Method of reducing a blocking artifact when coding moving picture
View Patent ↗A method of coding a moving picture is provided that reduces blocking artifacts. The method can include defining a plurality of defining pixels S 0 , S 1 , and S 2 , which are centered around a block boundary. If a default mode is selected then frequency information of the surroundings of the block boundary is obtained. A magnitude of a discontinuous component in a frequency domain belonging to the block boundary is adjusted based on a magnitude of a corresponding discontinuous component selected from a pixel contained entirely within a block adjacent the block boundary. The frequency domain adjustment is then applied to a spatial domain. Or, a DC offset mode can be selected to reduce blocking artifacts in smooth regions where there is little motion.
1. A method of reducing a blocking artifact appearing when coding a picture, comprising:
dividing the picture into blocks that each include multiple pixels, the picture including a first pixel of a first block separated from a second pixel of a neighboring second block by a block boundary;
calculating an adjustment magnitude based on performing a clipping operation; and
adjusting, if a value of the first pixel is not correlated to a value of a second pixel, the first pixel based on the adjustment magnitude.
2. The method of claim 1 , wherein adjusting, if the value of the first pixel is not correlated to the value of the second pixel, the first pixel based on the adjustment magnitude further comprises adjusting, if the value of the first pixel is not equal to the value of the second pixel, the first pixel based on the adjustment magnitude.
3. The method of claim 1 ,
wherein adjusting the first pixel further comprises replacing a pixel value v 3 of the first pixel with an adjusted pixel value v 3 ′,
wherein the adjusted pixel value v 3 ′ is expressed as:
v 3 ′=v 3 −d,
wherein d is expressed as:
d
=
CLIP
(
c
2
(
a
3
,
0
'
-
a
3
,
0
)
//
c
3
,
0
,
(
v
3
-
v
4
)
2
)
*
δ
(
a
3
,
0
<
QP
)
,
wherein a 3,0 ′ is expressed as:
a 3,0 ′=SIGN( a 3,0 )*MIN(| a 3,0 |,|a 3,1 |,|a 3,2 |), and
wherein QP represents a quantization parameter of the second block, c 2 and c 3 represent DCT kernel coefficients, and v 4 represents a pixel value of the second pixel.
4. The method of claim 3 , wherein δ(|a 3,0 |<QP)=1 if |a 3,0 |<QP, and wherein δ(|a 3,0 |<QP)=0 if |a 3,0 |≧QP.
5. The method of claim 3 , wherein c 2 is an integer and C 3 is a multiple of 2.
6. The method of claim 4 , wherein c 2 =5 and c 3 =8.
7. The method of claim 1 , further comprising applying the adjusting operation to a spatial domain of the first pixel.
8. The method of claim 1 , wherein the block boundary is a vertical or horizontal block boundary.
9. The method of claim 1 , further comprising adjusting the second pixel based upon the adjustment magnitude.
10. The method of claim 1 , wherein the adjustment magnitude is constrained to be no greater than half of the difference between a value of the first pixel and a value of the second pixel.
11. The method of claim 1 , wherein the clipping operation is performed using frequency information of the second pixel.
12. The method of claim 1 , wherein the clipping operation is performed using the first pixel and the second pixel.
13. The method of claim 12 , wherein the clipping operation is performed using a minimum magnitude of frequency information of the first and second pixels.
14. The method of claim 12 , wherein the clipping operation is performed using frequency information of the first pixel and the second pixel.
15. The method of claim 1 , further comprising obtaining frequency information for the second pixel, wherein the first pixel is adjusted if a magnitude of the blocking artifact is less than a quantization parameter of the second block.
16. The method of claim 1 , wherein the adjustment magnitude is further based upon a simple inner product of a DCT kernel and the first and second pixels.
17. An apparatus for reducing a blocking artifact appearing when coding a picture, the apparatus comprising a blocking filter configured to:
divide the picture into blocks that each include multiple pixels, the picture including a first pixel of a first block separated from a second pixel of a neighboring second block by a block boundary;
calculate an adjustment magnitude based on performing a clipping operation; and
adjust, if a value of the first pixel is not correlated to a value of a second pixel, the first pixel based on the adjustment magnitude.
18. An apparatus for reducing a blocking artifact appearing when coding a picture, the apparatus comprising:
means for dividing the picture into blocks that each include multiple pixels, the picture including a first pixel of a first block separated from a second pixel of a neighboring second block by a block boundary;
means for calculating an adjustment magnitude based on performing a clipping operation; and
means for adjusting, if a value of the first pixel is not correlated to a value of a second pixel, the first pixel based on the adjustment magnitude.