In, where the received samples are decimated?

Hi all,
I’m wondering in which function the received samples are decimated
before decoding in
it seems the signals (input_items) are sent to the class
"gr_make_mpsk_receiver_cc ", in which the member method ‘d_interp = new
gri_mmse_fir_interpolator_cc()’ performs the job by calling ‘gr_complex
interp_sample = d_interp->interpolate(&d_dl[d_dl_idx], d_mu)’ in the
‘general_work()’. Is it right?