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

A video decoding apparatus comprising:

• a buffer configured to store a block to be used in intra prediction;
• and
• a decoder configured to:
• obtain a residue of a first sampling rate regarding a current block by decoding a bitstream,
• when the current block is intra predicted, generate a prediction block of the current block of the first sampling rate which is same as the first sampling rate of the residue by using a block that is previously decoded at the first sampling rate and then is stored in the buffer, and
• when the current block is inter predicted, generate a prediction block of a second sampling rate which is different from the first sampling rate of the residue, by using an image previously decoded at the second sampling rate which is changed from at least one block of the first sampling rate comprised in the image previously decoded, wherein the at least one block of the first sampling rate is based on another residue of the first sampling rate, and wherein the another residue of the first sampling rate is obtained from the bitstream and is related to the image previously decoded, and generate the prediction of the current block of the first sampling rate which is same as the first sampling rate of the residue by changing the generated prediction block of the second sampling rate to the prediction block of the first sampling rate,
• generate a reconstruction block of the first sampling rate by using the prediction block and the residue of the first sampling rate,
• wherein the first sampling rate is higher than the second sampling rate.

A video encoding method comprising:

• when a current block is intra predicted, generating a prediction block of the current block of a first sampling rate which is same as a sampling rate of a residue by using a block that is previously decoded at the first sampling rate and then is stored in a buffer;
• when the current block is inter predicted, generating a prediction block of a second sampling rate which is different from the first sampling rate of the residue, by using an image previously decoded at the second sampling rate which is changed from at least one block of the first sampling rate comprised in the image previously decoded, wherein the at least one block of the first sampling rate is based on another residue of the first sampling rate, and the another residue of the first sampling rate is to be included in a bitstream and is related to the image previously decoded and generate the prediction block of the current block of the first sampling rate which is same as the first sampling rate of the residue by changing the generated prediction block of the second sampling rate to the prediction block of the first sampling rate;
• and
• determining the residue of the first sampling rate regarding the current block by using the generated prediction block of the first sampling rate, and generating the bitstream comprising the determined residue of the first sampling rate,
• wherein the first sampling rate is higher than the second sampling rate.