In the paper we advocate image compression technique in the scope of distributed source coding framework. The novelty of the proposed approach is twofold: classical image compression is considered from the positions o...
详细信息
ISBN:
(纸本)0819452114
In the paper we advocate image compression technique in the scope of distributed source coding framework. The novelty of the proposed approach is twofold: classical image compression is considered from the positions of source coding with side information and, contrarily to the existing scenarios, where side information is given explicitly, side information is created based on deterministic approximation of local image features. We consider an image in the transform domain as a realization of a source with a bounded codebook of symbols where each symbol represents a particular edge shape. The codebook is image independent and plays the role of auxiliary source. Due to the partial availability of side information at both encoder and decoder we treat our problem as a modification of Berger-Flynn-Gray problem and investigate a possible gain over the solutions when side information is either unavailable or available only at decoder. Finally. we present a practical compression algorithm for passport photo images based on our concept that demonstrates the superior performance in very low bit rate regime.
It is well known that trellis lossy source codes have better performance/complexity tradeoff than block codes, as shown by simulations. This makes the trellis coding technique attractive in practice. To get a better u...
详细信息
It is well known that trellis lossy source codes have better performance/complexity tradeoff than block codes, as shown by simulations. This makes the trellis coding technique attractive in practice. To get a better understanding of this fact, this paper studies the redundancy of trellis coding for memoryless sources and compares it with a similar result for block codes. It was known that for block codes of block length n, the nth-order distortion redundancy D-n(R) at fixed rate R greater than or equal to 0 equals - partial derivatived(p, R/partial derivativeR) ln n/2n + o(ln n/n), where partial derivatived(p, R/partial derivativeR) is the partial derivative of d(p, R), the distortion-rate function of a source p, evaluated at R and assumed to exist. Since e(nR), the number of codewords of the block code, can be used as an approximate measure of both the storage complexity C-s of the code and the computational complexity C-c per source symbol for full search encoding, the redundancy can be written as functions of the complexity measures in the form D(R, C-s) approximate to partial derivatived(p, R)/partial derivativeR R ln ln C-s/2 ln C-s and D(R, C-s) approximate to partial derivatived(p, R)/partial derivativeR R ln ln C-c/2 ln C-c In this paper, it is demonstrated that for a particular trellis lossy source code with storage complexity C-s = e(2nR) and computational complexity C-c = e(2nR) (assuming the Viterbi algorithm is used for encoding), the distortion redundancy satisfies D-n(R) less than or equal to c(p, R)/n where c(p, R) is a constant independent of n. For this code, the complexity/redundancy tradeoff can be written as D(R, C-s) approximate to 2Rc(p, R)/ln C-c + o(1/ln C-s) and D(R, C-c) approximate to 2Rc(p, R)/ln C-c + o(1/ln C-c) which shows that trellis coding improves the redundancy/complexity tradeoff over block coding by roughly a factor ln ln C-c.
The redundancy problem of universal lossy source coding at a fixed rate level is considered. Under some condition on the single-letter distortion measure, which implies that the cardinality K of the reproduction alpha...
详细信息
The redundancy problem of universal lossy source coding at a fixed rate level is considered. Under some condition on the single-letter distortion measure, which implies that the cardinality K of the reproduction alphabet is not greater than the cardinality J of the source alphabet, it is shown that the redundancy of universally coding memoryless sources p by nth-order block codes of rate R goes like \(partial derivative/partial derivativeR)d(p, R)\K In n/2n + o(ln n/n) for all memoryless sources p except a set whose volume goes to 0 as the block length n goes to infinity, where d(p, R) denotes the distortion rate function of p. Specifically, for any sequence {C-n}(n=1)(infinity) of block codes, where C-n is an nth-order block code at the fixed rate R, and any epsilon > 0, the redundancy D-n(C-n, p) of C-n for p is greater than or equal to \(partial derivative/partial derivativeR)d(p, R)\(K - epsilon) In n/2n for all p satisfying some regular conditions except a set whose volume goes to ) as n --> infinity. On the other hand, there exists a sequence {C-n}(n=1)(infinity), of block codes at the rate R such that for any p satisfying some regular conditions, the super limit of D-n(C-n,p)/(ln n/n) is less than or equal to \(partial derivative/partial derivativeR)d(p, R)\K/2.
The redundancy problem of lossy source coding with abstract source and reproduction alphabets is considered. For coding at a fixed rate level, it is shown that for any fixed rate R > 0 and any memoryless abstract a...
详细信息
The redundancy problem of lossy source coding with abstract source and reproduction alphabets is considered. For coding at a fixed rate level, it is shown that for any fixed rate R > 0 and any memoryless abstract alphabet source P satisfying some mild conditions, there exists a sequence {Cn}(n=1)(infinity) of block codes at the rate R such that the distortion redundancy of C-n (defined as the difference between the performance of C-n and the distortion rate function d(P, R) of P] is upper-bounded by \partial derivative d(P, R)/partial derivative R\ ln n/2n + o (In n/n), For coding at a fixed distortion level, it is demonstrated that for any d > 0 and any memoryless abstract alphabet source P satisfying some mild conditions, there exists a sequence {C-n}(n=1)(infinity) of block codes at the fixed distortion d such that the rate redundancy of C-n, (defined as the difference between the performance of C-n and the rate distortion function R(P, d) of P) is upper-bounded by (7 ln n)/(6n) + o(ln n/n). These results strengthen the traditional Berger's abstract alphabet source coding theorem, and extend the positive redundancy results of Zhang, Yang, and Wei on lossy source coding with finite alphabets and the redundancy result of Wyner on block coding of memoryless Gaussian sources.
暂无评论