gstreamer/docs/pwg/intro-preface.xml

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<chapter id="chapter-intro-preface" xreflabel="Preface">
  <title>Preface</title>

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  <sect1 id="section-preface-who" xreflabel="Who Should Read This Guide?">
    <title>Who Should Read This Guide?</title>
    <para>
      This guide explains how to write new modules for &GStreamer;. The guide is
      relevant to several groups of people:
    </para>
    <itemizedlist>
      <listitem>
        <para>
          Anyone who wants to add support for new ways of processing data in
          &GStreamer;. For example, a person in this group might want to create
          a new data format converter, a new visualization tool, or a new
          decoder or encoder.
        </para>
      </listitem>
      <listitem>
        <para>
          Anyone who wants to add support for new input and output devices. For
          example, people in this group might want to add the ability to write
          to a new video output system or read data from a digital camera or
          special microphone.
        </para>
      </listitem>
      <listitem>
        <para>
          Anyone who wants to extend &GStreamer; in any way. You need to have an
          understanding of how the plugin system works before you can understand
          the constraints that the plugin system places on the rest of the code.
          Also, you might be surprised after reading this at how much can be
          done with plugins.
        </para>
      </listitem>
    </itemizedlist>
    <para>
      This guide is not relevant to you if you only want to use the existing
      functionality of &GStreamer;, or if you just want to use an application
      that uses &GStreamer;. If you are only interested in using existing
      plugins to write a new application - and there are quite a lot of
      plugins already - you might want to check the &GstAppDevMan;. If you
      are just trying to get help with a &GStreamer; application, then you
      should check with the user manual for that particular application.
    </para>
  </sect1>

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  <sect1 id="section-preface-reading" xreflabel="Preliminary Reading">
    <title>Preliminary Reading</title>
    <para>
      This guide assumes that you are somewhat familiar with the basic workings
      of &GStreamer;. For a gentle introduction to programming concepts in
      &GStreamer;, you may wish to read the &GstAppDevMan; first. Also check out
      the documentation available on the <ulink type="http"
      url="http://gstreamer.freedesktop.org/documentation/">&GStreamer; web site</ulink>.
    </para>
    <para>
      Since &GStreamer; adheres to the GObject programming model, this guide
      also assumes that you understand the basics of <ulink type="http"
      url="http://developer.gnome.org/doc/API/2.0/gobject/index.html">GObject</ulink>
      programming. There are several good introductions to the GObject library,
      including the <emphasis><ulink type="http"
      url="http://www.gtk.org/tutorial/">GTK+ Tutorial</ulink></emphasis> and
      the <emphasis><ulink type="http"
      url="http://www.le-hacker.org/papers/gobject/index.html">Glib Object
      system</ulink></emphasis>.
    </para>
  </sect1>

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  <sect1 id="section-preface-structure" xreflabel="Structure of This Guide">
    <title>Structure of This Guide</title>
    <para>
      To help you navigate through this guide, it is divided into several large
      parts. Each part addresses a particular broad topic concerning &GStreamer;
      plugin development. The parts of this guide are laid out in the following
      order:
    </para>
    <itemizedlist>
      <listitem>
        <para>
          <xref linkend="part-building"/> -
          Introduction to the structure of a plugin, using an example audio
          filter for illustration.
        </para>
        <para>
          This part covers all the basic steps you generally need to perform to
          build a plugin. The discussion begins by giving examples of generating
          the basic structures with <xref linkend="chapter-building-boiler"/>. Then
          you will learn how to write the code to get a basic filter plugin
          working: These steps include chapters on <xref
          linkend="chapter-building-types"/>, <xref linkend="chapter-building-pads"/>,
          <xref linkend="chapter-building-chainfn"/>, and <!-- <xref
          linkend="chapter-building-state"/>--> (WRITEME: building state).
        </para>
        <para>
          After you have finished the first steps, you will be able to create a
          working plugin, but your new plugin might not have all the
          functionality you need. To provide some standard functionality, you
          will learn how to add more features to a new plugin. These features
          are described in the chapters on 
          <!--FIXME: WRITEME <xref linkend="chapter-building-props"/> -->
          (WRITEME)
          and <xref linkend="chapter-building-signals"/>.
          Finally, you will see in
          <!--<xref linkend="chapter-building-testapp"/>-->(WRITEME) 
          how to write a short test
          application to try out your new plugin.
        </para>
      </listitem>
      <listitem>
        <para>
          <xref linkend="part-advanced"/> -
          Information on advanced features of &GStreamer; plugin development.
        </para>
        <para>
          After learning about the basic steps, you should be able to create a
          functional audio or video filter plugin with some nice features.
          However, &GStreamer; offers more for plugin writers. This part of the
          guide includes chapters on more advanced topics, such as <xref
          linkend="chapter-advanced-request"/>, <!-- <xref
          linkend="chapter-advanced-clock"/>, <xref
          linkend="chapter-advanced-scheduling"/>, <xref
          linkend="chapter-advanced-dparams"/>, and <xref
          linkend="chapter-advanced-midi"/>-->. Since these features are more advanced,
          the chapters can basically be read in any order, as you find that your
          plugins require these features.
        </para>
      </listitem>
      <listitem>
        <para>
          <xref linkend="part-other"/> - Explanation
          of writing other plugin types.
        </para>
        <para>
          Because the first two parts of the guide use an audio filter as an
          example, the concepts introduced apply to filter plugins. But many of
          the concepts apply equally to other plugin types, including sources,
          sinks, and autopluggers. This part of the guide presents the issues
          that arise when working on these more specialized plugin types. The
          part includes chapters on <xref linkend="chapter-other-source"/>, <xref
          linkend="chapter-other-sink"/>, <!-- FIXME: WRITEME 
          <xref linkend="chapter-other-scheduler"/>,--> and
          <xref linkend="chapter-other-autoplugger"/>.
        </para>
      </listitem>
      <listitem>
        <para>
          <xref linkend="part-appendix"/> - Further
          information for plugin developers.
        </para>
        <para>
          The appendices contain some information that stubbornly refuses to fit
          cleanly in other sections of the guide. This information includes
          <!-- FIXME: WRITEME
          <xref linkend="chapter-appendix-checklist"/>--> (WRITEME) and 
          <!-- <xref
          linkend="chapter-appendix-python"/>.--> FIXME: organize better.
        </para>
      </listitem>
    </itemizedlist>

    <para>
      The remainder of this introductory part of the guide presents a short
      overview of the basic concepts involved in &GStreamer; plugin development.
      Topics covered include <xref linkend="section-basics-elements"/>, <xref
      linkend="section-basics-pads"/>, <xref linkend="section-basics-data"/> and
      <xref linkend="section-basics-types"/>. If you are already familiar with
      this information, you can use this short overview to refresh your memory,
      or you can skip to <xref linkend="part-building"/>.
    </para>
    <para>
      As you can see, there a lot to learn, so let's get started!
    </para>

    <itemizedlist>
      <listitem>
        <para>
          Creating compound and complex elements by extending from a GstBin.
          This will allow you to create plugins that have other plugins embedded
          in them.
        </para>
      </listitem>
      <listitem>
        <para>
          Adding new mime-types to the registry along with typedetect functions.
          This will allow your plugin to operate on a completely new media type.
        </para>
      </listitem>
    </itemizedlist>
  </sect1>
</chapter>