Intra block copy-based encoding/decoding method, device, and bitstream storage medium
An image encoding/decoding method and apparatus are disclosed. The image decoding method includes acquiring prediction mode information of a current block from a bitstream, decoding an intra block copy prediction mode of the current block using the prediction mode information of the current block, and reconstructing the current block based on the intra block copy prediction mode. The intra block copy prediction mode is at least one of a block copy based SKIP mode, a block copy based MERGE mode or a block copy based AMVP mode.
1. A method for decoding an image, the method comprising:
decoding enabled information indicating whether an Intra Block Copy (IBC) mode is enabled or not from sequence parameter set (SPS);
decoding maximum number information indicating a maximum number of candidates that can be included in a block vector candidate list, the maximum number information being decoded when the enabled information indicates that the IBC mode is enabled;
determining a prediction mode of the current block as the IBC mode;
deriving the block vector candidate list for the current block by inserting at least one block vector candidate; and
deriving a block vector for the current block based on the block vector candidate list,
wherein the block vector for the current block is derived from one of block vector candidates included in the block vector candidate list,
wherein when an IBC mode based merge mode is applied to the current block, the one of block vector candidates is selected by a merge index,
wherein when an IBC mode based advanced motion vector prediction mode is applied to the current block, the one of block vector candidates is selected by an L0 motion vector predictor flag, and
wherein when the maximum number of candidates is not greater than 1, decoding the L0 motion vector predictor flag is omitted, and a value of the L0 motion vector predictor flag is inferred to 0.
2. The method of claim 1 , wherein when the maximum number of candidates is set to 0, the IBC mode is not applicable for all slices referring to the SPS.
3. The method of claim 1 , wherein when a size of the current block is smaller than a predetermined size, spatial block vector candidates, derived from a top neighboring block and a left neighboring block, are not added to the block vector candidate list for the current block.
4. The method of claim 1 , wherein the maximum number information indicating a difference value between a predetermined positive integer and the maximum number of candidates.
5. The method of claim 1 , wherein when the maximum number of candidates is not greater than 1, decoding the merge index is omitted, and a value of the merge index is inferred to 0.
6. The method of claim 1 , wherein
the deriving the block vector candidate list for the current block comprises:
when the number of candidate block vectors included in the block vector candidate list is smaller than the maximum number of candidates, adding at least one or more history-based block vector candidates to the block vector candidate list until the number of candidate block vectors included in the block vector candidate list is equal to the maximum number of candidates.
7. The method of claim 6 , wherein the adding at least one or more history-based block vector candidates to the block vector candidate list comprises:
adding at least one or more history-based block vector candidates to the block vector candidate list based on whether a candidate block vector previously included in the block vector candidate list and the added history-based block vector candidate are the same.
8. The method of claim 7 , wherein when a size of the current block is 4×4, the block vector of the current block is not updated as a history-based block vector candidate.
9. A method for encoding an image, the method comprising:
encoding enabled information indicating whether an Intra Block Copy (IBC) mode is enabled or not into sequence parameter set (SPS);
encoding maximum number information indicating a maximum number of candidates that can be included in a block vector candidate list, the maximum number information being encoded when the enabled information is encoded with a value indicating that the IBC mode is enabled;
determining a prediction mode of the current block as the IBC mode;
deriving the block vector candidate list for the current block by inserting at least one block vector candidate; and
deriving a block vector for the current block based on the block vector candidate list,
wherein the block vector for the current block is derived from one of block vector candidates included in the block vector candidate list,
wherein when an IBC mode based merge mode is applied to the current block, a merge index representing the one of block vector candidates is selectively encoded, and
wherein when an IBC mode based advanced motion vector prediction mode is applied to the current block, an L0 motion vector predictor flag representing the one of block vector candidates is selectively encoded, and
wherein when the maximum number of candidates is not greater than 1, encoding the L0 motion vector predictor flag is omitted, and the one of block vectors has an index 0.
10. The method of claim 9 , wherein when the maximum number of candidates is set to 0, the IBC mode is not applicable for all slices referring to the SPS.
11. The method of claim 9 , wherein when a size of the current block is smaller than a predetermined size, spatial block vector candidates, derived from a top neighboring block and a left neighboring block, are not added to the block vector candidate list for the current block.
12. The method of claim 11 , wherein when the maximum number of candidates is not greater than 1, encoding the merge index is omitted, and the one of block vectors has an index 0.
13. A non-transitory computer-readable recording medium storing a bitstream generated by the encoding method, wherein the encoding method comprising:
encoding enabled information indicating whether an Intra Block Copy (IBC) mode is enabled or not into sequence parameter set (SPS);
encoding maximum number information indicating a maximum number of candidates that can be included in a block vector candidate list, the maximum number information being encoded when the enabled information is encoded with a value indicating that the IBC mode is enabled;
determining a prediction mode of the current block as the IBC mode;
deriving the block vector candidate list for the current block by inserting at least one block vector candidate; and
deriving a block vector for the current block based on the block vector candidate list,
wherein the block vector for the current block is derived from one of block vector candidates included in the block vector candidate list,
wherein when an IBC mode based merge mode is applied to the current block, a merge index representing the one of block vector candidates is selectively encoded, and
wherein when an IBC mode based advanced motion vector prediction mode is applied to the current block, an L0 motion vector predictor flag representing the one of block vector candidates is selectively encoded, and
wherein when the maximum number of candidates is not greater than 1, encoding the L0 motion vector predictor flag is omitted, and the one of block vectors has an index 0.