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111 lines
3.9 KiB
XML
111 lines
3.9 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN"
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"http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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<!ENTITY % local.common.attrib "xmlns:xi CDATA #FIXED 'http://www.w3.org/2003/XInclude'">
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]>
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<refentry id="ges-architecture" revision="25 mar 2009">
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<refmeta>
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<refentrytitle>Overview and architecture</refentrytitle>
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<manvolnum>1</manvolnum>
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<refmiscinfo>GStreamer Editing Services</refmiscinfo>
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</refmeta>
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<!-- <refnamediv> -->
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<!-- <refname>Overview</refname> -->
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<!-- <refpurpose> -->
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<!-- Goals of the GStreamer Editing Services. -->
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<!-- </refpurpose> -->
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<!-- </refnamediv> -->
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<refsect1>
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<title>Goals of GStreamer Editing Services</title>
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<para>The GStreamer multimedia framework and the accompanying GNonLin set
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of plugins for non-linear editing offer all the building blocks for:
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<itemizedlist>
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<listitem>
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<para>Decoding and encoding to a wide variety of formats, through
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all the available GStreamer plugins.</para>
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</listitem>
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<listitem>
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<para>Easily choosing segments of streams and arranging them through
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time through the GNonLin set of plugins.</para>
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</listitem>
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</itemizedlist></para>
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<para>But all those building blocks only offer stream-level access, which
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results in developers who want to write non-linear editors to write a
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consequent amount of code to get to the level of <emphasis>non-linear
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editing</emphasis> notions which are closer and more meaningful for the
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end-user (and therefore the application).</para>
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<para>The GStreamer Editing Services <remark>(hereafter GES)</remark> aims
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to fill the gap between GStreamer/GNonLin and the application developer by
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offering a series of classes to simplify the creation of many kind of
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editing-related applications.</para>
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</refsect1>
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<refsect1>
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<title>Architecture</title>
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<refsect2>
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<title>Timeline and TimelinePipeline</title>
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<para>The most top-level object encapsulating every other object is the
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<link linkend="GESTimeline">GESTimeline</link>. It is the central object
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for any editing project.</para>
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<para>The <classname>GESTimeline</classname> is a
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<classname>GstElement</classname>. It can therefore be used in any
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GStreamer pipeline like any other object.</para>
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</refsect2>
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<refsect2>
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<title>Tracks and Layers</title>
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<para>The GESTimeline can contain two types of objects (seen in <xref
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linkend="layer_tracks_diagram" />): <itemizedlist>
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<listitem>
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<para>Layers - Corresponds to the user-visible arrangement of clips,
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and what you primarily interact with as an application developer.
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A minimalistic timeline would only have one layer,
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but a more complex editing application could use as many as needed.
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</para>
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</listitem>
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<listitem>
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<para>Tracks - Corresponds to the output streams in GStreamer.
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A typical GESTimeline, aimed at a video editing application, would
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have an audio track and a video track.
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A GESTimeline for an audio editing application would only require
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an audio track. Multiple layers can be related to each track.</para>
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</listitem>
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</itemizedlist></para>
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<figure float="0" id="layer_tracks_diagram">
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<title>Layers and Tracks</title>
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<mediaobject>
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<imageobject>
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<imagedata fileref="layer_track_overview.png" scale="75" />
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</imageobject>
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</mediaobject>
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</figure>
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<para>In order to reduce even more the amount of GStreamer interaction
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the application developer has to deal with, a convenience GstPipeline
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has been made available specifically for Timelines : <link
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linkend="GESPipeline">GESPipeline</link>.</para>
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</refsect2>
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</refsect1>
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</refentry>
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