Optimal wavelet thresholding for various coding schemes

We propose a nonlinear, universal method based on wavelet thresholding to eeciently improve the performance of various coding schemes. Coarse quantization of the transform coeecients often results in some undesirable artifacts, such as ringing eeect, contouring eeect and blocking eeect, especially at very low bit rate. We perform the wavelet-domain thresholding on the decompressed image to attenuate the quantization noise eeect while maintaining the relatively sharp features (e.g. edges) of the original image. Both the objective quality and the subjective quality of the reconstructed image are signiicantly improved with the reduction of coding artifacts. Experimental results show that de-noising using the undecimated discrete wavelet transform (DWT) achieves better performance than using the orthonormal DWT, with an acceptable computational complexity (O(MN log 2 (MN)) for an image of size M N).