Method and apparatus for visual lossless image syntactic encoding

Abstract

A visual perception threshold unit for image processing identifies a plurality of visual perception threshold levels to be associated with the pixels of a video frame, wherein the threshold levels define contrast levels above which a human eye can distinguish a pixel from among its neighboring pixels of the video frame. The present invention also includes a method of generating visual perception thresholds by analysis of the details of the video frames, estimating the parameters of the details, and defining a visual perception threshold for each detail in accordance with the estimated detail parameters. The present invention further includes a method of describing images by determining which details in the image can be distinguished by the human eye and which ones can only be detected by it.

1. A visual perception threshold unit for image processing, the threshold unit comprising:
 a parameter generator to generate a multiplicity of parameters that describe at least some of the  information content of at least one video frame to be processed; and  
 a threshold generator to generate from said parameters, a plurality of visual perception threshold levels to be associated with the  pixels of the at least one video frame,  
 wherein said threshold levels define contrast levels above which a human eye can distinguish a pixel from among its neighboring pixels of said at least one video frame.  
 
     
     
       2. A unit according to  claim 1  and , wherein said parameter generator comprises at least one of the following units:
 a volume unit which determines the  a volume of information in said at least one video frame;  
 a color unit which determines a per pixel color; and  
 an intensity unit which determines a cross-frame change of intensity.  
 
     
     
       3. A method of generating visual perception thresholds for image processing implemented by one or more elements of a video encoding device, the method comprising:
 analyzing details of frames of a video signal;  
 estimating parameters of said details; and  
 defining a visual perception threshold for each of said details in accordance with said estimated detail parameters,  
 
       wherein said estimating comprises at least one of the following:
 determining a per-pixel signal intensity change between a current frame and a previous frame, normalized by a maximum intensity;  
 determining a normalized volume of intraframe change by high frequency filtering of said current frame, summing the intensities of said filtered frame and normalizing the resultant sum by the  a maximum possible amount of information within a frame;  
 generating a volume of inter-frame changes between a  said current frame and its  said previous frame normalized by said maximum possible amount of information volume  within a frame;  
 generating a normalized volume of inter-frame changes for a group of pictures  frames from the output of said previous step of generating;  
 evaluating a signal-to-noise ratio by high pass filtering a difference frame between said current frame and its  said previous frame by selecting those  intensities of said difference frame lower than a threshold defined as three times a noise level under which noise intensities are not perceptible to the human eye, summing the intensities of the pixels in the filtered difference frame and normalizing said sum by said maximum intensity and by the  a total number of pixels in a frame;  
 generating a normalized intensity value per-pixel;  
 generating a per-pixel color saturation level;  
 generating a per-pixel hue value; and  
 determining a per-pixel response to said hue value.  
 
     
     
       4. A method for describing an image implemeneted by one or more elements of a video encoding device, the method comprising
 determining which details in said image can be distinguished by the human eye and which ones can only be detected by it;  
 providing one bit to describe a pixel which can only be detected by the human eye; and  
 providing three bits to describe a pixel which can be distinguished by the human eye.  
 
     
     
       5. A video compression system comprising:
   a parameter generator to generate one or more parameters that describe information content of a video frame; and        a threshold generator to generate, from at least one of the parameters, a plurality of visual perception threshold levels to be associated with pixels of the video frame, wherein said threshold levels define contrast levels above which a pixel of the video frame can be visually distinguished from its neighboring pixels of the video frame.      
     
     
       6. A video compression system according to  claim 5 , wherein the parameter generator comprises a volume unit configured to determine a volume of information in the video frame.  
     
     
       7. A video compression system according to  claim 5 , wherein the parameter generator comprises a color unit configured to determine a per pixel color.  
     
     
       8. A video compression system according to  claim 5 , wherein the parameter generator comprises an intensity unit configured to determine a cross- frame change of intensity.    
     
     
       9. A video compression system according to  claim 5 , wherein the parameter generator and the threshold generator are implemented in a field programmable gate array ( FPGA ).  
     
     
       10. A video encoder comprising:
   a parameter generator to generate multiple parameters that describe information content of a video frame; and        a threshold generator to generate, from at least one of the multiple parameters, a plurality of visual perception threshold levels to be associated with pixels of the video frame, wherein said threshold levels define contrast levels above which a pixel of the video frame can be visually distinguished from its neighboring pixels of the video frame.      
     
     
       11. A video encoder according to  claim 10 , wherein the parameter generator comprises a volume unit configured to determine a volume of information in the video frame.  
     
     
       12. A video encoder according to  claim 10 , wherein the parameter generator comprises a color unit configured to determine a per pixel color.  
     
     
       13. A video encoder according to  claim 10 , wherein the parameter generator comprises an intensity unit configured to determine a cross- frame change of intensity.    
     
     
       14. A video encoder according to  claim 10 , wherein the video encoder is embodied in a field programmable gate array ( FPGA ).  
     
     
       15. A video encoder according to  claim 10 , wherein the video encoder comprises a visual lossless syntactic encoder.  
     
     
       16. A system comprising:
   means for generating one or more parameters that describe information content of a video frame; and        means for generating, from at least one of the parameters, a plurality of visual perception threshold levels to be associated with pixels of the video frame, wherein said threshold levels define contrast levels above which a pixel of the video frame can be visually distinguished from its neighboring pixels of the video frame.      
     
     
       17. A system according to  claim 16 , wherein the one or more parameters are associated with at least one of:
   a volume of information in the video frame;        a cross - frame change of intensity; or        a per pixel color.      
     
     
       18. A system according to  claim 16 , wherein the system is embodied in a field programmable gate array ( FPGA ).  
     
     
       19. A video compression system comprising:
   means for analyzing one or more details associated with one or more frames of a video signal;        means for estimating parameters of individual analyzed details; and        means for defining a visual perception threshold for individual analyzed details in accordance with at least one of the estimated parameters,        wherein said means for estimating comprises at least one of:      means for determining a per - pixel signal intensity change between a current frame and a previous frame, normalized by a maximum intensity;        means for determining a normalized volume of intraframe change by high frequency filtering of said current frame, summing the intensities of said filtered frame and normalizing the resultant sum by a maximum possible amount of information within a frame;        means for generating a volume of inter - frame changes between said current frame and said previous frame normalized by said maximum possible amount of information within a frame;        means for generating a normalized volume of inter - frame changes within a group of frames normalized by said maximum possible amount of information within a frame and by a number of frames comprising said group of frames;        means for evaluating a signal - to - noise ratio by high pass filtering a difference frame between said current frame and said previous frame by selecting intensities of said difference frame lower than a threshold defined as three times a noise level under which noise intensities are not visually perceptible, summing the intensities of pixels in the filtered difference frame and normalizing said sum by said maximum intensity and by the total number of pixels in a frame;        means for generating a normalized intensity value per - pixel;        means for generating a per - pixel color saturation level;        means for generating a per - pixel hue value; or        means for determining a per - pixel response to said hue value.        
     
     
       20. A video compression system according to  claim 19 , embodied in a field programmable gate array ( FPGA ).  
     
     
       21. A method implemented by one or more elements of a video encoding device comprising:
   identifying one or more distinguishable details in an image, individual distinguishable details being associated with a contrast level at which a pixel can be visually distinguished from among its neighboring pixels;        using a plurality of bits to describe individual identified distinguishable details; and        using less than said plurality of bits to describe one or more individual details in the image not identified as distinguishable.      
     
     
       22. A method according to  claim 21 , further comprising identifying the one or more of the individual details in the image not identified as distinguishable as being visually detectable.  
     
     
       23. A method according to  claim 21 , wherein using the plurality of bits comprises using three bits.  
     
     
       24. A method according to  claim 21 , further comprising performing the identifying, the using the plurality of bits, and the using less than said plurality of bits by the one or more elements embodied in a field programmable gate array ( FPGA ).  
     
     
       25. A system comprising:
   means for identifying one or more distinguishable details in an image, individual distinguishable details being associated with a contrast level at which a pixel can be visually distinguished from among its neighboring pixels;        means for using a plurality of bits to describe individual identified distinguishable details; and        means for using less than said plurality of bits to describe one or more individual details in the image not identified as distinguishable.      
     
     
       26. A system according to  claim 25 , wherein one or more of the individual details in the image not identified as distinguishable are identified as being visually detectable.  
     
     
       27. A system according to  claim 25 , wherein the plurality of bits comprises three bits.  
     
     
       28. A system according to  claim 25  comprising part of a field programmable gate array ( FPGA ).  
     
     
       29. A visual perception threshold unit according to  claim 1 , wherein one or both of the parameter generator or the threshold generator are implemented in a video encoder.  
     
     
       30. A visual perception threshold unit according to  claim 29 , wherein the video encoder comprises a visual lossless syntactic encoder.  
     
     
       31. A visual perception threshold unit according to  claim 1  comprising part of a field programmable gate array ( FPGA ).