This function returns the current input sampling frequency (in samples per second per signal), which is either the raw sampling frequency for the record (as would be returned by WFDB_sampfreq (see section 3.6.5), or the frequency chosen using a previous invocation of WFDB_setifreq.
See also: WFDB_sampfreq (3.6.5), WFDB_setifreq (3.2.1)