Device and method for decoding video data

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

receiving the video data;

determining a block unit from an image frame retrieved from the video data;

determining, for the block unit, a first mode list including a plurality of intra candidate modes selected from a plurality of intra default modes;

predicting at least one template region, that is adjacent to the block unit, to generate a plurality of template predictions based on a plurality of intra template modes, wherein:

each of the plurality of intra template modes indicates one of the plurality of intra candidate modes and one of a plurality of template reference lines, and

the plurality of template reference lines includes at least one template neighboring line nonadjacent to the at least one template region;

determining a plurality of template cost values, each of the plurality of template cost values comprising a template cost value between the at least one template region and a corresponding one of the plurality of template predictions;

determining, for the block unit, a second mode list based on the plurality of template cost values; and

reconstructing the block unit based on the second mode list, wherein:

a template prediction mode is determined, based on a template mode index included in the video data, from the second mode list to reconstruct the block unit,

the template prediction mode indicates a specific one of the plurality of intra candidate modes and a specific one of the plurality of template reference lines selected for the block unit,

the specific one of the plurality of template reference lines is selected based on a reference line index of the block unit included in the video data, and

the specific one of the plurality of intra candidate modes is determined, based on the template mode index, from the second mode list after determining the specific one of the plurality of template reference lines.

2. The method according to claim 1 , wherein determining, for the block unit, the first mode list comprises:

determining a plurality of neighboring blocks neighboring the block unit;

determining at least one intra neighboring mode of the plurality of neighboring blocks, wherein each of the plurality of neighboring blocks is reconstructed based on one of the at least one intra neighboring mode; and

selecting the plurality of intra candidate modes from the plurality of intra default modes based on the at least one intra neighboring mode to generate the first mode list of the block unit.

3. The method according to claim 2 , wherein the plurality of intra candidate modes comprises a plurality of most probable modes (MPMs) determined based on the at least one intra neighboring mode.

4. The method according to claim 1 , wherein the at least one template region comprises at least one of an above adjacent region located above the block unit, a left adjacent region located at a left side of the block unit, or an above-left adjacent region located at a top-left side of the block unit.

5. The method according to claim 1 , wherein the plurality of template reference lines further comprises a template adjacent line adjacent to the at least one template region.

6. The method according to claim 1 , wherein determining, for the block unit, the second mode list comprises:

determining an arrangement of the plurality of intra template modes based on the plurality of template cost values; and

determining the second mode list based on the arrangement.

7. The method according to claim 6 , wherein the arrangement is generated by ordering the plurality of intra template modes in an ascending order of the plurality of template cost values.

8. The method according to claim 6 , wherein:

the second mode list comprises a first K candidate modes of the plurality of intra candidate modes ordered based on the arrangement, and

K is a positive integer less than a number of the plurality of intra candidate modes in the first mode list.

9. The method according to claim 1 , wherein the template cost value for each of the plurality of template predictions is a template-matching cost value determined by comparing a plurality of reconstructed samples in the at least one template region with a plurality of predicted samples in one of the plurality of template predictions.

10. 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 a block unit from an image frame retrieved from the video data;

determine, for the block unit, a first mode list including a plurality of intra candidate modes selected from a plurality of intra default modes;

predict at least one template region, that is adjacent to the block unit, to generate a plurality of template predictions based on a plurality of intra template modes, wherein:

each of the plurality of intra template modes indicates one of the plurality of intra candidate modes and one of a plurality of template reference lines, and

the plurality of template reference lines includes at least one template neighboring line nonadjacent to the at least one template region;

determine a plurality of template cost values, each of the plurality of template cost values comprising a template cost value between the at least one template region and a corresponding one of the plurality of template predictions;

determine, for the block unit, a second mode list based on the plurality of template cost values; and

reconstruct the block unit based on the second mode list, wherein:

a template prediction mode is determined, based on a template mode index included in the video data, from the second mode list to reconstruct the block unit,

the template prediction mode indicates a specific one of the plurality of intra candidate modes and a specific one of the plurality of template reference lines selected for the block unit,

the specific one of the plurality of template reference lines is selected based on a reference line index of the block unit included in the video data, and

the specific one of the plurality of intra candidate modes is determined, based on the template mode index, from the second mode list after determining the specific one of the plurality of template reference lines.

11. The electronic device according to claim 10 , wherein determining, for the block unit, the first mode list comprises:

determining a plurality of neighboring blocks neighboring the block unit;

determining at least one intra neighboring mode of the plurality of neighboring blocks, wherein each of the plurality of neighboring blocks is reconstructed based on one of the at least one intra neighboring mode; and

selecting the plurality of intra candidate modes from the plurality of intra default modes based on the at least one intra neighboring mode to generate the first mode list of the block unit.

12. The electronic device according to claim 10 , wherein the at least one template region comprises at least one of an above template located above the block unit, a left template located at a left side of the block unit, or an above-left template located at a top-left side of the block unit.

13. The electronic device according to claim 10 , wherein the plurality of template reference lines further comprises a template adjacent line adjacent to the at least one template region.

14. The electronic device according to claim 10 , wherein determining, for the block unit, the second mode list comprises:

determining an arrangement of the plurality of intra template modes based on the plurality of template cost values; and

determining the second mode list based on the arrangement.

15. The electronic device according to claim 14 , wherein the arrangement is generated by ordering the plurality of intra template modes in an ascending order of the plurality of template cost values.

16. The electronic device according to claim 14 , wherein:

the second mode list comprises a first K candidate modes of the plurality of intra candidate modes ordered based on the arrangement, and

K is a positive integer less than a number of the plurality of intra candidate modes in the first mode list.