Optimization of Discrete Anamorphic Stretch Transform and Phase Recovery for ECG Signal Compression.

An ECG signal compression scheme using both Discrete Anamorphic Stretch Transform (DAST) and Discrete wavelet transform (DWT) is reported in the literature. In this scheme, a linear filter is used for the recovery of the phase of the DAST for the computation of inverse DAST. However, at a higher compression ratio, the phase recovered and the reconstructed signal became increasingly inaccurate. To overcome this problem, a phase recovery technique that uses only an adder with fixed offset is proposed in this paper. A scheme for optimizing the DAST kernels to increase the compression ratio is also proposed. To evaluate their effectiveness, the ECG signals of the MIT-BIH Arrhythmia database are compressed using 6 level 1D DWT and run-length encoding with and without DAST pre-compressor and their performances are compared. The phase of DAST of the ECG signals recovered using both linear filter and adder are computed and compared for different kernels. The proposed phase recovery scheme with the optimized sublinear and linear kernels provides a 12.2% and 10.91% increase in data compression ratio and 24.63% and 28.73% decrease in percentage root mean square difference (PRD) with 99.9% of energy packing efficiency (EPE) compared to the scheme using the filter. The compression scheme using DAST provides a 2.81 times higher compression ratio compared to that without DAST. The proposed compression scheme yields a higher Compression Ratio and lower PRD than those reported in the literature. It can be used as pre-compressor for the real time transmission of ECG signal with lower bandwidth. [ABSTRACT FROM AUTHOR]