deinvert-difficult.pl

$fs = 48000; # sample rate
$fc = 3729;  # carrier frequency
$filter = " sinc -$fc"; # optional LP filter

$fc = freq($fc);

open(IN, "sox scrambled.wav -c 1 -b 16 -e signed -t .raw -|");
open(OUT,"|sox -r $fs -c 1 -b 16 -e signed -t .raw - descrambled.wav".
         $filter);

while (not eof IN) {

  $acc += $fc;
  $acc -= 65536 if ($acc > 32767);

  read(IN,$a,2);
  print OUT pack("s",unpack("s",$a) * sin($acc/32768*3.141592653589793));
}

sub freq { int(.5 + $_[0] * 65536 / $fs); }