Image sequence compression and decompression
First Claim
1. A method of compressing and decompressing a sequence of images, comprising the steps of:
- compressing the sequence of images into a compressed sequence, by performing the steps of;
digitizing each image in the sequence into an image frame comprising an array of intensity coefficients arranged in first and second directions;
performing an intraframe decomposition of each image frame by the steps of;
performing averaging and differencing of the image frame in a first direction to generate average and difference coefficient sequences;
downsampling the average and difference coefficient sequences;
performing averaging and differencing of the image frame in a second direction; and
downsampling sequences from the step of performing averaging and differencing of the image frame in the second direction, to generate a decomposed image frame;
performing an interframe decomposition of groups of decomposed image frames to generate a compressed sequence of image frames;
decompressing the compressed sequence of images into a reconstructed sequence, by performing the steps of;
performing an interframe reconstruction of the groups of decomposed image frames; and
then performing an intraframe reconstruction of each image frame by the steps of;
upsampling the average and difference coefficient sequences;
performing average and difference combining of the upsampled sequences in the second direction;
upsampling sequences resulting from the step of performing average and difference combining; and
performing averaging and differencing of the image frame in the first direction, to generate a reconstructed image frame;
wherein one of the intraframe decomposition and intraframe reconstruction steps further comprises;
performing Cholesky filtering upon coefficient sequences corresponding to the image frame.
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Abstract
A method and system for compressing and decompressing a sequence of image frames is disclosed. According to the disclosed embodiments of the invention, the compression process includes an intraframe decomposition process (24, 24'"'"') performed upon each frame in both the row and column directions, including an mth order averaging and differencing operation (56, 62). Each frame is then combined with others in an adjacent pair or group of four by way of an interframe decomposition (28). Quantization (30) is then performed, preferably by division of each coefficient by a quantizer (ρ) associated with the one of the frequency component subbands containing the coefficient. Reconstruction of the compressed frames is accomplished by performing the inverse of the compression process. According to the disclosed embodiments, either the compression or decompression processes and systems performs Cholesky filtering (60, 66; 170, 172), preferably in a recursive manner by way of forward and backward filtering. In this way, one or the other of the compression system (CS) or decompression system (DS) is relieved from a significant amount of computing burden.
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Citations
16 Claims
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1. A method of compressing and decompressing a sequence of images, comprising the steps of:
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compressing the sequence of images into a compressed sequence, by performing the steps of; digitizing each image in the sequence into an image frame comprising an array of intensity coefficients arranged in first and second directions; performing an intraframe decomposition of each image frame by the steps of; performing averaging and differencing of the image frame in a first direction to generate average and difference coefficient sequences; downsampling the average and difference coefficient sequences; performing averaging and differencing of the image frame in a second direction; and downsampling sequences from the step of performing averaging and differencing of the image frame in the second direction, to generate a decomposed image frame; performing an interframe decomposition of groups of decomposed image frames to generate a compressed sequence of image frames; decompressing the compressed sequence of images into a reconstructed sequence, by performing the steps of; performing an interframe reconstruction of the groups of decomposed image frames; and then performing an intraframe reconstruction of each image frame by the steps of; upsampling the average and difference coefficient sequences; performing average and difference combining of the upsampled sequences in the second direction; upsampling sequences resulting from the step of performing average and difference combining; and performing averaging and differencing of the image frame in the first direction, to generate a reconstructed image frame; wherein one of the intraframe decomposition and intraframe reconstruction steps further comprises; performing Cholesky filtering upon coefficient sequences corresponding to the image frame. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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Specification