LPFのみIIRで実装

techno-cat · Oct 30, 2011 · 4eeb3b6 · 4eeb3b6
1 parent bba81f3
commit 4eeb3b6
Showing 1 changed file with 88 additions and 29 deletions.
diff --git a/p5-NeSynth/lib/Sound/NeSynth/Filter.pm b/p5-NeSynth/lib/Sound/NeSynth/Filter.pm
@@ -4,7 +4,7 @@ use 5.008009;
 use strict;
 use warnings;
 use Readonly;
-use Math::Trig qw( pi );
+use Math::Trig qw( tan pi );
 use base qw( Exporter );
 
 our %EXPORT_TAGS = ( 'all' => [ qw(
@@ -16,19 +16,86 @@ our @EXPORT_OK = ( @{ $EXPORT_TAGS{'all'} } );
 
 our $VERSION = '0.01';
 
+# Qの最小と最大値（このフィルターの仕様）
+Readonly my $Q_MIN =>  0.1;
+Readonly my $Q_MAX => 20.0;
+Readonly my $CUTOFF_MIN => 0.0;
+Readonly my $CUTOFF_MAX => 0.499; # cutoffが0.5だと計算途中でエラーになるのでこの値でガード
+
 sub create_filter {
 	my $samples_per_sec = shift;
 	my $arg_ref = shift;
 
-	my $freq = $arg_ref->{freq};
-	my $q = ( exists $arg_ref->{q} ) ? $arg_ref->{q} : (1 / (2 ** 0.5));
+	if ( not exists $arg_ref->{type} ) {
+		die '"type" not found. type: lpf, hpf, bpf, bef'
+	}
+
+	my $type = $arg_ref->{type};
+	my $cutoff = 0.0;
+	if ( exists $arg_ref->{cutoff} ) {
+		$cutoff = $arg_ref->{cutoff};
+	}
+	else {
+		die '"cutoff" not found. cutoff: ' . sprintf( "%f <= cutoff <= %f", $CUTOFF_MIN, $CUTOFF_MAX );
+	}
+
+	if ( $cutoff < $CUTOFF_MIN ) {
+		die '"cutoff" must be or more ' . $CUTOFF_MIN;
+	}
+
+	if ( $CUTOFF_MAX < $cutoff ) {
+		die '"cutoff" must be or less ' . $CUTOFF_MAX;
+	}
+
+	my $q = 1.0 / sqrt(2);
+	if ( exists $arg_ref->{Q} ) {
+		$q = $arg_ref->{Q};
 
-	# hoge
-	printf( "filter: freq = %.2f, Q = %.2f\n", $freq, $q );
+		if ( $q < $Q_MIN ) {
+			die '"Q" must be or more ' . $Q_MIN;
+		}
 
+		if ( $Q_MAX < $q ) {
+			die '"Q" must be or less ' . $Q_MAX;
+		}
+	}
+
+	printf( "filter: type: %s, cutoff = %.2f, Q = %.2f\n", $type, $cutoff, $q );
+
+	return _create_filter_func( $type, $cutoff, $q );
+}
+
+sub _create_filter_func {
+	my ( $type, $cutoff, $q ) = @_;
+
+	if ( $type eq 'lpf' ) {
+		# todo: LPFの係数算出
+	}
+	else {
+		die 'sorry, coming soon ...';
+	}
+
+	# for LPF
+	my $fc = tan(pi() * $cutoff) / (2.0 * pi());
+	my $tmp = 1.0 + ((2.0 * pi() * $fc) / $q) + (4.0 * pi() * pi() * $fc * $fc); # 各係数の分母
+	my $b0 = (4.0 * pi() * pi() * $fc * $fc) / $tmp;
+	my $b1 = (8.0 * pi() * pi() * $fc * $fc) / $tmp;
+	my $b2 = (4.0 * pi() * pi() * $fc * $fc) / $tmp;
+	my $a1 = ((8.0 * pi() * pi() * $fc * $fc) - 2.0) / $tmp;
+	my $a2 = (1.0 - ((2.0 * pi() * $fc) / $q) + (4.0 * pi() * pi() * $fc * $fc)) / $tmp;
+
+	printf( "%.4f, %.4f, %.4f, %.4f, %.4f\n", $b0, $b1, $b2, $a1, $a2 );
+
+	my @buf_a = ( 0.0, 0.0 );
+	my @buf_b = ( 0.0, 0.0, 0.0 );
 	return sub {
-		my $val = shift;
-		return $val;
+		unshift @buf_b, $_[0];
+		pop @buf_b;
+		my $ret = ($buf_b[2] * $b2) + ($buf_b[1] * $b1) + ($buf_b[0] * $b0)
+		        - ($buf_a[1] * $a2) - ($buf_a[0] * $a1);
+		unshift @buf_a, $ret;
+		pop @buf_a;
+		return $ret;
 	};
 }
 
@@ -41,34 +108,26 @@ Sound::NeSynth:Modulator - Modulator module for NeSynth
 
 =head1 SYNOPSIS
 
-  use Sound::NeSynth::Modulator;
+  my $samples_per_sec = 30;
+  my $type = 'lpf';
+  my $cutoff = 0.2; # must 0.0 <= cutoff <= 0.499
+  my $q = 0.7; # must 0.01 <= q <= 20.0
+  my $filter = create_filter( $samples_per_sec, { type => $type, cutoff => $cutoff, Q => $q } );
   
-  my $samples_per_sec = 4;
-  my $freq = 1;
-  my $osc = create_osc( $samples_per_sec, $freq );
-
-  $osc->(); #  0.0
-  $osc->(); #  1.0
-  $osc->(); #  0.0
-  $osc->(); # -1.0
-  $osc->(); #  0.0
-  $osc->(); #  1.0
-  # -- repeat --
+  # get response of 0.0 -> 1.0
+  my @result = map {
+    printf( "%f\n", $filter->(1.0) );
+  } 1..10;
 
 =head1 DESCRIPTION
 
-=head2 create_osc
+  This filter module is for Sound::NeSynth.
+  it's using IIR filter.
 
-  samples per sec = 4
-  frequency 1(Hz)
+=head1 SEE ALSO
+
+  Sound::NeSynth
 
-      <-- 1sec --><-- 1sec -
-+1.0  |  o           o
-      |
- 0.0  o-----o-----o-----> t
-      |
-+1.0  |        o
-  
 =head1 AUTHOR
 
 techno-cat, E<lt>techno.cat.miau(at)gmail.comE<gt>