Image encoding and decoding apparatus, and image encoding and decoding method using contour mode based intra prediction

A video encoding method performed by a video encoding apparatus, the method comprising:

• determining that intra skip coding is not applied to a current block;
• determining, based on the determination that the intra skip coding is not applied to the current block, that a contour mode based intra prediction is to be applied to the current block;
• generating, based on the determination that the contour mode based intra prediction is to be applied to the current block, information specifying that the contour mode based intra prediction is performed for the current block;
• encoding the current block by performing the contour mode based intra prediction for the current block;
• and
• providing a bitstream that includes the encoded current block and the information specifying that the contour mode based intra prediction is performed for the current block,
• wherein the contour mode based intra prediction comprises:
• deriving a first depth value relating to the current block by performing the contour mode based intra prediction for the current block;
• deriving, based on the first depth value, a first index value using a first look up table specifying an index value corresponding to a depth value;
• deriving a second index value using the first index value and a residual index value, wherein the residual index value specifies a difference between the first index value and the second index value;
• obtaining a second depth value relating to the current block based on the second index value and a second look up table specifying a depth value corresponding to an index value;
• and
• generating a prediction block for the current block based on the second depth value, wherein the first depth value is derived from a depth value of a neighboring pixel of the current block.

A bitstream transmitting method for transmitting a bitstream which is generated by a video encoding method, the bitstream transmitting method comprising:

• generating the bitstream by encoding a video by the video encoding method;
• and
• transmitting the bitstream,
• wherein the video encoding method comprises:
• determining that intra skip coding is not applied to a current block;
• determining, based on the determination that the intra skip coding is not applied to the current block, that a contour mode based intra prediction is to be applied to the current block;
• generating, based on the determination that the contour mode based intra prediction is to be applied to the current block, information specifying that the contour mode based intra prediction is performed for the current block;
• encoding the current block by performing the contour mode based intra prediction for the current block;
• and
• providing a bitstream that includes the encoded current block and the information specifying that the contour mode based intra prediction is performed for the current block,
• wherein the contour mode based intra prediction comprises:
• deriving a first depth value relating to the current block by performing the contour mode based intra prediction for the current block;
• deriving, based on the first depth value, a first index value using a first look up table specifying an index value corresponding to a depth value;
• deriving a second index value using the first index value and a residual index value, wherein the residual index value specifies a difference between the first index value and the second index value;
• obtaining a second depth value relating to the current block based on the second index value and a second look up table specifying a depth value corresponding to an index value;
• and
• generating a prediction block for the current block based on the second depth value,
• wherein the first depth value is derived from a depth value of a neighboring pixel of the current block.