Methods and apparatuses for encoding and decoding motion vector difference using sequence MMVD information

A video decoding apparatus comprising:

• a syntax element obtainer configured to obtain, from a sequence parameter set (SPS), sequence merge mode with a motion vector difference (MMVD) information indicating whether an MMVD mode is enabled for a current sequence, and when the MMVD mode is enabled for the current sequence according to the sequence MMVD information, obtain, from a bitstream, MMVD information indicating whether the MMVD mode is applied in an inter prediction mode for a current block comprised in the current sequence;
• and
• a decoder configured to, when the MMVD mode is used for the current block in the inter prediction mode according to the MMVD information, obtain a first bin of a distance index of a merge motion vector difference by performing entropy decoding using context information on the bitstream, and obtain other bins of the distance index of the merge motion vector difference by performing entropy decoding in a bypass mode on the bitstream, obtain the distance index of the merge motion vector difference corresponding to the first bin and the other bins of the distance index of the merge motion vector difference, obtain bins indicating a direction index of the merge motion vector difference by performing entropy decoding on the bitstream in the bypass mode, and obtain the direction index of the merge motion vector difference corresponding to the bins indicating the direction index of the merge motion vector difference, and reconstruct a motion vector of the current block based on the merge motion vector difference determined using the distance index of the merge motion vector difference and the direction index of the merge motion vector difference, and reconstruct the current block by using the motion vector of the current block,
• wherein, one bit of the direction index of the merge motion vector difference indicates one of an x-axis direction and an y-axis direction, and another bit of the direction index of the merge motion vector difference indicates a positive or negative sign of the x-axis direction or the positive or negative sign of the y-axis direction.

A video encoding method comprising:

• encoding, into a sequence parameter set (SPS), sequence merge mode with a motion vector difference (MMVD) information indicating whether an MMVD mode is enabled for a current sequence;
• when the MMVD mode is enabled for the current sequence, encoding MMVD information indicating whether the MMVD mode is used for a current block comprised in the current sequence in an inter prediction mode;
• and
• when the MMVD mode is used for the current block in the inter prediction mode, obtaining bins of a distance index of a merge motion vector difference, performing entropy encoding using context information on a first bin among the bins of the distance index of the merge motion vector difference into a bitstream and performing entropy encoding in a bypass mode on other bins among the bins of the distance index of the merge motion vector difference into the bitstream, obtaining bins of a direction index of the merge motion vector difference, and performing entropy encoding in the bypass mode on the bins indicating the direction index of the merge motion vector difference of the current block into the bitstream,
• wherein, one bit of the direction index of the merge motion vector difference indicates one of an x-axis direction and an y-axis direction, and another bit of the direction index of the merge motion vector difference indicates a positive or negative sign of the x-axis direction or the positive or negative sign of the y-axis direction.

A method of transmitting a bitstream generated by encoding a video, the method comprising:

• encoding, into a sequence parameter set (SPS), sequence merge mode with a motion vector difference (MMVD) information indicating whether an MMVD mode is enabled for a current sequence;
• when the MMVD mode is enabled for the current sequence, encoding the MMVD information indicating whether the MMVD mode is used for a current block comprised in the current sequence in an inter prediction mode;
• when the MMVD mode is used for the current block in the inter prediction mode, obtaining bins of a distance index of a merge motion vector difference, performing entropy encoding using context information on a first bin among the bins of the distance index of the merge motion vector difference into information about the distance index of the merge motion vector difference, and performing entropy encoding in a bypass mode on other bins among the bins of the distance index of the merge motion vector difference into the information about the distance index of the merge motion vector difference, obtaining bins of a direction index of the merge motion vector difference, and performing entropy encoding in the bypass mode on the bins indicating the direction index of the merge motion vector difference of the current block into the information about the direction index of the merge motion vector difference;
• and
• transmitting the bitstream including the information about the distance index of the merge motion vector difference and the information about the direction index of the merge motion vector difference,
• wherein, one bit of the direction index of the merge motion vector difference indicates one of an x-axis direction and an y-axis direction, and another bit of the direction index of the merge motion vector difference indicates a positive or negative sign of the x-axis direction or the positive or negative sign of the y-axis direction.