[Discuss-gnuradio] atsci_equalizer_lsm NTAPS

[Charles Swiger]

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