I’ve been playing with Gstreamer Perl binding lately and find out there is not good tutorial abouy how to make it. Ogg playing is not so straight forward as you excpect. This just stupid example that shows how to use Perl and Gstreamer in real job.

gst-launch filesrc location=test.ogg ! oggdemux name=muxer muxer. ! vorbisdec ! audioconvert ! lame bitrate=320 ! filesink location=test.mp3

#!/usr/bin/perl
# How to convert OGG to MP3 (Why you want to do that?)
# But good way to make exampe in Gstreamer in perl
use strict;
use warnings;
use Glib qw(TRUE FALSE);
use GStreamer;

GStreamer -> init();

if ($#ARGV < 1) {
  printf "usage: %s   %dn", $0, $#ARGV;
  exit -1;
}

print $ARGV[0]." to ";
print $ARGV[1];
print "n";

# create a new pipeline to hold the elements
my $l_SPipeline = GStreamer::Pipeline -> new("pipeline");

# Create Source read file
my $l_SSource = GStreamer::ElementFactory->make(filesrc  =>  "file-source");
# Mux OGG
my $l_SOggDemuxer = GStreamer::ElementFactory->make(oggdemux => "ogg-demuxer");
# Decode Vorbis audio
my $l_SVorbisDecoder = GStreamer::ElementFactory->make(vorbisdec => "vorbis-decoder");
# If needed convert audio
my $l_SAudioConverter = GStreamer::ElementFactory->make(audioconvert => "converter");
# Queue it if needed
my $l_SQueue = GStreamer::ElementFactory -> make(queue => "queue");
# Sink it to file
my $l_SSink = GStreamer::ElementFactory->make(filesink  =>  "file-sink");
# Mp3 encode
my $l_SEncode = GStreamer::ElementFactory->make(lame  =>  "mp3-encoder");

# Set up lame
$l_SEncode->set(bitrate => 320);

# Set filenames
$l_SSource->set(location => Glib::filename_to_unicode $ARGV[0]);
# Sink
$l_SSink->set(location => Glib::filename_to_unicode $ARGV[1]);

# add objects to the main pipeline
$l_SPipeline -> add($l_SSource, $l_SOggDemuxer, $l_SVorbisDecoder, $l_SAudioConverter, $l_SQueue, $l_SEncode, $l_SSink);

# Link source to Ogg muxer
$l_SSource->link($l_SOggDemuxer) or die "Can't link source to OGG-muxer";
# Link rest of pipeline
$l_SVorbisDecoder->link($l_SQueue, $l_SAudioConverter, $l_SEncode, $l_SSink)  or die "Can't link rest of stuff";

# Link Pads from Source to Sink
$l_SOggDemuxer->link_pads("src", $l_SVorbisDecoder, "sink");

# listen for newly created pads
$l_SOggDemuxer->signal_connect(pad_added => &pgotm_addPads) or die "Can't link Pads to vorbis";;

# start playing
$l_SPipeline -> set_state("playing");

# Listen for EOS
pgotm_eventLoop($l_SPipeline);

$l_SPipeline -> set_state("null");

# Add pads
sub pgotm_addPads {
  my ($element, $pad, $data) = @_;

  my $l_SCaps = $pad->get_caps();
  my $l_SMime = $l_SCaps->get_structure(0) -> { name };

  printf "Mime that is added is: %sn", $l_SMime;
  printf "A new pad %s was created %sn", $pad->get_name(), $pad->get_parent()->get_name();

  # If it's vorbis audio
  if( $l_SMime eq "audio/x-vorbis" ) {
    # Can it link to the audiopad?
    my $l_SSinkPad = $l_SVorbisDecoder->get_pad("sink");

   # Check if vorbis not linked..
   if(  !$l_SSinkPad->is_linked() ) {
      if( $pad->link( $l_SSinkPad ) ) {
         die "Can't link pads!rn";
     }
     print "Audio pads linked!n";
   } else {
     print "Audio is allready linked.. can't do it!n";
   }
  }
}

# Event loop to listen to events posted on the GstBus from the pipeline. Exits
# on EOS or ERROR events
sub pgotm_eventLoop {
  my ($l_SPipe) = @_;

  my $l_SBus = $l_SPipe->get_bus();

  while (TRUE) {
    my $l_SMessage = $l_SBus->poll("any", -1);

    if ($l_SMessage->type & "eos") {
      print "EOSn";
      return;
    } elsif ($l_SMessage->type & "warning") {
      print "Warning".$l_SMessage -> error."n";
    } elsif ($l_SMessage->type & "error") {
      $l_SSource->set_state("null");
      $l_SAudioConverter->set_state("null");
      $l_SVorbisDecoder->set_state("null");
      $l_SPipeline->set_state("null");
      die $l_SMessage -> error;
    }
  }
}

and what this all has to do with openSUSE you may ask? I packaged RPM from perl-Gstreamer 0.15 it can be found on build.opensuse.org. Problem was I got stuck when I was doing mp3 to ogg conversion. Nothing happens, I assume I have to links pads some how . Anybody how have been doing this with python??