Device and method for coding video data in multiple reference line prediction

1. A method of decoding a bitstream by an electronic device, the method comprising:

determining a block unit having an intra prediction mode from an image frame according to the bitstream;

determining, based on at least one of a reference line index and a most probable mode (mpm) flag, one of a plurality of mode indices that is indicative of the intra prediction mode of the block unit;

determining the intra prediction mode of the block unit based on a first one of the plurality of mode indices, when the reference line index is different from a first predefined value, wherein the first one of the plurality of mode indices is an mpm index, the first predefined value indicates a first one of a plurality of reference line candidates and the first one of the plurality of reference line candidates is immediately adjacent to the block unit;

determining the intra prediction mode of the block unit based on the mpm index, when the reference line index is equal to the first predefined value and the mpm flag is equal to a second predefined value; and

reconstructing the block unit of the image frame based on the intra prediction mode, wherein:

the intra prediction mode is selected from a plurality of most probable modes when the intra prediction mode is determined based on the mpm index,

the plurality of most probable modes is derived according to the reference line index,

a Planar mode is included in the plurality of most probable modes when the reference line index is equal to the first predefined value, and

the Planar mode is excluded from the plurality of most probable modes when the reference line index is different from the first predefined value.

2. The method according to claim 1 , wherein the reference line index is determined for selecting one of the plurality of reference line candidates to reconstruct the block unit.

3. The method according to claim 2 , further comprising:

determining the mpm flag of the block unit according to the bitstream;

determining the reference line index of the block unit according to the bitstream, when the mpm flag is equal to the second predefined value; and

determining, without parsing the reference line index, that the selected one of the plurality of reference line candidates is the first one of the plurality of reference line candidates, when the mpm flag is different from to the second predefined value.

4. The method according to claim 1 , wherein the plurality of most probable modes is derived from a plurality of intra mode candidates including the Planar mode, a DC mode and a plurality of angular modes.

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

determining the intra prediction mode from a plurality of remaining prediction modes generated by removing the plurality of most probable modes from the plurality of intra mode candidates, when the mpm flag is different from the second predefined value.

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

determining the reference line index of the block unit according to the bitstream;

determining the mpm flag of the block unit for determining the one of the plurality of mode indices that is indicative of the intra prediction mode of the block unit, when the reference line index is equal to the first predefined value; and

determining, without parsing the mpm flag, that the intra prediction mode is determined based on the mpm index, when the reference line index is different from the first predefined value.

7. An electronic device for decoding a bitstream, the electronic device comprising:

at least one processor; and

a storage device coupled to the at least one processor and storing a plurality of instructions which, when executed by the at least one processor, causes the at least one processor to:

determine a block unit having an intra prediction mode from the image frame according to bitstream;

determine, based on at least one of a reference line index and a most probable mode (mpm) flag, one of a plurality of mode indices that is indicative of the intra prediction mode of the block unit;

determine the intra prediction mode of the block unit based on a first one of the plurality of mode indices, when the reference line index is different from a first predefined value, wherein the first one of the plurality of mode indices is an mpm index, the first predefined value indicates a first one of a plurality of reference line candidates and the first one of the plurality of reference line candidates is immediately adjacent to the block unit;

determine the intra prediction mode of the block unit based on the mpm index, when the reference line index is equal to the first predefined value and the mpm flag is equal to a second predefined value; and

reconstruct the block unit of the image frame based on the intra prediction mode, wherein:

the intra prediction mode is selected from a plurality of most probable modes when the intra prediction mode is determined based on the mpm index,

the plurality of most probable modes is derived according to the reference line index,

a Planar mode is included in the plurality of most probable modes when the reference line index is equal to the first predefined value, and

the Planar mode is excluded from the plurality of most probable modes when the reference line index is different from the first predefined value.

8. The electronic device according to claim 7 , wherein the reference line index is determined for selecting one of the plurality of reference line candidates to reconstruct the block unit.

9. The electronic device according to claim 8 , wherein the plurality of instructions, when executed by the at least one processor, further causes the at least one processor to:

determine the mpm flag of the block unit according to the bitstream;

determine the reference line index of the block unit according to the bitstream, when the mpm flag is equal to the second predefined value; and

determine, without parsing the reference line index, that the selected one of the plurality of reference line candidates is the first one of the plurality of reference line candidates, when the mpm flag is different from to the second predefined value.

10. The electronic device according to claim 7 , wherein the plurality of most probable modes is selected from a plurality of intra mode candidates including the Planar mode, a DC mode and a plurality of angular modes.

11. The electronic device according to claim 10 , wherein the intra prediction mode is selected from a plurality of remaining prediction modes generated by removing the plurality of most probable modes from the plurality of intra mode candidates, when the mpm flag is different from the second predefined value.

12. The electronic device according to claim 7 , wherein the plurality of instructions, when executed by the at least one processor, further causes the at least one processor to:

determine the reference line index of the block unit according to the bitstream;

determine the mpm flag of the block unit for determining the one of the plurality of mode indices that is indicative of the intra prediction mode of the block unit, when the reference line index is equal to the first predefined value; and

determining, without parsing the mpm flag, that the intra prediction mode is determined based on the mpm index, when the reference line index is different from the first predefined value.

13. A method of decoding a bitstream by an electronic device, the method comprising:

determining a block unit having an intra prediction mode from an image frame according to the bitstream, wherein the intra prediction mode is selected from a plurality of intra mode candidates;

determining a reference line index of the block unit according to the bitstream;

determining a most probable mode (mpm) flag of the block unit after the reference line index is determined to be equal to a first predefined value, wherein the first predefined value indicates a first one of a plurality of reference line candidates and the first one of the plurality of reference line candidates is immediately adjacent to the block unit;

determining the intra prediction mode from a plurality of most probable modes, when the mpm flag is equal to a second predefined value, wherein:

the plurality of most probable modes is derived based on the reference line index,

a Planar mode is included in the plurality of most probable modes when the reference line index is equal to the first predefined value, and

the Planar mode is excluded from the plurality of most probable modes when the reference line index is different from the first predefined value;

determining the intra prediction mode from a plurality of remaining prediction modes generated by removing the plurality of most probable modes from the plurality of intra mode candidates, when the mpm flag is different from the second predefined value; and

reconstructing the block unit of the image frame based on the intra prediction mode.

14. The method according to claim 13 , wherein the reference line index is determined for selecting one of the plurality of reference line candidates to reconstruct the block unit.

15. The method according to claim 13 , further comprising:

determining, without parsing the mpm flag, that the intra prediction mode is selected from the plurality of most probable modes, when the reference line index is different from the first predefined value.

16. The method according to claim 13 , wherein the plurality of most probable modes is selected from the plurality of intra mode candidates including the Planar mode, a DC mode and a plurality of angular modes.