Method and device for transmitting image information, and decoding method and device using same

An encoding apparatus for encoding an image, the encoding apparatus comprising:

• a memory;
• and
• at least one processor connected to the memory, the at least one processor configured to:
• derive long term reference pictures (LTRPs) for a current picture;
• generate first LTRP information and second LTRP information used for configuring a reference picture set for the current picture;
• and
• encode the first LTRP information in a sequence parameter set (SPS) and the second LTRP information in a slice header,
• wherein the reference picture set comprises an LTRP set including at least one LTRP,
• wherein the first LTRP information in the SPS includes a long term reference pictures present flag,
• wherein based on a value of the long term reference pictures present flag being equal to 1,
• the first LTRP information in the SPS further includes an LTRP number syntax element specifying a number of the candidate LTRPs specified in the SPS and LTRP picture order count (POC) least significant bit (LSB) information specifying an LSB of a POC of each of the candidate LTRPs,
• the first LTRP information in the SPS further includes used by current picture long term SPS flag information specifying whether each of the candidate LTRPs specified in the SPS is not used for a reference picture by the current picture, and
• wherein the second LTRP information in the slice header includes LTRP index information specifying an LTRP to be included in the LTRP set among the candidate LTRPs specified in the SPS.

An apparatus for transmitting data for an image, the apparatus comprising:

• at least one processor configured to obtain a bitstream for the image, wherein the bitstream is generated based on deriving long term reference pictures (LTRPs) for a current picture, generating first LTRP information and second LTRP information used for configuring a reference picture set for the current picture, and encoding the first LTRP information in a sequence parameter set (SPS) and the second LTRP information in a slice header;
• and
• a transmitter configured to transmit the data comprising the bitstream,
• wherein the reference picture set comprises an LTRP set including at least one LTRP,
• wherein the first LTRP information in the SPS includes a long term reference pictures present flag,
• wherein based on a value of the long term reference pictures present flag being equal to 1,
• the first LTRP information in the SPS further includes an LTRP number syntax element specifying a number of the candidate LTRPs specified in the SPS and LTRP picture order count (POC) least significant bit (LSB) information specifying an LSB of a POC of each of the candidate LTRPs,
• the first LTRP information in the SPS further includes used by current picture long term SPS flag information specifying whether each of the candidate LTRPs specified in the SPS is not used for a reference picture by the current picture, and
• wherein the second LTRP information in the slice header includes LTRP index information specifying an LTRP to be included in the LTRP set among the candidate LTRPs specified in the SPS.