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lib/MPEG/Audio/Frame.pm  view on Meta::CPAN

###

my @protbits = (
	[ 128, 256 ], # layer one
	undef,
	[ 136, 256 ], # layer three
);


my @consts;
sub B ($) { $_[0] == 12 ? 3 : (1 + ($_[0] / 4)) }
sub M ($) {
	my $s = 0;
	$s += $consts[$_][1] for (0 .. $_[0]-1);
	$s%=8;
	my $v = '';
	vec($v,8-$_,1) = 1 for $s+1 .. $s+$consts[$_[0]][1];
	"0x" . unpack("H*", $v);
}
sub R ($) { 
	my $i = 0;
	my $m = eval "M_$consts[$_[0]][0]()";
	$i++ until (($m >> $i) & 1);
	$i;
}

BEGIN {
	@consts = (
		# [ $name, $width ]
		[ SYNC => 3 ],