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407c7a3ce8
Original commit message from CVS: + changed connection/connect/conn/disconnect/connected/... to link/link/link/unlink/linked/... and moved connectish files to linkish files (closes bug#103843)
148 lines
4.8 KiB
XML
148 lines
4.8 KiB
XML
<chapter id="cha-goals">
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<title>Goals</title>
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<para>
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GStreamer was designed to provide a solution to the current Linux media
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problems.
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</para>
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<sect1 id="sec-goals-design">
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<title>The design goals</title>
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<para>
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We describe what we try to achieve with GStreamer.
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</para>
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<sect2 id="sec-goals-clean">
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<title>Clean and powerful</title>
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<para>
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GStreamer wants to provide a clean interface to:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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The application programmer who wants to build a media pipeline.
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The programmer can use an extensive set of powerful tools to create
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media pipelines without writing a single line of code. Performing
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complex media manipulations becomes very easy.
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</para>
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</listitem>
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<listitem>
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<para>
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The plugin programmer. Plugin programmers are provided a clean and
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simple API to create self contained plugins. An extensive debugging
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and tracing mechanism has been integrated. GStreamer also comes with
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an extensive set of real-life plugins that serve as an example too.
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</para>
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</listitem>
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</itemizedlist>
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</sect2>
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<sect2 id="sec-goals-object">
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<title>Object oriented</title>
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<para>
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Adhere to the GLib 2.0 object model. A programmer familiar with GLib 2.0 or older versions
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of Gtk+ will be comfortable with GStreamer.
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</para>
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<para>
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GStreamer uses the mechanism of signals and object properties.
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</para>
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<para>
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All objects can be queried at runtime for their various properties and
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capabilities.
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</para>
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</sect2>
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<sect2 id="sec-goals-extensible">
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<title>Extensible</title>
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<para>
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All GStreamer Objects can be extended using the GObject inheritance methods.
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</para>
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<para>
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All plugins are loaded dynamically and can be extended and upgraded
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independently.
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</para>
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</sect2>
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<sect2 id="sec-goals-binary">
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<title>Allow binary only plugins</title>
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<para>
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Plugins are shared libraries that are loaded at runtime. Since all the properties of the
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plugin can be set using the GObject properties, there is no need (and in fact no way) to
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have any header files installed for the plugins.
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</para>
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<para>
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Special care has been taken to make plugins completely self contained.
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All relevant aspects of plugins can be queried at run-time.
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</para>
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</sect2>
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<sect2 id="sec-goals-performance">
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<title>High performance</title>
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<para>
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High performance is obtained by:
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</para>
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<itemizedlist>
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<listitem>
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<para>
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Using GLib g_mem_chunk and fast non-blocking allocation algorithms
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where possible to minimize dynamic memory allocation.
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</para>
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</listitem>
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<listitem>
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<para>
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Extremely light-weight links between plugins. Data can travel
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the pipeline with minimal overhead. Data passing between plugins only involves
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a pointer dereference in a typical pipeline.
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</para>
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</listitem>
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<listitem>
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<para>
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Providing a mechanism to directly work on the target memory. A plugin can for example
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directly write to the X server's shared memory space. Buffers can also point to
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arbitrary memory, such as a sound card's internal hardware buffer.
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</para>
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</listitem>
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<listitem>
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<para>
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Refcounting and copy on write minimize usage of memcpy(3).
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Sub-buffers efficiently split buffers into manageable pieces.
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</para>
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</listitem>
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<listitem>
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<para>
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The use of cothreads to minimize the threading overhead. Cothreads are a simple and fast
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user-space method for switching between subtasks. Cothreads were measured to
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consume as little as 600 cpu cycles.
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</para>
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</listitem>
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<listitem>
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<para>
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Allowing hardware acceleration by the use of specialized plugins.
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</para>
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</listitem>
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<listitem>
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<para>
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Using a plugin registry with the specifications of the plugins so
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that the plugin loading can be delayed until the plugin is actually
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used.
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</para>
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</listitem>
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<listitem>
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<para>
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All critical data passing is free of locks and mutexes.
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</para>
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</listitem>
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</itemizedlist>
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</sect2>
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<sect2 id="sec-goals-testbed">
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<title>Provide a framework for codec experimentation</title>
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<para>
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GStreamer also wants to be an easy framework where codec
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developers can experiment with different algorithms, speeding up
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the development of open and free multimedia codecs like <ulink
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url="http://www.xiph.org/ogg/index.html" type="http">tarkin and
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vorbis</ulink>.
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</para>
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</sect2>
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</sect1>
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</chapter>
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