Method and device for processing video signal by using transform having low complexity

A device for processing a video signal by using a transform having a low complexity, the device comprising:

• a memory storing the video signal;
• and
• a processor connected to the memory,
• wherein the processor is configured to
• acquire a transform index related to one of a plurality of transform combinations including combinations of one or more transform kernels for transforming of a current block of the video signal,
• derive a transform combination including a horizontal transform and a vertical transform related to the transform index, and
• apply each of the vertical transform and the horizontal transform of the transform combination to the current block,
• wherein the transform kernels include Discrete Sine Transform Type-7 (DST-7) or Discrete Cosine Transform Type-8 (DCT-8), and
• wherein the DST-7 or DCT-8 is designed based on a discrete Fourier transform (DFT) to which a scale value in a form of a power of 2 related to a bit length of a transform coefficient is applied.

A non-transitory computer-readable storage medium storing a computer-executable component configured to be executed in one or more processors of a computing device, wherein the computer-executable component is configured to

• acquire a transform index related to one of a plurality of transform combinations including combinations of one or more transform kernels for transforming of a current block of the video signal,
• derive a transform combination including a horizontal transform and a vertical transform related to the transform index, and
• apply each of the vertical transform and the horizontal transform of the transform combination to the current block,
• wherein the transform kernels include Discrete Sine Transform Type-7 (DST-7) or Discrete Cosine Transform Type-8 (DCT-8), and
• wherein the DST-7 or DCT-8 is designed based on a discrete Fourier transform (DFT) to which a scale value in a form of a power of 2 related to a bit length of a transform coefficient is applied.