Usage of keep_one_in_n in fftsink_nongl

GNU Radio
#1

Dear All,
I am exploring the fftsink_nongl.py file because i want to modify it to
be
the sensing method of my project. in the fft_sink_c class, there is a
signal
processing block call keep_one_in_n. I think that this block is use to
slowing down the sampling of the spectrum sense, am I correct? if i
remove
this block from the flow graph, the output value will be unexpected
(unreliable). can any one tell me what is actually happen? what did i
need
if i want to remove this block? because this block make my sensing speed
extremely slow…

best regards,
Adib

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#2

sample_rate/fft_size/N = fft_rate

N = sample_rate/fft_size/fft_rate

The fftsink_nongl.py wants to decimate the stream of fft vectors by N to
achieve fft rate (aka frames per second).

If you tell fftsink_nongl.py a sample rate that is greater than your
actual sample rate, then N will be too large, and the frame rate will be
very slow.

-Josh