Method for encoding/decoding image and device using same

1. A video decoding method comprising:

determining whether intra block copy (IBC) prediction is used or not based on information signaled by a sequence parameter set;

deriving, in case IBC prediction is determined to be used, a vector predictor of a block vector indicating a reference block for a current block to be predicted in a current picture;

deriving the block vector based on the vector predictor and a vector difference corresponding to a difference between the block vector and the vector predictor; and

generating a prediction block for the current block based on the block vector,

wherein both the current block and the reference block are included in the current picture,

wherein the deriving the vector predictor comprises

generating a candidate list including a plurality of vector predictor candidates based on block vectors of blocks decoded by IBC prediction before the current block;

determining whether a number of vector predictor candidates included in the candidate list is less than a predetermined number;

adding a zero vector candidate into the candidate list in case the number of vector predictor candidates included in the candidate list is less than the predetermined number; and

deriving the vector predictor based on a predictor index indicating one of the vector predictor candidates included in the candidate list,

wherein the predictor index is obtained by

determining whether or not the predetermined number is greater than 1;

decoding, in case the predetermined number is greater than 1, information on the predictor index included in a bitstream; and

assigning, in case the predetermined number is 1, a predetermined value as the predictor index without decoding the information on the predictor index, and

wherein a block vector is not included in the candidate list in case the candidate list includes a vector predictor candidate as same as the block vector.

2. The video decoding method according to claim 1 , wherein the prediction block is generated by filtering a sample value of the reference block.

3. The video decoding method according to claim 2 , wherein the filtering is performed using a filter preset between an encoder and a decoder, or a filter indicated by signaling information in a bit stream.

4. The video decoding method according to claim 1 , wherein if a plurality of predictor indexes are parsed, the generation of a prediction block comprises generating the predictor block based on a plurality of reference blocks indicated by a plurality of block vectors.

5. The video decoding method according to claim 4 , wherein a value of the prediction block is a weighted average of values of the reference blocks.

6. The video decoding method according to claim 1 , wherein the candidate list includes a predetermined initial value as one of the vector predictors.

7. A video encoding method comprising:

determining whether intra block copy (IBC) prediction is used or not;

deriving, in case IBC prediction is determined to be used, a vector predictor of a block vector indicating a reference block for a current block to be predicted in a current picture;

encoding information indicating the vector predictor and a vector difference corresponding to a difference between the block vector and the vector predictor, and

encoding information indicating whether IBC prediction is used or not into a sequence parameter set,

wherein both the current block and the reference block are included in the current picture,

wherein the encoding the information indicating the vector predictor comprises

generating a candidate list including a plurality of vector predictor candidates based on block vectors of blocks encoded by IBC prediction before the current block;

determining whether a number of vector predictor candidates included in the candidate list is less than a predetermined number;

adding a zero vector candidate into the candidate list in case the number of vector predictor candidates included in the candidate list is less than the predetermined number;

determining a predictor index indicating one of the vector predictor candidates included in the candidate list; and

encoding the information indicating the vector predictor based on the predictor index,

wherein the information indicating the vector predictor is encoded by

determining whether or not the predetermined number is greater than 1;

encoding, in case the predetermined number is greater than 1, the information indicating the vector predictor into a bitstream; and

skipping the encoding of the information indicating the vector predictor into a bitstream in case the predetermined number is 1, and

wherein a block vector is not included in the candidate list in case the candidate list includes a vector predictor candidate as same as the block vector.

8. The video encoding method according to claim 7 , further comprising:

generating a candidate list including a plurality of vector predictors; and

encoding a predictor index indicating at least one of the vector predictors included in the candidate list, and signaling the encoded predictor index.

9. The video encoding method according to claim 7 , wherein the candidate list includes a predetermined initial value as one of the vector predictors.