Fast embedded image coding technique using wavelet difference reduction

We propose two modified versions of the original wavelet difference reduction (WDR) algorithm proposed by Tian and Wells. The first algorithm encodes an image without entropy coding and achieves comparable PSNR performance with the original WDR at low bit rate while exceeding the PSNR performance of original WDR algorithm at medium to high bitrates. The second algorithm achieves slightly higher PSNR performance than that of original WDR with similar computational complexity. The modification to the original WDR is based on the observation that encoding the symbol streams generated in the sorting pass (significance map) and refinement pass (magnitudes) separately can be beneficial. We can either encode the symbol streams under different contexts using entropy coder, or output the raw symbol streams without entropy coding stage. It is shown in the experiments that up to 1/3 of both the encoding time and the decoding time can be saved without sacrificing any PSNR performance when compared to the original WDR.