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

A video decoding method, by a decoding apparatus, the method comprising:

• acquiring first long term reference picture (LTRP) information in a sequence parameter set (SPS) from a bitstream;
• acquiring second LTRP information in a slice header from the bitstream;
• configuring a reference picture set based on the first LTRP information and the second LTRP information;
• and
• performing an inter prediction on a current block in the current picture by using an LTRP in the reference picture set, wherein the LTRP is one of candidate LTRPs specified by the first LTRP information in the SPS,
• 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 when a value of the long term reference pictures present flag is 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 an 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 reference 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 at least one of the candidate LTRPs.

A video encoding method, by an encoding apparatus, the method comprising:

• 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,
• 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 when a value of the long term reference pictures present flag is 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 an 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 reference 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 at least one of the candidate LTRPs.

A non-transitory decoder-readable storage medium storing encoded data comprising encoded first LTRP information and encoded second LTRP information generated by an video encoding process comprising:

• 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,
• 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 when a value of the long term reference pictures present flag is 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 an 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 reference 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 at least one of the candidate LTRPs.