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The method of optimal directions (MOD) is an iterative method for designing frames for sparse representation purposes using a training set. In this paper we use frames designed by MOD in a multiframe compression (MFC) scheme. Both the MOD and the MFC need a vector selection algorithm, and orthogonal matching pursuit (OMP) is used in this paper. In the MFC scheme several different frames are used, each optimized for a fixed number of selected frame vectors in each approximation. We apply the MOD and the MFC scheme to ECG signals, and do experiments with both fixed size and variable size on the different frames used in the MFC scheme. Compared to traditional transform based compression, the experiments demonstrate improved rate-distortion performance by 1-4 dB, and that variable sized frames perform better than fixed sized frames.
Engan et al. (Mon,) studied this question.