Method and apparatus for video signal processing using sub-block based motion compensation
A video signal processing method and apparatus for encoding or decoding a video signal is disclosed. More particularly, a video signal processing method and a video signal processing apparatus using the same are disclosed, wherein a method for processing a video signal comprises the steps of: obtaining a set of control point motion vectors for prediction of a current block; obtaining the motion vector of each sub-block of the current block using control point motion vectors of the set of control point motion vectors; obtaining a predictor of the each sub-block of the current block using the motion vectors of the each sub-block; obtaining a predictor of the current block by combining predictors of the each sub-block; and restoring the current block using the predictor of the current block.
1. A method for decoding a video signal, the method performed by an apparatus and comprising:
obtaining a candidate list comprising control point motion vector set candidates,
wherein the control point motion vector set candidates include a first control point motion vector set, a second control point motion vector set, and a third control point motion vector set,
wherein the first control point motion vector set includes a first control point motion vector, a second control point motion vector, and a third control point motion vector,
wherein the second control point motion vector set includes the first control point motion vector, the second control point motion vector, and a fourth control point motion vector,
wherein the third control point motion vector set includes the first control point motion vector and a fifth control point motion vector,
wherein the first control point motion vector corresponds to an upper left corner of a current block,
wherein the second control point motion vector corresponds to an upper right corner of the current block,
wherein the third control point motion vector corresponds to a lower left corner of the current block,
wherein the fourth control point motion vector is determined based on the first control point motion vector and the second control point motion vector,
wherein the fifth control point motion vector is determined based on the first control point motion vector and the third control point motion vector, and
wherein the fourth control point motion vector and the fifth control point motion vector are respectively included in different control point motion vector sets;
obtaining a motion vector of a subblock of the current block based on a control point motion vector set indicated by index information among the candidate list; and
reconstructing the current block based on the motion vector of the subblock of the current block.
2. The method of claim 1 , wherein reconstructing the current block comprises:
obtaining a predictor of the subblock of the current block based on the motion vector of the subblock of the current block;
obtaining a predictor of the current block by combining the predictor of the subblock of the current block; and
reconstructing the current block based on the predictor of the current block.
3. A method for encoding a video signal, the method performed by an apparatus and comprising:
obtaining a bitstream to be decoded using a decoding method,
wherein the decoding method comprises:
obtaining a candidate list comprising control point motion vector set candidates,
wherein the control point motion vector set candidates include a first control point motion vector set, a second control point motion vector set, and a third control point motion vector set,
wherein the first control point motion vector set includes a first control point motion vector, a second control point motion vector, and a third control point motion vector,
wherein the second control point motion vector set includes the first control point motion vector, the second control point motion vector, and a fourth control point motion vector,
wherein the third control point motion vector set includes the first control point motion vector and a fifth control point motion vector,
wherein the first control point motion vector corresponds to an upper left corner of a current block,
wherein the second control point motion vector corresponds to an upper right corner of the current block,
wherein the third control point motion vector corresponds to a lower left corner of the current block,
wherein the fourth control point motion vector is determined based on the first control point motion vector and the second control point motion vector,
wherein the fifth control point motion vector is determined based on the first control point motion vector and the third control point motion vector, and
wherein the fourth control point motion vector and the fifth control point motion vector are respectively included in different control point motion vector sets;
obtaining a motion vector of a subblock of the current block based on a control point motion vector set indicated by index information among the candidate list; and
reconstructing the current block based on the motion vector of the subblock of the current block.
4. The method of claim 3 , wherein reconstructing the current block comprises:
obtaining a predictor of the subblock of the current block based on the motion vector of the subblock of the current block;
obtaining a predictor of the current block by combining the predictor of the subblock of the current block; and
reconstructing the current block based on the predictor of the current block.
5. A non-transitory computer-readable medium storing a bitstream, the bitstream being decoded by a decoding method,
wherein the decoding method comprises:
obtaining a candidate list comprising control point motion vector set candidates,
wherein the control point motion vector set candidates include a first control point motion vector set, a second control point motion vector set, and a third control point motion vector set,
wherein the first control point motion vector set includes a first control point motion vector, a second control point motion vector, and a third control point motion vector,
wherein the second control point motion vector set includes the first control point motion vector, the second control point motion vector, and a fourth control point motion vector,
wherein the third control point motion vector set includes the first control point motion vector and a fifth control point motion vector,
wherein the first control point motion vector corresponds to an upper left corner of a current block,
wherein the second control point motion vector corresponds to an upper right corner of the current block,
wherein the third control point motion vector corresponds to a lower left corner of the current block,
wherein the fourth control point motion vector is determined based on the first control point motion vector and the second control point motion vector,
wherein the fifth control point motion vector is determined based on the first control point motion vector and the third control point motion vector, and
wherein the fourth control point motion vector and the fifth control point motion vector are respectively included in different control point motion vector sets;
obtaining a motion vector of a subblock of the current block based on a control point motion vector set indicated by index information among the candidate list; and
reconstructing the current block based on the motion vector of the subblock of the current block.