Video encoding method and device, and video decoding method and device
Provided is an image decoding method including: obtaining, from a bitstream, a syntax element regarding multiple transform selection (MTS) with respect to a current coding unit or a current transform unit included in the current coding unit; determining a horizontal transform kernel or a vertical transform kernel with respect to the current transform unit based on the obtained syntax element; obtaining a residual signal by performing inverse transformation on the current transform unit, based on the determined horizontal transform kernel or vertical transform kernel with respect to the current transform unit; and generating a reconstruction block including the current coding unit or the current transform unit based on the residual signal with respect to the current transform unit.
1 . An image decoding method comprising:
obtaining one or more coding units comprising a current coding unit by splitting a current image;
obtaining a sub-block transform flag, from a bitstream, indicating whether or not a sub-block transform is used for the current coding unit;
obtaining, from a coding unit syntax structure in the bitstream, a syntax element regarding multiple transform selection (MTS) based on the sub-block transform flag indicating that the sub-block transform is not used for the current coding unit, with respect to the current coding unit, wherein the current coding unit includes a plurality of transform units and the syntax element regarding the MTS is index information indicating a type of a horizontal transform kernel and a type of a vertical transform kernel with respect to the plurality of transform units included in the current coding unit;
determining the horizontal transform kernel and the vertical transform kernel with respect to the plurality of transform units included in the current coding unit based on the obtained syntax element regarding the MTS;
obtaining a residual block with respect to a current transform unit among the plurality of transform units by applying the determined horizontal transform kernel and vertical transform kernel to the current transform unit; and
generating a reconstruction block for the current coding unit based on the residual block with respect to the current transform unit,
wherein a same horizontal transform kernel is applied to the plurality of transform units included in the current coding unit and a same vertical transform kernel is applied to the plurality of transform units included in the current coding unit.
2 . An image decoding apparatus comprising at least one processor configured to:
obtain one or more coding units comprising a current coding unit by splitting a current image;
obtain a sub-block transform flag from a bitstream indicating whether or not a sub-block transform is used for the current coding unit;
obtain, from a coding unit syntax structure in the bitstream, a syntax element regarding multiple transform selection (MTS) based on the sub-block transform flag indicating that the sub-block transform is not used for the current coding unit, with respect to the current coding unit, wherein the current coding unit includes a plurality of transform units and the syntax element regarding the MTS is index information indicating a type of a horizontal transform kernel and a type of a vertical transform kernel with respect to the plurality of transform units included in the current coding unit;
determine the horizontal transform kernel and the vertical transform kernel with respect to the plurality of transform units included in the current coding unit based on the obtained syntax element regarding the MTS;
obtain a residual block with respect to a current transform unit among the plurality of transform units by applying the determined horizontal transform kernel and vertical transform kernel to the current transform unit; and
generate a reconstruction block for the current coding unit based on the residual block with respect to the current transform unit,
wherein a same horizontal transform kernel is applied to the plurality of transform units included in the current coding unit and a same vertical transform kernel is applied to the plurality of transform units included in the current coding unit.
3 . An image encoding method comprising:
obtaining one or more coding units comprising a current coding unit by splitting a current image;
determining a horizontal transform kernel and a vertical transform kernel with respect to a plurality of transform units included in the current coding unit by performing transformation on the plurality of transform units included in the current coding unit; and
generating a syntax element regarding multiple transform selection (MTS) with respect to the current coding unit based on the horizontal transform kernel and the vertical transform kernel with respect to the plurality of transform units included in the current coding unit, wherein the syntax element regarding the MTS is index information indicating a type of a horizontal transform kernel and a type of a vertical transform kernel with respect to the plurality of transform units included in the current coding unit and the syntax element regarding the MTS is included in a coding unit syntax structure;
generating a sub-block transform flag indicating whether or not a sub-block transform is used for the current coding unit;
encoding a transform coefficient generated by performing transformation on a current transform unit among the plurality of transform units; and
generating a bitstream including the encoded transform coefficient with respect to the current transform unit, the sub-block transform flag and the syntax element regarding the MTS based on the sub-block transform flag indicating that the sub-block transform is not used for the current coding unit,
wherein a same horizontal transform kernel is applied to the plurality of transform units included in the current coding unit and a same vertical transform kernel is applied to the plurality of transform units included in the current coding unit.
4 . A method for transmitting a bitstream comprising:
obtaining one or more coding units comprising a current coding unit by splitting a current image;
determining a horizontal transform kernel and a vertical transform kernel with respect to a plurality of transform units included in the current coding unit by performing transformation on the plurality of transform units included in the current coding unit; and
generating a syntax element regarding multiple transform selection (MTS) with respect to the current coding unit based on the horizontal transform kernel and the vertical transform kernel with respect to the plurality of transform units included in the current coding unit, wherein the syntax element regarding the MTS is index information indicating a type of a horizontal transform kernel and a type of a vertical transform kernel with respect to the plurality of transform units included in the current coding unit and the syntax element regarding the MTS is included in a coding unit syntax structure;
generating sub-block transform flag indicating whether or not a sub-block transform is used for the current coding unit;
encoding a transform coefficient generated by performing transformation on a current transform unit among the plurality of transform units;
generating the bitstream including the encoded transform coefficient with respect to the current transform unit, the sub-block transform flag and the syntax element regarding the MTS based on the sub-block transform flag indicating that the sub-block transform is not used for the current coding unit; and
transmitting the bitstream to a non-transitory computer-readable recording medium,
wherein a same horizontal transform kernel is applied to the plurality of transform units included in the current coding unit and a same vertical transform kernel is applied to the plurality of transform units included in the current coding unit.