Abstract: Provided is a video decoding method including obtaining a residue of a first bit-depth with respect to a current block by decoding a bitstream; when intra predicting the current block, generating a prediction block of the current block by using a block that is previously decoded at the first bit-depth and then stored in a buffer; and generating a reconstruction block of the first bit-depth by using the prediction block and the residue of the first bit-depth. When the current block is inter predicted, the video decoding method may further include generating a prediction block of a second bit-depth by using an image previously decoded at the second bit-depth, and generating the prediction block of the current block by changing the generated prediction block of the second bit-depth to the first bit-depth. The first bit-depth is higher than the second bit-depth.

Abstract: Provided is a video decoding method including obtaining a residue of a first bit-depth with respect to a current block by decoding a bitstream; when intra predicting the current block, generating a prediction block of the current block by using a block that is previously decoded at the first bit-depth and then stored in a buffer; and generating a reconstruction block of the first bit-depth by using the prediction block and the residue of the first bit-depth. When the current block is inter predicted, the video decoding method may further include generating a prediction block of a second bit-depth by using an image previously decoded at the second bit-depth, and generating the prediction block of the current block by changing the generated prediction block of the second bit-depth to the first bit-depth. The first bit-depth is higher than the second bit-depth.

Abstract: An image encoding method includes generating symbols by performing transformation and quantization according to a transformation block, on a block that performs prediction according to a prediction mode; updating a probability index of a current sub block by using a probability index of a previous sub block among sub blocks included in the transformation block; determining a rate according to a bit length of the current sub block by using the probably index; determining a rate of the transformation block by using rates of the sub blocks; determining a distortion by using a difference between an original image and a reconstruction image according to transformation and quantization; and determining a rate-distortion (R-D) cost by using the distortion and the rate.

Abstract: Provided is a video encoding method including: calculating a difference value between a rate-distortion (R-D) cost of a first coefficient level from among coefficient levels of a sub-block and an R-D cost of a second coefficient level adjacent to the first coefficient level by using a distortion difference calculated by using an integer of the first coefficient level and an integer of the second coefficient level and a rate variation between the first coefficient level and the second coefficient level; selecting one of the integer values of the first and second coefficient levels as a modified value of the first coefficient level based on the difference value; and outputting the modified value of the first coefficient level.

Abstract: Provided is a video encoding method including: calculating a difference value between a rate-distortion (R-D) cost of a first coefficient level from among coefficient levels of a sub-block and an R-D cost of a second coefficient level adjacent to the first coefficient level by using a distortion difference calculated by using an integer of the first coefficient level and an integer of the second coefficient level and a rate variation between the first coefficient level and the second coefficient level; selecting one of the integer values of the first and second coefficient levels as a modified value of the first coefficient level based on the difference value; and outputting the modified value of the first coefficient level.

Abstract: An image encoding method includes generating symbols by performing transformation and quantization according to a transformation block, on a block that performs prediction according to a prediction mode; updating a probability index of a current sub block by using a probability index of a previous sub block among sub blocks included in the transformation block; determining a rate according to a bit length of the current sub block by using the probably index; determining a rate of the transformation block by using rates of the sub blocks; determining a distortion by using a difference between an original image and a reconstruction image according to transformation and quantization; and determining a rate-distortion (R-D) cost by using the distortion and the rate.

Abstract: Provided is a method of encoding an image, the method including determining a scanning sequence for transforming one or more sub-blocks included in a transformation block to be identical to a sequence of quantizing the one or more sub-blocks; determining a sub-block for transformation from among the one or more sub-blocks according to the determined scanning sequence; and performing transformation by applying one or more transformation matrixes with respect to the sub-block for transformation.