  We present high-statistic data on charged pion emission from Au+Au collisions
at $\sqrt{s_{\rm{NN}}}$ = 2.4 GeV (corresponding to $E_{beam}$ = 1.23 A GeV) in
four centrality classes in the range 0 - 40$\%$ of the most central collisions.
The data are analyzed as a function of transverse momentum, transverse mass,
rapidity, and polar angle. Pion multiplicity per participating nucleon
decreases moderately with increasing centrality. The polar angular
distributions are found to be non-isotropic even for the most central event
class. Our results on pion multiplicity fit well into the general trend of the
world data, but undershoot by $2.5 \sigma$ data from the FOPI experiment
measured at slightly lower beam energy. We compare our data to state-of-the-art
transport model calculations (PHSD, IQMD, PHQMD, GiBUU and SMASH) and find
substantial differences between the measurement and the results of these
calculations.
