=head1 NAME

write_wav

=head1 SYNOPSYS

perl write_wav

=head1 DESCRIPTION

This routine writes a test .wav file and prints out the waveform so that
it can be played with the sound player.

This creates an 8 bit sound file.

=cut
$note= "sininvx";
open (WAV, ">$note.wav");
open (GRAPH, ">graph.out");
print WAV "RIFF";
print WAV pack("C*", (52,62,0,0));
print WAV "WAVEfmt ";
print WAV pack("C*", (16,0,0,0));  #length of fmt  chunk
print WAV pack("C*", (1,0));  # Format number
print WAV pack("C*", (1,0));  # Number of channels
print WAV pack("C*", (34,86,0,0));  #22050 samples per sec
print WAV pack("C*", (34,86,0,0));  #22050 bytes per sec
print WAV pack("C*", (1,0));  # Block size
print WAV pack("C*", (8,0));  # Garbage
print WAV "fact";
print WAV pack("C*", (4,0,0,0,4,62,0,0));  # ?
print WAV "data";
print WAV pack("C*", (4,62,0,0));  # ?
$pi2= atan2(1,1)*8;

if ($note eq "sin")
{
  $freq=300;
  $tscale=1/22050;
  $om= $pi2*$freq*$tscale;
  for ($i=0; $i<15876; $i++)
  {
    $k=int(sin($i*$om)*100+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
}

elsif ($note eq "sininvx")
{
  $om= .0001;
  for ($i=0; $i<15876; $i++)
  {
    $k=int(sin(1000/($i*$om+1))*100+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
}

elsif ($note eq "ramp")
{
  # Need to look at the old FORTRAN DSP solution for the
  # phase through a frequency sweep.
  $pi2= atan2(1,1)*8;
  $freq1=1000;
  $freq2=2000;
  $tscale=1/22050;
  $om1= $pi2*$freq1*$tscale;
  $om2= $pi2*$freq2*$tscale;
  for ($i=0; $i<15876; $i++)
  {
    $k=int(sin($i*$i*$om1/$om2)*50+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
}

elsif ($note eq "noise")
{
  for ($i=0; $i<15876; $i++)
  {
    $k=int((rand(1)-0.5)*100+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
}

elsif ($note eq "pops")
{
  for ($i=0; $i<15876; $i++)
  {
    $m= $i % 3000;
    if ($m < 100) 
    { $j=$m * $m / 100 ; } 
    elsif ($m < 200) 
    { $j=(200 - $m)*(200 - $m)/100; }
    else 
    { $j=0 ; }
    $k=int($j+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
} 

elsif ($note eq "tan")
{
  $freq=300;
  $tscale=1/22050;
  $om= $pi2*$freq*$tscale;
  for ($i=0; $i<15876; $i++)
  {
    $j= &lim_tan($i*$om); 
    $k= int($j*10+128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
} 

elsif ($note eq "square")
{
  $freq= 300;
  $tsamp= 22050;
  $hperiod= $tsamp/(2*$freq);
  $phase_flip_point= $hperiod;
  $ampl=1;
  for ($i=0; $i<15876; $i++)
  {
    if ($i > $phase_flip_point)
    {
      $phase_flip_point= $phase_flip_point + $hperiod;
      $ampl= -$ampl;
    }
    $k= int($ampl * 100 + 128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
} 

elsif ($note eq "saw")
{
  $freq= 300;
  $tsamp= 22050;
  $ampl_env= 100;
  $hperiod= $tsamp/(2*$freq);
  $phase_flip_point= $hperiod;
  $slew= $ampl_env/$hperiod;
  $ampl= -100;
  for ($i=0; $i<15876; $i++)
  {
    if ($i > $phase_flip_point)
    {
      $phase_flip_point= $phase_flip_point + $hperiod;
      if ($slew > 0) 
      {
        $ampl= $ampl_env;
      }
      else
      {
        $ampl= -$ampl_env;
      }
      $slew= -$slew;
    }
    else
    {
      $ampl=$ampl + $slew;
    }
    $k= int($ampl + 128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
} 

elsif ($note eq "tri")
{
  $freq= 300;
  $tsamp= 22050;
  $ampl_env= 100;
  $hperiod= $tsamp/(2*$freq);
  $phase_flip_point= $hperiod;
  $slew= 2 * $ampl_env/$hperiod;
  $ampl= -100;
  for ($i=0; $i<15876; $i++)
  {
    if ($i > $phase_flip_point)
    {
      $phase_flip_point= $phase_flip_point + $hperiod;
      if ($slew > 0) 
      {
        $ampl= $ampl_env;
      }
      else
      {
        $ampl= -$ampl_env;
      }
      $slew= -$slew;
    }
    else
    {
      $ampl=$ampl + $slew;
    }
    $k= int($ampl + 128);
    if ($k > 255){$k=255;}
    if ($k < 0)  {$k=0;  }
    print WAV pack("C", $k);
    print GRAPH $i." ".$k."\n";
  }
} 

close WAV;
close GRAPH;
system("c:\\windows\\mplayer.exe /play /close $note.wav");
# unlink("$note.wav");

sub lim_tan()
{
  my $arg= shift;
  my $tan;
  my $cos= cos($arg);
  if ($cos != 0)
  {
    $tan= sin($arg)/$cos;
  }
  else
  {
    $tan=10;
  }
  if ($tan > 10) {$tan=10;}
  if ($tan < -10) {$tan=-10;}
  $tan;
}