Intra-prediction with multiple reference lines
A video coding device receives a bitstream including video data. The device determines an intra-prediction mode subset. The intra-prediction mode subset include intra-prediction modes that correlate to a plurality of reference lines for a current image block and excludes intra-prediction modes that correlate to a primary reference line for the current image block. When a first intra-prediction mode is included in the intra-prediction mode subset, the device decodes the first intra-prediction mode by an alternative intra-prediction mode index. When the first intra-prediction mode is not included in the intra-prediction mode subset, the device decodes the first intra-prediction mode by an intra-prediction mode index. The device presents video data including an image block decoded based on the first intra-prediction mode.
1. A video coding device comprising:
a receiver configured to receive a bitstream; and
a processor coupled to the receiver and configured to:
determine an intra-prediction mode subset of an intra-prediction mode set including intra-prediction modes, wherein the intra-prediction mode subset includes intra-prediction modes that correlate to a plurality of reference lines for a current image block, and wherein all of the intra-prediction modes excluded from the intra-prediction mode subset are limited to correlate only to a single primary reference line immediately adjacent to the current image block;
when a first intra-prediction mode is included in the intra-prediction mode subset, decode the first intra-prediction mode by an alternative intra-prediction mode index; and
forward video data toward a display for presentation, the video data including an image block decoded based on the first intra-prediction mode.
2. The video coding device of claim 1 , wherein the processor is further configured to:
decode a reference line index when the first intra-prediction mode is included in the intra-prediction mode subset, the reference line index indicating a first reference line from the plurality of reference lines for the first intra-prediction mode; and
decode no reference line index when the first intra-prediction mode is not included in the intra-prediction mode subset.
3. The video coding device of claim 2 , wherein the reference line index is positioned after the first intra-prediction mode in the bitstream.
4. The video coding device of claim 1 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), and every Nth directional intra-prediction mode between DirS and DirE, where N is a predetermined integer value.
5. The video coding device of claim 1 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.
6. The video coding device of claim 1 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), a middle directional intra-prediction mode (DirD), a horizontal directional intra-prediction mode (DirH), a vertical directional intra-prediction mode (DirV), and valid directional intra-prediction modes at directions of plus or minus N of DirS, DirE, DirD, DirH, and DirV, where N is a predetermined integer value.
7. The video coding device of claim 6 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.
8. The video coding device of claim 1 , wherein the intra-prediction mode subset includes intra-prediction modes selected for decoded neighbor blocks, the decoded neighbor blocks positioned at a predetermined adjacency to the current image block.
9. The video coding device of claim 1 , wherein the intra-prediction mode subset includes modes associated with a most probable mode (MPM) list for the current image block.
10. A method implemented in a video coding device, the method comprising:
receiving, by a receiver of the video coding device, a bitstream;
determining, by a processor of the video coding device, an intra-prediction mode subset of an intra-prediction mode set including intra-prediction modes, wherein the intra-prediction mode subset includes intra-prediction modes that correlate to a plurality of reference lines for a current image block, and wherein all of the intra-prediction modes excluded from the intra-prediction mode subset are limited to correlate only to a single primary reference line immediately adjacent to the current image block;
decoding, by the processor, a first intra-prediction mode by an alternative intra-prediction mode index when the first intra-prediction mode is included in the intra-prediction mode subset; and
forwarding, by the processor, video data toward a display for presentation, the video data including an image block decoded based on the first intra-prediction mode.
11. The method of claim 10 , further comprising decoding, by the processor, a reference line index when the first intra-prediction mode is included in the intra-prediction mode subset, the reference line index indicating a first reference line from the plurality of reference lines for the first intra-prediction mode.
12. The method of claim 11 , further comprising decoding, by the processor, no reference line index when the first intra-prediction mode is not included in the intra-prediction mode subset.
13. The method of claim 12 , wherein the reference line index is positioned after the first intra-prediction mode in the bitstream.
14. The method of claim 10 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), and every Nth directional intra-prediction mode between DirS and DirE, where N is a predetermined integer value.
15. The method of claim 10 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.
16. The method of claim 10 , wherein the intra-prediction mode subset includes a starting directional intra-prediction mode (DirS), an ending directional intra-prediction mode (DirE), a middle directional intra-prediction mode (DirD), a horizontal directional intra-prediction mode (DirH), a vertical directional intra-prediction mode (DirV), and valid directional intra-prediction modes at directions of plus or minus N of DirS, DirE, DirD, DirH, and DirV, where N is a predetermined integer value.
17. The method of claim 16 , wherein the intra-prediction mode subset further includes planar prediction mode and Direct Current (DC) prediction mode.
18. The method of claim 10 , wherein the intra-prediction mode subset includes intra-prediction modes selected for decoded neighbor blocks, the decoded neighbor blocks positioned at a predetermined adjacency to the current image block.
19. The method of claim 10 , wherein the intra-prediction mode subset includes modes associated with a most probable mode (MPM) list for the current image block.