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64 lines
2.7 KiB
Markdown
64 lines
2.7 KiB
Markdown
---
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title: Interfaces
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...
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# Interfaces
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In [Using an element as a
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GObject](manual-elements.md#using-an-element-as-a-gobject), you have
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learned how to use `GObject` properties as a simple way to do
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interaction between applications and elements. This method suffices for
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the simple'n'straight settings, but fails for anything more complicated
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than a getter and setter. For the more complicated use cases, GStreamer
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uses interfaces based on the GObject
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[`GTypeInterface`](http://library.gnome.org/devel/gobject/stable/gtype-non-instantiable-classed.html)
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type.
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Most of the interfaces handled here will not contain any example code.
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See the API references for details. Here, we will just describe the
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scope and purpose of each interface.
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## The URI interface
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In all examples so far, we have only supported local files through the
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“filesrc” element. GStreamer, obviously, supports many more location
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sources. However, we don't want applications to need to know any
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particular element implementation details, such as element names for
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particular network source types and so on. Therefore, there is a URI
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interface, which can be used to get the source element that supports a
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particular URI type. There is no strict rule for URI naming, but in
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general we follow naming conventions that others use, too. For example,
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assuming you have the correct plugins installed, GStreamer supports
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“file:///\<path\>/\<file\>”, “http://\<host\>/\<path\>/\<file\>”,
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“mms://\<host\>/\<path\>/\<file\>”, and so on.
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In order to get the source or sink element supporting a particular URI,
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use `gst_element_make_from_uri ()`, with the URI type being either
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`GST_URI_SRC` for a source element, or `GST_URI_SINK` for a sink
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element.
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You can convert filenames to and from URIs using GLib's
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`g_filename_to_uri ()` and `g_uri_to_filename ()`.
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## The Color Balance interface
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The colorbalance interface is a way to control video-related properties
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on an element, such as brightness, contrast and so on. It's sole reason
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for existence is that, as far as its authors know, there's no way to
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dynamically register properties using `GObject`.
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The colorbalance interface is implemented by several plugins, including
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xvimagesink and the Video4linux2 elements.
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## The Video Overlay interface
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The Video Overlay interface was created to solve the problem of
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embedding video streams in an application window. The application
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provides an window handle to the element implementing this interface to
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draw on, and the element will then use this window handle to draw on
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rather than creating a new toplevel window. This is useful to embed
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video in video players.
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This interface is implemented by, amongst others, the Video4linux2
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elements and by ximagesink, xvimagesink and sdlvideosink.
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