Subband Lossy and Lossless Coding

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We proposed two method for lossy and lossless image coding. One is based on wavelet transform which is implemented by two-channel IIR filter banks consisted of the parallel connection of allpass filters. This structure is very simple and less computational complexity, but the parameters for each mode are individual each other to get good performance. Another is based on lapped biorthogonal transform which is consisted of integer DCT and lifting steps to overcome the problem as mentioned above. By this method. Both lossy and lossless codings are implemented by the same structure or software. This is called reversible transform and is based on lossless mode. Lossy mode is realized by cutting bit stream. Taking consideration with the transfer function of lifting step, the length of bases function on each subband is variable. The blocking artifacts of which causes in DCT are reduced by making the length of lowpass filter long in the synthesis bank. Ringing artifacts are also reduced by making the length of bandpass and high pass filters short. Computer simulations show that the proposed method is compatible with the conventiona method in lossy mode and is sometimes much better than the conventional method in lossless mode.