Image encoding method and device, and image decoding method and device

An image decoding apparatus comprising:

• at least one processor configured to:
• obtain one or more coding units comprising a current coding unit, by hierarchically splitting at least one largest coding unit, based on a split shape mode;
• when a prediction mode of the current coding unit is an inter mode, obtain, from a bitstream, a first coded block flag indicating whether the current coding unit comprises one or more non-zero significant transform coefficients;
• when the first coded block flag indicates that the current coding unit comprises one or more non-zero significant transform coefficients, identify whether at least one of a height and a width of the current coding unit is greater than a predetermined size;
• based on an intra sub partition mode is not used for the current coding unit and whether the at least one of the height and the width of the current coding unit is greater than the predetermined size, obtain at least one transform unit included in the current coding unit;
• when a tree type of the current coding unit is a dual-tree chroma type, obtain, from the bitstream, a second coded block flag indicating whether a block of at least one chroma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• when the at least one of the height and the width of the current coding unit is greater than the predetermined size, obtain, from the bitstream, a third coded block flag indicating whether a block of a luma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• obtain a residual signal of the block of the luma component included in the at least one transform unit, based on the third coded block flag;
• reconstruct the current coding unit based on the residual signal;
• and
• reconstruct a current image comprising the current coding unit, based on the reconstructed current coding unit,
• wherein the split shape mode indicates at least one of whether to perform splitting, a split direction, or a split type, and
• wherein the split type corresponds to one of binary splitting, tri splitting, and quad splitting,
• wherein the current coding unit has a square shape or a rectangular shape.

An image encoding method comprising:

• obtaining one or more coding units comprising a current coding unit, by hierarchically splitting at least one largest coding unit, based on a split shape mode;
• when a prediction mode of the current coding unit is an inter mode, generating a first coded block flag indicating whether the current coding unit comprises one or more non-zero significant transform coefficients;
• based on determining that the current coding unit comprises one or more non-zero significant transform coefficients, identifying whether at least one of a height and a width of the current coding unit is greater than a predetermined size;
• based on an intra sub partition mode is not used for the current coding unit and whether the at least one of the height and the width of the current coding unit is greater than the predetermined size, obtaining at least one transform unit included in the current coding unit;
• encoding residual signal of a block of luma component and a block of at least one chroma component included in the at least one transform unit;
• when a tree type of the current coding unit is a dual-tree chroma type, generating a second coded block flag indicating whether a block of at least one chroma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• when the at least one of the height and the width of the current coding unit is greater than the predetermined size, generating a third coded block flag indicating whether a block of a luma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• and
• generating a bitstream including the encoded residual signal, the first coded block flag, the second coded block flag, and the third coded block flag;
• wherein the split shape mode indicates at least one of whether to perform splitting, a split direction, or a split type, and
• wherein the split type corresponds to one of binary splitting, tri splitting, and quad splitting,
• wherein the current coding unit has a square shape or a rectangular shape.

A method of transmitting a bitstream, the method comprising:

• obtaining one or more coding units comprising a current coding unit, by hierarchically splitting at least one largest coding unit, based on a split shape mode;
• when a prediction mode of the current coding unit is an inter mode, generating a first coded block flag indicating whether the current coding unit comprises one or more non-zero significant transform coefficients;
• based on determining that the current coding unit comprises one or more non-zero significant transform coefficients, identifying whether at least one of a height and a width of the current coding unit is greater than a predetermined size;
• based on an intra sub partition mode is not used for the current coding unit and whether the at least one of the height and the width of the current coding unit is greater than the predetermined size, obtaining at least one transform unit included in the current coding unit;
• encoding residual signal of a block of luma component and at least one chroma component included in the at least one transform unit;
• when a tree type of the current coding unit is a dual-tree chroma type, generating a second coded block flag indicating whether a block of at least one chroma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• when the at least one of the height and the width of the current coding unit is greater than the predetermined size, generating a third coded block flag indicating whether a block of a luma component included in the at least one transform unit comprises one or more non-zero significant transform coefficients;
• generating the bitstream including the encoded residual signal, the first coded block flag, the second coded block flag, and the third coded block flag;
• and
• transmitting the bitstream from an image encoding apparatus to an image decoding apparatus,
• wherein the split shape mode indicates at least one of whether to perform splitting, a split direction, or a split type, and
• wherein the split type corresponds to one of binary splitting, tri splitting, and quad splitting,
• wherein the current coding unit has a square shape or a rectangular shape.