#!/usr/bin/env perl
 
 # Copyright (c) 2012 Nicolas George
 #
 # This file is part of FFmpeg.
 #
 # FFmpeg is free software; you can redistribute it and/or
 # modify it under the terms of the GNU Lesser General Public
 # License as published by the Free Software Foundation; either
 # version 2.1 of the License, or (at your option) any later version.
 #
 # FFmpeg is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of
 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
 # See the GNU Lesser General Public License for more details.
 #
 # You should have received a copy of the GNU Lesser General Public License
 # along with FFmpeg; if not, write to the Free Software Foundation, Inc.,
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
 
 =head1 NAME
 
 make_chlayout_test - produce a multichannel test file with the channels
 clearly identified
 
 =head1 SYNOPSIS
 
 tools/make_chlayout_test I<channels> I<out_options>
 
 =head1 DESCRIPTION
 
 This script uses B<ffmpeg> and B<libflite> to produce a file with audio
 channels clearly identified by their name. The resulting file can be used to
 check that the layout and order of channels is correctly handled by a piece
 of software, either a part of B<FFmpeg> or not.
 
 I<channels> is a list of channels or channel layouts, separated by '+'.
 
 I<out_options> is a list of valid ffmpeg outout options, including the
 output file.
 
 Note that some output codecs or formats can not handle arbitrary channel
 layout.
 
 This script requires a B<ffmpeg> binary, either in the source tree or in the
 search path; it must have the flite audio source enabled.
 
 =head1 EXAMPLES
 
 Check that the speakers are correctly plugged:
 
   tools/make_chlayout_test FL+FR -f alsa default
 
 Produce a 5.1 FLAC file:
 
   tools/make_chlayout_test 5.1 surround.flac
 
 =cut
 
 use strict;
 use warnings;
 use Getopt::Long ":config" => "require_order";
 use Pod::Usage;
 
 GetOptions (
   "help|usage|?|h" => sub { pod2usage({ -verbose => 1, -exitval => 0 }) },
   "manpage|m"      => sub { pod2usage({ -verbose => 2, -exitval => 0 }) },
 ) and @ARGV >= 2 or pod2usage({ -verbose => 1, -exitval => 1 });
 
 my $channels = shift @ARGV;
 my @out_options = @ARGV;
 
 my $ffmpeg = exists $ENV{FFMPEG} ? $ENV{FFMPEG} :
              $0 =~ /(.*)\// && -e "$1/../ffmpeg" ? "$1/../ffmpeg" :
              "ffmpeg";
 
 my %channel_label_to_descr;
 my %layout_to_channels;
 
 {
   open my $stderr, ">&STDERR";
   open STDERR, ">", "/dev/null";
   open my $f, "-|", $ffmpeg, "-layouts" or die "$ffmpeg: $!\n";
   open STDERR, ">&", $stderr;
   while (<$f>) {
     chomp;
     next if /^NAME/ or /:$/ or /^$/; # skip headings
     my ($name, $descr) = split " ", $_, 2;
     next unless $descr;
     if ($descr =~ /^[[:upper:]]+(?:\+[[:upper:]]+)*$/) {
       $layout_to_channels{$name} = [ split /\+/, $descr ];
     } else {
       $channel_label_to_descr{$name} = $descr;
     }
   }
 }
 
 my @channels = map { @{$layout_to_channels{$_} // [$_]} } split /\+/, $channels;
 
 my $layout = join "+", @channels;
 my $graph = "";
 my $concat_in = "";
 for my $i (0 .. $#channels) {
   my $label = $channels[$i];
   my $descr = $channel_label_to_descr{$label}
     or die "Channel $label not found\n";
   $graph .= "flite=text='${descr}', aformat=channel_layouts=mono, " .
             "pan=${layout}:${label}=c0 [ch$i] ;\n";
   $concat_in .= "[ch$i] ";
 }
 $graph .= "${concat_in}concat=v=0:a=1:n=" . scalar(@channels);
 
 exec $ffmpeg, "-f", "lavfi", "-i", $graph, @out_options
   or die "$ffmpeg: $!\n";