Memory-efficient parallelization of JPEG-LS with relaxed context update

Abstract

Many state-of-the-art lossless image compression standards feature adaptive error modelling. This, however, leads to data dependency loops of the compression scheme such that a parallel compression of neighboring pixels is not possible. In this paper, we propose a relaxation to the context update of JPEG-LS by delaying the update procedure, in order to achieve a guaranteed degree of parallelism with a negligible effect on the compression ratio. The lossless mode of JPEG-LS including the run-mode is considered. A descewing scheme is provided generating a bit-stream that preserves the order needed for the decoder to mimic the prediction in a consistent way. This system is memory efficient in a sense that no additional memory for the large context-set is needed.