Class: PWN::SDR::Decoder::P25::DemodIQ

Inherits:
Object
  • Object
show all
Defined in:
lib/pwn/sdr/decoder/p25.rb

Overview

Streaming C4FM demod for Base.run_iq — I/Q → NAC/DUID frames.

Constant Summary collapse

AUDIO_RATE = 
48_000

Instance Method Summary collapse

Constructor Details

#initialize(rate:) ⇒ DemodIQ

Returns a new instance of DemodIQ.



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# File 'lib/pwn/sdr/decoder/p25.rb', line 41

def initialize(rate:)
  @rate = rate.to_f
  @dibits = []
  @seen_fs = 0
end

Instance Method Details

#feed_iq(samples, rate: nil) ⇒ Object 



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# File 'lib/pwn/sdr/decoder/p25.rb', line 47

def feed_iq(samples, rate: nil, &)
  @rate = rate.to_f if rate
  @fm_state ||= {}
  @audio ||= []
  @audio.concat(DSP.fm_demod_iq(iq: samples, state: @fm_state))
  # Fixed 10 ms analysis windows keep resampler and slicer resets
  # independent of USB/file/UDP chunk boundaries.
  window = [(@rate * 0.01).round, 1].max
  while @audio.length >= window
    audio = DSP.resample(samples: @audio.shift(window), src_rate: @rate, dst_rate: AUDIO_RATE)
    @dibits.concat(DSP.slice_4fsk(samples: audio, rate: AUDIO_RATE, baud: 4800))
    scan(&) if block_given?
  end
  @dibits.shift(@dibits.length - 4096) if @dibits.length > 8192
end