Method for encoding video, method for decoding video, and apparatus using same

A video encoding method by a video encoder, comprising:

• deriving an inter-layer reference picture for a current block from at least one of pictures in a reference layer;
• constructing a reference picture list comprising the inter-layer reference picture in the reference layer and a reference picture in the current layer;
• deriving a predicted sample of a current block in a current layer based on the reference picture list;
• deriving a residual sample of the current block based on the predicted sample and an original sample of the current block;
• generating residual information for the residual sample of the current block;
• generating flag information for whether a picture in the reference layer is not used for the inter-layer prediction;
• and
• generating a bitstream including the residual information and the flag information,
• wherein when the flag information indicate that a specific picture in the reference layer is not used for the inter-layer prediction, the specific picture is not comprised in the reference picture set, and
• wherein the flag information is transmitted through a slice segment header, and in all slice segment header of the picture in the reference layer, a value of the flag information is set to the same.

A non-transitory computer-readable storage medium storing a bitstream comprising:

• residual information for a residual sample derived based on a predicted sample and an original sample of a current block;
• flag information for whether a picture in a reference layer is not used for an inter-layer prediction of the current block,
• wherein when the flag information indicate that a specific picture in the reference layer is not used for the inter-layer prediction, the specific picture is not comprised in a reference picture set, and
• wherein the flag information is received through a slice segment header, and in all slice segment header of the picture in the reference layer, a value of the flag information is set to the same, and the value of the flag information is equal to one of 0 and 1.