A two-stage modelling schema to be used together with arithmetic codin
g is proposed. The main motivation of the work has been the relatively
slow operation of arithmetic coding. The new modelling schema reduces
the use of arithmetic coding by applying to large white regions globa
l modelling which consumes less time. This composite method works well
and with a set of test images it took only about 41% of the time requ
ired by a QM-coder. At the same time the loss in compression ratio is
only marginal.