Image information encoding and decoding method

A non-transitory computer-readable storage medium storing a bitstream generated by performing:

• deriving a prediction sample in a current picture;
• generating a reconstructed picture based on the prediction sample;
• applying an in-loop filter process to the reconstructed picture,
• wherein the step of applying the in-loop filter process includes applying a deblocking filtering process to the reconstructed picture;
• and
• applying a sample adaptive offset (SAO) process to at least one of a luma sample or a chroma sample in the reconstructed picture after completing the deblocking filtering process;
• encoding image information including prediction information for the prediction sample and offset information for the SAO process;
• and
• generating the bitstream including the image information,
• wherein the offset information includes first flag information indicating whether the SAO process is enabled for the luma sample and second flag information indicating whether the SAO process is enabled for the chroma sample,
• wherein the offset information includes start band information indicating one of 32 bands as a starting band of a band group consisting of n bands among the 32 bands, the band group is determined based on the starting band, and an offset corresponding to a band among the n bands is applied to the luma sample or the chroma sample, wherein n is an integer.