Method and apparatus of video coding
Aspects of the disclosure include a method for video coding. The method includes receiving input data associated with a current block in an image frame, selecting a reference pixel set from a plurality of candidate neighboring pixel sets adjacent to an edge of the current block, generating an intra predictor of the current block based on the selected reference pixel set and an intra prediction mode of the current block, and encoding or decoding the current block based on the intra predictor to output encoded video data or a decoded block. Each set of the candidate neighboring pixel sets is arranged in parallel with the edge of the current block.
1. A method of video coding, comprising:
receiving input data associated with a current block in an image frame;
selecting a plurality of reference pixel sets from a plurality of first candidate neighboring pixel sets adjacent to a first edge of the current block, each of the first candidate neighboring pixel sets being arranged in parallel with the first edge of the current block;
generating an intra predictor of the current block based on a plurality of sample values respectively derived from the selected reference pixel sets and an intra prediction mode of the current block; and
encoding or decoding the current block based on the intra predictor to output encoded video data or a decoded block,
wherein
the selected reference pixel sets from the plurality of first candidate neighboring pixel sets adjacent to the first edge of the current block are K selected reference pixel sets, K being a positive integer greater than one,
the K selected reference pixel sets define K reference lines, respectively,
a direction of prediction of the intra prediction mode of the current block defines prediction reference lines, and
the generating the intra predictor includes:
determining K sample values based on the K selected reference pixel sets, respectively, each of the K sample values corresponding to a respective position where the respective reference line and one of the prediction reference lines intersect; and
calculating a value of a pixel of the intra predictor that overlaps the one of the prediction reference lines based on the K sample values and K weightings applicable to the K sample values, respectively.
2. The method according to claim 1 , further comprising extracting from the input data or including in the encoded video data information that indicates the selected reference pixel sets.
3. The method according to claim 1 , further comprising deriving the selected reference pixel sets based on the intra prediction mode or a shape of the current block.
4. The method according to claim 1 , wherein the determining K sample values comprises:
determining a first sample value based on a first reference pixel set of the K selected reference pixel sets by interpolation using pixel values of at least two pixels of the first reference pixel set that are adjacent to a first position where a first reference line defined by the first reference pixel set and the one of the prediction reference lines intersect.
5. The method according to claim 1 , wherein the selecting the plurality of reference pixel sets from the first candidate neighboring pixel sets comprises selecting a closest one of the first candidate neighboring pixel sets to the first edge of the current block.
6. The method according to claim 1 , further comprising extracting from the input data or including in the encoded video data information that indicates the K weightings.
7. The method according to claim 1 , further comprising determining the K weightings based on a location of the pixel in the current block, the direction of prediction of the intra prediction mode of the current block, or a primary reference pixel set among the K selected reference pixel sets.
8. The method according to claim 1 , further comprising:
selecting another plurality of reference pixel sets from a plurality of second candidate neighboring pixel sets adjacent to a second edge of the current block, each set of the second candidate neighboring pixel sets being arranged in parallel with the second edge of the current block and not in parallel with the first edge of the current block,
wherein
generating the intra predictor of the current block is further based on the another plurality of selected reference pixel sets.
9. The method according to claim 8 , wherein
the first edge is an upper edge of the current block,
the second edge is a left edge of the current block, and
a shortest distance between the plurality of selected reference pixel sets and the upper edge of the current block is different from a shortest distance between the another plurality of selected reference pixel sets and the left edge of the current block.
10. The method according to claim 1 , wherein generating the intra predictor comprises:
generating a raw intra predictor;
calculating gradient information based on the selected reference pixel sets; and
adjusting the raw intra predictor to become a final intra predictor based on the calculated gradient information.
11. The method according to claim 1 , further comprising deriving the intra prediction mode of the current block based on the selected reference pixel sets.
12. The method according to claim 1 , wherein
the current block is a chroma block, and
the method further comprises deriving the selected reference pixel sets based on selected reference pixel sets for a luma block that corresponds to the chroma block.
13. The method according to claim 1 , wherein
the current block is a luma block, and
the method further comprises encoding or decoding a chroma block that corresponds to the luma block using a neighboring reference pixel set that is immediately adjacent to an edge of the chroma block.
14. The method according to claim 1 , wherein information indicating the selected reference pixel sets is incorporated in the encoded video data only if the current block has a block size greater than a predetermined block size.
15. A video coding apparatus, comprising:
a processing circuit configured to:
receive input data associated with a current block in an image frame;
select a plurality of reference pixel sets from a plurality of candidate neighboring pixel sets adjacent to a first edge of the current block, each of the candidate neighboring pixel sets being arranged in parallel with the first edge of the current block;
generate an intra predictor of the current block based on a plurality of sample values respectively derived from the selected reference pixel sets and an intra prediction mode of the current block; and
encode or decode the current block based on the intra predictor to output encoded video data or a decoded block,
wherein
the selected reference pixel sets from the plurality of first candidate neighboring pixel sets adjacent to the first edge of the current block are K selected reference pixel sets, K being a positive integer greater than one,
the K selected reference pixel sets define K reference lines, respectively,
a direction of prediction of the intra prediction mode of the current block defines prediction reference lines, and
the processing circuit is further configured to:
determine K sample values based on the K selected reference pixel sets, respectively, each of the K sample values corresponding to a respective position where the respective reference line and one of the prediction reference lines intersect; and
calculate value of a pixel of the intra predictor that overlaps the one of the prediction reference lines based on the K sample values and K weightings applicable to the K sample values, respectively.
16. A non-transitory computer readable medium storing program instructions for causing a processing circuit of an apparatus to perform a video coding method, and the method comprising:
receiving input data associated with a current block in an image frame;
selecting a plurality of reference pixel sets from a plurality of candidate neighboring pixel sets adjacent to a first edge of the current block, each of the candidate neighboring pixel sets being arranged in parallel with the first edge of the current block;
generating an intra predictor of the current block based on a plurality of sample values respectively derived from the selected reference pixel sets and an intra prediction mode of the current block; and
encoding or decoding the current block based on the intra predictor to output encoded video data or a decoded block,
wherein
the selected reference pixel sets from the plurality of first candidate neighboring pixel sets adjacent to the first edge of the current block are K selected reference pixel sets, K being a positive integer greater than one,
the K selected reference pixel sets define K reference lines, respectively,
a direction of prediction of the intra prediction mode of the current block defines prediction reference lines, and
the generating the intra predictor includes:
determining K sample values based on the K selected reference pixel sets, respectively, each of the K sample values corresponding to a respective position where the respective reference line and one of the prediction reference lines intersect; and
calculating a value of a pixel of the intra predictor that overlaps the one of the prediction reference lines based on the K sample values and K weightings applicable to the K sample values, respectively.
17. The non-transitory computer readable medium of claim 16 , wherein
the method further comprises selecting another plurality of reference pixel sets from a plurality of second candidate neighboring pixel sets adjacent to a second edge of the current block, each set of the second candidate neighboring pixel sets being arranged in parallel with the second edge of the current block and not in parallel with the first edge of the current block, and
the generating the intra predictor of the current block is further based on the another plurality of selected reference pixel sets.
18. The non-transitory computer readable medium of claim 17 , wherein
the first edge is an upper edge of the current block,
the second edge is a left edge of the current block, and
a shortest distance between the plurality of selected reference pixel sets and the upper edge of the current block is different from a shortest distance between the another plurality of selected reference pixel sets and the left edge of the current block.
19. The video coding apparatus of claim 15 , wherein the processing circuit is further configured to:
select another plurality of reference pixel sets from a plurality of second candidate neighboring pixel sets adjacent to a second edge of the current block, each set of the second candidate neighboring pixel sets being arranged in parallel with the second edge of the current block and not in parallel with the first edge of the current block; and
generate the intra predictor of the current block further based on the another plurality of selected reference pixel sets.
20. The video coding apparatus of claim 19 , wherein
the first edge is an upper edge of the current block,
the second edge is a left edge of the current block, and
a shortest distance between the plurality of selected reference pixel sets and the upper edge of the current block is different from a shortest distance between the another plurality of selected reference pixel sets and the left edge of the current block.