Method and device for determining reference unit

An inter prediction method performed by a decoding apparatus, comprising:

• selecting candidate units among reconstructed neighboring units adjacent to a decoding target unit, the candidate units belong to a same picture as the decoding target unit;
• generating a candidate unit set for the decoding target unit using the selected candidate units;
• determining, based on a reference unit identifier, a reference unit among the candidate units configuring the generated candidate unit set, the reference unit identifier being representative of index information which is signaled to indicate that a sequence or a position of the reference unit among the candidate units in the candidate unit set;
• and
• performing inter prediction on the decoding target unit using motion information of the determined reference unit,
• wherein the reconstructed neighboring units include an upper neighboring unit adjacent to an upper portion of the decoding target unit, a left neighboring unit adjacent to the left of the decoding target unit, a right upper corner unit positioned at a right upper corner of the decoding target unit, a left upper corner unit positioned at a left upper corner of the decoding target unit, and a left lower corner unit positioned at a left lower corner of the decoding target unit.