Image coding method, image decoding method, image coding apparatus, image decoding apparatus, and image coding and decoding apparatus

A transmission method for sending a bitstream, the bitstream being generated by performing encoding method comprising:

• writing, into a sequence header, buffer descriptions that specify reference pictures to be held in a buffer for coding the pictures, the buffer descriptions including long-term information which identifies a reference picture, among a plurality of reference pictures covered by the buffer descriptions, to be assigned as a long-term reference picture;
• selecting one of the buffer descriptions for a slice in one of the pictures;
• writing, into a header of the slice, selecting information for specifying the selected buffer description;
• and
• coding the slice using the reference picture to be assigned as the long-term reference picture identified by the selected buffer description,
• wherein the long-term information, which is written into the sequence header includes, (i) a long-term index for identifying the reference picture to be assigned as the long-term reference picture and (ii) a unique picture order count (POC) number for specifying the reference picture identified by the long-term index, and
• wherein the header of the slice further includes information for updating the long-term information by updating the buffer descriptions obtained from the sequence header.

A non-transitory computer-readable medium storing a bitstream, the bitstream being generated by performing an encoding method, the bitstream comprising:

• a sequence header;
• and
• pictures,
• wherein the sequence header includes buffer descriptions that specify reference pictures to be held in a buffer for decoding the pictures, the buffer descriptions including long-term information which identifies a reference picture, among a plurality of reference pictures covered by the buffer descriptions, to be assigned as a long-term reference picture,
• wherein a slice header in one of the pictures includes selecting information for selecting one of the buffer descriptions for decoding a slice,
• wherein the long-term information includes, (i) a long-term index for identifying the reference picture to be assigned as the long term reference picture and (ii) a unique picture order count (POC) number for specifying the reference picture identified by the long-term index, and
• wherein the header of the slice further includes information for updating the long-term information by updating the buffer descriptions obtained from the sequence header.