[Discuss-gnuradio] Squelch developments

[Johnathan Corgan]

I am creating a new squelch block:

gr.pwr_squelch_cc

..that will replicate the current functionality of simple_squelch_cc,
and add an optional gating function.  When gating is on, there will be
no output samples when the historical power is below threshold.  With
gating off (the default), the block will output zeros.  This latter is
identical to the existing simple_squelch_cc.

I had previously implemented this as a 'skipping' patch to
simple_squelch_cc but because it changes the block from a 1:1
synchronous block to a variable output block (when skipping is on), it
really needs to be a new class derived from gr_block instead of
gr_sync_block.

As far as naming goes, calling this pwr_squelch_xx is anticipation of
other squelch type blocks:

gr.pwr_squelch_ff - same as pwr_squelch_cc but for audio, like a "VOX"
switch

gr.ctcss_squelch_ff - gate or zero audio output when a ctcss tone is not
present

gr.noise_squelch_ff - gate or zero audio output when noise is present (I
think this what standard_squelch is detecting)

gr.dcs_squelch_ff - gate or zero audio output when digitally coded
squelch is not present

etc.

(Not that I'm signing up to write all these!)

If anyone thinks this is a misguided approach let me know.

-Johnathan, AE6HO