I'm trying to write an MP3 daemon. After realizing Audio::Play::MPG123 must've been buggy somewhere, I decided to write my own interface to MPG321. And so here is Audio::Play::MPG321:

#!/usr/bin/perl

package Audio::Play::MPG321;

use strict;
use warnings;
use IPC::Open2;
use IO::Select;
$| = 1;

sub new {
 my $class = shift;
 my ($read, $write);
 my $pid = open2($read, $write, "mpg321", "--aggressive",
                 "--skip-printing-frames=39", "-R", "start");
 my $handle = IO::Select->new($read);
 my $self = {
  pid => $pid,
  read => $read,
  write => $write,
  handle => $handle,
  song => undef,
  sofar => "0:00",
  remains => "0:00",
  state => 2
 };
 bless($self, $class);
 return $self;
}

sub poll {
 my $self = shift;
 while ($self->{handle}->can_read(0.5)) {
  my $in;
  sysread($self->{read}, $in, 1024);
  $self->parse($in);
 }
}

sub parse {
 my $self = shift;
 my $in = shift;
 if ($in =~ m/^\@P /) {
  $in =~ s/^\@P //;
  $self->{state} = $in;
 } elsif ($in =~ m/^\@F /) {
  $in =~ s/^\@F //;
  my ($sofar, $remains) = split(/ /, $in);
  $self->{sofar} = sprintf("%d:%02d", int($sofar / 60), $sofar % 60);
  $self->{remains} = sprintf("%d:%02d", int($remains / 60), $remains %
+ 60);
 }
}

sub play {
 my $self = shift;
 my $song = shift;
 print { $self->{write} } "load $song\n";
}

sub state {
 my $self = shift;
 return $self->{state};
}

sub toggle {
 my $self = shift;
 print { $self->{write} } "pause\n";
}

sub pause {
 my $self = shift;
 print { $self->{write} } "pause\n" if $self->state() == 2;
}

sub resume {
 my $self = shift;
 print { $self->{write} } "pause\n" if $self->state() == 1;
}

sub seek {
 my $self = shift;
 my $position = shift;
 $position *= 39;
 print { $self->{write} } "jump $position\n";
}

sub stop {
 my $self = shift;
 print { $self->{write} } "quit\n";
}

1;

__END__
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Note that I took the mpg321 source code and modified it in several ways to produce different output in -R (remote) mode. I did this simply for simplicity. Basically mpg321 will give the following types of output, which are read by poll() and parsed by parse(). @F x x # x are digits that show the number of seconds passed and the number remaining @P x # Where x is 0 (stopped), 1 (paused), or 2 (playing) The module works pretty well. The only problem I have is the single most frustrating bug I have ever encountered. If I pause it, the {state} of the player will change to 1. In resume(), I test for the return value of state(), which is simply an accessor for {state}, to be 1 (meaning the song is paused.) Oddly enough though, when the song is paused, resume has no effect! Why? I inserted a print statement before the test, and apparently $self->{state} magically returns to 2! I inserted print tests everywhere and found out nothing. The only places that {state} seemed to be set are in new(), which is only caused once, and in parse() when it encounters '@P x', but I made sure it's not being set incorrectly there with print statements. I have absolutely no clue what is going wrong. Any advice or code is appreciated. As always, I can be found on #perl, irc.freenode.net, alias dabreegster. Here's a client for A::P::M, if needed:

#!/usr/bin/perl

$| = 1;
use Audio::Play::MPG321;

$player = new Audio::Play::MPG321;

$SIG{CHLD} = 'IGNORE';
$SIG{INT} = sub {
 $player->stop();
 exit 1;
};

do {
 while (1) {
  $player->poll();
  select(undef, undef, undef, 0.5);
 }
} unless fork();

while (1) {
 print "\n> ";
 chomp(my $in = <STDIN>);
 my ($method, @args) = split(/\s+/, $in);
 $player->$method(@args);
 print $player->state(), "\n";
}
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Considered by ewijaya; "There are too many similarity with this node written by the same author."
Unconsidered by davido: Keep votes blocked reaping. Also, node wasn't an exact duplicate.