Image decoding method and apparatus using same

A method of decoding video, the method comprising:

• receiving, by a decoding apparatus, a bitstream comprising a network abstraction layer (NAL) unit including information on an encoded picture;
• obtaining, by the decoding apparatus, NAL unit type information from a NAL unit header of the NAL unit;
• specifying, by the decoding apparatus, a NAL unit type of the current picture based on the NAL unit type information;
• and
• decoding, by the decoding apparatus, a current picture based on the NAL unit type,
• wherein the NAL unit type for the current picture is one of NAL unit types including a clean random access (CRA) type to specify a CRA picture and a broken link access (BLA) type to specify a BLA picture,
• wherein the CRA picture is a random access point picture and the CRA picture has a uniform NAL unit type regardless of a type of a leading picture associated with the CRA picture, wherein an output order of the leading picture is prior to an output order of the CRA picture.