Method and system for improving compressed image chroma information

Abstract

Methods, systems, and computer programs for improving compressed image chroma information. In one aspect of the invention, a resolution for a red color component of a color video image is used that is higher than the resolution for a blue color component of the color video image. Another aspect includes utilizing a lower or higher value of a quantization parameter (QP) for one or more chroma channels as compared to the luminance channel. Another aspect is use of a logarithmic representation of a video image to benefit image coding. Another aspect uses more than two chroma channels to represent a video image.

What is claimed is:  
     
         1 . A method for compressing image chroma information of a color video image in a video image compression system, including selecting a resolution for a red color component of the color video image that is higher than the resolution for a blue color component of the color video image.  
     
     
         2 . A method for compressing image chroma information of a color video image in a video image compression system, including: 
 (a) downfiltering a blue color component of the color video image to a processed blue color component having a first resolution along at least one of the horizontal and vertical image axes of the color video image; and    (b) filtering a red color component of the color video image to a processed red color component having a second resolution higher than the first resolution.    
     
     
         3 . The method of  claim 2 , wherein the second resolution is in the range from 0.5 to 1.0 of the full resolution of the red color component along at least one of the horizontal and vertical image axes of the color video image.  
     
     
         4 . The method of  claim 2 , further including compressing at least the processed blue color and red color components to a compressed output image.  
     
     
         5 . The method of  claim 4 , further including decompressing the compressed output image to obtain uncompressed processed blue and red color components.  
     
     
         6 . The method of  claim 5 , further including upsize filtering the processed blue and red color components to the full resolution of the color video image.  
     
     
         7 . The method of claims  1  or  2 , wherein the video image compression system is a motion-compensated video image compression system.  
     
     
         8 . A method for reducing chroma noise during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, including utilizing a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is less than the first QP value.  
     
     
         9 . The method of  claim 8 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         10 . The method of  claim 8 , further including compressing the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         11 . The method of  claim 10 , further including decompressing the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         12 . A method for achieving higher compression during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, including utilizing a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is greater than the first QP value.  
     
     
         13 . The method of  claim 12 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         14 . The method of  claim 12 , further including compressing the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         15 . The method of  claim 14 , further including decompressing the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         16 . A method for improving the coding efficiency for a color space representation of a video image originally represented as linear RGB pixel values in a video image compression system, including transforming the linear RGB pixel values of the video image to a logarithmic representation of luminance and chroma channel information.  
     
     
         17 . The method of  claim 16 , wherein transforming includes applying the following equations to obtain a YUV logarithmic representation of the video image: 
 Ylog=Log(Wr*R+Wg*G+Wb*B)    U chroma channel=Log(R)−Ylog    V chroma channel=Log(B)−Ylog    where Wr, Wg, and Wb are linear weightings for red, green, and blue components of luminance of the video image.    
     
     
         18 . The method of  claim 17 , further including reducing the resolution of the U and V chroma channels of the YUV logarithmic representation.  
     
     
         19 . The method of  claim 17 , further including compressing the YUV logarithmic representation of the video image to a compressed video image.  
     
     
         20 . The method of  claim 19 , further including decompressing the compressed video image to a restored YUV logarithmic representation of the video image.  
     
     
         21 . The method of  claim 20 , further including transforming restored YUV logarithmic representation of the video image to linear RGB pixel values.  
     
     
         22 . The method of  claim 21 , wherein transforming includes applying the following equations to obtain the linear RGB pixel values: 
 R=anti-log(Y+U)    B=anti-log(Y+V)    G=(anti-log(Y)−Wr*R−Wb*B)/Wg.    
     
     
         23 . A method for improving the video characteristics of a color video image in a video compression system, including: 
 (a) selecting a set of image channels to represent the color video image, including a luminance channel and n chroma channels, where n is at least three; and    (b) compressing the luminance channel and the n additional chroma channels to a compressed video image.    
     
     
         24 . The method of  claim 23 , wherein at least one chroma channel represents non-visible wavelengths.  
     
     
         25 . The method of  claim 23 , wherein the luminance channel is the image channel having the highest dynamic range and resolution.  
     
     
         26 . The method of  claim 23 , further including coding each chroma channel independently from each other channel.  
     
     
         27 . The method of  claim 23 , further including coding each chroma channel differentially with respect to a selected other channel.  
     
     
         28 . The method of  claim 23 , further including reducing the resolution of at least one chroma channel.  
     
     
         29 . The method of  claim 23 , further including applying a quantization parameter (QP) value to at least one chroma channel biased with respect to a QP value applied to the luminance channel.  
     
     
         30 . A computer program, stored on a computer-readable medium, for compressing image chroma information of a color video image in a video image compression system, the computer program comprising instructions for causing a computer to permit selection of a resolution for a red color component of the color video image that is higher than the resolution for a blue color component of the color video image.  
     
     
         31 . A computer program, stored on a computer-readable medium, for compressing image chroma information of a color video image in a video image compression system, the computer program comprising instructions for causing a computer to: 
 (a) downfilter a blue color component of the color video image to a processed blue color component having a first resolution along at least one of the horizontal and vertical image axes of the color video image; and    (b) filter a red color component of the color video image to a processed red color component having a second resolution higher than the first resolution.    
     
     
         32 . The computer program of  claim 31 , wherein the second resolution is in the range from 0.5 to 1.0 of the full resolution of the red color component along at least one of the horizontal and vertical image axes of the color video image.  
     
     
         33 . The computer program of  claim 31 , further including instructions for causing the computer to compress at least the processed blue color and red color components to a compressed output image.  
     
     
         34 . The computer program of  claim 33 , further including instructions for causing a decompression computer to decompress the compressed output image to obtain uncompressed processed blue and red color components.  
     
     
         35 . The computer program of  claim 34 , further including instructions for causing the decompression computer to upsize filter the processed blue and red color components to the full resolution of the color video image.  
     
     
         36 . The computer program of claims  30  or  31 , wherein the video image compression system is a motion-compensated video image compression system.  
     
     
         37 . A computer program, stored on a computer-readable medium, for reducing chroma noise during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, the computer program comprising instructions for causing a computer to utilize a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is less than the first QP value.  
     
     
         38 . The computer program of  claim 37 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         39 . The computer program of  claim 37 , further including instructions for causing the computer to compress the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         40 . The computer program of  claim 39 , further including instructions for causing a decompression computer to decompress the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         41 . A computer program, stored on a computer-readable medium, for achieving higher compression during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, the computer program comprising instructions for causing a computer to utilize a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is greater than the first QP value.  
     
     
         42 . The computer program of  claim 41 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         43 . The computer program of  claim 41 , further including instructions for causing the computer to compress the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         44 . The computer program of  claim 14 , further including instructions for causing a decompression computer to decompress the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         45 . A computer program, stored on a computer-readable medium, for improving the coding efficiency for a color space representation of a video image originally represented as linear RGB pixel values in a video image compression system, the computer program comprising instructions for causing a computer to transform the linear RGB pixel values of the video image to a logarithmic representation of luminance and chroma channel information.  
     
     
         46 . The computer program of  claim 45 , wherein the instructions for causing the computer to transform include instructions for causing the computer to apply the following equations to obtain a YUV logarithmic representation of the video image: 
 Ylog=Log(Wr*R+Wg*G+Wb*B)    U chroma channel=Log(R)−Ylog    V chroma channel=Log(B)−Ylog    where Wr, Wg, and Wb are linear weightings for red, green, and blue components of luminance of the video image.    
     
     
         47 . The computer program of  claim 46 , further including instructions for causing the computer to reduce the resolution of the U and V chroma channels of the YUV logarithmic representation.  
     
     
         48 . The computer program of  claim 46 , further including instructions for causing the computer to compress the YUV logarithmic representation of the video image to a compressed video image.  
     
     
         49 . The computer program of  claim 48 , further including instructions for causing a decompression computer to decompress the compressed video image to a restored YUV logarithmic representation of the video image.  
     
     
         50 . The computer program of  claim 49 , further including instructions for causing the decompression computer to transform restored YUV logarithmic representation of the video image to linear RGB pixel values.  
     
     
         51 . The computer program of  claim 50 , wherein the instructions for causing the computer to transform includes instructions for causing the computer to apply the following equations to obtain the linear RGB pixel values: 
 R=anti-log(Y+U)    B=anti-log(Y+V)    G=(anti-log(Y)−Wr*R−Wb*B)/Wg.    
     
     
         52 . A computer program, stored on a computer-readable medium, for improving the video characteristics of a color video image in a video compression system, the computer program comprising instructions for causing a computer to: 
 (a) select a set of image channels to represent the color video image, including a luminance channel and n chroma channels, where n is at least three; and    (b) compress the luminance channel and the n additional chroma channels to a compressed video image.    
     
     
         53 . The computer program of  claim 52 , wherein at least one chroma channel represents non-visible wavelengths.  
     
     
         54 . The computer program of  claim 52 , wherein the luminance channel is the image channel having the highest dynamic range and resolution.  
     
     
         55 . The computer program of  claim 52 , further including instructions for causing a computer to code each chroma channel independently from each other channel.  
     
     
         56 . The computer program of  claim 52 , further including instructions for causing a computer to code each chroma channel differentially with respect to a selected other channel.  
     
     
         57 . The computer program of  claim 52 , further including instructions for causing a computer to reduce the resolution of at least one chroma channel.  
     
     
         58 . The computer program of  claim 52 , further including instructions for causing a computer to apply a quantization parameter (QP) value to at least one chroma channel biased with respect to a QP value applied to the luminance channel.  
     
     
         59 . A system for compressing image chroma information of a color video image a video image compression system, including: 
 (a) means for selecting a resolution for a red color component of the color video image that is higher than the resolution for a blue color component of the color video image; and    (b) means for applying the selected resolution to compress the color video image.    
     
     
         60 . A system for compressing image chroma information of a color video image in a video image compression system, including means for: 
 (a) downfiltering a blue color component of the color video image to a processed blue color component having a first resolution along at least one of the horizontal and vertical image axes of the color video image; and    (b) filtering a red color component of the color video image to a processed red color component having a second resolution higher than the first resolution.    
     
     
         61 . The system of  claim 60 , wherein the second resolution is in the range from 0.5 to 1.0 of the full resolution of the red color component along at least one of the horizontal and vertical image axes of the color video image.  
     
     
         62 . The system of  claim 60 , further including means for compressing at least the processed blue color and red color components to a compressed output image.  
     
     
         63 . The system of  claim 62 , further including means for decompressing the compressed output image to obtain uncompressed processed blue and red color components.  
     
     
         64 . The system of  claim 63 , further including means for upsize filtering the processed blue and red color components to the full resolution of the color video image.  
     
     
         65 . The system of claims  59  or  60 , wherein the video image compression system is a motion-compensated video image compression system.  
     
     
         66 . A system for reducing chroma noise during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, including 
 (a) means for utilizing a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is less than the first QP value; and    (b) means for applying the selected QP values during compression of the color video image.    
     
     
         67 . The system of  claim 66 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         68 . The system of  claim 66 , further including means for compressing the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         69 . The system of  claim 68 , further including means for decompressing the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         70 . A system for achieving higher compression during compression of a color video image in a YUV video image compression system utilizing a quantization parameter (QP) during compression, including: 
 (a) means for utilizing a first QP value for the Y color channel of a color video image, and a second QP value for at least one of the U and V color channels of the color video image, wherein the second QP value is greater than the first QP value    (b) means for applying the selected QP values during compression of the color video image.    
     
     
         71 . The system of  claim 70 , wherein the second QP value is determined by applying a bias value to the first QP value.  
     
     
         72 . The system of  claim 70 , further including means for compressing the color video image, after application of the first and second QP values, to a compressed output image.  
     
     
         73 . The system of  claim 72 , further including means for decompressing the compressed output image using the first and second QP values to obtain an uncompressed video image.  
     
     
         74 . A system for improving the coding efficiency for a color space representation of a video image originally represented as linear RGB pixel values in a video image compression system, including: 
 (a) means for inputting linear RGB pixel values of a video image; and    (b) means for transforming the linear RGB pixel values of the video image to a logarithmic representation of luminance and chroma channel information.    
     
     
         75 . The system of  claim 74 , wherein transforming includes applying the following equations to obtain a YUV logarithmic representation of the video image: 
 Ylog=Log(Wr*R+Wg*G+Wb*B)    U chroma channel=Log(R)−Ylog    V chroma channel=Log(B)−Ylog    where Wr, Wg, and Wb are linear weightings for red, green, and blue components of luminance of the video image.    
     
     
         76 . The system of  claim 75 , further including means for reducing the resolution of the U and V chroma channels of the YUV logarithmic representation.  
     
     
         77 . The system of  claim 75 , further including means for compressing the YUV logarithmic representation of the video image to a compressed video image.  
     
     
         78 . The system of  claim 77 , further including means for decompressing the compressed video image to a restored YUV logarithmic representation of the video image.  
     
     
         79 . The system of  claim 78 , further including means for transforming restored YUV logarithmic representation of the video image to linear RGB pixel values.  
     
     
         80 . The system of  claim 79 , wherein transforming includes applying the following equations to obtain the linear RGB pixel values: 
 R=anti-log(Y+U)    B=anti-log(Y+V)    G=(anti-log(Y)−Wr*R−Wb*B)/Wg.    
     
     
         81 . A system for improving the video characteristics of a color video image in a video compression system, including means for: 
 (a) selecting a set of image channels to represent the color video image, including a luminance channel and n chroma channels, where n is at least three; and    (b) compressing the luminance channel and the n additional chroma channels to a compressed video image.    
     
     
         82 . The system of  claim 81 , wherein at least one chroma channel represents non-visible wavelengths.  
     
     
         83 . The system of  claim 81 , wherein the luminance channel is the image channel having the highest dynamic range and resolution.  
     
     
         84 . The system of  claim 81 , further including means for coding each chroma channel independently from each other channel.  
     
     
         85 . The system of  claim 81 , further including means for coding each chroma channel differentially with respect to a selected other channel.  
     
     
         86 . The system of  claim 81 , further including means for reducing the resolution of at least one chroma channel.  
     
     
         87 . The system of  claim 81 , further including means for applying a quantization parameter (QP) value to at least one chroma channel biased with respect to a QP value applied to the luminance channel.