Encoding method and decoding method, and device implementing the same

A video encoding method, comprising:

• scanning transform coefficients of a current block based on a scanning type of the current block, the scanning type of the current block being determined based on a direction of an intra-prediction mode of the current block when a prediction mode of the current block is equal to an intra prediction;
• obtaining dequantized transform coefficients of the current block by dequantizing the transform coefficients;
• obtaining residual samples of the current block by performing an inverse transform on the dequantized transform coefficients, the inverse-transform being performed in a horizontal direction and a vertical direction,
• wherein the inverse-transform is performed by using one of discrete cosine transform (DCT) and discrete sine transform (DST), and
• wherein when a size of the current block is 4×4, the DST is applied both in the horizontal direction and the vertical direction for all intra prediction direction mode and a planar mode of the current block
• reconstructing the current block using the residual samples and prediction samples of the current block;
• and
• applying a deblocking filter on the reconstructed current block.

A method for transmitting a bitstream, the method comprising:

• scanning transform coefficients of a current block based on a scanning type of the current block, the scanning type of the current block being determined based on a direction of an intra-prediction mode of the current block when a prediction mode of the current block is equal to an intra prediction;
• obtaining dequantized transform coefficients of the current block by dequantizing the transform coefficients;
• obtaining residual samples of the current block by performing an inverse transform on the dequantized transform coefficients, the inverse-transform being performed in a horizontal direction and a vertical direction,
• wherein the inverse-transform is performed by using one of discrete cosine transform (DCT) and discrete sine transform (DST), and
• wherein when a size of the current block is 4×4, the DST is applied both in the horizontal direction and the vertical direction for all intra prediction direction mode and a planar mode of the current block;
• reconstructing the current block using the residual samples and prediction samples of the current block;
• and
• applying a deblocking filter on the reconstructed current block.