SEMG signal compression based on two-dimensional techniques.
BACKGROUND
Recently, two-dimensional techniques have been successfully employed for compressing surface electromyographic (SEMG) records as images, through the use of image and video encoders. Such schemes usually provide specific compressors, which are tuned for SEMG data, or employ preprocessing techniques, before the two-dimensional encoding procedure, in order to provide a suitable data organization, whose correlations can be better exploited by off-the-shelf encoders. Besides preprocessing input matrices, one may also depart from those approaches and employ an adaptive framework, which is able to directly tackle SEMG signals reassembled as images.


METHODS
This paper proposes a new two-dimensional approach for SEMG signal compression, which is based on a recurrent pattern matching algorithm called multidimensional multiscale parser (MMP). The mentioned encoder was modified, in order to efficiently work with SEMG signals and exploit their inherent redundancies. Moreover, a new preprocessing technique, named as segmentation by similarity (SbS), which has the potential to enhance the exploitation of intra- and intersegment correlations, is introduced, the percentage difference sorting (PDS) algorithm is employed, with different image compressors, and results with the high efficiency video coding (HEVC), H.264/AVC, and JPEG2000 encoders are presented.


RESULTS
Experiments were carried out with real isometric and dynamic records, acquired in laboratory. Dynamic signals compressed with H.264/AVC and HEVC, when combined with preprocessing techniques, resulted in good percent root-mean-square difference [Formula: see text] compression factor figures, for low and high compression factors, respectively. Besides, regarding isometric signals, the modified two-dimensional MMP algorithm outperformed state-of-the-art schemes, for low compression factors, the combination between SbS and HEVC proved to be competitive, for high compression factors, and JPEG2000, combined with PDS, provided good performance allied to low computational complexity, all in terms of percent root-mean-square difference [Formula: see text] compression factor.


CONCLUSIONS
The proposed schemes are effective and, specifically, the modified MMP algorithm can be considered as an interesting alternative for isometric signals, regarding traditional SEMG encoders. Besides, the approach based on off-the-shelf image encoders has the potential of fast implementation and dissemination, given that many embedded systems may already have such encoders available, in the underlying hardware/software architecture.
State University of Amazonas, Av. Darcy Vargas, 1200, Parque 10, 69050-020, Manaus, Brazil. wmelo@uea.edu.br.
Wheidima Carneiro
WC
de Melo
Federal University of Amazonas, Av. General Rodrigo Octávio, 6200, Coroado I, 69077-000, Manaus, Brazil.
Eddie Batista
EB
de Lima Filho
Federal University of Amazonas, Av. General Rodrigo Octávio, 6200, Coroado I, 69077-000, Manaus, Brazil.
Waldir Sabino
WS
da Silva Júnior
D000465:Algorithms; D044962:Data Compression / Q000379:methods*; D004576:Electromyography; D012815:Signal Processing, Computer-Assisted
HEVC; Multidimensional multiscale parser; Preprocessing technique; SEMG