Module: PWN::SDR::Decoder::DSP

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

Overview

DSP primitives shared by every PWN::SDR::Decoder::* module.

Default path is pure Ruby operating on Array samples normalised to -1.0..1.0 (48 kHz s16le mono from GQRX UDP — no sox / multimon-ng / minimodem dependency).

When the matching system library is present the hot paths transparently accelerate via PWN::FFI::Volk,Liquid,FFTW:

unpack_s16le  → PWN::FFI::Volk   (SIMD s16→f32 convert)
unpack_cs16le → pure / Volk path (interleaved I/Q s16 → f32)
unpack_cu8    → pure path (RTL-SDR u8 I/Q → f32)
resample      → PWN::FFI::Liquid (msresamp multi-stage)
dc_block      → PWN::FFI::Liquid (firfilt DC blocker)
rms_dbfs      → PWN::FFI::Volk   (accumulate of squares)
mag_sq / fm_demod_iq → true-air I/Q paths for Base.run_iq

Each accelerated method falls back to the pure-Ruby body when the backend is missing or raises, so decoders never require a native library at install time. Force pure Ruby for testing with PWN::SDR::Decoder::DSP.native = false

Constant Summary collapse

TWO_PI = 
Math::PI * 2
BAUDOT_LTRS =

ITA2 / Baudot 5-bit → ASCII (LTRS + FIGS shift tables). Index = code.

[
  "\0", 'E', "\n", 'A', ' ', 'S', 'I', 'U',
  "\r", 'D', 'R', 'J', 'N', 'F', 'C', 'K',
  'T',  'Z', 'L',  'W', 'H', 'Y', 'P', 'Q',
  'O',  'B', 'G',  nil, 'M', 'X', 'V', nil
].freeze
BAUDOT_FIGS = 
[
  "\0", '3', "\n", '-', ' ', "'", '8', '7',
  "\r", '$', '4',  "\a", ',', '!', ':', '(',
  '5',  '+', ')',  '2', '#', '6', '0', '1',
  '9',  '?', '&',  nil, '.', '/', ';', nil
].freeze
MORSE_TABLE =

International Morse Code (dit='.', dah='-') → ASCII.

{
  '.-' => 'A', '-...' => 'B', '-.-.' => 'C', '-..' => 'D', '.' => 'E',
  '..-.' => 'F', '--.' => 'G', '....' => 'H', '..' => 'I', '.---' => 'J',
  '-.-' => 'K', '.-..' => 'L', '--' => 'M', '-.' => 'N', '---' => 'O',
  '.--.' => 'P', '--.-' => 'Q', '.-.' => 'R', '...' => 'S', '-' => 'T',
  '..-' => 'U', '...-' => 'V', '.--' => 'W', '-..-' => 'X', '-.--' => 'Y',
  '--..' => 'Z', '-----' => '0', '.----' => '1', '..---' => '2',
  '...--' => '3', '....-' => '4', '.....' => '5', '-....' => '6',
  '--...' => '7', '---..' => '8', '----.' => '9', '.-.-.-' => '.',
  '--..--' => ',', '..--..' => '?', '-..-.' => '/', '-....-' => '-',
  '-.--.' => '(', '-.--.-' => ')', '.-...' => '&', '---...' => ':',
  '-...-' => '=', '.-.-.' => '+', '.--.-.' => '@'
}.freeze
CA_G2_TAPS = 
{
  1 => [2, 6], 2 => [3, 7], 3 => [4, 8], 4 => [5, 9], 5 => [1, 9],
  6 => [2, 10], 7 => [1, 8], 8 => [2, 9], 9 => [3, 10], 10 => [2, 3],
  11 => [3, 4], 12 => [5, 6], 13 => [6, 7], 14 => [7, 8], 15 => [8, 9],
  16 => [9, 10], 17 => [1, 4], 18 => [2, 5], 19 => [3, 6], 20 => [4, 7],
  21 => [5, 8], 22 => [6, 9], 23 => [1, 3], 24 => [4, 6], 25 => [5, 7],
  26 => [6, 8], 27 => [7, 9], 28 => [8, 10], 29 => [1, 6], 30 => [2, 7],
  31 => [3, 8], 32 => [4, 9]
}.freeze

Class Attribute Summary collapse

Class Method Summary collapse

Class Attribute Details

.native ⇒ Object

Returns the value of attribute native.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 31

def native
  @native
end

Class Method Details

.authors ⇒ Object

Author(s)

0day Inc. support@0dayinc.com



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 1001

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

.baudot_decode(opts = {}) ⇒ Object

Supported Method Parameters

txt = PWN::SDR::Decoder::DSP.baudot_decode(bits: Array<0|1>) 5-bit ITA2 with LTRS(31)/FIGS(27) shift, LSB-first per character.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 380

public_class_method def self.baudot_decode(opts = {})
  bits = opts[:bits]
  figs = false
  out  = +''
  bits.each_slice(5) do |ch|
    next if ch.length < 5

    code = ch.each_with_index.sum { |b, i| b << i }
    case code
    when 31 then figs = false
    when 27 then figs = true
    else
      tbl = figs ? BAUDOT_FIGS : BAUDOT_LTRS
      c = tbl[code]
      out << c if c
    end
  end
  out
end

.bch_31_21_syndrome(opts = {}) ⇒ Object

BCH(31,21) syndrome — generator poly 0b11101101001 (0x769). Used by POCSAG and FLEX codewords (bits 31..1 are BCH, bit 0 parity).

Supported Method Parameters

syn = PWN::SDR::Decoder::DSP.bch_31_21_syndrome(word: Integer)



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 366

public_class_method def self.bch_31_21_syndrome(opts = {})
  word = (opts[:word].to_i >> 1) & 0x7FFFFFFF
  gen  = 0x769
  reg  = word
  30.downto(10) do |i|
    reg ^= (gen << (i - 10)) if (reg >> i).odd?
  end
  reg & 0x3FF
end

.bits_to_int(opts = {}) ⇒ Object

Supported Method Parameters

int = PWN::SDR::Decoder::DSP.bits_to_int(bits: [1,0,1,...])



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 343

public_class_method def self.bits_to_int(opts = {})
  bits = opts[:bits]
  v = 0
  bits.each { |b| v = (v << 1) | (b & 1) }
  v
end

.bytes_from_bits(opts = {}) ⇒ Object

Supported Method Parameters

bytes = PWN::SDR::Decoder::DSP.bytes_from_bits( bits: Array<0|1>, lsb_first: false )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 777

public_class_method def self.bytes_from_bits(opts = {})
  bits = opts[:bits]
  lsb  = opts[:lsb_first]
  out  = []
  bits.each_slice(8) do |oct|
    next if oct.length < 8

    v = 0
    if lsb
      oct.each_with_index { |b, i| v |= (b & 1) << i }
    else
      oct.each { |b| v = (v << 1) | (b & 1) }
    end
    out << v
  end
  out
end

.ca_code(opts = {}) ⇒ Object

Supported Method Parameters

chips = PWN::SDR::Decoder::DSP.ca_code(prn: 1..32) Returns Array of ±1.0 length 1023 (GPS L1 C/A Gold code).



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 953

public_class_method def self.ca_code(opts = {})
  prn  = opts[:prn].to_i
  taps = CA_G2_TAPS[prn]
  raise "ERROR: PRN #{prn} unsupported" unless taps

  g1 = Array.new(10, 1)
  g2 = Array.new(10, 1)
  out = Array.new(1023)
  1023.times do |i|
    g2i = g2[taps[0] - 1] ^ g2[taps[1] - 1]
    out[i] = (g1[9] ^ g2i) == 1 ? -1.0 : 1.0
    fb1 = g1[2] ^ g1[9]
    fb2 = g2[1] ^ g2[2] ^ g2[5] ^ g2[7] ^ g2[8] ^ g2[9]
    g1.unshift(fb1)
    g1.pop
    g2.unshift(fb2)
    g2.pop
  end
  out
end

.cfft_mag(opts = {}) ⇒ Object

Supported Method Parameters

mag = PWN::SDR::Decoder::DSP.cfft_mag( iq: 'required - interleaved I/Q', n: 'optional - FFT size', shift: 'optional - fftshift so DC is centred (default true)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 889

public_class_method def self.cfft_mag(opts = {})
  iq = opts[:iq]
  n  = (opts[:n] || (iq.length / 2)).to_i
  sh = opts.fetch(:shift, true)
  bins =
    if native && PWN::FFI.available?(mod: :FFTW)
      begin
        PWN::FFI::FFTW.cfft(iq: iq, n: n)
      rescue StandardError
        dft_naive(iq: iq, n: n)
      end
    else
      dft_naive(iq: iq, n: n)
    end
  mag = bins.map { |re, im| Math.sqrt((re * re) + (im * im)) }
  sh ? mag.rotate(n / 2) : mag
end

.cmul(opts = {}) ⇒ Object

Supported Method Parameters

out = PWN::SDR::Decoder::DSP.cmul(a: [I,Q,…], b: [I,Q,…], conj_b: false) Element-wise complex multiply (interleaved). Used for correlation / dechirp: X = A · conj(B).



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 979

public_class_method def self.cmul(opts = {})
  a = opts[:a]
  b = opts[:b]
  cj = opts[:conj_b]
  n  = [a.length, b.length].min / 2
  out = Array.new(n * 2)
  i = 0
  while i < n
    ar = a[i * 2].to_f
    ai = a[(i * 2) + 1].to_f
    br = b[i * 2].to_f
    bi = b[(i * 2) + 1].to_f
    bi = -bi if cj
    out[i * 2]       = (ar * br) - (ai * bi)
    out[(i * 2) + 1] = (ar * bi) + (ai * br)
    i += 1
  end
  out
end

.correlate(opts = {}) ⇒ Object

Correlate a real template against magnitude-squared energy for PPM / OOK preambles. Returns best lag + score.

Supported Method Parameters

hit = PWN::SDR::Decoder::DSP.correlate( samples: 'required - Array', template: 'required - Array (same units)' ) → { lag:, score: } or nil



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 551

public_class_method def self.correlate(opts = {})
  samples  = opts[:samples]
  template = opts[:template]
  tlen = template.length
  return nil if tlen.zero? || samples.length < tlen

  best_lag = 0
  best_sc  = -Float::INFINITY
  upto = samples.length - tlen
  i = 0
  while i <= upto
    sc = 0.0
    j = 0
    while j < tlen
      sc += samples[i + j] * template[j]
      j += 1
    end
    if sc > best_sc
      best_sc = sc
      best_lag = i
    end
    i += 1
  end
  { lag: best_lag, score: best_sc }
end

.crc16(opts = {}) ⇒ Object

Supported Method Parameters

crc = PWN::SDR::Decoder::DSP.crc16( bytes: Array, poly: 0x1021, init: 0xFFFF, refin: false, refout: false, xorout: 0x0000 )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 801

public_class_method def self.crc16(opts = {})
  bytes  = opts[:bytes]
  poly   = (opts[:poly]   || 0x1021).to_i
  crc    = (opts[:init]   || 0xFFFF).to_i
  refin  = opts[:refin]
  refout = opts[:refout]
  xorout = (opts[:xorout] || 0).to_i
  bytes.each do |b|
    b = Integer(format('%08b', b & 0xFF).reverse, 2) if refin
    crc ^= (b & 0xFF) << 8
    8.times do
      crc = crc.anybits?(0x8000) ? ((crc << 1) ^ poly) : (crc << 1)
      crc &= 0xFFFF
    end
  end
  crc = Integer(format('%016b', crc).reverse, 2) if refout
  crc ^ xorout
end

.dc_block(opts = {}) ⇒ Object

Supported Method Parameters

y = PWN::SDR::Decoder::DSP.dc_block( samples: 'required - Array', alpha: 'optional - pole (default 0.995)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 180

public_class_method def self.dc_block(opts = {})
  samples = opts[:samples]
  # Prefer liquid FIR DC blocker when caller asks for it (m:) or when
  # alpha is the default AND liquid is available — otherwise keep the
  # classic single-pole IIR so call sites that pass a custom alpha
  # stay bit-identical to pure Ruby.
  if native && opts[:m] && PWN::FFI.available?(mod: :Liquid)
    begin
      return PWN::FFI::Liquid.dc_block(
        samples: samples,
        m: opts[:m],
        as_db: opts[:as_db] || 60.0
      )
    rescue StandardError
      # fall through
    end
  end

  alpha  = (opts[:alpha] || 0.995).to_f
  y_prev = 0.0
  x_prev = 0.0
  samples.map do |x|
    y = x - x_prev + (alpha * y_prev)
    x_prev = x
    y_prev = y
    y
  end
end

.dft_naive(opts = {}) ⇒ Object

Naive O(n²) complex DFT — pure-Ruby fallback for small n.

Supported Method Parameters

bins = PWN::SDR::Decoder::DSP.dft_naive(iq:, n:)



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 911

public_class_method def self.dft_naive(opts = {})
  iq = opts[:iq]
  n  = (opts[:n] || (iq.length / 2)).to_i
  n  = [n, 512].min
  Array.new(n) do |k|
    re = 0.0
    im = 0.0
    j = 0
    while j < n
      ph = -TWO_PI * k * j / n
      c = Math.cos(ph)
      s = Math.sin(ph)
      xr = iq[j * 2].to_f
      xi = iq[(j * 2) + 1].to_f
      re += (xr * c) - (xi * s)
      im += (xr * s) + (xi * c)
      j += 1
    end
    [re, im]
  end
end

.diff_decode(opts = {}) ⇒ Object

Supported Method Parameters

bits = PWN::SDR::Decoder::DSP.diff_decode(bits: Array<0|1>) NRZ-I / DBPSK: output 1 on transition, 0 on hold.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 759

public_class_method def self.diff_decode(opts = {})
  bits = opts[:bits]
  prev = bits.first || 0
  out  = Array.new(bits.length - 1)
  i = 1
  while i < bits.length
    out[i - 1] = bits[i] == prev ? 0 : 1
    prev = bits[i]
    i += 1
  end
  out
end

.envelope(opts = {}) ⇒ Object

Supported Method Parameters

env = PWN::SDR::Decoder::DSP.envelope( samples: 'required - Array', window: 'optional - moving-average window in samples (default 32)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 157

public_class_method def self.envelope(opts = {})
  samples = opts[:samples]
  window  = (opts[:window] || 32).to_i
  window  = 1 if window < 1
  acc = 0.0
  buf = Array.new(window, 0.0)
  out = Array.new(samples.length)
  samples.each_with_index do |x, i|
    v = x.abs
    slot = i % window
    acc += v - buf[slot]
    buf[slot] = v
    out[i] = acc / window
  end
  out
end

.envelope_signed(opts = {}) ⇒ Object

Signed moving average (like envelope but keeps sign).

Supported Method Parameters

y = PWN::SDR::Decoder::DSP.envelope_signed(samples:, window:)



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 252

public_class_method def self.envelope_signed(opts = {})
  samples = opts[:samples]
  window  = (opts[:window] || 8).to_i
  window  = 1 if window < 1
  acc = 0.0
  buf = Array.new(window, 0.0)
  out = Array.new(samples.length)
  samples.each_with_index do |x, i|
    slot = i % window
    acc += x - buf[slot]
    buf[slot] = x
    out[i] = acc / window
  end
  out
end

.even_parity_ok?(opts = {}) ⇒ Boolean

Supported Method Parameters

ok = PWN::SDR::Decoder::DSP.even_parity_ok?(word: Integer, width: 32)

Returns:

  • (Boolean) 


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# File 'lib/pwn/sdr/decoder/dsp.rb', line 353

public_class_method def self.even_parity_ok?(opts = {})
  word  = opts[:word].to_i
  width = (opts[:width] || 32).to_i
  p = 0
  width.times { |i| p ^= (word >> i) & 1 }
  p.zero?
end

.find_sync(opts = {}) ⇒ Object

Supported Method Parameters

idx = PWN::SDR::Decoder::DSP.find_sync( bits: 'required - Array<0|1>', pattern: 'required - Array<0|1> or Integer (MSB-first)', width: 'optional - bit-width when pattern is Integer', max_err: 'optional - allowed bit errors (default 0)', from: 'optional - start index (default 0)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 309

public_class_method def self.find_sync(opts = {})
  bits    = opts[:bits]
  pattern = opts[:pattern]
  width   = opts[:width]
  max_err = (opts[:max_err] || 0).to_i
  from    = (opts[:from] || 0).to_i
  pat = if pattern.is_a?(Integer)
          w = width || pattern.bit_length
          Array.new(w) { |i| (pattern >> (w - 1 - i)) & 1 }
        else
          pattern
        end
  plen = pat.length
  upto = bits.length - plen
  i = from
  while i <= upto
    err = 0
    j = 0
    while j < plen
      err += 1 if bits[i + j] != pat[j]
      break if err > max_err

      j += 1
    end
    return i if err <= max_err

    i += 1
  end
  nil
end

.fm_demod_iq(opts = {}) ⇒ Object

Supported Method Parameters

audio = PWN::SDR::Decoder::DSP.fm_demod_iq( iq: 'required - interleaved Array [I0,Q0,…]', kf: 'optional - modulation index scale (default 1.0)' ) Polar-discriminant FM demod. Prefers PWN::FFI::Liquid.freq_demod when available; otherwise atan2 difference of consecutive samples.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 495

public_class_method def self.fm_demod_iq(opts = {})
  iq = opts[:iq]
  kf = (opts[:kf] || 1.0).to_f
  n  = iq.length / 2
  return [] if n < 2

  if native && PWN::FFI.available?(mod: :Liquid)
    begin
      return PWN::FFI::Liquid.freq_demod(iq: iq, kf: kf)
    rescue StandardError
      # fall through
    end
  end

  out = Array.new(n - 1)
  prev_re = iq[0].to_f
  prev_im = iq[1].to_f
  i = 1
  while i < n
    re = iq[i * 2].to_f
    im = iq[(i * 2) + 1].to_f
    # arg(z * conj(z_prev)) = atan2 cross/dot
    dot   = (re * prev_re) + (im * prev_im)
    cross = (im * prev_re) - (re * prev_im)
    out[i - 1] = Math.atan2(cross, dot) * kf
    prev_re = re
    prev_im = im
    i += 1
  end
  out
end

.fsk_slice(opts = {}) ⇒ Object

Supported Method Parameters

bits = PWN::SDR::Decoder::DSP.fsk_slice( samples: 'required - Array', rate: 'required - sample rate (Hz)', baud: 'required - symbol rate', mark_hz: 'required - mark tone (bit=1)', space_hz:'required - space tone (bit=0)' ) Non-coherent 2-FSK: per-symbol Goertzel on mark/space, pick the winner.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 278

public_class_method def self.fsk_slice(opts = {})
  samples  = opts[:samples]
  rate     = opts[:rate].to_f
  baud     = opts[:baud].to_f
  mark_hz  = opts[:mark_hz].to_f
  space_hz = opts[:space_hz].to_f
  spb      = rate / baud
  nsym     = (samples.length / spb).floor
  bits     = Array.new(nsym)
  i = 0
  while i < nsym
    a = (i * spb).floor
    b = ((i + 1) * spb).floor
    win = samples[a...b]
    pm = goertzel(samples: win, rate: rate, freq: mark_hz)
    ps = goertzel(samples: win, rate: rate, freq: space_hz)
    bits[i] = pm >= ps ? 1 : 0
    i += 1
  end
  bits
end

.gfsk_slice(opts = {}) ⇒ Object

Supported Method Parameters

bits = PWN::SDR::Decoder::DSP.gfsk_slice( iq: 'required - interleaved I/Q', rate:, baud:, bt: 'optional - Gaussian BT (default 0.35)', invert: false ) GFSK/GMSK/2-FSK: prefer liquid gmskdem at integer sps, else fm_demod_iq → nrz_slice.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 671

public_class_method def self.gfsk_slice(opts = {})
  iq   = opts[:iq]
  rate = opts[:rate].to_f
  baud = opts[:baud].to_f
  bt   = (opts[:bt] || 0.35).to_f
  inv  = opts[:invert]
  return [] if iq.empty? || baud <= 0

  sps = rate / baud
  if native && PWN::FFI.available?(mod: :Liquid) && sps >= 2.0
    begin
      k = sps.round
      riq = (sps - k).abs < 0.02 ? iq : resample_iq(iq: iq, src_rate: rate, dst_rate: baud * k)
      bits = PWN::FFI::Liquid.gmsk_demod(iq: riq, sps: k, bt: bt)
      return inv ? bits.map { |b| b ^ 1 } : bits
    rescue StandardError
      # fall through
    end
  end
  audio = fm_demod_iq(iq: iq)
  nrz_slice(samples: audio, rate: rate, baud: baud, invert: inv)
end

.goertzel(opts = {}) ⇒ Object

Supported Method Parameters

power = PWN::SDR::Decoder::DSP.goertzel( samples: 'required - Array', rate: 'required - sample rate (Hz)', freq: 'required - target tone frequency (Hz)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 131

public_class_method def self.goertzel(opts = {})
  samples = opts[:samples]
  rate    = opts[:rate].to_f
  freq    = opts[:freq].to_f
  n       = samples.length
  return 0.0 if n.zero?

  k     = (0.5 + ((n * freq) / rate)).floor
  w     = (TWO_PI * k) / n
  coeff = 2.0 * Math.cos(w)
  s1 = 0.0
  s2 = 0.0
  samples.each do |x|
    s0 = x + (coeff * s1) - s2
    s2 = s1
    s1 = s0
  end
  ((s1 * s1) + (s2 * s2) - (coeff * s1 * s2)) / n
end

.help ⇒ Object

Display Usage for this Module



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 1007

public_class_method def self.help
  puts "USAGE (pure-Ruby DSP + optional PWN::FFI acceleration):
    #{self}.native = true|false   # toggle VOLK/liquid/FFTW backends
    #{self}.unpack_s16le(data: raw_bytes)              # → Volk
    #{self}.unpack_cs16le(data: raw_cs16)              # I/Q s16 → f32
    #{self}.unpack_cu8(data: raw_u8)                  # RTL-SDR u8 I/Q
    #{self}.mag_sq(iq:) / #{self}.iq_rms_dbfs(iq:)
    #{self}.fm_demod_iq(iq:, kf: 1.0)                 # → Liquid
    #{self}.correlate(samples:, template:)
    #{self}.resample(samples:, src_rate:, dst_rate:)   # → Liquid
    #{self}.goertzel(samples:, rate:, freq:)
    #{self}.envelope(samples:, window: 32)
    #{self}.envelope_signed(samples:, window: 8)
    #{self}.dc_block(samples:, alpha: 0.995, m: nil)   # → Liquid if m:
    #{self}.nrz_slice(samples:, rate:, baud:, invert: false)
    #{self}.fsk_slice(samples:, rate:, baud:, mark_hz:, space_hz:)
    #{self}.find_sync(bits:, pattern:, width:, max_err: 0, from: 0)
    #{self}.bits_to_int(bits:)
    #{self}.even_parity_ok?(word:, width: 32)
    #{self}.bch_31_21_syndrome(word:)
    #{self}.baudot_decode(bits:)
    #{self}.rms_dbfs(samples:)                         # → Volk (≥64)
#{self}.resample_iq(iq:, src_rate:, dst_rate:)     # → Liquid crcf
#{self}.mix_iq(iq:, rate:, freq:)                  # → Liquid nco
#{self}.gfsk_slice(iq:, rate:, baud:, bt: 0.35)    # → Liquid gmskdem
#{self}.slice_4fsk(samples:, rate:, baud:)         # C4FM/4-GFSK
#{self}.manchester_decode(bits:, ieee: false)
#{self}.diff_decode(bits:)
#{self}.bytes_from_bits(bits:, lsb_first: false)
#{self}.crc16(bytes:, poly: 0x1021, init: 0xFFFF)
#{self}.whiten_lfsr(bytes:, poly:, init:, width: 7)
#{self}.ook_pulses(iq:, rate:, min_us: 20)
#{self}.cfft_mag(iq:, n:, shift: true)             # → FFTW
#{self}.cmul(a:, b:, conj_b: false)
#{self}.zadoff_chu(root:, n: 63)                   # LTE PSS
#{self}.ca_code(prn: 1..32)                        # GPS L1 C/A

    Constants: MORSE_TABLE, BAUDOT_LTRS, BAUDOT_FIGS
    Backends:  PWN::FFI.backends  # { Volk: true, Liquid: true, AdalmPluto: true, … }

    #{self}.authors
  "
end

.iq_rms_dbfs(opts = {}) ⇒ Object

Supported Method Parameters

power = PWN::SDR::Decoder::DSP.iq_rms_dbfs( iq: 'required - interleaved Array [I0,Q0,…]' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 532

public_class_method def self.iq_rms_dbfs(opts = {})
  m2 = mag_sq(iq: opts[:iq])
  return -120.0 if m2.empty?

  ms = m2.sum / m2.length
  return -120.0 if ms <= 0

  10.0 * Math.log10(ms)
end

.mag_sq(opts = {}) ⇒ Object

Supported Method Parameters

m2 = PWN::SDR::Decoder::DSP.mag_sq( iq: 'required - interleaved Array [I0,Q0,I1,Q1,…]' ) Returns Array of I²+Q² per sample (length = iq.length/2).



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 466

public_class_method def self.mag_sq(opts = {})
  iq = opts[:iq]
  n  = iq.length / 2
  if native && n >= 64 && PWN::FFI.available?(mod: :Volk)
    begin
      return PWN::FFI::Volk.magnitude_squared(iq: iq)
    rescue StandardError
      # fall through
    end
  end
  out = Array.new(n)
  i = 0
  while i < n
    re = iq[i * 2].to_f
    im = iq[(i * 2) + 1].to_f
    out[i] = (re * re) + (im * im)
    i += 1
  end
  out
end

.manchester_decode(opts = {}) ⇒ Object

Supported Method Parameters

bits = PWN::SDR::Decoder::DSP.manchester_decode( bits: 'required - Array<0|1> at 2×data rate', ieee: 'optional - true = 01→1 10→0 (IEEE 802.3), else 10→1 01→0' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 737

public_class_method def self.manchester_decode(opts = {})
  bits = opts[:bits]
  ieee = opts[:ieee]
  out  = []
  i = 0
  while i < bits.length - 1
    a = bits[i]
    b = bits[i + 1]
    if a == b
      i += 1 # phase slip — resync on next transition
      next
    end
    out << (ieee ? b : a)
    i += 2
  end
  out
end

.mix_iq(opts = {}) ⇒ Object

Supported Method Parameters

out = PWN::SDR::Decoder::DSP.mix_iq( iq: 'required - interleaved I/Q', rate: 'required - Hz', freq: 'required - offset Hz to shift DOWN by' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 633

public_class_method def self.mix_iq(opts = {})
  iq   = opts[:iq]
  rate = opts[:rate].to_f
  freq = opts[:freq].to_f
  return iq.dup if freq.abs < 1e-3 || iq.empty?

  if native && PWN::FFI.available?(mod: :Liquid)
    begin
      return PWN::FFI::Liquid.mix_down(iq: iq, freq: TWO_PI * freq / rate)
    rescue StandardError
      # fall through
    end
  end
  n = iq.length / 2
  w = TWO_PI * freq / rate
  out = Array.new(n * 2)
  i = 0
  while i < n
    ph = w * i
    c = Math.cos(ph)
    s = Math.sin(ph)
    re = iq[i * 2].to_f
    im = iq[(i * 2) + 1].to_f
    out[i * 2] = (re * c) + (im * s)
    out[(i * 2) + 1] = (im * c) - (re * s)
    i += 1
  end
  out
end

.nrz_slice(opts = {}) ⇒ Object

Supported Method Parameters

bits = PWN::SDR::Decoder::DSP.nrz_slice( samples: 'required - Array (post-FM-discriminator baseband)', rate: 'required - sample rate (Hz)', baud: 'required - symbol rate', invert: 'optional - flip bit polarity (default false)' ) Simple mid-bit sampler with zero-crossing resync. Returns Array<0|1>.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 218

public_class_method def self.nrz_slice(opts = {})
  samples = opts[:samples]
  rate    = opts[:rate].to_f
  baud    = opts[:baud].to_f
  invert  = opts[:invert]
  spb     = rate / baud
  return [] if spb < 2.0 || samples.empty?

  # DC-block then low-pass via short moving average (~1/4 symbol).
  lp_win = [(spb / 4.0).round, 1].max
  filt   = envelope_signed(samples: dc_block(samples: samples), window: lp_win)

  bits  = []
  phase = spb / 2.0
  prev  = filt.first.to_f
  filt.each do |v|
    # zero-crossing → resync to mid-symbol
    phase = spb / 2.0 if (prev.negative? && v >= 0) || (prev.positive? && v.negative?)
    phase -= 1.0
    if phase <= 0
      b = v.negative? ? 0 : 1
      b ^= 1 if invert
      bits << b
      phase += spb
    end
    prev = v
  end
  bits
end

.ook_pulses(opts = {}) ⇒ Object

Supported Method Parameters

pulses = PWN::SDR::Decoder::DSP.ook_pulses( iq: 'required - interleaved I/Q', rate:, min_us: 'optional - drop shorter pulses (default 20)' ) → Array of { level: 0|1, us: Float, samples: Int } run-length list.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 853

public_class_method def self.ook_pulses(opts = {})
  iq     = opts[:iq]
  rate   = opts[:rate].to_f
  min_us = (opts[:min_us] || 20).to_f
  m2     = mag_sq(iq: iq)
  return [] if m2.length < 32

  # Adaptive threshold: 0.5·(floor + peak) on power domain
  sorted = m2.sort
  floor  = sorted[m2.length / 10] || m2.min
  peak   = sorted[(m2.length * 9) / 10] || m2.max
  thr    = floor + ((peak - floor) * 0.5)
  us_per = 1_000_000.0 / rate
  runs = []
  state = m2.first >= thr ? 1 : 0
  cnt = 0
  m2.each do |v|
    s = v >= thr ? 1 : 0
    if s == state
      cnt += 1
    else
      runs << { level: state, us: cnt * us_per, samples: cnt } if (cnt * us_per) >= min_us
      state = s
      cnt = 1
    end
  end
  runs << { level: state, us: cnt * us_per, samples: cnt } if (cnt * us_per) >= min_us
  runs
end

.resample(opts = {}) ⇒ Object

Supported Method Parameters

out = PWN::SDR::Decoder::DSP.resample( samples: 'required - Array', src_rate: 'required - input sample rate (Hz)', dst_rate: 'required - output sample rate (Hz)' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 90

public_class_method def self.resample(opts = {})
  samples  = opts[:samples]
  src_rate = opts[:src_rate].to_f
  dst_rate = opts[:dst_rate].to_f
  return samples.dup if (src_rate - dst_rate).abs < 1e-6

  if native && PWN::FFI.available?(mod: :Liquid)
    begin
      # liquid rate = output/input
      return PWN::FFI::Liquid.resample(
        samples: samples,
        rate: dst_rate / src_rate
      )
    rescue StandardError
      # fall through to pure Ruby
    end
  end

  ratio = src_rate / dst_rate
  out_len = (samples.length / ratio).floor
  out = Array.new(out_len)
  i = 0
  while i < out_len
    pos  = i * ratio
    idx  = pos.floor
    frac = pos - idx
    a = samples[idx] || 0.0
    b = samples[idx + 1] || a
    out[i] = a + ((b - a) * frac)
    i += 1
  end
  out
end

.resample_iq(opts = {}) ⇒ Object

Supported Method Parameters

out = PWN::SDR::Decoder::DSP.resample_iq( iq: 'required - interleaved [I0,Q0,…] Array', src_rate: 'required - Hz', dst_rate: 'required - Hz' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 595

public_class_method def self.resample_iq(opts = {})
  iq  = opts[:iq]
  src = opts[:src_rate].to_f
  dst = opts[:dst_rate].to_f
  return iq.dup if (src - dst).abs < 1.0 || iq.empty?

  if native && PWN::FFI.available?(mod: :Liquid)
    begin
      return PWN::FFI::Liquid.resample_iq(iq: iq, rate: dst / src)
    rescue StandardError
      # fall through
    end
  end
  n_in  = iq.length / 2
  ratio = src / dst
  n_out = (n_in / ratio).floor
  out = Array.new(n_out * 2)
  i = 0
  while i < n_out
    pos  = i * ratio
    idx  = pos.floor
    frac = pos - idx
    2.times do |c|
      a = iq[(idx * 2) + c] || 0.0
      b = iq[((idx + 1) * 2) + c] || a
      out[(i * 2) + c] = a + ((b - a) * frac)
    end
    i += 1
  end
  out
end

.rms_dbfs(opts = {}) ⇒ Object

Supported Method Parameters

dbfs = PWN::SDR::Decoder::DSP.rms_dbfs(samples: Array)



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 403

public_class_method def self.rms_dbfs(opts = {})
  samples = opts[:samples]
  return -120.0 if samples.nil? || samples.empty?

  if native && PWN::FFI.available?(mod: :Volk) && samples.length >= 64
    begin
      # Σ x² via volk: scale-square in Ruby is still the bottleneck for
      # tiny buffers so keep the pure-Ruby path under 64 samples.
      sq = samples.map { |v| v * v }
      ms = PWN::FFI::Volk.accumulate(samples: sq) / samples.length
      return -120.0 if ms <= 0

      return 10.0 * Math.log10(ms)
    rescue StandardError
      # fall through
    end
  end

  ms = samples.sum { |v| v * v } / samples.length
  return -120.0 if ms <= 0

  10.0 * Math.log10(ms)
end

.slice_4fsk(opts = {}) ⇒ Object

Supported Method Parameters

dibits = PWN::SDR::Decoder::DSP.slice_4fsk( samples: 'required - real FM-discriminator baseband', rate:, baud: ) → Array<0..3> per symbol (4-level decision, adaptive thresholds). C4FM/4-GFSK maps +3 → 01, +1 → 00, −1 → 10, −3 → 11 in P25/DMR.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 702

public_class_method def self.slice_4fsk(opts = {})
  samples = opts[:samples]
  rate    = opts[:rate].to_f
  baud    = opts[:baud].to_f
  spb     = rate / baud
  return [] if spb < 2.0 || samples.empty?

  lp   = envelope_signed(samples: dc_block(samples: samples), window: [(spb / 4.0).round, 1].max)
  nsym = (lp.length / spb).floor
  # sample mid-symbol values, then quantise into 4 levels
  vals = Array.new(nsym) { |i| lp[((i + 0.5) * spb).floor] || 0.0 }
  return [] if vals.empty?

  sorted = vals.sort
  lo = sorted[(nsym * 0.1).floor] || vals.min
  hi = sorted[(nsym * 0.9).floor] || vals.max
  step = (hi - lo) / 3.0
  step = 1e-9 if step.abs < 1e-9
  t_lo = lo + step
  t_hi = hi - step
  vals.map do |v|
    if v >= t_hi then 1        # +3
    elsif v >= 0 then 0        # +1
    elsif v >= t_lo then 2     # −1
    else 3                     # −3
    end
  end
end

.unpack_cs16le(opts = {}) ⇒ Object

Supported Method Parameters

iq = PWN::SDR::Decoder::DSP.unpack_cs16le( data: 'required - raw String of interleaved little-endian s16 I/Q' ) Returns interleaved Array [I0,Q0,I1,Q1,…] normalised ±1.0.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 435

public_class_method def self.unpack_cs16le(opts = {})
  data = opts[:data].to_s
  if native && PWN::FFI.available?(mod: :Volk)
    begin
      return PWN::FFI::Volk.unpack_s16le(data: data)
    rescue StandardError
      # fall through
    end
  end
  norm = 1.0 / 32_768.0
  data.unpack('s<*').map { |v| v * norm }
end

.unpack_cu8(opts = {}) ⇒ Object

Supported Method Parameters

iq = PWN::SDR::Decoder::DSP.unpack_cu8( data: 'required - raw String of interleaved u8 I/Q (RTL-SDR)' ) Returns interleaved Array [I0,Q0,…] centred & normalised ±1.0.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 454

public_class_method def self.unpack_cu8(opts = {})
  data = opts[:data].to_s
  norm = 1.0 / 128.0
  data.unpack('C*').map { |v| (v - 127.5) * norm }
end

.unpack_s16le(opts = {}) ⇒ Object

Supported Method Parameters

samples = PWN::SDR::Decoder::DSP.unpack_s16le( data: 'required - raw String of little-endian signed 16-bit PCM' )



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 70

public_class_method def self.unpack_s16le(opts = {})
  data = opts[:data].to_s
  if native && PWN::FFI.available?(mod: :Volk)
    begin
      return PWN::FFI::Volk.unpack_s16le(data: data)
    rescue StandardError
      # fall through to pure Ruby
    end
  end
  norm = 1.0 / 32_768.0
  data.unpack('s<*').map { |v| v * norm }
end

.whiten_lfsr(opts = {}) ⇒ Object

Supported Method Parameters

out = PWN::SDR::Decoder::DSP.whiten_lfsr( bytes: Array, poly: Integer, init: Integer, width: 7 ) Galois LFSR (MSB-first). BLE: poly 0x11 (x^7+x^4+1), init (ch|0x40).



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 826

public_class_method def self.whiten_lfsr(opts = {})
  bytes = opts[:bytes]
  poly  = opts[:poly].to_i
  reg   = opts[:init].to_i
  w     = (opts[:width] || 7).to_i
  top   = 1 << (w - 1)
  out   = Array.new(bytes.length)
  bytes.each_with_index do |byte, bi|
    v = byte & 0xFF
    8.times do |i|
      msb = reg.anybits?(top) ? 1 : 0
      reg = ((reg << 1) & ((1 << w) - 1))
      reg ^= poly if msb == 1
      v ^= (msb << i)
    end
    out[bi] = v
  end
  out
end

.zadoff_chu(opts = {}) ⇒ Object

Supported Method Parameters

zc = PWN::SDR::Decoder::DSP.zadoff_chu(root:, n: 63) Returns interleaved [I0,Q0,…] Array. LTE PSS uses roots 25/29/34.



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# File 'lib/pwn/sdr/decoder/dsp.rb', line 937

public_class_method def self.zadoff_chu(opts = {})
  u = opts[:root].to_i
  n = (opts[:n] || 63).to_i
  out = Array.new(n * 2)
  n.times do |k|
    ph = -Math::PI * u * k * (k + 1) / n
    out[k * 2]       = Math.cos(ph)
    out[(k * 2) + 1] = Math.sin(ph)
  end
  out
end