This patch replaces in topology sof-hda-generic.m4 the use of macro
pipe-volume-capture.m4 usage with a new macro pipe-highpass-capture.m4.
The used 40 Hz cut-off is sufficient to suppress the DC pulse in the
beginning of capture from headset with minimal impact to other
applications such as recording music.
The capture volume ramp length is changed from 250 ms to 400 ms. The
longer ramp is feasible because the microphone path seems to open
at 500 ms from capture. It helps to attenuate the remaining noises
in the beginning of capture.
The patch also adds additional high-pass responses macros for
topology with different 20-50 Hz cut-off frequencies into
SOF/tools/topology/m4.
The changes for Matlab/Octave script example_iir_eq.m that
generated the filter coefficients are included here as well.
Signed-off-by: Seppo Ingalsuo <seppo.ingalsuo@linux.intel.com>
Seppo Ingalsuo