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 using the first pixel and the second pixel, wherein the adjustment magnitude is no greater than half of the difference between a value of the first pixel and a value of the second pixel; and
adjusting the first pixel based on the adjustment magnitude.
2. 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
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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.
3. The method of claim 2 , 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.
4. The method of claim 2 , wherein c 2 is an integer and c 3 is a multiple of 2.
5. The method of claim 4 , wherein c 2 =5 and c 3 =8.
6. The method of claim 1 , further comprising applying the adjusting operation to a spatial domain of the first pixel.
7. The method of claim 1 , wherein the block boundary is a vertical or horizontal block boundary.
8. The method of claim 1 , further comprising adjusting the second pixel based upon the adjustment magnitude.
9. The method of claim 1 , wherein the clipping operation is performed using frequency information of the second pixel.
10. The method of claim 1 , wherein the clipping operation is performed using a minimum magnitude of frequency information of the first and second pixels.
11. The method of claim 1 , wherein the clipping operation is performed using frequency information of the first pixel and the second pixel.
12. 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.
13. 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.
14. 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 using the first pixel and the second pixel, wherein the adjustment magnitude is no greater than half of the difference between a value of the first pixel and a value of the second pixel; and
adjust the first pixel based on the adjustment magnitude.
15. 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 using the first pixel and the second pixel, wherein the adjustment magnitude is no greater than half of the difference between a value of the first pixel and a value of the second pixel; and
means for adjusting the first pixel based on the adjustment magnitude.