Image decoding device and image coding device

An image decoding method comprising:

• receiving a bitstream comprising one or more coding parameters used in decoding a target picture of the video sequence
• deriving, based on the bitstream, a reference picture set to be applied to the target picture;
• generating a reference picture list based on reference picture list (RPL) modification information decoded from a slice header and the reference picture set;
• determining a value of a first flag included in the one or more coding parameters, the first flag indicating whether information regarding list sorting is present within the slice header;
• and
• omitting decoding of a part of information included in the RPL modification information,
• wherein the RPL modification information includes at least a reference picture list sorting presence or absence flag and a reference list sorting order, and
• wherein decoding of the reference picture list sorting presence or absence flag and the reference list sorting order is omitted based on the number of current picture referable pictures and the value of the first flag.