Method and apparatus for video compression using block and wavelet techniques
First Claim
1. A method for compressing an image of a first color space, wherein said image is divided into a plurality of blocks, comprising the steps of:
- computing an average color of a block of said plurality of blocks, said block comprising a plurality of pixels;
computing an average luminance of said block dependent on said average color and a differential luminance of each pixel of said plurality of pixels of said block, wherein said differential luminance is the difference in luminance value between each particular luminance value of each said pixel of said plurality of pixels and a average luminance value of said block; and
, encoding a quantized average color difference and a second plurality of frequency details of said block, wherein said second plurality of frequency details is less than or equal to a first plurality of frequency details of said block.
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Abstract
A method and apparatus are disclosed for symmetrically compressing and decompressing video information in real time by coupling block and wavelet techniques. In the compression pipeline, the image is divided into blocks comprising 2k×2k pixels (in the preferred embodiment, k=1). The average color of each block is computed. The system computes an average luminance for each block and differential luminances of each pixel of the plurality of pixels of each block. A first plurality of frequency details of each block are determined by Haar transforming the differential luminances. The system computes an average color difference between each block and the preceding block, and quantizes the average color difference and the first plurality of frequency details using Lloyd-Max quantization. In an alternate embodiment, skip codes are generated for blocks having the same quantized average color difference and second plurality of frequency details. The quantized average color difference and a second plurality of frequency details are encoded using variable length codes. The system employs lookup tables to decompress the compressed image and to format output pixels. The output of the compression pipeline containing variable length codes is decoded into fixed-length codes, which are then decoded using a first lookup table into three device-independent components that represent each block. The three components index a second lookup table containing precomputed RGB values that include precomputed display dependent formatting to produce the output image. In the alternate embodiment, skip codes contained in the output of the variable length decoder are decoded.
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Citations
23 Claims
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1. A method for compressing an image of a first color space, wherein said image is divided into a plurality of blocks, comprising the steps of:
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computing an average color of a block of said plurality of blocks, said block comprising a plurality of pixels;
computing an average luminance of said block dependent on said average color and a differential luminance of each pixel of said plurality of pixels of said block, wherein said differential luminance is the difference in luminance value between each particular luminance value of each said pixel of said plurality of pixels and a average luminance value of said block; and
,encoding a quantized average color difference and a second plurality of frequency details of said block, wherein said second plurality of frequency details is less than or equal to a first plurality of frequency details of said block. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. An apparatus for compressing an image, said image comprising a plurality of blocks, comprising the steps of:
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average color computation means for computing an average color of a block of said plurality of blocks, said block comprising a plurality of pixels;
average and differential luminance computation means coupled to said average color computation means for computing an average luminance of said block dependent on said average color and a differential luminance of each pixel of said plurality of pixels of said block, wherein said differential luminance is the difference in luminance value between each particular luminance value of each said pixel of said plurality of pixels and a average luminance value of said block; and
,encoding means for variable length encoding of a quantized average color difference and a second plurality of frequency details of said block, wherein said second plurality of frequency details is less than or equal to a first plurality of frequency details of said block. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22)
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23. A method for compressing an image of a first color space, comprising the steps of:
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dividing said image into a plurality of blocks in image space, wherein said blocks are comprised of a plurality of adjacent pixels in image space;
computing an average color of a block of said plurality of blocks, said block comprising a plurality of pixels;
computing an average luminance of said block dependent on said average color and a differential luminance of each pixel of said plurality of pixels of said block, wherein said differential luminance is the difference in luminance value between each particular luminance value of each said pixel of said plurality of pixels and a average luminance value of said block; and
encoding a quantized average color difference and a second plurality of frequency details of said block, wherein said second plurality of frequency details is less than or equal to a first plurality of frequency details of said block.
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Specification