Film grain simulation method

Abstract

Briefly, in accordance with a preferred embodiment of the present principles, simulation of a block of film grain for addition to a block of an image occurs by first establishing at least one image parameter in accordance with at least one attribute of the block. Thereafter, a block of film grain is established in accordance with the image parameter. Deblocking filtering can be applied to the film grain block.

1 . A method for simulating a film grain block for addition to a block of an image, comprising the steps of: 
 establishing at least one parameter at least in part in accordance with an attribute of the block; and    establishing at least one block of film grain in accordance with the at least one parameter.    
   
   
       2 . The method according to  claim 1  further including the step of deblocking filtering the film grain block  [JL3]   
   
   
       3 . The method according to  claim 1  wherein the step of establishing at least one block of film grain comprises the steps of: 
 providing a plurality of film grain patterns for selection; and    selecting from among the plurality of film grain patterns a source pattern;    selecting from the source pattern a block of film grain.    
   
   
       4 . The method according to  claim 1  wherein the at least one image parameter comprises average pixel intensity.  
   
   
       5 . The method according to  claim 4  further comprising the step of thresholding the average pixel intensity in accordance with upper and lower pixel intensity thresholds contained in supplemental information accompanying the image.  
   
   
       6 . The method according to  claim 3  wherein the step of selecting the film grain block from the film grain pattern further comprises the step of randomly selecting the film grain block.  
   
   
       7 . The method according to  claim 6  wherein the step of randomly selecting the film grain block from the film grain pattern comprises the steps of: 
 generating first and second pseudo-random numbers;    generating first and second offsets within the film grain pattern based on the first and second pseudo-random numbers; and    extracting the film grain block at a location in the film grain pattern specified by the first and second offsets.    
   
   
       8 . The method according to  claim 7  further comprising the step of scaling the extracted film grain block.  
   
   
       9 . The method according to  claim 7  wherein the step of generating the first and second numbers further comprises the steps of: 
 seeding a shift register with a seed value selected in accordance with a color component of the macroblock, and    extracting a set of most significant bits as the first random number; and    extracting a set of least significant bits as the second random number.    
   
   
       10 . The method according to  claim 3  wherein the step of providing a plurality of film grain patterns for selection further comprises the step of populating a database of pre-determined film grain patterns.  
   
   
       11 . The method according to  claim 1  further comprising the step of blending the deblocked film grain pattern with the image block.  
   
   
       12 . The method according to  claim 1  wherein the deblocking step further comprises the step of deblocking the vertical edges between adjacent blocks of film grain.  
   
   
       13 . A method for simulating film grain in a 4:2:0 chroma format in at least one block of an image, comprising the steps of: 
 establishing at least one film grain parameter in 4:4:4 chroma format in accordance with at least one attribute of the at least one block; and    deriving a film grain block from a database of film grain patterns by randomly selecting the film grain block from the database in accordance with the at least one film grain parameter;    
   
   
       14 . The method according to  claim 13  further comprising the step of deblocking at least a portion of the derived film grain block [JL5] .  
   
   
       15 . The method according to  claim 13  further comprising the step of blending the deblocked film grain block with the at least one image block [JL6] .  
   
   
       16 . Apparatus for simulating a film grain block for addition to a block of an image, comprising: 
 a film grain simulator for establishing at least one parameter at least in part in accordance with an attribute of the block, and for establishing at least one block of film grain in accordance with the parameter    
   
   
       17 . The apparatus according to  claim 16  further comprising a deblocking filter for deblocking filtering the film grain block [JL7] .  
   
   
       18 . The apparatus according to  claim 16  wherein the film grain simulator further comprises: 
 a database providing a plurality of film grain patterns for selection;    means for selecting from among the plurality of film grain patterns a source pattern; and    means for selecting from the source pattern a block of film grain.    
   
   
       19 . The apparatus according to  claim 16  wherein the at least one image parameter comprises average pixel intensity.  
   
   
       20 . The apparatus according to claim method 19 further including means for thresholding the average pixel intensity in accordance with upper and lower pixel intensity thresholds contained in supplemental information accompanying the image.  
   
   
       21 . The apparatus according to  claim 18  wherein the means for selecting the film grain block from the film grain pattern further comprises means for randomly selecting the film grain block.  
   
   
       22 . The apparatus according to  claim 21  wherein the means for randomly selecting the film grain block from the film grain pattern comprises: 
 means for generating first and second pseudo-random numbers;    means for generating first and second offsets within the film grain pattern based on the first and second pseudo-random numbers; and    means for extracting the film grain block at a location in the film grain pattern specified by the first and second offsets.    
   
   
       23 . The apparatus according to  claim 22  further comprising means for scaling the extracted film grain block.  
   
   
       24 . The apparatus according to  claim 22  wherein the means for generating the first and second pseudo random numbers further comprises: 
 a shift register seeded with a value selected in accordance with a color component of the macroblock, for yielding a set of most significant bits as the first random number and a set of least significant bits as the second random number.    
   
   
       25 . The apparatus according to  claim 18  wherein the database includes predetermined film grain patterns.  
   
   
       26 . The apparatus according to  claim 16  further comprises means for blending the deblocked film grain pattern with the macroblock.  
   
   
       27 . The apparatus according to  claim 17  wherein the deblocking filter deblocks vertical edges between adjacent blocks of film grain.