Method and apparatus for low-complexity bi-directional intra prediction in video encoding and decoding
A method for video decoding is disclosed. A directional intra prediction mode is decoded ( 910 ) for a current block of a picture in a video, said directional intra prediction mode having a direction. Based on said directional intra prediction mode, a first predictor for a sample is accessed ( 7010 ), the sample being within said current block. Based on said directional intra prediction mode, a second predictor for said sample, is accessed ( 7020 ) said first and second predictors being on a line at least approximating said direction. A sample value of said sample is predicted ( 7030 ) by using said first and second predictors; and said sample of said current block is reconstructed ( 965 ) based on said predicted sample value.
1. A method for video decoding, comprising:
decoding a directional intra prediction mode for a block of a picture in a video, said directional intra prediction mode having a direction;
accessing, based on said directional intra prediction mode, a first predictor for a sample, the sample being within said block;
accessing, based on said directional intra prediction mode, a second predictor for said sample, said first and second predictors being on a line at least approximating said direction;
predicting a sample value of said sample, by interpolation using said first and second predictors, wherein said interpolation is responsive to a difference between said second predictor and said first predictor values, wherein said difference is scaled by at least a ratio, and wherein a denominator of said ratio is based at least on W+H, where W is a width of said block and H is a height of said block; and
decoding said sample of said block based on said predicted sample value.
2. The method of claim 1 , wherein said ratio is approximated by
1
+
y
W
+
H
,
where y is a coordinate of said sample along a vertical axis in said block.
3. The method of claim 1 , wherein said direction is a positive direction and wherein said ratio is approximated by
W
+
y
-
x
H
+
W
or
W
+
H
+
y
-
x
2
×
(
H
+
W
)
,
where y and x are respectively coordinates of said sample along a vertical axis and an horizontal axis in said block.
4. The method of claim 1 , wherein said direction is a negative direction and wherein said ratio is approximated by
1
+
y
+
x
H
+
W
,
where y and x are respectively coordinates of said sample along a vertical axis and a horizontal axis in said block.
5. A method for video encoding, comprising:
accessing a directional intra prediction mode for a block of a picture in a video, said directional intra prediction mode having a direction;
accessing, based on said directional intra prediction mode, a first predictor for a sample, the sample being within said block;
accessing, based on said directional intra prediction mode, a second predictor for said sample, said first and second predictors being on a line at least approximating said direction;
predicting a sample value of said sample, by interpolation using said first and second predictors, wherein said interpolation is responsive to a difference between said second predictor and said first predictor values, wherein said difference is scaled by at least a ratio, and wherein a denominator of said ratio is based at least on W+H, where W is a width of said block and H is a height of said block; and
encoding said sample of said block based on said predicted sample value.
6. The method of claim 5 , wherein said ratio is approximated by
1
+
y
W
+
H
,
where y is a coordinate of said sample along a vertical axis in said block.
7. The method of claim 5 , wherein said direction is a positive direction and wherein said ratio is approximated by
W
+
y
-
x
H
+
W
or
W
+
H
+
y
-
x
2
×
(
H
+
W
)
,
where y and x are respectively coordinates of said sample along a vertical axis and an horizontal axis in said block.
8. The method of claim 5 , wherein said direction is a negative direction and wherein said ratio is approximated by
1
+
y
+
x
H
+
W
,
where y and x are respectively coordinates of said sample along a vertical axis and a horizontal axis in said block.
9. An apparatus for video decoding, comprising one or more processors, wherein said one or more processors are configured to:
decode a directional intra prediction mode for a block of a picture in a video, said directional intra prediction mode having a direction;
access, based on said directional intra prediction mode, a first predictor for a sample, the sample being within said block;
access, based on said directional intra prediction mode, a second predictor for said sample, said first and second predictors being on a line at least approximating said direction;
predict a sample value of said sample, by interpolation using said first and second predictors; wherein said interpolation is responsive to a difference between said second predictor and said first predictor values, wherein said difference is scaled by at least a ratio, and wherein a denominator of said ratio is based at least on W+H, where W is a width of said block and H is a height of said block; and
decode said sample of said block based on said predicted sample value.
10. The apparatus of claim 9 , wherein said ratio is approximated by
1
+
y
W
+
H
,
where y is a coordinate of said sample along a vertical axis in said block.
11. The apparatus of claim 9 , wherein said direction is a positive direction and wherein said ratio is approximated by
W
+
y
-
x
H
+
W
or
W
+
H
+
y
-
x
2
×
(
H
+
W
)
,
where y and x are respectively coordinates of said sample along a vertical axis and an horizontal axis in said block.
12. The apparatus of claim 9 , wherein said direction is a negative direction and wherein said ratio is approximated by
1
+
y
+
x
H
+
W
,
where y and x are respectively coordinates of said sample along a vertical axis and a horizontal axis in said block.
13. An apparatus for video encoding, comprising one or more processors, wherein said one or more processors are configured to:
access a directional intra prediction mode for a block of a picture in a video, said directional intra prediction mode having a direction;
access, based on said directional intra prediction mode, a first predictor for a sample, the sample being within said block;
access, based on said directional intra prediction mode, a second predictor for said sample, said first and second predictors being on a line at least approximating said direction;
predict a sample value of said sample, by interpolation using said first and second predictors, wherein said interpolation is responsive to a difference between said second predictor and said first predictor values, wherein said difference is scaled by at least a ratio, and wherein a denominator of said ratio is based at least on W+H, where W is a width of said block and H is a height of said block; and
encode said sample of said block based on said predicted sample value.
14. The apparatus of claim 13 , wherein said ratio is approximated by
1
+
y
W
+
H
,
where y is a coordinate of said sample along a vertical axis in said block.
15. The apparatus of claim 13 , wherein said direction is a positive direction and wherein said ratio is approximated by
W
+
y
-
x
H
+
W
or
W
+
H
+
y
-
x
2
×
(
H
+
W
)
,
where y and x are respectively coordinates of said sample along a vertical axis and an horizontal axis in said block.
16. The apparatus of claim 13 , wherein said direction is a negative direction and wherein said ratio is approximated by
1
+
y
+
x
H
+
W
,
where y and x are respectively coordinates of said sample along a vertical axis and a horizontal axis in said block.