Reversible integer-to-integer mapping of N-point orthonormal block transforms

摘要

Reversible integer-to-integer (I2I) mapping of orthonormal transforms are vital for developing lossless coding with scalable decoding functionalities. A general framework for reversible I2I mapping of N-point, where N is a positive integer power of 2, orthonormal block transforms using recursive factorization of such transform matrices and the lifting scheme is presented. Designs include the discrete cosine transform (DCT) that maps integers to integers (I2I-DCT), the discrete sine transform that maps integers to integers (I2I-DST) and the Walsh-Hadamard transform that maps integer to integers (I2I-WHT). The main significant feature of these designs is that the transform coefficients are normalized according to the conventional scaling factors, which is vital for embedded coding, while preserving the integer-to-integer mapping and perfect reconstruction. This makes these transforms usable in both lossless and lossy image coding, especially in scalable lossless coding. These generic N-point design of the above transforms enables evaluating the effect of block sizes of such transforms in lossless coding. The performance is evaluated in terms of lossless image and video coding, quality scalable decoding, complexity and lifting step rounding effects.