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@windytan
Last active Sep 14, 2021
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use warnings;
use strict;
# Required: csdr, sox
my $infile = "one_morning.wav";
my $rate = 44100;
my $fscale = 24000;
# Shift fundamental to baseband
# And filter harmonics out
system("sox $infile -t .f32 -c 2 - | ".
"csdr shift_math_cc -0.005 | ".
"sox -t .f32 -r $rate -c 2 - shifted.wav sinc -140 -n 1024");
# FM demodulation to find fundamental frequency
system("sox shifted.wav -t .f32 - | ".
"csdr shift_math_cc 0.005 | ".
"csdr fmdemod_quadri_cf | ".
"sox -t .f32 -c 1 -r $rate - fmdemod.wav");
# AM demodulation to use as a "squelch"
system("sox shifted.wav -t .f32 - | ".
"csdr amdemod_cf | ".
"sox -t .f32 -r $rate -c 1 - amdemod.wav sinc -70 -n 1024");
open my $fm_in, "sox fmdemod.wav -t .f32 - sinc -70 -n 1024|";
open my $amp_in, "sox amdemod.wav -t .f32 -|";
open my $out, "|sox -t .f32 -c 1 -r $rate - birdson3.wav";
my $phase = 0;
my $t = 0;
while (not eof $fm_in) {
read $fm_in, my $fmdemod, 4;
$fmdemod = unpack "f", $fmdemod;
read $amp_in, my $amdemod, 4;
$amdemod = unpack "f", $amdemod;
my $freq = $fmdemod * 2 * 3.14159265 / $rate;
$phase += $freq * $fscale;
print $out pack "f", sin($phase * 6) * $amdemod;
$t += 1 / $rate;
}
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