Transcoder *->m4a jig

m4a.pl

#!/usr/bin/env perl
use strict;
use warnings;
use threads;
use sigtrap qw(die INT QUIT);

use File::Basename;
use File::Path qw/make_path/;
use Data::Dumper;
use POSIX;
use Thread::Queue;
local @_;
while (<>){
	chomp;
	push @_, $_ if $_;
}
our $N = scalar @_;

exit unless $N > 0;

sub lg {
	my $n = shift;
	return log($n)/log(10);
}
sub compose {
	my $f = shift;
	my $g = shift;
	die unless ref $f eq 'CODE';
	die unless ref $g eq 'CODE';
	return sub {
		return $f->($g->(@_));
	}
};

our ($nthr, $pn, $tn, @workers, $wq);
$nthr = $N > 8 ? 8 : $N;
my $clg = compose(\&POSIX::ceil, \&lg);
$pn = $clg->(do "/proc/sys/kernel/pid_max");
$tn = $clg->($nthr);
our $do_jpg = $ENV{DO_JPG} // 1;
our $skip_m4a = $ENV{SKIP_M4A} // undef;
@workers = ();
$wq = Thread::Queue->new();

for (my $i = 0; $i < $nthr; ++$i) {
	push @workers, async {
		my $th = sprintf("%0".$pn."d_%0".$tn."d", $$, $i);
		while (local $_ = $wq->dequeue) {
			my ($S, $D, $SF, $DF);
			$S=$_;
			$D="../SS/".$S;
			make_path(dirname $D);
			if ($D =~ /\.m4a$/ and $skip_m4a) {
				system('cp', $S, $D) == 0 or die "cp.m4a \"$S\" \"$D\"";
				next;
			}
			$SF="/tmp/AEAE_$th";
			$DF="/tmp/AEAF_$th.m4a";
			if ($D =~ /\.(?:jpe?g|png)$/i) {
				next unless $do_jpg;
				system('cp', $S, $D) == 0 or die "cp.jpg \"$S\" \"$D\"";
				next;
			}
			$D =~ s/\.[^.]+$/.m4a/; 
			system('cp', $S, $SF) == 0 or die "cp";
			system(qw/ffmpeg -i/, $SF, qw/-vn -c:a libfdk_aac -vbr 3 -y/, $DF) == 0 or die "ffmpeg (\"$S\") (\"$D\")";
			system('cp', $DF, $D) == 0 or die "cp";
			unlink $SF;
			unlink $DF;
		}
	};
}

for (@_) {
	$wq->enqueue($_);
}
$wq->end();
$_->join() for (@workers);