Video signal processing method and apparatus using multi-assumption prediction

A video signal decoding device, the device comprising:

• a processor,
• wherein the processor is configured to:
• determine whether a merge mode is applied to a current block;
• if the merge mode is applied to the current block, obtain a first syntax element indicating whether combined prediction is applied to the current block, the combined prediction is a prediction mode that combines inter-prediction and intra-prediction, and a mode for the intra-prediction is a planar mode;
• if the first syntax element indicates that the combined prediction is not applied to the current block, obtain a second syntax element indicating whether sub-block transform is applied to the current block, and the sub-block transform indicates a transform mode that applies transform to one of sub-blocks of the current block divided in a horizontal direction or in a vertical direction;
• if the first syntax element indicates that the combined prediction is applied to the current block, reconstruct the current block based on the combined prediction;
• and
• if the first syntax element indicates that the combined prediction is not applied to the current block and the second syntax element indicates that the sub-block transform is applied to the current block, reconstruct the current block based on the sub-block transform.

A video signal encoding device comprising:

• a processor,
• wherein the processor is configured to
• obtain a bitstream to be decoded by a decoder using a decoding method,
• wherein the decoding method comprising:
• determining whether a merge mode is applied to a current block;
• if the merge mode is applied to the current block, obtaining a first syntax element indicating whether combined prediction is applied to the current block, the combined prediction is a prediction mode that combines inter-prediction and intra-prediction, and a mode for the intra-prediction is a planar mode;
• if the first syntax element indicates that the combined prediction is not applied to the current block, obtaining a second syntax element indicating whether sub-block transform is applied to the current block, and the sub-block transform indicates a transform mode that applies transform to one of sub-blocks of the current block divided in a horizontal direction or in a vertical direction;
• if the first syntax element indicates that the combined prediction is applied to the current block, reconstructing the current block based on the combined prediction;
• and
• if the first syntax element indicates that the combined prediction is not applied to the current block and the second syntax element indicates that the sub-block transform is applied to the current block, reconstructing the current block based on the sub-block transform.