oscillo.pl

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); }

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?

@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!

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.