Image encoding/decoding method and device

An image decoding method, comprising:

• determining a prediction mode for a current block;
• performing prediction for the current block using the prediction mode;
• and
• performing a transform on at least one coefficient of the current block, based on a transform kernel, to generate residual samples,
• wherein the transform comprises a primary transform and a secondary transform,
• the residual samples are generated by performing the primary transform using the transform kernel on a result of the secondary transform which is performed on the at least one coefficient,
• transform kernel information is obtained from a bitstream,
• the transform kernel information indicates one of predefined transform kernel sets as the transform kernel of the current block,
• each of the predefined transform kernel sets comprises a predefined horizontal transform kernel and a predefined vertical transform kernel,
• the transform kernel of the current block comprises a horizontal transform kernel and a vertical transform kernel, and
• the horizontal transform kernel and the vertical transform kernel of the transform kernel of the current block are determined based on a size of the current block, whether inter prediction is used for the prediction for the current block or not and whether intra prediction is used for the prediction for the current block or not.

A non-transitory computer-readable recording medium storing a bitstream,

• wherein the bitstream is configured to be decoded by an image decoding method, the image decoding method comprising:
• determining a prediction mode for a current block;
• performing prediction for the current block using the prediction mode;
• determining a transform kernel of the current block;
• and
• performing a transform on at least one coefficient of the current block, based on the transform kernel, to generate residual samples, wherein
• the transform comprises a primary transform and a secondary transform,
• the residual samples are generated by performing the primary transform using the transform kernel on a result of the secondary transform which is performed on the at least one coefficient,
• transform kernel information is obtained from the bitstream,
• the transform kernel information indicates one of predefined transform kernel sets as the transform kernel of the current block,
• each of the predefined transform kernel sets comprises a predefined horizontal transform kernel and a predefined vertical transform kernel,
• the transform kernel of the current block comprises a horizontal transform kernel and a vertical transform kernel, and
• the horizontal transform kernel and the vertical transform kernel of the transform kernel of the current block are determined based on a size of the current block, whether inter prediction is used for the prediction for the current block or not and whether intra prediction is used for the prediction for the current block or not.

A method of transmitting a bitstream, the method comprising:

• obtaining a bitstream comprising transform kernel information;
• and
• transmitting the bitstream, wherein
• the bitstream is structured to be decoded by an image decoding method,
• the bitstream is used to determine a prediction mode for a current block,
• the prediction mode is information used to perform prediction for the current block,
• the bitstream is used to determine a transform kernel of the current block,
• the transform kernel is used to perform a transform on at least one coefficient of the current block to generate residual samples,
• the transform comprises a primary transform and a secondary transform,
• the residual samples are generated by performing the primary transform using the transform kernel on a result of the secondary transform which is performed on the at least one coefficient,
• the transform kernel information indicates one of predefined transform kernel sets as the transform kernel of the current block,
• each of the predefined transform kernel sets comprises a predefined horizontal transform kernel and a predefined vertical transform kernel,
• the transform kernel of the current block comprises a horizontal transform kernel and a vertical transform kernel, and
• the horizontal transform kernel and the vertical transform kernel of the transform kernel of the current block are determined based on a size of the current block, whether inter prediction is used for the prediction for the current block or not and whether intra prediction is used for the prediction for the current block or not.

A non-transitory computer-readable recording medium storing a bitstream representing an encoded image, the bitstream comprising:

• transform kernel information of a current block, wherein
• the bitstream is decoded by an image decoding method comprising:
• determining a prediction mode for the current block;
• performing prediction for the current block using the prediction mode;
• and
• performing a transform on at least one coefficient of the current block, based on a transform kernel, to generate residual samples, wherein
• the transform comprises a primary transform and a secondary transform,
• the residual samples are generated by performing the primary transform using the transform kernel on a result of the secondary transform which is performed on the at least one coefficient,
• the transform kernel information indicates one of predefined transform kernel sets as the transform kernel of the current block,
• each of the predefined transform kernel sets comprises a predefined horizontal transform kernel and a predefined vertical transform kernel,
• the transform kernel of the current block comprises a horizontal transform kernel and a vertical transform kernel, and
• the horizontal transform kernel and the vertical transform kernel of the transform kernel of the current block are determined based on a size of the current block, whether inter prediction is used for the prediction for the current block or not and whether intra prediction is used for the prediction for the current block or not.