The Linux Experiment

For something to do I decided to see if I could create a very simple Java media player. After doing some research, and finding out that the Java Media Framework was no longer in development, I decided to settle on GStreamer to power my media player.

GStreamer for the uninitiated is a very powerful multimedia framework that offers both low-level pipeline building as well as high-level playback abstraction. What’s nice about GStreamer, besides being completely open source, is that it presents a unified API no matter what type of file it is playing. For instance if the user only has the free, high quality GStreamer codecs installed, referred to as the good plugins, then the API will only play those files. If however the user installs the other plugins as well, be it the bad or ugly sets, the API remains the same and thus you don’t need to update your code. Unfortunately being a C library this approach does have some drawbacks, notably the need to include the JNA jar as well as the system specific libraries. This approach can be considered similar to how SWT works.

Setup

Assuming that you already have a Java development environment, the first thing you’ll need is to install GStreamer. On Linux odds are you already have it, unless you are running a rather stripped down distro or don’t have many media players installed (both Rhythmbox and Banshee use GStreamer). If you don’t it should be pretty straight forward to install along with your choice of plugins. On Windows you’ll need to head over to ossbuild where they have downloadable installers.

The second thing you’ll need is gstreamer-java which you can grab over at their website here. You’ll need to download both gstreamer-java-1.4.jar and jna-3.2.4.jar. Both might contain some extra files that you probably don’t need and can prune out later if you’d like. Setup your development environment so that both of these jar files are in your build path.

Simple playback

GStreamer offers highly abstracted playback engines called PlayBins. This is what we will use to actually play our files. Here is a very simple code example that demonstrates how to actually make use of a PlayBin:

public static void main(String[] args) {
     args = Gst.init("MyMediaPlayer", args);

     Playbin playbin = new PlayBin("AudioPlayer");
     playbin.setVideoSink(ElementFactory.make("fakesink", "videosink"));
     playbin.setInputFile("song.mp3");

     playbin.setState(State.PLAYING);
     Gst.main();
     playbin.setState(State.NULL);
}

So what does it all mean?

public static void main(String[] args) {
     args = Gst.init("MyMediaPlayer", args);

The above line takes the incoming command line arguments and passes them to the Gst.init function and returns a new set of arguments. If you have every done any GTK+ programming before this should be instantly recognizable to you. Essentially what GStreamer is doing is grabbing, and removing, any GStreamer specific arguments before your program will actually process them.

     Playbin playbin = new PlayBin("AudioPlayer");
     playbin.setVideoSink(ElementFactory.make("fakesink", "videosink"));
     playbin.setInputFile("song.mp3");

The first line of code requests a standard “AudioPlayer” PlayBin. This PlayBin is built right into GStreamer and automatically sets up a default pipeline for you. Essentially this lets us avoid all of the low-level craziness that we would have to normally deal with if we were starting from scratch.

The next line sets the PlayBin’s VideoSink, think of sinks as output locations, to a “fakesink” or null sink. The reason we do this is because PlayBin’s can play both audio and video. For the purposes of this player we only want audio playback so we automatically redirect all video output to the “fakesink”.

The last line is pretty straight forward and just tells GStreamer what file to play.

     playbin.setState(State.PLAYING);
     Gst.main();
     playbin.setState(State.NULL);

Finally with the above lines of code we tell the PlayBin to actually start playing and then enter the GStreamer main loop. This loop continues for the duration. The last line is used to reset the PlayBin state and do some cleanup.

Bundle it with a quick GUI

To make it a little more friendly I wrote a very quick GUI to wrap all of the functionality with. The download links for that (binary only package), as well as the source (all package) is below. And there you have it: a very simple cross-platform media player that will playback pretty much anything you throw at it.

Please note that I have provided this software purely as a quick example. If you are really interested in developing a GStreamer powered Java application you would do yourself a favor by reading the official documentation.

	Binary Only Package	All Package
File name:	my_media_player_binary.zip	my_media_player_all.zip
Screenshots:
Version:	March 13, 2011
File size:	1.5MB	1.51MB
File download:	Download Here	Download Here

Originally posted on my personal website here.