Intra prediction method and encoding apparatus and decoding apparatus using same

An image decoding method using intra prediction, by a decoding apparatus, the method comprising:

• obtaining residual information for a current block and prediction information including prediction mode information representing an intra prediction mode for the current block;
• deriving the intra prediction mode for the current block based on the prediction mode information, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode;
• deriving neighboring reference samples of the current block;
• performing filtering on at least one of the reference samples;
• generating a prediction sample of the current block based on a filtered reference sample;
• generating a residual sample of the current block based on the residual information;
• and
• generating a reconstructed picture based on the prediction sample and the residual sample,
• wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a vertical intra prediction mode and the first neighboring reference sample being located on a top side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a second neighboring reference sample located on a left side of the first neighboring reference sample and a third neighboring reference sample located on a right side of the first neighboring reference sample,
• r(x−1)+2*r(x)+r(x+1)+2)>>2
• wherein, the r(x) represents a sample value of the first neighboring reference sample, the r(x−1) represents a value of the second neighboring reference sample and the r(x+1) represents a sample value of the third neighboring reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a horizontal intra prediction mode and the first neighboring reference sample being located on a left side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a fourth neighboring reference sample located on an upper side of the first neighboring reference sample and a fifth neighboring reference sample located on a lower side of the first neighboring reference sample,
• (r(y−1)+2*r(y)+r(y+1)+2)>>2
• wherein, the r(y) represents a sample value of the first neighboring reference sample, the r(y−1) represents a value of the fourth neighboring reference sample and the r(y+1) represents a sample value of the fifth neighboring reference sample.

An image encoding method using intra prediction, by an encoding apparatus, the method comprising:

• determining an intra prediction mode for a current block, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode;
• deriving neighboring reference samples of the current block;
• performing filtering on at least one of the reference samples;
• generating a prediction sample of the current block based on a filtered reference sample;
• generating a residual sample of the current block based on the prediction sample;
• and
• encoding a bitstream including residual information for the current block and prediction information including prediction mode information representing the intra prediction mode for the current block,
• wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a vertical intra prediction mode and the first neighboring reference sample being located on a top side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a second neighboring reference sample located on a left side of the first neighboring reference sample and a third neighboring reference sample located on a right side of the first neighboring reference sample,
• (r(x−1)+2*r(x)+r(x+1)+2)>>2
• wherein, the r(x) represents a sample value of the first neighboring reference sample, the r(x−1) represents a value of the second neighboring reference sample and the r(x+1) represents a sample value of the third neighboring reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a horizontal intra prediction mode and the first neighboring reference sample being located on a left side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a fourth neighboring reference sample located on an upper side of the first neighboring reference sample and a fifth neighboring reference sample located on a lower side of the first neighboring reference sample,
• (r(y−1)+2*r(y)+r(y+1)+2)>>2
• wherein, the r(y) represents a sample value of the first neighboring reference sample, the r(y−1) represents a value of the fourth neighboring reference sample and the r(y+1) represents a sample value of the fifth neighboring reference sample.

A non-transitory computer-readable storage medium storing a bitstream encoded by a method, the method comprising:

• determining an intra prediction mode for a current block, wherein the intra prediction mode is determined as a directional prediction mode from intra prediction modes including 33 directional prediction modes and at least one non-directional prediction mode;
• deriving neighboring reference samples of the current block;
• performing filtering on at least one of the reference samples;
• generating a prediction sample of the current block based on a filtered reference sample;
• generating a residual sample of the current block based on the prediction sample;
• and
• encoding the bitstream including residual information for the current block and prediction information including prediction mode information representing the intra prediction mode for the current block,
• wherein the filtered reference sample is filtered by using a first reference sample located in a prediction direction of the intra prediction mode with regard to a location of the prediction sample and reference samples adjacent to the first reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a vertical intra prediction mode and the first neighboring reference sample being located on a top side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a second neighboring reference sample located on a left side of the first neighboring reference sample and a third neighboring reference sample located on a right side of the first neighboring reference sample,
• (r(x−1)+2*r(x)+r(x+1)+2)>>2
• wherein, the r(x) represents a sample value of the first neighboring reference sample, the r(x−1) represents a value of the second neighboring reference sample and the r(x+1) represents a sample value of the third neighboring reference sample,
• wherein, based on the intra prediction mode for the current block being derived as a horizontal intra prediction mode and the first neighboring reference sample being located on a left side of the current block, a filtered sample value for the first neighboring reference sample is derived based on following equation by using the first neighboring reference sample, a fourth neighboring reference sample located on an upper side of the first neighboring reference sample and a fifth neighboring reference sample located on a lower side of the first neighboring reference sample,
• (r(y−1)+2*r(y)+r(y+1)+2)>>2
• wherein, the r(y) represents a sample value of the first neighboring reference sample, the r(y−1) represents a value of the fourth neighboring reference sample and the r(y+1) represents a sample value of the fifth neighboring reference sample.