Module: PWN::SDR::Decoder::APT

Defined in:
lib/pwn/sdr/decoder/apt.rb

Overview

NOAA APT (Automatic Picture Transmission) decoder for the 137 MHz polar-orbiting weather satellites (NOAA-15/18/19). APT is a 2400 Hz AM subcarrier inside a 34 kHz-wide FM downlink; GQRX's UDP audio is recorded to a WAV, then handed to noaa-apt (or satdump) to render the two-channel visible/IR image strip.

Class Method Summary collapse

Class Method Details

.authors ⇒ Object

Author(s)

0day Inc. support@0dayinc.com



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# File 'lib/pwn/sdr/decoder/apt.rb', line 54

public_class_method def self.authors
  "AUTHOR(S):\n  0day Inc. <support@0dayinc.com>\n"
end

.decode(opts = {}) ⇒ Object

Supported Method Parameters

PWN::SDR::Decoder::APT.decode( freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq' )



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# File 'lib/pwn/sdr/decoder/apt.rb', line 19

public_class_method def self.decode(opts = {})
  freq_obj = opts[:freq_obj]
  raise 'ERROR: :freq_obj is required' unless freq_obj.is_a?(Hash)

  stamp   = Time.now.strftime('%Y%m%d_%H%M%S')
  wav_out = "/tmp/apt_#{stamp}.wav"
  png_out = "/tmp/apt_#{stamp}.png"

  # Record 11 025 Hz WAV (noaa-apt's native rate) until [ENTER],
  # emitting a heartbeat line per second so the spinner stays live,
  # then decode to PNG on exit.
  inner = 'sox -t raw -e signed-integer -b 16 -r 22050 -c 1 - ' \
          "-t wav -r 11025 #{Shellwords.escape(wav_out)} & SOXPID=$!; " \
          'trap "kill $SOXPID 2>/dev/null" EXIT INT TERM; ' \
          'while kill -0 $SOXPID 2>/dev/null; do ' \
          "echo APT_REC seconds=$SECONDS file=#{wav_out}; sleep 1; done"

  PWN::SDR::Decoder::Base.run_pipeline(
    freq_obj: freq_obj,
    protocol: 'NOAA-APT',
    required_bins: %w[sox noaa-apt],
    decode_cmd: "bash -c #{Shellwords.escape(inner)}",
    line_match: /^APT_REC/,
    parser: proc { |line| { protocol: 'NOAA-APT', wav: wav_out, png: png_out, summary: line.strip } }
  )

  return unless File.exist?(wav_out) && File.size(wav_out).positive?

  system('noaa-apt', wav_out, '-o', png_out)

  puts "[*] APT image written: #{png_out}" if File.exist?(png_out)
end

.help ⇒ Object

Display Usage for this Module



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# File 'lib/pwn/sdr/decoder/apt.rb', line 60

public_class_method def self.help
  puts "USAGE:
    #{self}.decode(
      freq_obj: 'required - freq_obj returned from PWN::SDR::GQRX.init_freq'
    )

    NOTE: Requires `sox` and `noaa-apt`. Set GQRX to FM, ~34 kHz BW.
          Records the pass to /tmp/apt_<ts>.wav, decodes to PNG on exit.

    #{self}.authors
  "
end