Coding distortion removal method, video encoding method, video decoding method, and apparatus and program for the same

Abstract

Mosaic-shaped block noise occurs when a compressed video signal is reproduced. This block noise is removed, but removing block noise from every block using a deblocking filter imposes a significant load on the deblocking filter. This load is therefore reduced by determining whether coding distortion removal (deblocking) is necessary, and applying a deblocking filter only when needed.

1 . A coding distortion removal method for removing coding distortion from a picture, whereby when a motion compensation block size is larger than a coding block size, coding distortion is removed by using different methods at a block boundary depending on whether the boundary is a motion compensation block boundary or not.  
     
     
         2 . A coding distortion removal method as described in  claim 1 , wherein when coded motion compensation error is 0, coding distortion is removed only at the motion compensation block boundary.  
     
     
         3 . A coding distortion removal method for removing coding distortion from a picture, comprising: 
 a step for extracting picture parameters from a picture containing coding distortion;    a first step for identifying pixels for coding distortion removal using the picture parameters;    a second step for identifying a method for coding distortion removal using the picture parameters; and    a third step for removing coding distortion from the pixels identified by the first step using the coding distortion removal method identified by the second step.    
     
     
         4 . A coding distortion removal method for removing coding distortion from a picture, whereby pixels to be coding distortion removal processed are identified by block based determination whether to remove coding distortion, and pixel based determination whether to remove coding distortion for each pixel in the blocks determined to be removed by the block based determination.  
     
     
         5 . A coding distortion removal method for removing coding distortion in an area disposed on both sides of a block boundary between a first block and an adjacent second block in a picture having a plurality of blocks forming a moving picture image, comprising: 
 a comparison step for comparing a difference of pixel values of the first block and pixel values of the second block, and a parameter, corresponding to an average of a quantization parameter for the first block and a quantization parameter for the second block, for determining the method for removing coding distortion; and    a removal step for removing coding distortion based on the result from the comparison step.    
     
     
         6 . A coding distortion removal method for removing coding distortion in an area disposed on both sides of a boundary line between a first block and an adjacent second block in a picture having a plurality of blocks forming a moving picture image, comprising: 
 a decoding step for decoding a parameter for setting a threshold value when removing coding distortion;    a comparison step for comparing a difference of pixel values in pixels of the first block and pixel values in pixels of the second block, and a specific threshold value based on the decoded parameter; and    a removal step for switching the method for removing coding distortion based on the result from the comparison step.    
     
     
         7 . A coding distortion removal method as described in  claim 6 , wherein: 
 the moving picture comprises a slice containing plural blocks; and    the parameter is stored in slice header information in a code stream obtained by encoding image data for the moving picture.    
     
     
         8 . A moving picture coding apparatus for picture coding with reference to at least one of multiple reference images, wherein a plurality of coded images obtained by removing coding distortion using plural methods are the reference images.  
     
     
         9 . A moving picture coding apparatus as described in  claim 8 , wherein a first method of the plural methods is a method that does not remove coding distortion in the coded picture, and 
 a second method is a method that removes coding distortion in the coded picture.    
     
     
         10 . A moving picture decoding apparatus for decoding with reference to at least one of multiple reference images, wherein a plurality of decoded images obtained by removing coding distortion using plural methods are the reference images.  
     
     
         11 . A moving picture decoding apparatus as described in  claim 10 , wherein a first method of the plural methods is a method that does not remove coding distortion in the decoded picture, and 
 a second method is a method that removes coding distortion in the decoded picture.    
     
     
         12 . A picture coding apparatus, wherein the coding distortion removal unit removes coding distortion by a method as described in any one of  claims 1  to  7 , said picture coding apparatus comprising: 
 a decoding unit for decoding a coded difference picture and outputting the difference picture;  
 a motion compensation unit for outputting a motion compensated picture from a reference image;  
 an adder for adding the difference picture and motion compensated picture, and outputting the merged picture;  
 a coding distortion removal unit for removing coding distortion in the merged picture and outputting a reconstructed picture; and  
 memory for storing the reconstructed picture as the reference image.  
 
     
     
         13 . A program for removing coding distortion from a picture, wherein coding distortion is removed by a method as described in any one of  claims 1  to  7 .  
     
     
         14 . A program for picture coding using a decoding unit for decoding a coded difference picture and outputting the difference picture; 
 a motion compensation unit for outputting a motion compensated picture from a reference image;    an adder for adding the difference picture and motion compensated picture, and outputting the merged picture;    a coding distortion removal unit for removing coding distortion in the merged picture and outputting a reconstructed picture; and    memory for storing the reconstructed picture as the reference image;    whereby coding distortion removal by the coding distortion removal unit using a method as described in any one of  claims 1  to  7  is executed on a computer.