Interchannel dependency analysis of biomedical signals for efficient lossless compression by MPEG-4 ALS

This paper describes a new search algorithm that quickly finds interchannel relationships between a coding channel and a reference channel in the multichannel coding tool of the MPEG-4 Audio Lossless Coding (ALS) international standard. The algorithm has tree structure and can reduce data size with significantly smaller computation load than that of the conventional one. The devised method is based on a restricted greedy algorithm. It chooses the most efficient branch which does not make any loops in the existing path. The results of comprehensive evaluations show that this method maintains the compression performance (compression to around 1/3) and performs 1000 times as fast as the conventional method for the 512-channel magnetoencephalography signals. This algorithm enables practical lossless compression of biomedical data by the ALS, and at the same time, opens the way to a new multichannel analysis tool that may be used for purposes other than compression. The continual maintenance of this standard will make it possible to perfectly reconstruct encoded files even 100 years from now.