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title: Interfaces
...

# Interfaces

In [Using an element as a
GObject](manual-elements.md#using-an-element-as-a-gobject), you have
learned how to use `GObject` properties as a simple way to do
interaction between applications and elements. This method suffices for
the simple'n'straight settings, but fails for anything more complicated
than a getter and setter. For the more complicated use cases, GStreamer
uses interfaces based on the GObject
[`GTypeInterface`](http://library.gnome.org/devel/gobject/stable/gtype-non-instantiable-classed.html)
type.

Most of the interfaces handled here will not contain any example code.
See the API references for details. Here, we will just describe the
scope and purpose of each interface.

## The URI interface

In all examples so far, we have only supported local files through the
“filesrc” element. GStreamer, obviously, supports many more location
sources. However, we don't want applications to need to know any
particular element implementation details, such as element names for
particular network source types and so on. Therefore, there is a URI
interface, which can be used to get the source element that supports a
particular URI type. There is no strict rule for URI naming, but in
general we follow naming conventions that others use, too. For example,
assuming you have the correct plugins installed, GStreamer supports
“file:///\<path\>/\<file\>”, “http://\<host\>/\<path\>/\<file\>”,
“mms://\<host\>/\<path\>/\<file\>”, and so on.

In order to get the source or sink element supporting a particular URI,
use `gst_element_make_from_uri ()`, with the URI type being either
`GST_URI_SRC` for a source element, or `GST_URI_SINK` for a sink
element.

You can convert filenames to and from URIs using GLib's
`g_filename_to_uri ()` and `g_uri_to_filename ()`.

## The Color Balance interface

The colorbalance interface is a way to control video-related properties
on an element, such as brightness, contrast and so on. It's sole reason
for existence is that, as far as its authors know, there's no way to
dynamically register properties using `GObject`.

The colorbalance interface is implemented by several plugins, including
xvimagesink and the Video4linux2 elements.

## The Video Overlay interface

The Video Overlay interface was created to solve the problem of
embedding video streams in an application window. The application
provides an window handle to the element implementing this interface to
draw on, and the element will then use this window handle to draw on
rather than creating a new toplevel window. This is useful to embed
video in video players.

This interface is implemented by, amongst others, the Video4linux2
elements and by ximagesink, xvimagesink and sdlvideosink.