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1. WO2020111982 - METHOD OF INTRA PREDICTING A BLOCK OF A PICTURE

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[ EN ]

CLAIMS

1. A method of intra predicting a block of a picture, comprising for a sample of the block:

obtaining (SI 00) a predicted sample value from one or more reference sample values by intra-prediction using a DC intra-prediction mode;

multiplying (SI 10) the predicted sample value by a sample weighting factor, resulting in a weighted predicted sample value;

adding (S120) an additional value to the weighted predicted sample value, resulting in a non-normalized predicted sample value; and

normalizing (SI 30) the non-normalized predicted sample value by an arithmetic right shift of an integer representation of the non-normalized predicted sample value, wherein

the sample weighting factor is ((2 « p)—wL— wT ), wherein

£> is a parameter of the sample weighting factor,

wL is a horizontal weighting factor, and

wT is a vertical weighting factor.

2. A method of intra predicting a first block and a second block of a picture, comprising for a sample of the first block and for a sample of the second block:

obtaining (SI 00) a predicted sample value from one or more reference sample values by intra-prediction using an intra-prediction mode;

multiplying (SI 10) the predicted sample value by a sample weighting factor, resulting in a weighted predicted sample value;

adding (S120) an additional value to the weighted predicted sample value, resulting in a non-normalized predicted sample value; and

normalizing (SI 30) the non-normalized predicted sample value by an arithmetic right shift of an integer representation of the non-normalized predicted sample value, wherein

the sample weighting factor is ((2 « p)— wL— wT ),

£> is a parameter of the sample weighting factor,

wL is a horizontal weighting factor, and

wT is a vertical weighting factor,

wherein the intra-prediction mode used for obtaining the predicted sample value for the first block is a DC intra-prediction mode, and the intra-prediction mode used for obtaining the predicted sample value for the second block is a PLANAR intra prediction mode.

3. The method of claim 1 or 2, wherein

a PLANAR intra prediction mechanism is used to calculate the additional value.

4. The method of any one of claims 1 to 3, wherein the sample weighting factor is (64— wL— wT ).

5. The method of any one of claims 1 to 4, wherein the additional value is a sum of one or more summands, including a summand depending on one or more of the reference samples.

6. The method of claim 5, wherein the summand depending on one or more reference samples is wL x R_ l y + wT x Rx -i , and Rx _ and R-1 V represent values of the nearest reference samples located above and to the left of the predicted sample

7. The method of any one of claims 1 to 6, wherein the horizontal weighting factor wL and/or the vertical weighting factor wT is a power of two.

8. The method of any one of claims 1 to 7, wherein

the horizontal weighting factor is wL = (2 « (p— 1)) » ((x « 1) » nScale ) , wherein x is a horizontal coordinate of the sample,

the vertical weighting factor is wT = (2 « (p— 1)) » ((y « 1) » nScale ) , wherein y is a vertical coordinate of the sample, and

nScale is a scale parameter.

9. The method of claim 8, wherein the scale parameter nScale is derived from a size of the block.

10. The method of claim 8, wherein the scale parameter nScale is determined as
width of the block and nTbH is a height of the block.

11. The method of any one of claims 1 to 10, wherein a normalized predicted sample value is computed from the predicted sample value, including calculating


where

P(x, y) is the predicted sample value,

Rx -i, R-i,y represent values of the nearest reference samples located above and to the left of the predicted sample,

wL is the horizontal weighting factor, and

wT is the vertical weighting factor.

12. A method of encoding or decoding a picture, comprising

obtaining normalized predicted sample values by performing the steps of a method according to any one of claims 1 to 11; and

adding residual values to the normalized predicted sample values resulting in reconstructed sample values.

13. A device for encoding or decoding a picture, comprising processing circuitry (1040) configured to perform the method of any one of claims 1 to 12.

14. The device of claim 13, wherein the processing circuitry (1040) comprises one or more processors (1050) and a non-transitory computer-readable medium (1060) connected to the one or more processors (1050), wherein the non-transitory computer-readable medium (1060) carries a program code which, when executed by the one or more processors (1050), causes the device to perform the method of any one of claims 1 to 13.

15. A non-transitory computer-readable medium carrying a program code which, when executed by a computer device, causes the computer device to perform the method of any one of claims 1 to 12.

16. A computer program comprising a program code for performing the method according to any one of claims 1 to 12.

17. A predictor device for intra predicting a block of a picture, comprising:

an obtainer configured to obtain, for a sample of the block, a predicted sample value from one or more reference sample values by intra-prediction using a DC intra prediction mode;

a multiplier configured to multiply the predicted sample value by a sample weighting factor, resulting in a weighted predicted sample value;

an adder configured to add an additional value to the weighted predicted sample value, resulting in a non-normalized predicted sample vale; and

a normalizer configured to normalize the non-normalized predicted sample value by an arithmetic right shift of an integer representation of the non-normalized predicted sample value, wherein

the sample weighting factor is ((2 « p)—wL— wT ), wherein

£> is a parameter of the sample weighting factor,

wL is a horizontal weighting factor, and

wT is a vertical weighing factor.

18. A predictor device for intra predicting a first block and a second block of a picture, comprising:

an obtainer configured to obtain, for a sample of the first block or the second block, a predicted sample value from one or more reference sample values by intra-prediction using an intra-prediction mode;

a multiplier configured to multiply the predicted sample value by a sample weighting factor, resulting in a weighted predicted sample value;

an adder configured to add an additional value to the weighted predicted sample value, resulting in a non-normalized predicted sample vale; and

a normalizer configured to normalize the non-normalized predicted sample value by an arithmetic right shift of an integer representation of the non-normalized predicted sample value, wherein

the sample weighting factor is ((2 « p)—wL— wT ),

£> is a parameter of the sample weighting factor,

wL is a horizontal weighting factor, and

wT is a vertical weighing factor,

wherein the intra-prediction mode used for obtaining the predicted sample value for the first block is a DC intra-prediction mode, and the intra prediction mode used for obtaining the predicted sample value for the second block is a planar intra prediction mode.