Deblocking filter

1. A method comprising

performing, at a video decoding apparatus, a test of pixel lines crossing a boundary between first and second blocks in a block-wise coded video picture; and

modifying, at the video decoding apparatus, neighboring pixels on the pixel lines crossing the boundary with a Δ value calculated by a function based on a weighted sum of a third closest pixel on a left hand side of the boundary, a second closest pixel on the left hand side of the boundary, a closest pixel on the left hand side of the boundary, a closest pixel on a right hand side of the boundary, a second closest pixel on the right hand side of the boundary, and a third closest pixel on the right hand side of the boundary, wherein

the function is w1*a−w2*b−w3*c+w4*d+w5*e−w6*f, where w1, w2, w3, w4, w5 and w6 are weighting factors greater than or equal to zero, and

a being the third closest pixel on the left hand side, b being the second closest pixel on the left hand side, c being the closest pixel on the left hand side, d being the closest pixel on the right hand side, e being the second closest pixel on the right hand side, and f being the third closest pixel on the right hand side.

2. The method of claim 1 , wherein w1=1, w2=1, w3=2, w4=2, w5=1 and w6=1.

3. A method comprising

performing, at a video decoding apparatus, a test of pixel lines crossing a boundary between first and second blocks in a block-wise coded video picture; and

modifying, at the video decoding apparatus, neighboring pixels on the pixel lines crossing the boundary with a Δ value calculated by a function based on a weighted sum of a third closest pixel on a left hand side of the boundary, a second closest pixel on the left hand side of the boundary, a closest pixel on the left hand side of the boundary, a closest pixel on a right hand side of the boundary, a second closest pixel on the right hand side of the boundary, and a third closest pixel on the right hand side of the boundary, wherein

the performing the test includes testing the following relation for the pixel lines

∑

i

=

∈

S

⁢

(



a

i

-

2

⁢

⁢

b

i

+

c

i



+



d

i

-

2

⁢

⁢

e

i

+

f

i



)

<

β

′

⁡

(

Q

⁢

⁢

P

)

,

wherein i is a line number of lines in the subset S, and β′(QP) is a threshold value dependent on a first quantization parameter for video decoding.

4. The method of claim 1 , wherein modifying the neighboring pixels further comprises:

clipping the Δ within a value range (−γ,γ), wherein γ is a second quantization parameter found in a look-up table dependent on a first quantization parameter and a strength value for the boundary; and

calculating modified neighboring pixels according to the following relations

b′=b+Δ/ 2,

c′=c+Δ,

d′=d −Δ, and

e′=e−Δ/ 2,

wherein b′, c′, d′ and e′ are re-calculated values of corresponding original neighboring pixels values.