GStreamer

GStreamer

Stable release	0.10.21 / 2 October, 2008
Repository	gitlab.freedesktop.org/gstreamer/gstreamer.git
Written in	C
Operating system	Cross-platform
Type	Multimedia framework
License	GNU Lesser General Public License
Website	http://gstreamer.freedesktop.org/

GStreamer is a pipeline based multimedia framework written in the C programming language with the type system based on GObject. GStreamer allows you to create a variety of media-handling components, including simple audio playback, audio and video playback, recording, streaming, and editing. The pipeline design serves as a base to create many types of multimedia applications such as video editors, streaming media broadcasters, and media players.

Designed to be cross-platform, it is known to work on Linux (x86, PowerPC and ARM), Solaris (x86 and SPARC), Mac OS X, Microsoft Windows and OS/400. GStreamer has bindings for programming-languages like Python, C++, Perl, GNU Guile and Ruby. GStreamer is free software, licensed under the GNU Lesser General Public License.

Distribution

The GNOME desktop environment, the primary user of GStreamer technology, has included GStreamer since GNOME version 2.2 and encourages GNOME and GTK+ applications to use it. Other projects also use it, such as Chameleo media platform, Phonon and the Songbird media player.

GStreamer also operates in embedded devices like the Nokia 770, N800 and N810 Internet Tablets running the Internet Tablet OS.

History and development

Erik Walthinsen founded the GStreamer project in 1999. Many of its core design ideas came from a research project at the Oregon Graduate Institute. Wim Taymans joined the project soon thereafter and greatly expanded on many aspects of the system. Many others around the world have contributed to various degrees since then. Brock A. Frazier designed the GStreamer logo; Frazier worked for an embedded Linux company called RidgeRun, which also became the first corporate sponsor of GStreamer in the form of hiring Erik Walthinsen to develop methods for embedding GStreamer in smaller (cell phone-class) devices.

freedesktop.org hosts the GStreamer project, which accordingly aims to improve interoperability and to share technology between free desktops. As of 2008, Wim Taymans maintains GStreamer.

The current 0.10 stable release series began with the 0.10.0 release in December 2005 . It has maintained API and ABI compatibility since.

Technical overview

GStreamer processes media by connecting a number of processing elements into a pipeline. Each element is provided by a plugin. Elements can be grouped into bins, which can be further aggregated, thus forming a hierarchical graph. This is an example of a filter graph.

Elements communicate by means of pads. A source pad on one element can be connected to a sink pad on another. When the pipeline is in the playing state, data buffers flow from the source pad to the sink pad. Pads negotiate the kind of data that will be sent using capabilities.

The diagram to the right could exemplify playing an MP3 file using GStreamer. The file source reads an MP3 file from a computer's hard-drive and sends it to the MP3 decoder. The decoder decodes the file data and converts it into PCM samples which then pass to the ALSA sound-driver. The ALSA sound-driver sends the PCM sound samples to the computer's speakers.

Plugins

GStreamer uses a plugin architecture which makes the most of GStreamer's functionality implemented as shared libraries. GStreamer's base functionality contains functions for registering and loading plugins and for providing the fundamentals of all classes in the form of base classes. Plugin libraries get dynamically loaded to support a wide spectrum of codecs, container formats, input/output drivers and effects.

Plugins can be installed semiautomatically when they are first needed. For that purpose distributions can register a backend that resolves feature-descriptions to package-names.

Since version 0.10 the plugins come grouped into three sets (named after the film The Good, the Bad and the Ugly),

Plugin set name	Description
Good	This package contains the GStreamer plugins from the "good" set, a set of high quality plug-ins under the LGPL license. or according to Gstreamer, "contains a set of well-supported plug-ins under our preferred license"
Bad	GStreamer Bad Plug-ins comprises a set of plug-ins not up-to-par compared to the rest. They might closely approach good-quality plugins, but they lack something: perhaps a good code review, some documentation, a set of tests, a real live maintainer, or some actual wide use.
Ugly	This packages contains plugins from the "ugly" set, a set of good-quality plug-ins that might pose distribution problems

Individual distributions may further sub-classify these plugins: for example Ubuntu groups the "bad" and "ugly" sets into the "Universe" or the "Multiverse" components.

External links

• GStreamer home page
• An introduction to GStreamer
• GStreamer project on Ohloh
• #gstreamer on freenode