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use warnings;
use Getopt::Std;
getopt('xytGgwsf',\%opts);
# pcm file = $opts{f}
# samples per pixel x
$xscale = $opts{x} // 1200;
# quant levels per pixel y
$yscale = $opts{y} // 100;
# oversampling target rate
$targetrate = $opts{t} // 1_099_961;
# wave preamplification, dB
$ygain = $opts{G} // 0;
# brightness added by one sample
$gain = $opts{g} // 6;
# img width
$w = $opts{w} // 1000;
# skip amount of seconds
$skip_sec = $opts{s} // 0.05;
############
# turquoise tint
for (0..127) { @{$gradient[$_]} = ($_/2, $_*1.5 ,$_*1.5); }
for (128..255) { @{$gradient[$_]} = (64+ ($_-128)*1.5, 192+($_-128)/2, 192+($_-128)/2); }
open(S,"sox \"".$opts{f}."\" -r $targetrate -b 16 -c 2 -t .raw -e signed - trim $skip_sec gain $ygain|");
$n=0;
while(not eof(S)) {
read(S,$a,2);
$a = -unpack("s",$a);
# pixel position of this sample
$x = $n/$xscale;
$y = ($a+32768)/$yscale;
# bilinear interpolation
$xdec = $x-int($x);
$ydec = $y-int($y);
$pix[$x][$y] += (1-$xdec) * (1-$ydec);
$pix[$x+1][$y] += ($xdec) * (1-$ydec);
$pix[$x][$y+1] += (1-$xdec) * ($ydec);
$pix[$x+1][$y+1] += ($xdec) * ($ydec);
last if ($n/$xscale > $w);
read(S,$a,2);
$n++;
}
close(S);
open(U,"|convert -depth 8 -size ".$w."x".int(65536/$yscale)." rgb:- osc.png");
for $y (0..65536/$yscale-1) {
for $x (0..$w-1) {
$p = ($pix[$x][$y] // 0) * $gain;
$p = 255 if ($p > 255);
if ($y == round(65536/$yscale/2)) {
@a = @{$gradient[$p]};
for (@a) { $_ += 64; $_ = 255 if ($_ > 255); }
print U pack("CCC",@a);
} else {
print U pack("CCC",@{$gradient[$p]});
}
}
}
close(U);
sub round { int($_[0]+.5); }
@kragen

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commented Dec 9, 2013

@alankila

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commented Feb 2, 2014

Would you have the audio file for this? I'd like to see if I can replicate this with direct sinc interpolation.

@tvillingett

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commented Oct 10, 2015

I could not get this to work, I'm new to perl also... I installed perl 5 on my mac, and then run the oscillo.pl name of the .wav file as an argument.
First it wrote: print() on closed filehandle U at oscillo.pl line 71.
all over all the time (until i quit with ctrl+c)
then i added use autodie; in row 3 to try to catch the real problem, and then I got:
MacBook-Air:perl_test tvillingett$ perl oscillo.pl 198376__bunting__dscn0099.wav Use of uninitialized value $opts{"f"} in concatenation (.) or string at oscillo.pl line 36. sh: sox: command not found Can't close filehandle 'S': '' at oscillo.pl line 60

Any ideas?

@arunganesan

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commented Nov 18, 2015

@tvillingett you need to use the "-f" option for specifying the wave file. It is something like this:

perl oscillo.pl -f file.wav

All the other options change how the script works. Also make sure you have imagemagick and sox installed.

Works and looks great, windytan! Thank you!

@thodnev

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commented May 8, 2016

I've seen your article, and that's great. But in my opinion in would be nice if you could also write a textual/pseudocode algorithm to make it easier to understand. There aren't much perl jedi knights nowadays.

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