Video decoding method and apparatus, and video encoding method and apparatus

A video decoding method comprising:

• when a quad split of a first block is not allowed, obtaining split direction information indicating whether the first block is split horizontally or vertically, and split type information indicating whether the first block is split using ternary split or binary split;
• when the split direction information indicates that the first block is split vertically and the split type information indicates that the first block is split using binary split, obtaining a second block and a third block by vertically splitting the first block;
• splitting the second block horizontally into a fourth block and a fifth block and splitting the third block horizontally into a sixth block and a seventh block;
• when an intra prediction mode of the seventh block is a DC mode and lengths of a width of the seventh block is greater than lengths of a height of the seventh block, determining an average of upper reference samples of the seventh block as a DC value;
• and
• performing intra prediction on the seventh block, based on the DC value,
• wherein the fourth block, the fifth block, the sixth block, and the seventh block are decoded according to a decoding order of the fourth block, the fifth block, the sixth block, and the seventh block, and
• wherein the second block is adjacent to a left side of the third block, the fourth block is adjacent to an upper side of the fifth block, and the sixth block is adjacent to an upper side of the seventh block,
• wherein the number of the upper reference samples of the seventh block is equal to the width of the seventh block.