• wherein the offset information includes offset type information representing that a band offset type is applied to the sample,
• wherein the offset information includes information on n offset values, and
• wherein the offset information includes explicit band information indicating one of 32 bands as a starting band of a band group consisting of n bands, and an offset value related to a band among the n bands is applied to the sample, wherein n is an integer.

A non-transitory computer readable digital storage medium storing a bitstream causing a decoding apparatus to perform an image decoding method, the method comprising:

• obtaining prediction information, residual information, and offset information for a sample adaptive offset (SAO) process from a bitstream;
• deriving prediction samples based on the prediction information;
• deriving residual samples based on the residual information;
• generating a reconstructed picture based on the prediction samples and the residual samples;
• and
• applying an in-loop filtering process to the reconstructed picture,
• wherein applying the in-loop filtering process includes applying a deblocking filtering process to the reconstructed picture, and applying the SAO process to a sample in the reconstructed picture to which the deblocking filtering process is completed,
• wherein the offset information includes offset type information representing that a band offset type is applied to the sample,
• wherein the offset information includes information on n offset values, and
• wherein the offset information includes explicit band information indicating one of 32 bands as a starting band of a band group consisting of n bands, and an offset value related to a band among the n bands is applied to the sample, wherein n is an integer.