Methods and apparatuses for filtering intra predicted video blocks
The present disclosure provides methods and apparatuses for applying intra prediction refinement to intra predicted samples. An exemplary method includes: determining a filter based on neighboring samples of intra predicted samples of a picture; generating an offset value based on the neighboring samples; refining the intra predicted samples by adding the offset value; and applying the filter to the intra predicted samples.
1. A computer-implemented method for processing video data, comprising:
generating an intra predicted block having a size of M×N pixels;
determining:
a vertical array of M neighboring samples on a left side of the intra predicted block,
a horizontal array of N neighboring samples above the intra predicted block, and
a top-left neighboring sample of the intra predicted block;
generating an offset value based on differences between:
an intra predicted sample associated with a first pixel of the intra predicted block, and
each of the vertical array of M neighboring samples, the horizontal array of N neighboring samples, and the top-left neighboring sample; and
applying the offset value to the intra predicted sample associated with the first pixel,
wherein the offset value is equal to a weighted sum of the differences, wherein:
the weighted sum is calculated using a plurality of weights W kn ,
k refers to a k-th sample of the intra predicted block in a raster scan order,
n refers to a n-th un-filtered neighboring sample of the k-th sample, and
the plurality of weights W kn has following values for 4×4 intra predicted blocks:
k
W k0
W k1
W k2
W k3
W k4
W k5
W k6
W k7
W k8
0
4
16
4
0
0
16
4
0
0
1
2
4
16
4
0
8
2
0
0
2
1
0
4
16
4
4
1
0
0
3
0
0
2
4
16
2
0
0
0
4
2
8
2
0
0
4
16
4
0
5
0
2
8
2
0
2
8
2
0
6
0
0
2
8
2
1
4
1
0
7
0
0
0
2
8
1
2
0
0
8
0
4
0
0
0
0
4
16
4
9
0
0
4
0
0
0
2
8
2
10
0
0
1
4
1
0
1
4
1
11
0
0
0
2
4
0
0
4
0
12
0
0
1
0
0
0
2
4
16
13
0
0
0
1
0
0
1
2
8
14
0
0
1
2
1
0
0
1
4
15
0
0
0
1
2
0
0
1
2.
2. The method according to claim 1 , further comprising:
selecting the first pixel from the M×N pixels, based on an intra prediction mode associated with the intra predicted block.
3. The method according to claim 2 , further comprising:
in response to the intra prediction mode being a DC mode or a smooth mode, selecting the pixel from a top boundary row or a left boundary row of the M×N pixels.
4. The method according to claim 2 , further comprising:
in response to the intra prediction mode being a vertical mode or a smooth vertical mode, selecting the pixel from a left boundary row of the M×N pixels.
5. The method according to claim 2 , further comprising:
in response to the intra prediction mode being a horizontal mode or a smooth horizontal mode, selecting the pixel from a top boundary row of the M×N pixels.
6. The method according to claim 1 , wherein the method is used for decoding a bitstream and comprises:
decoding an angle delta parameter signaled in the bitstream; and
determining whether to apply the offset value to the intra predicted sample, based on a value of the angle delta parameter.
7. The method according to claim 6 , wherein a value of the angle delta parameter is equal to 4.
8. The method according to claim 1 , wherein the method is used for encoding video data and comprises:
encoding, in a bitstream, an angle delta parameter indicating whether to apply the offset value to the intra predicted sample.
9. The method according to claim 8 , further comprising:
setting a value of the angle delta parameter to be equal to 4.
10. An apparatus, comprising:
a memory configured to store a set of instructions; and
one or more processors configured to execute the set of instructions to cause the apparatus to perform:
generating an intra predicted block having a size of M×N pixels;
determining:
a vertical array of M neighboring samples on a left side of the intra predicted block,
a horizontal array of N neighboring samples above the intra predicted block, and
a top-left neighboring sample of the intra predicted block;
generating an offset value based on differences between:
an intra predicted sample associated with a first pixel of the intra predicted block, and
each of the vertical array of M neighboring samples, the horizontal array of N neighboring samples, and the top-left neighboring sample; and
applying the offset value to the intra predicted sample associated with the first pixel,
wherein the offset value is equal to a weighted sum of the differences, wherein:
the weighted sum is calculated using a plurality of weights W kn ,
k refers to a k-th sample of the intra predicted block in a raster scan order,
n refers to a n-th un-filtered neighboring sample of the k-th sample, and
the plurality of weights W kn has following values for 4×4 intra predicted blocks:
k
W k0
W k1
W k2
W k3
W k4
W k5
W k6
W k7
W k8
0
4
16
4
0
0
16
4
0
0
1
2
4
16
4
0
8
2
0
0
2
1
0
4
16
4
4
1
0
0
3
0
0
2
4
16
2
0
0
0
4
2
8
2
0
0
4
16
4
0
5
0
2
8
2
0
2
8
2
0
6
0
0
2
8
2
1
4
1
0
7
0
0
0
2
8
1
2
0
0
8
0
4
0
0
0
0
4
16
4
9
0
0
4
0
0
0
2
8
2
10
0
0
1
4
1
0
1
4
1
11
0
0
0
2
4
0
0
4
0
12
0
0
1
0
0
0
2
4
16
13
0
0
0
1
0
0
1
2
8
14
0
0
1
2
1
0
0
1
4
15
0
0
0
1
2
0
0
1
2.
11. The apparatus according to claim 10 , wherein the one or more processors are further configured to execute the set of instructions to cause the apparatus to perform:
selecting the first pixel from the M×N pixels, based on an intra prediction mode associated with the intra predicted block.
12. The apparatus according to claim 11 , wherein the one or more processors are further configured to execute the set of instructions to cause the apparatus to perform:
in response to the intra prediction mode being a DC mode or a smooth mode, selecting the pixel from a top boundary row or a left boundary row of the M×N pixels;
in response to the intra prediction mode being a vertical mode or a smooth vertical mode, selecting the pixel from the left boundary row of the M×N pixels; and
in response to the intra prediction mode being a horizontal mode or a smooth horizontal mode, selecting the pixel from the top boundary row of the M×N pixels.
13. The apparatus according to claim 10 , wherein the one or more processors are further configured to execute the set of instructions to cause the apparatus to perform:
decoding an angle delta parameter signaled in the bitstream; and
determining whether to apply the offset value to the intra predicted sample, based on a value of the angle delta parameter.
14. The apparatus according to claim 13 , wherein a value of the angle delta parameter is equal to 4.
15. The apparatus according to claim 10 , wherein the one or more processors are further configured to execute the set of instructions to cause the apparatus to perform:
encoding, in a bitstream, an angle delta parameter indicating whether to apply the offset value to the intra predicted sample.
16. The apparatus according to claim 15 , wherein the one or more processors are further configured to execute the set of instructions to cause the apparatus to perform:
setting a value of the angle delta parameter to be equal to 4.
17. A non-transitory computer readable medium storing a bitstream of video data for processing according to operations comprising:
generating an intra predicted block having a size of M×N pixels;
determining:
a vertical array of M neighboring samples on a left side of the intra predicted block,
a horizontal array of N neighboring samples above the intra predicted block, and
a top-left neighboring sample of the intra predicted block;
generating an offset value based on differences between:
an intra predicted sample associated with a first pixel of the intra predicted block, and
each of the vertical array of M neighboring samples, the horizontal array of N neighboring samples, and the top-left neighboring sample; and
applying the offset value to the intra predicted sample associated with the first pixel,
wherein the offset value is equal to a weighted sum of the differences, wherein:
the weighted sum is calculated using a plurality of weights W kn ,
k refers to a k-th sample of the intra predicted block in a raster scan order,
n refers to a n-th un-filtered neighboring sample of the k-th sample, and
the plurality of weights W kn has following values for 4×4 intra predicted blocks:
k
W k0
W k1
W k2
W k3
W k4
W k5
W k6
W k7
W k8
0
4
16
4
0
0
16
4
0
0
1
2
4
16
4
0
8
2
0
0
2
1
0
4
16
4
4
1
0
0
3
0
0
2
4
16
2
0
0
0
4
2
8
2
0
0
4
16
4
0
5
0
2
8
2
0
2
8
2
0
6
0
0
2
8
2
1
4
1
0
7
0
0
0
2
8
1
2
0
0
8
0
4
0
0
0
0
4
16
4
9
0
0
4
0
0
0
2
8
2
10
0
0
1
4
1
0
1
4
1
11
0
0
0
2
4
0
0
4
0
12
0
0
1
0
0
0
2
4
16
13
0
0
0
1
0
0
1
2
8
14
0
0
1
2
1
0
0
1
4
15
0
0
0
1
2
0
0
1
2.