Method of Reducing a Blocking Artifact When Coding Moving Picture

Abstract

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 . (canceled) 
     
     
         2 . A method for performing a filter operation on a boundary between a first block including a first pixel and a second pixel and a second block including a third pixel and a fourth pixel, the second pixel and the third pixel neighboring each other and separated by the boundary, the first pixel, the second pixel, the third pixel, and the fourth pixel being successive in a horizontal or vertical direction, the method comprising:
 obtaining a parameter using a difference between the first pixel and the fourth pixel and a difference between the second pixel and the third pixel;   obtaining an adjustment value by performing a clipping operation on the parameter;   adjusting the second pixel by adding the adjustment value to a value of the second pixel; and   adjusting the third pixel by subtracting the adjustment value from a value of the third pixel.   
     
     
         3 . The method according to  claim 2 , wherein obtaining the parameter comprises:
 applying a first constant to the difference between the first pixel and the fourth pixel, and   applying a second constant to the difference between the second pixel and the third pixel.   
     
     
         4 . The method according to  claim 3 , wherein the first constant and the second constant are different from each other. 
     
     
         5 . The method according to  claim 2 , further comprising:
 comparing an absolute value of the parameter with a value related to quantization information,   wherein the second pixel is adjusted and the third pixel is adjusted based on the absolute value of the parameter being less than the value related to quantization information.   
     
     
         6 . The method according to  claim 5 , wherein obtaining an adjustment value by performing a clipping operation on the obtained parameter comprises setting the adjustment value to zero based on the absolute value of the parameter being equal to or greater than the value related to quantization information. 
     
     
         7 . The method according to  claim 2 , wherein the filter operation is performed to reduce a blocking artifact. 
     
     
         8 . A system comprising:
 one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations for performing a filter operation on a boundary between a first block including a first pixel and a second pixel and a second block including a third pixel and a fourth pixel, the second pixel and the third pixel neighboring each other and separated by the boundary, the first pixel, the second pixel, the third pixel, and the fourth pixel being successive in a horizontal or vertical direction, the operations comprising:
 obtaining a parameter using a difference between the first pixel and the fourth pixel and a difference between the second pixel and the third pixel; 
 obtaining an adjustment value by performing a clipping operation on the parameter; 
 adjusting the second pixel by adding the adjustment value to a value of the second pixel; and 
 adjusting the third pixel by subtracting the adjustment value from a value of the third pixel. 
   
     
     
         9 . The system according to  claim 8 , wherein obtaining the parameter comprises:
 applying a first constant to the difference between the first pixel and the fourth pixel, and   applying a second constant to the difference between the second pixel and the third pixel.   
     
     
         10 . The system according to  claim 9 , wherein the first constant and the second constant are different from each other. 
     
     
         11 . The system according to  claim 8 , wherein the operations further comprise:
 comparing an absolute value of the parameter with a value related to quantization information,   wherein the second pixel is adjusted and the third pixel is adjusted based on the absolute value of the parameter being less than the value related to quantization information.   
     
     
         12 . The system according to  claim 11 , wherein obtaining an adjustment value by performing a clipping operation on the obtained parameter comprises setting the adjustment value to zero based on the absolute value of the parameter being equal to or greater than the value related to quantization information. 
     
     
         13 . The system according to  claim 8 , wherein the filter operation is performed to reduce a blocking artifact.