Method for processing video signal by using transform, and apparatus therefor

An apparatus for encoding image information, the apparatus comprising:

• a memory;
• and
• at least one processor coupled to the memory, the at least one processor configured to:
• determine transform kernels to be applied to horizontal and vertical directions of a current block including a residual signal except a predicted signal in the image information, the transform kernels including a horizontal transform kernel and a vertical transform kernel;
• generate transform information about the transform kernels, the transform information including a horizontal transform type index for the horizontal transform kernel and a vertical transform type index for the vertical transform kernel;
• generate residual information for a transformed block by respectively applying horizontal transform and vertical transform to the horizontal direction and the vertical direction of the current block based on the transform kernels related to the transform information;
• and
• encode the image information including the transform information and the residual information,
• wherein a width and a height of the transformed block is determined based on the horizontal transform type index, the vertical transform type index, and a width and a height of the transform block,
• wherein coefficients existing in a region other than a region in which the transformed block is generated in the current block are regarded as 0, and
• wherein a transformation matrix, which has 32 columns and 16 rows, for at least one of the horizontal transform or the vertical transform is derived based on at least one of (i) the horizontal transform type index being greater than 0 and the width of the transform block being 32 or (ii) the vertical transform type index being greater than 0 and the height of the transform block being 32.

An apparatus for transmitting image information, the apparatus comprising:

• at least one processor configured to generate a bitstream for the image information, the image information generated by determining transform kernels to be applied to horizontal and vertical directions of a current block including a residual signal except a predicted signal in the image information, the transform kernels including a horizontal transform kernel and a vertical transform kernel, generating transform information about the transform kernels, the transform information including a horizontal transform type index for the horizontal transform kernel and a vertical transform type index for the vertical transform kernel, generating residual information for a transformed block by respectively applying horizontal transform and vertical transform to the horizontal direction and the vertical direction of the current block based on the transform kernels related to the transform information, and encoding the image information including the transform information and the residual information;
• and
• a transmitter configured to transmit the image information comprising the bitstream,
• wherein a width and a height of the transformed block is determined based on the horizontal transform type index, the vertical transform type index, and a width and a height of the transform block,
• wherein coefficients existing in a region other than a region in which the transformed block is generated in the current block are regarded as 0, and
• wherein a transformation matrix, which has 32 columns and 16 rows, for at least one of the horizontal transform or the vertical transform is derived based on at least one of (i) the horizontal transform type index being greater than 0 and the width of the transform block being 32 or (ii) the vertical transform type index being greater than 0 and the height of the transform block being 32.