CLAIMS

1. An intra prediction method, comprising:

determining a prediction value for a sample of a current block from one or more reference samples outside the current block by using an intra predication mode;

deriving a weighted prediction value, when one or more predefined conditions are not satisfied, wherein the one or more predefined conditions relate to at least one of a width and/or a height of the current block and the intra prediction mode; and

coding the current block using the weighted prediction value, when the one or more predefined conditions are not satisfied.

2. The method of claim 1, wherein the current block is comprised in a current frame of a video sequence or a still image.

3. The method of claim 1 or 2, further comprising:

coding the current block using the prediction value and not using the weighted prediction value, when the one or more predefined conditions are satisfied.

4. The method of any one of claims 1-3, wherein the weighted prediction value is derived based on

a) the prediction value at the position (x, y) of the sample in the current block, where x is a horizontal coordinate of the sample andy is a vertical coordinate of the sample,

b) the width and/or the height of the current block,

c) a value of a top reference sample of the current block located adjacent to the current block in a row atop of the current block at the x-th column of the current block and a value of a left reference sample of the current block located adjacent to the current block in a column on the left-hand side of the current block at the y-th row of the current block, and

d) the intra prediction mode.

5. The method of claim 4, wherein the weighted prediction value is derived according to the following formula:

P(x, y ) is the weighted prediction value of the sample;

P(x, y) is the prediction value of the sample;

Rx -1, R- i,y represent the values of the top and the left reference samples of the current block;

R- 1,-1 represents the value of a reference sample of the current block located adjacent to the current block at the top-left corner of the current block;

wL , wT and wTL represent weights;

wherein the function CliplCmp is set equal to a clipping function CliplY, when the current block is a luma block, and is set equal to a clipping function Clip 1C, when the current block is a chroma block, wherein

and where BitDepthy is the bit depth of luma samples and BitDepthc is the bit depth of chroma samples.

6. The method of claim 5, wherein the weights are derived by

wL = V » ( ( x « 1 ) » nScaleX );

wT= V» ( ( y « 1 ) » nScaleY );

where V, nScaleX , nScaleY are predetermined values;

and

wTL =— (wL » 4)— ( wT » 4), when the intra prediction mode is a DC mode, wTL=0, when the intra prediction mode is a planar mode,

wTL=wT, when the intra prediction mode is a horizontal mode, and

wTL=wL, when the intra prediction mode is a vertical mode.

7. The method of claim 6, wherein V is 16 or 32.

8. The method of claim 6 or 7, wherein

NScaleX = NScaleY = (log2 (w) + log2 (h) + 2) » 2,

where w and h are the width and height in units of samples, respectively, of the current block.

9. The method of claim 6 or 7, wherein NScaleX is different from NScaleY.

10. The method of any one of claims 1-9, wherein the one or more predefined conditions consist of at least one of the following conditions:

a) the sum of the width and the height of the current block is smaller than a first threshold and/or the sum of the width and the height of the current block is larger than a second threshold;

b) the sum of the width and the height of the current block is smaller than a first threshold or the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is a planar mode or one of the skew non-diagonal modes satisfying ((predMode >= VDIA IDX - numModes && predMode != VDIA_IDX) || (predMode != 2 && predMode <= (2 + numModes))),

wherein VDIA IDX is an index of the diagonal modes, numModes is a predefined integer and predMode is an index of the intra prediction mode;

c) the sum of the width and the height of the current block is smaller than a first threshold; the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is a planar mode or one of the skew non-diagonal modes satisfying: ((predMode >= VDIA IDX - numModes && predMode != VDIA_IDX) || (predMode != 2 && predMode <= (2 + numModes)));

d) the sum of the width and the height of the current block is smaller than a first threshold; the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is a planar mode; and

e) the sum of the width and the height of the current block is smaller than a first threshold; the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is one of the skew non-diagonal modes satisfying ((predMode >= VDIA IDX - numModes && predMode != VDIA_IDX) II (predMode != 2 && predMode <= (2 + numModes))).

11. The method of any one of claims 1-10, wherein the current block is a chroma block, and wherein the one or more predefined conditions consist of at least one of the following conditions:

a) the sum of the width and the height of the current block is smaller than a first threshold or the sum of the width and the height of the current block is larger than a second threshold;

b) the sum of the width and the height of the current block is smaller than a first threshold; and the intra prediction mode is a cross-component linear modeling mode;

c) the sum of the width and the height of the current block is smaller than a first threshold and the intra prediction mode is a cross-component linear modeling mode and; the sum of the width and the height of the current block is larger than a second threshold;

d) the sum of the width and the height of the current block is smaller than a first threshold; and the intra prediction mode is a planar mode;

e) the sum of the width and the height of the current block is smaller than a first threshold; and the intra prediction mode is one of the skew non-diagonal modes satisfying ((predMode >= VDIA IDX - numModes && predMode != VDIA_IDX) II (predMode != 2 && predMode <= (2 + numModes)));

f) the sum of the width and the height of the current block is smaller than a first threshold; and the intra prediction mode is a cross-component linear modeling mode or a planar mode;

g) the sum of the width and the height of the current block is smaller than a first threshold; and the intra prediction mode is a cross-component linear modeling mode or one of the skew non-diagonal modes satisfying: ((predMode >= VDIA_IDX - numModes && predMode != VDIA_IDX) || (predMode != 2 && predMode <= (2 + numModes)));

h) the sum of the width and the height of the current block is smaller than a first threshold or the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is a cross-component linear modeling mode, a planar mode or one of the skew non-diagonal modes: ((predMode >= VDIA_IDX - numModes && predMode != VDIA_IDX) || (predMode != 2 && predMode <= (2 + numModes))); and

i) the sum of the width and the height of the current block is smaller than a first threshold; the intra prediction mode is a cross-component linear modeling mode, a planar mode or one of the skew non-diagonal modes satisfying ((predMode >= VDIA_IDX - numModes && predMode != VDIA_IDX) || (predMode != 2 && predMode <= (2 + numModes))); the sum of the width and the height of the current block is larger than a second threshold; and the intra prediction mode is a planar mode or one of the skew non-diagonal modes satisfying: ((predMode >= VDIA IDX - numModes && predMode != VDIA_IDX) II (predMode != 2 && predMode <= (2 + numModes))).

12. The method of claim 10 or 11, wherein numModes is 8.

13. The method of any one of claims 1-12, wherein the first threshold is 8.

14. The method of any one of claims 1-13, wherein the second threshold is 64.

15. An encoder (20) comprising processing circuitry configured for carrying out the method according to any one of preceding claims 1 to 14.

16. A decoder (30) comprising processing circuitry configured for carrying out the method according to any one of claims 1 to 14.

17. A computer program product comprising a program code for performing the method according to any one of claims 1 to 14.

18. A decoder (30), comprising:

one or more processors (502); and

a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the decoder to carry out the method according to any one of claims 1 to 14.

19. An encoder (20), comprising:

one or more processors (502); and

a non-transitory computer-readable storage medium coupled to the processors and storing programming for execution by the processors, wherein the programming, when executed by the processors, configures the encoder to carry out the method according to any one of claims 1 to 14.