Power Squelch

This will either pass the input unchanged, or block it, depending on whether its envelope is over a certain threshold. The envelope is calculated by taking the squared magnitude of the signal and lowpassing it with a single pole IIR filter (with the specified alpha).

The ramp parameter specifies the attack / release time, in samples. A sinusodial ramp is used to progressively mute / unmute the input. If ramp is set to 0, input is muted / unmuted without a ramp.

For realtime applications you'll want to set the gate parameter to false, which produces zeros when the input is muted. If it is true, the block will stop producing samples when in muted state.

The block will emit a tag with the key "squelch_sob" with the value of PMT_NIL on the first item it passes, and with the key "squelch_eob" on the last item it passes.

Parameters
(R): Run-time adjustable


 * Threshold (R)
 * Threshold (in dB) for power squelch


 * Alpha (R)
 * Gain of averaging filter. Defaults to 0.0001.


 * Ramp
 * Attack/release time in samples; a sinusodial ramp is used. Set to 0 to disable.


 * Gate
 * If true, no output if no squelch tone. if false, output 0's if no squelch tone.

Example Flowgraph
Insert description of flowgraph here, then show a screenshot of the flowgraph and the output if there is an interesting GUI. Currently we have no standard method of uploading the actual flowgraph to the wiki or git repo, unfortunately. The plan is to have an example flowgraph showing how the block might be used, for every block, and the flowgraphs will live in the git repo.

Source Files

 * C++ files
 * TODO


 * Header files
 * TODO


 * Public header files
 * TODO


 * Block definition
 * TODO