On compressing method of EEG data for their digital database

The authors propose a compression method for storing the electroencephalogram (EEG) waveforms into digital storage under the condition of keeping the quality sufficient for diagnosis. The method is designed on the basis of features of the EEG waveforms. The data volume is reduced by storing the coefficients of the functions approximating the EEG waveforms. The waveforms are divided into segments, in each of which the difference velocity is similar, and are decomposed into two wave components for efficient compression. The effectiveness of the method has been evaluated by applying it to several EEG waveforms. The quality of the reconstructed waveforms is bandwidth of 0.5~120 Hz, dynamic range of 60 dB, and maximum error of 2 μV_p-p . The compression ratio is 0.648 on the average