Just poking around - since atsci_equalizer_lms::filter1 is at the top of
the oprofile report, I tried setting NTAPS to 64 instead of 256 and that
certainly made it faster, and decoding still turns in zero errors on an
excellent signal.
NTAPS 256:
samples % app name symbol name
757958 29.0206 _atsc.so atsci_equalizer_lms::filter1(float const*)
NTAPS 64:
samples % app name symbol name
281449 19.2442 _atsc.so atsci_single_viterbi::decode(float)
257098 17.5792 libgnuradio-core.so.0.0.0 float_dotprod_3dnow
206711 14.1340 libgnuradio-core.so.0.0.0 fcomplex_dotprod_3dnow
143798 9.8322 _atsc.so atsci_equalizer_lms::filter1(float const*)
The Wayne Bretl paper “ATSC/VSB Tutorial - Receiver Technology” at
http://www.zenith.com/index.asp?url=./sub_hdtv/hdtv_index.html
under Technical Papers says: “The equalizer filter consists of two
parts, a 64 tap feed-forward transversal filter followed by a 192 tap
decision feedback filter.”
–Chuck