<sect1 id="chapter-using">
  <title id="title-using">Using GStreamer</title>
  <qandaset defaultlabel="qanda">

    <qandaentry>
      <question id="using-getting-started">
        <para>Ok, I've installed GStreamer.  What can I do next ?</para>
      </question>

      <answer>
        <para>
First of all, verify that you have a working registry and that you can
inspect them by typing
<programlisting>
$ gst-inspect-1.0 fakesrc
</programlisting>
This should print out a bunch of information about this particular element.
If this tells you that there is "no such element or plugin", you haven't
installed GStreamer correctly.  Please check
<link linkend="chapter-getting">how to get GStreamer</link>
If this fails with any other message, we would appreciate a
<link linkend="using-bugs-where">bug report</link>.
        </para>
        <para>
It's time to try out a few things.  Start with gst-launch and two plug-ins
that you really should have : fakesrc and fakesink.  They do nothing except
pass empty buffers. Type this at the command-line :
<programlisting>
$ gst-launch-1.0 -v fakesrc silent=0 num-buffers=3 ! fakesink silent=0
</programlisting>
This will print out output that looks similar to this :
<programlisting>
RUNNING pipeline ...
fakesrc0: last-message = "get      ******* (fakesrc0:src)gt; (0 bytes, 0) 0x8057510"
fakesink0: last-message = "chain   ******* (fakesink0:sink)lt; (0 bytes, 0) 0x8057510"
fakesrc0: last-message = "get      ******* (fakesrc0:src)gt; (0 bytes, 1) 0x8057510"
fakesink0: last-message = "chain   ******* (fakesink0:sink)lt; (0 bytes, 1) 0x8057510"
fakesrc0: last-message = "get      ******* (fakesrc0:src)gt; (0 bytes, 2) 0x8057510"
fakesink0: last-message = "chain   ******* (fakesink0:sink)lt; (0 bytes, 2) 0x8057510"
execution ended after 5 iterations (sum 301479000 ns, average 60295800 ns, min 3000 ns, max 105482000 ns)
</programlisting>
(Some parts of output have been removed for clarity)  If it looks similar, then
GStreamer itself is running correctly.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="using-sound">
        <para>Can my system play sound through GStreamer ?</para>
      </question>

      <answer>
        <para>
You can test this by trying to play a sine tone.  For this, you need to
link the audiotestsrc element to an output element that matches your hardware.
A (non-complete) list of output plug-ins for audio is
<itemizedlist>
<listitem><para>pulsesink for Pulseaudio output</para></listitem>
<listitem><para>osssink for OSS output</para></listitem>
<listitem><para>esdsink for ESound output</para></listitem>
<listitem><para>alsasink for ALSA output</para></listitem>
<listitem><para>alsaspdifsink for ALSA S/PDIF output</para></listitem>
<listitem><para>jackaudiosink for JACK output</para></listitem>
</itemizedlist>
First of all, run gst-inspect-1.0 on the output plug-in you want to use to
make sure you have it installed.  For example, if you use Pulseaudio, run
<programlisting>
$ gst-inspect-1.0 pulsesink
</programlisting>
and see if that prints out a bunch of properties for the plug-in.
        </para>
        <para>
Then try to play the sine tone by running
<programlisting>
$ gst-launch-1.0 audiotestsrc ! audioconvert ! audioresample ! pulsesink
</programlisting>
and see if you hear something.  Make sure your volume is turned up,
but also make sure it is not too loud and you are not wearing your headphones.
        </para>
        <para>
In GNOME, you can configure audio output for most applications by running
<programlisting>
$ gstreamer-properties
</programlisting>
which can also be found in the start menu (Applications -> Preferences ->
Multimedia Systems Selector). In KDE, there is not yet a shared way of
setting audio output for all applications; however, applications such
as Amarok allow you to specify an audio output in their preferences dialog.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="using-gst-inspect">
        <para>How can I see what GStreamer plugins I have on my system ?</para>
      </question>

      <answer>
        <para>
To do this you use the gst-inspect
command-line tool, which comes standard with GStreamer.
Invoked without any arguments,
<programlisting>
$ gst-inspect-1.0
</programlisting>
will print out a listing of installed plugins.
To learn more about a particular plugin, pass its name on the command line. 
For example,
<programlisting>
$ gst-inspect-1.0 volume
</programlisting>
will give you information about the volume plugin.
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="using-bugs-where">
        <para>Where should I report bugs ?</para>
      </question>

      <answer>
        <para>
Bug management is now hosted on GNOME's Bugzilla at
<ulink url="http://bugzilla.gnome.org">http://bugzilla.gnome.org</ulink>,
under the product GStreamer. 
Using bugzilla you can view past bug history, report new bugs, etc.
Bugzilla requires you to make an account here, which might seem cumbersome,
but allows us to at least have a chance at contacting you for further
information, as we will most likely have to.
        </para>
      </answer>
    </qandaentry>


    <qandaentry>
      <question id="using-bugs-how">
        <para>How should I report bugs ?</para>
      </question>

      <answer>
        <para>
When doing a bug report, you should at least describe
<itemizedlist>
<listitem><para>your distribution</para></listitem>
<listitem><para>
how you installed GStreamer (from git, source, packages, which ?)</para></listitem>
<listitem><para>if you installed GStreamer before</para></listitem>
</itemizedlist>
        </para>
        <para>
If the application you are having problems with is segfaulting, then
provide us with the necessary gdb output.  See
<xref linkend="troubleshooting-segfault" endterm="troubleshooting-segfault"/>
        </para>
      </answer>
    </qandaentry>

    <qandaentry>
      <question id="using-gst-launch">
        <para>How do I use the GStreamer command line interface ?</para>
      </question>
      <answer>
        <para>
You access the GStreamer command line interface using the command gst-launch.
To decode an mp3 and play it through Pulseaudio, you could use
<programlisting>
gst-launch-1.0 filesrc location=thesong.mp3 ! mad ! pulsesink
</programlisting>.
More examples can be found in the gst-launch man page.
        </para>
        <para>
To automatically detect the right codec in a pipeline, try 
<programlisting>
gst-launch-1.0 filesrc location=my-random-media-file.mpeg ! decodebin !
 pulsesink
</programlisting>.
or
<programlisting>
gst-launch-1.0 filesrc location=my-random-media-file.mpeg ! decodebin !
 videoconvert ! xvimagesink
</programlisting>
Something more complicated:
<programlisting>
gst-launch-1.0 filesrc location=my-random-media-file.mpeg ! decodebin name=decoder
   decoder. ! videoconvert ! xvimagesink
   decoder. ! audioconvert ! pulsesink
</programlisting>
        </para>
        <para>
We also have a basic media playing plugin that will take care of most things
for you. This plugin is called playbin. Try this:
<programlisting>
gst-launch-1.0 playbin uri=file:///home/joe/my-random-media-file.mpeg
</programlisting>
This should play the file if the format is supported, ie. you have all the
necessary demuxing and decoding and some output plugins installed.
        </para>
      </answer>
    </qandaentry>
  </qandaset>
</sect1>
