  A general algorithm for handling the energy dependence of meson-nucleon
amplitudes in the nuclear medium has been recently applied to antikaons and to
eta mesons. Here we test this approach on $\pi N$ amplitudes in pionic atoms
where direct comparison can be made with ample experimental results. Applying
this algorithm to a large-scale fit of 100 pionic-atom data points across the
periodic table, which also include the `deeply-bound' states in Sn and Pb,
reaffirms earlier conclusions on the density-dependent renormalization of the
$\pi N$ threshold isovector amplitude $b_1$, or equivalently the
renormalization of the pion decay constant $f_{\pi}$ in the nuclear medium.
