  Within the framework of the improved isospin dependent quantum molecular
dynamics (ImIQMD) model, the pion emission in heavy-ion collisions in the
region 1 A GeV is investigated systematically, in which the pion is considered
to be mainly produced by the decay of resonances $\triangle$(1232) and
N*(1440). The in-medium dependence and Coulomb effects of the pion production
are included in the calculation. Total pion multiplicity and $\pi^{-}/\pi^{+}$
yields are calculated for the reaction $^{197}$Au+$^{197}$Au in central
collisions for selected Skyrme parameters SkP, SLy6, Ska, SIII and compared
them with the measured data by the FOPI collaboration.
