Ramakrishnan A G, Saha S
Department of Electrical Engineering, Indian Institute of Science, Bangalore, India.
IEEE Trans Biomed Eng. 1997 Dec;44(12):1253-61. doi: 10.1109/10.649997.
This paper presents a novel coding scheme for electrocardiogram (ECG). Following beat delineation, the periods of the beats are normalized by multirate processing. After amplitude normalization, discrete wavelet transform is applied to each beat. Due to the period and amplitude normalization, the wavelet transform coefficients bear a high correlation across beats at identical locations. To increase the compression ratio, the residual sequence obtained after linear prediction of the significant wavelet coefficients is transmitted to the decoder. The difference between the actual period and the mean beat period, and that between the actual scale factor and the average amplitude scale factor are also transmitted for each beat. At the decoder, the inverse wavelet transform is computed from the reconstructed wavelet transform coefficients. The original amplitude and period of each beat are then recovered. The approximation achieved, at an average rate of 180 b/s, is of high quality. We have evaluated the normalized maximum amplitude error and its position in each cycle, in addition to the normalized root mean square error. The significant feature of the proposed technique is that, while the error is nearly uniform throughout the cycle, the diagnostically crucial QRS region is kept free of maximal reconstruction error.
本文提出了一种用于心电图（ECG）的新型编码方案。在心跳划分之后，通过多速率处理对心跳周期进行归一化。在幅度归一化之后，对每个心跳应用离散小波变换。由于周期和幅度归一化，小波变换系数在相同位置的不同心跳之间具有高度相关性。为了提高压缩率，将对显著小波系数进行线性预测后得到的残差序列传输到解码器。还会为每个心跳传输实际周期与平均心跳周期之间的差值，以及实际比例因子与平均幅度比例因子之间的差值。在解码器处，根据重构的小波变换系数计算逆小波变换。然后恢复每个心跳的原始幅度和周期。以平均180比特每秒的速率实现的近似结果具有高质量。除了归一化均方根误差之外，我们还评估了归一化最大幅度误差及其在每个周期中的位置。所提出技术的显著特点是，虽然误差在整个周期内几乎是均匀的，但诊断关键的QRS区域没有最大重构误差。
