Method and device for encoding and decoding image
An image decoding method according to the present invention includes reconstructing a residual block by inverse-quantizing and inverse-transforming an entropy-decoded residual block, generating a prediction block by performing intra prediction on a current block, and reconstructing an picture by adding the reconstructed residual block to the prediction block, wherein generating the prediction block includes generating a final prediction value of a prediction target pixel included in the current block based on a first prediction value of the prediction target pixel and a final correction value calculated by performing an arithmetic right shift on a two's complementary integer representation for an initial correction value of the prediction target pixel by a binary digit of 1. Accordingly, upon image encoding/decoding, computation complexity may be reduced.
1 . A video decoding method comprising:
determining whether to perform scaling on a motion vector of a temporal reference block based on picture order count (POC) values of a reference picture referred to by a current block and a reference picture referred to by the temporal reference block;
calculating a first value and a second value based on the POC values;
calculating an offset value by performing an arithmetic right shift on an absolute value of the first value by a binary digit of 1;
calculating an inverse-proportional value of the first value using the offset value; and
calculating a scaling factor based on the inverse-proportional value of the first value and the second value;
scaling the motion vector of the temporal reference block by using the scaling factor; and
performing inter-prediction on the current block based on the motion vector,
wherein the temporal reference block is located at a position corresponding to a position of the current block within a co-located picture,
wherein the first value is derived based on a first POC difference between the co-located picture comprising the temporal reference block and the reference picture referred to by the temporal reference block, and
wherein the second value is derived based on a second POC difference between a current picture comprising the current block and the reference picture referred to by the current block,
wherein the motion vector of the temporal reference block is scaled in case the first POC difference between the co-located picture and the reference picture referred to by the temporal reference block is different from the second POC difference between the current picture and the reference picture referred to by the current block.
2 . A video encoding method comprising:
determining whether to perform scaling on a motion vector of a temporal reference block based on picture order count (POC) values of a reference picture referred to by a current block and a reference picture referred to by the temporal reference block;
calculating a first value and a second value based on the POC values;
calculating an offset value by performing an arithmetic right shift on an absolute value of the first value by a binary digit of 1;
calculating an inverse-proportional value of the first value using the offset value; and
calculating a scaling factor based on the inverse-proportional value of the first value and the second value;
scaling the motion vector of the temporal reference block by using the scaling factor; and
performing inter-prediction on the current block based on the motion vector,
wherein the temporal reference block is located at a position corresponding to a position of the current block within a co-located picture,
wherein the first value is derived based on a first POC difference between a co-located picture comprising the temporal reference block and the reference picture referred to by the temporal reference block, and
wherein the second value is derived based on a second POC difference between a current picture comprising the current block and the reference picture referred to by the current block,
wherein the motion vector of the temporal reference block is scaled in case the first POC difference between the co-located picture and the reference picture referred to by the temporal reference block is different from the second POC difference between the current picture and the reference picture referred to by the current block.
3 . A method for transmitting a bitstream performed by a video encoding apparatus, wherein the method comprising:
determining whether to perform scaling on a motion vector of a temporal reference block based on picture order count (POC) values of a reference picture referred to by a current block and a reference picture referred to by the temporal reference block;
calculating a first value and a second value based on the POC values;
calculating an offset value by performing an arithmetic right shift on an absolute value of the first value by a binary digit of 1;
calculating an inverse-proportional value of the first value using the offset value; and
calculating a scaling factor based on the inverse-proportional value of the first value and the second value;
scaling the motion vector of the temporal reference block by using the scaling factor; and
performing inter-prediction on the current block based on the motion vector,
wherein the temporal reference block is located at a position corresponding to a position of the current block within a co-located picture,
wherein the first value is derived based on a first POC difference between a co-located picture comprising the temporal reference block and the reference picture referred to by the temporal reference block, and
wherein the second value is derived based on a second POC difference between a current picture comprising the current block and the reference picture referred to by the current block,
wherein the motion vector of the temporal reference block is scaled in case the first POC difference between the co-located picture and the reference picture referred to by the temporal reference block is different from the second POC difference between the current picture and the reference picture referred to by the current block.