An efficient lossless compression of multichannel time-series signals by MPEG-4 ALS

This paper presents enhanced codec software of the MPEG-4 Audio Lossless Coding (ALS) international standard for compressing multichannel time-series signals. By combining efficient software implementation and a fast search algorithm, multichannel data are efficiently compressed with practical computational load and extracted from the bitstream without any losses. Experimental results for instrumental sounds (IS), microphone array (MA), and electrocardiography (ECG) signals show that MA and ECG data are compressed to around 1/3 of the original file size and that the encoding and decoding speed achieves about a hundred times as fast as real time. In addition, IS data are compressed to about 45% and processing speed is around ten times as fast as real time. This ALS-compliant software can save time in transmitting or accessing files, and reduce disk space. It will therefore be useful for up-/down-loading and archiving any kinds of time-series signals.