Device and method for decoding video data by reconstructing chroma block unit based on bi-predictive-IBC-based candidate

1 . A method of decoding video data performed by an electronic device, the method comprising:

receiving the video data;

determining, from a current frame that is included in the video data, a chroma block unit and a luma reconstruction block, the luma reconstruction block being collocated with the chroma block unit and reconstructed in a bi-predictive intra block copy (IBC) mode;

deriving at least one bi-predictive-IBC-based candidate of the chroma block unit based on two luma block vectors, the two luma block vectors used to reconstruct the luma reconstruction block in the bi-predictive IBC mode, wherein:

a specific one of the at least one bi-predictive-IBC-based candidate includes a chroma prediction model that is derived based on a model reference block when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a block-vector-guided convolutional cross-component model (BVG-CCCM) mode, and

the model reference block is indicated by a specific one of the two luma block vectors that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate; and

reconstructing the chroma block unit based on the at least one bi-predictive-IBC-based candidate.

2 . The method according to claim 1 , wherein:

the specific one of the at least one bi-predictive-IBC-based candidate includes a chroma block vector that is proportional to the specific one of the two luma block vectors, and

the one of the at least one bi-predictive-IBC-based candidate is derived based on the one of the two luma block vectors.

3 . The method according to claim 1 , further comprising:

determining a chroma candidate list that includes one or more of a plurality of uni-predictive-based candidates or a plurality of bi-predictive-based candidates, wherein:

each of the at least one bi-predictive-IBC-based candidate is included in the plurality of bi-predictive-based candidates, and

reconstructing the chroma block unit is further based on the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates in the chroma candidate list.

4 . The method according to claim 3 , further comprising:

determining, from the video data, a chroma prediction index that indicates one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates, wherein:

reconstructing the chroma block unit is further based on the indicated one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates.

5 . The method according to claim 3 , further comprising:

determining, from the current frame, a chroma template region that neighbors the chroma block unit;

predicting the chroma template region using the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates to generate one or more chroma template predictions; and

determining one or more template cost values, each of the one or more template cost values comprising a template cost value between a chroma template reconstruction of the chroma template region and a corresponding one of the one or more chroma template predictions.

6 . The method according to claim 5 , further comprising:

selecting one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates based on the one or more template cost values, wherein

reconstructing the chroma block unit is further based on the selected one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates.

7 . The method according to claim 5 , further comprising:

selecting two chroma prediction modes from the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates;

predicting the chroma block unit based on the two chroma prediction modes to generate two chroma prediction blocks;

deriving two weighting parameters based on the one or more template cost values of the two chroma prediction modes; and

weightedly combining the two chroma prediction blocks based on the two derived weighting parameters to generate a weighted block, wherein reconstructing the chroma block unit is further based on the weighted block.

8 . The method according to claim 1 , wherein:

the specific one of the at least one bi-predictive-IBC-based candidate includes a chroma block vector that is derived based on the specific one of the two luma block vectors, that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a direct block vector (DBV) mode.

9 . The method according to claim 1 , wherein:

the specific one of the at least one bi-predictive-IBC-based candidate includes a chroma intra prediction mode that is derived based on a mode reference block when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a chroma direct mode (DM), and

the mode reference block is indicated by the specific one of the two luma block vectors that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate.

10 . The method according to claim 1 , wherein:

at least one luma block unit, including the luma reconstruction block, is collocated with the chroma block unit,

the number of the at least one luma block unit is equal to one when the chroma block unit is included in a single-tree block unit, determined from the current frame, and

the number of the at least one luma block unit is equal to or greater than one when the chroma block unit is included in a dual-tree block unit, determined from the current frame.

11 . An electronic device for decoding video data, the electronic device comprising:

at least one processor; and

at least one non-transitory computer-readable medium coupled to the at least one processor and storing one or more computer-executable instructions that, when executed by the at least one processor, cause the electronic device to:

receive the video data;

determine, from a current frame that is included in the video data, a chroma block unit and a luma reconstruction block, the luma reconstruction block being collocated with the chroma block unit and reconstructed in a bi-predictive intra block copy (IBC) mode;

derive at least one bi-predictive-IBC-based candidate of the chroma block unit based on two luma block vectors, the two luma block vectors used to reconstruct the luma reconstruction block in the bi-predictive IBC mode, wherein:

a specific one of the at least one bi-predictive-IBC-based candidate includes a chroma prediction model that is derived based on a model reference block when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a block-vector-guided convolutional cross-component model BVG-CCCM) mode, and

the model reference block indicated by a specific one of the two luma block vectors that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate; and

reconstruct the chroma block unit based on the at least one bi-predictive-IBC-based candidate.

12 . The electronic device according to claim 11 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:

determine a chroma candidate list that includes one or more of a plurality of uni-predictive-based candidates or a plurality of bi-predictive-based candidates, wherein:

each of the at least one bi-predictive-IBC-based candidate is included in the plurality of bi-predictive-based candidates, and

reconstructing the chroma block unit is further based on the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates in the chroma candidate list.

13 . The electronic device according to claim 12 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:

determine, from the video data, a chroma prediction index that indicates one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates, wherein:

reconstructing the chroma block unit is further based on the indicated one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates.

14 . The electronic device according to claim 12 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:

determine, from the current frame, a chroma template region that neighbors the chroma block unit;

predict the chroma template region using the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates to generate one or more chroma template predictions; and

determine one or more template cost values, each of the one or more template cost values comprising a template cost value between a chroma template reconstruction of the chroma template region and a corresponding one of the one or more chroma template predictions.

15 . The electronic device according to claim 14 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:

select one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates based on the one or more template cost values, wherein

reconstructing the chroma block unit is further based on the selected one of the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates.

16 . The electronic device according to claim 14 , wherein the one or more computer-executable instructions, when executed by the at least one processor, further cause the electronic device to:

select two chroma prediction modes from the one or more of the plurality of uni-predictive-based candidates or the plurality of bi-predictive-based candidates;

predict the chroma block unit based on the two chroma prediction modes to generate two chroma prediction blocks;

derive two weighting parameters based on the one or more template cost values of the two chroma prediction modes; and

weightedly combine the two chroma prediction blocks based on the two derived weighting parameters to generate a weighted block, wherein reconstructing the chroma block unit is further based on the weighted block.

17 . The electronic device according to claim 11 , wherein:

the specific one of the at least one bi-predictive-IBC-based candidate includes a chroma block vector that is derived based on the specific one of the two luma block vectors, that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a direct block vector (DBV) mode.

18 . The electronic device according to claim 11 , wherein:

the specific one of the at least one bi-predictive-IBC-based candidate includes a chroma intra prediction mode that is derived based on a mode reference block when the specific one of the at least one bi-predictive-IBC-based candidate is derived in a chroma direct mode (DM), and

the mode reference block is indicated by the specific one of the two luma block vectors that corresponds to the specific one of the at least one bi-predictive-IBC-based candidate.