Luma intra mode signaling
A method of coding implemented by a coding apparatus. The method includes selecting an intra prediction mode for a current block, and encoding the selected intra prediction mode using truncated binary coding when the selected intra prediction mode is a remaining mode.
1. A method of coding implemented by a coding apparatus, the method comprising:
selecting, using the coding apparatus, an intra prediction mode for a current block;
encoding, using the coding apparatus, the selected intra prediction mode using truncated binary coding every time the selected intra prediction mode is a remaining mode; and
encoding the selected intra prediction mode using N bits when the selected intra prediction mode is included in a first portion from remaining modes and using N+1 bits when the selected intra prediction mode is included in a second portion of the remaining modes.
2. The method of claim 1 , further comprising determining that the selected intra prediction mode falls outside a most probable modes (MPM) list.
3. The method of claim 2 , wherein the MPM list contains 6 modes and the remaining mode is one of 61 remaining modes.
4. The method of claim 3 , wherein all intra prediction modes either belong to the MPM list or to the remaining modes.
5. The method of claim 3 , wherein all of the remaining modes are subject to a truncated binary coding scheme.
6. The method of claim 2 , further comprising filling initial modes in a remaining modes list using an offset to angular modes included in the MPM list.
7. The method of claim 6 , wherein the offset is +/−N, where N is an integer with a value of 1, 2, 3, or 4.
8. The method of claim 6 , wherein the offset is added only to a first of two of the angular modes in the MPM list.
9. The method of claim 2 , further comprising filling initial modes in a remaining modes list based on a location of a majority of modes in the MPM list relative to one of a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
10. The method of claim 2 , further comprising filling initial modes in a remaining modes list by:
comparing each of the modes in the MPM list to a location of different modes within a default mode list;
determining that a winning one of the different modes within the default mode list is nearest to a majority of the modes in the MPM list; and
filling a first three modes in the remaining mode list with modes nearest to the winning one of the different modes within the default mode list.
11. The method of claim 10 , wherein the different modes within a mode category comprise a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
12. The method of claim 1 , wherein the remaining mode is one of 61 remaining modes.
13. The method of claim 1 , further comprising filling initial modes in a remaining modes list using a predetermined default mode list.
14. The method of claim 13 , wherein the predetermined default mode list comprises a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
15. The method of claim 1 , further comprising filling initial modes of a remaining mode list using modes of neighboring blocks not immediately adjacent to the current block.
16. The method of claim 1 , further comprising filling initial modes of a remaining modes list using modes of second tier neighbors of the current block instead of first tier neighbors.
17. A method of coding implemented by a coding apparatus, the method comprising:
selecting, using the coding apparatus, an intra prediction mode for a current block;
encoding, using the coding apparatus, the selected intra prediction mode using truncated binary coding every time the selected intra prediction mode is a remaining mode; and
encoding the selected intra prediction mode using 5 bits when the selected intra prediction mode is one of a first three modes from remaining modes.
18. A method of coding implemented by a coding apparatus, the method comprising:
selecting, using the coding apparatus, an intra prediction mode for a current block; encoding, using the coding apparatus, the selected intra prediction mode using truncated binary coding every time the selected intra prediction mode is a remaining mode; and
encoding the intra prediction mode using 6 bits when the selected intra prediction mode is not one of a first three modes from remaining modes.
19. A method of decoding implemented by a decoding apparatus, the method comprising:
obtaining, by the decoding apparatus, truncated binary code every time an intra prediction mode is a remaining mode;
decoding, by the decoding apparatus, the truncated binary code to obtain the intra prediction mode comprising the remaining mode;
decoding, by the decoding apparatus, the intra prediction mode using 5 bits when the intra prediction mode was one of a first three modes from remaining modes; and
generating, by the decoding apparatus, a current block using the intra prediction mode that was obtained.
20. The method of claim 19 , further comprising determining that the intra prediction mode is outside a most probable modes (MPM) list.
21. The method of claim 20 , wherein there are 6 modes in the MPM list and 61 modes in remaining modes.
22. The method of claim 21 , wherein all intra prediction modes either belong to the MPM list or to the remaining modes.
23. The method of claim 21 , wherein all of the remaining modes are subject to a truncated binary coding scheme.
24. The method of claim 20 , wherein initial modes in a remaining modes list are based on an offset to angular modes included in the MPM list.
25. The method of claim 24 , wherein the offset is +/−N, where N is an integer with a value of 1, 2, 3, or 4.
26. The method of claim 24 , wherein the offset is added only to a first of two of the angular modes in the MPM list.
27. The method of claim 20 , wherein initial modes in a remaining modes list are based on a location of a majority of modes in the MPM list relative to one of a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
28. The method of claim 20 , wherein initial modes in the remaining modes list were determined by:
comparing each of the modes in the MPM list to a location of different modes within a default mode list;
determining that a winning one of the different modes within the default mode list is nearest to a majority of the modes in the MPM list; and
filling a first three modes in the remaining mode list with modes nearest to the winning one of the different modes within the default mode list.
29. The method of claim 28 , wherein the different modes within a mode category comprise a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
30. The method of claim 19 , wherein the remaining mode is one of 61 remaining modes.
31. The method of claim 19 , wherein initial modes in a remaining modes list are from a predetermined default mode list.
32. The method of claim 31 , wherein the predetermined default mode list comprises a planar mode (PLANAR_IDX), a dc mode (DC_IDX), a vertical mode (VER_IDX), a horizontal mode (HOR_IDX), an intra mode 2 (2), a vertical diagonal mode (VDIA_IDX), and a diagonal mode (DIA_IDX).
33. The method of claim 19 , wherein initial modes in a remaining modes list are based on modes of neighboring blocks not immediately adjacent to the current block.
34. The method of claim 19 , wherein initial modes in a remaining modes list are based on modes of second tier neighbors of the current block instead of first tier neighbors.
35. A method of decoding implemented by a decoding apparatus, the method comprising:
obtaining, by the decoding apparatus, truncated binary code every time an intra prediction mode is a remaining mode;
decoding, by the decoding apparatus, the truncated binary code to obtain the intra prediction mode comprising the remaining mode;
decoding the intra prediction mode using 6 bits when the intra prediction mode is outside a first three modes from remaining modes; and
generating, by the decoding apparatus, a current block using the intra prediction mode that was obtained.