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100 lines
3.7 KiB
Text
100 lines
3.7 KiB
Text
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<chapter id="cha-autoplug">
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<title>Autoplugging</title>
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<para>
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<application>GStreamer</application> provides an API to automatically
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construct complex pipelinebased on source and destination capabilities.
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This feature is very usefull if you want to convert type X to type Y but
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don't care about the plugins needed to accomplish this task. The
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autoplugger will consult the plugin repository, select and connect the
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elements needed for the conversion.
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</para>
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<para>
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The autoplugger API is implemented in an abstract class. Autoplugger implementations
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reside in plugins and are therefore optional and can be optimized for a specific
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task. Two types of autopluggers exist: renderer ones and non
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renderer ones. the renderer autopluggers will not have any src pads while the
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non renderer ones do. The renderer autopluggers are mainly used for media
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playback while the non renderer ones are used for arbitrary format conversion.
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</para>
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<sect1>
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<title>Using autoplugging</title>
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<para>
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You first need to create a suitable autoplugger with gst_autoplugfactory_make().
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The name of the autoplugger must be one of the registered autopluggers..
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</para>
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<para>
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A list of all available autopluggers can be obtained with gst_autoplugfactory_get_list().
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</para>
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<para>
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If the autoplugger supports the RENDERER API, use gst_autoplug_to_renderers() call to
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create a bin that connectes the src caps to the specified render elements. You can
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then add the bin to a pipeline and run it.
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<programlisting>
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GstAutoplug *autoplug;
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GstElement *element;
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GstElement *sink;
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/* create a static autoplugger */
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autoplug = gst_autoplugfactory_make ("staticrender");
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/* create an osssink */
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sink = gst_elementfactory_make ("osssink", "our_sink");
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/* create an element that can play audio/mp3 through osssink */
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element = gst_autoplug_to_renderers (autoplug,
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gst_caps_new (
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"sink_audio_caps",
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"audio/mp3",
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NULL
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),
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sink,
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NULL);
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/* add the element to a bin and connect the sink pad */
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...
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</programlisting>
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</para>
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<para>
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If the autoplugger supports the CAPS API, use the gst_autoplug_to_caps() function to
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connect the src caps to the destination caps. The created bin will have src and sink
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pads compatible with the provided caps.
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<programlisting>
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GstAutoplug *autoplug;
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GstElement *element;
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/* create a static autoplugger */
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autoplug = gst_autoplugfactory_make ("static");
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/* create an element that converts audio/mp3 to audio/raw */
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element = gst_autoplug_to_caps (autoplug,
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gst_caps_new (
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"sink_audio_caps",
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"audio/mp3",
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NULL
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),
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gst_caps_new (
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"src_audio_caps",
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"audio/raw",
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NULL
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),
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NULL);
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/* add the element to a bin and connect the src/sink pads */
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...
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</programlisting>
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</para>
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</sect1>
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<sect1>
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<title>A complete autoplugging example</title>
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<para>
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We will create and explain how a complete media player can be built with the
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autoplugger.
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</para>
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</sect1>
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</chapter>
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