gstreamer/docs/manual/programs.xml

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<chapter id="cha-programs">
<title>Programs</title>
<para>
</para>
<sect1>
<title><command>gstreamer-config</command></title>
<para>
<command>gstreamer-config</command> is a script to get information about the installed
version of <application>GStreamer</application>.
This program "knows" what compiler switches are needed to compile programs that use
<application>GStreamer</application>.
</para>
<para>
<command>gstreamer-config</command> accepts the following options:
<itemizedlist>
<listitem>
<para>
<option>--version</option> Print the currently installed version of
<application>GStreamer</application> on the standard output.
</para>
</listitem>
<listitem>
<para>
<option>--libs</option> Print the linker flags that are necessary to link a
<application>GStreamer</application> program.
</para>
</listitem>
<listitem>
<para>
<option>--cflags</option> Print the compiler flags that are necessary to compile a
<application>GStreamer</application> program.
</para>
</listitem>
<listitem>
<para>
<option>--prefix=<replaceable>PREFIX</replaceable></option>
If specified, use <replaceable>PREFIX</replaceable> instead of the installation
prefix that <application>GStreamer</application> was built with when computing the
output for the <option>--cflags</option> and <option>--libs</option> options.
This option is also used for the exec prefix if
<option>--exec-prefix</option> was not specified. This option must be specified before any
<option>--libs</option> or <option>--cflags</option> options.
</para>
</listitem>
<listitem>
<para>
<option>--exec-prefix=<replaceable>PREFIX</replaceable></option>
If specified, use <replaceable>PREFIX</replaceable> instead of the installation exec
prefix that <application>GStreamer</application> was built with when computing the
output for the <option>--cflags</option> and <option>--libs</option> options. This option must be
specified before any <option>--libs</option> or <option>--cflags</option>
options.
</para>
</listitem>
</itemizedlist>
</para>
<para>
A simple <filename>Makefile</filename> will contain something like:
<programlisting>
CC = gcc
helloworld2: helloworld2.c
$(CC) -Wall `gstreamer-config --cflags --libs` helloworld2.c -o helloworld2
clean:
rm -f *.o helloworld2
</programlisting>
</para>
</sect1>
<sect1>
<title><command>gstreamer-register</command></title>
<para>
<command>gstreamer-register</command> is used to rebuild the database of plugins.
It is used after a new plugin has been added to the system. The plugin database
can be found in <filename>/etc/gstreamer/reg.xml</filename>.
</para>
</sect1>
<sect1>
<title><command>gstreamer-launch</command></title>
<para>
This is a tool that will construct pipelines based on a command-line
syntax.
</para>
<para>
A simple commandline looks like:
<screen>
gstreamer-launch filesrc location=hello.mp3 ! mp3parse ! mpg123 ! audiosink
</screen>
A more complex pipeline looks like:
<screen>
gstreamer-launch filesrc redpill.vob audio_00! (ac3parse ! ac3dec ! audiosink) \
video_00! (mpeg2dec ! videosink)
</screen>
</para>
<para>
Note that the parser isn't capable of more complex pipelines yet, including
the VOB player above. The minor tweaks will be made post 0.2.1.
</para>
<para>
You can also use the the parser in you own code. <application>GStreamer</application>
provides a function gst_parse_launch () that you can use to construt a pipeline.
The following programs lets you create an mp3 pipeline using the gst_parse_launch ()
function:
</para>
<programlisting>
#include &lt;gst/gst.h&gt;
int
main (int argc, char *argv[])
{
GstElement *pipeline;
GstElement *filesrc;
gst_init (&amp;argc, &amp;argv);
if (argc != 2) {
g_print ("usage: %s &lt;filename&gt;\n", argv[0]);
return -1;
}
pipeline = gst_pipeline_new ("my_pipeline");
gst_parse_launch ("filesrc[my_filesrc] ! mp3parse ! mpg123 ! osssink", GST_BIN (pipeline));
filesrc = gst_bin_get_by_name (GST_BIN (pipeline), "my_filesrc");
g_object_set (G_OBJECT (filesrc), "location", argv[1], NULL);
gst_element_set_state (pipeline, GST_STATE_PLAYING);
while (gst_bin_iterate (GST_BIN (pipeline)));
gst_element_set_state (pipeline, GST_STATE_NULL);
return 0;
}
</programlisting>
<para>
Note how we can retrieve the filesrc element from the constructed bin using the
element name.
</para>
</sect1>
<sect1>
<title><command>gstreamer-inspect</command></title>
<para>
This is a tool to query a plugin or an element about its properties.
</para>
<para>
To query the information about the element mpg123, you would specify:
</para>
<screen>
gstreamer-inspect mpg123
</screen>
<para>
Below is the output of a query for the audiosink element:
</para>
<screen>
Factory Details:
Long name: Audio Sink (OSS)
Class: Sink/Audio
Description: Output to a sound card via OSS
Version: 0.1.0
Author(s): Erik Walthinsen &lt;omega@cse.ogi.edu&gt;
Copyright: (C) 1999
Pad Templates:
SINK template: 'sink'
Exists: Always
Capabilities:
'audiosink_sink':
MIME type: 'audio/raw':
format: Integer: 16
depth: List:
Integer: 8
Integer: 16
rate: Integer range: 8000 - 48000
channels: Integer range: 1 - 2
Element Flags:
GST_ELEMENT_THREADSUGGESTED
no flags set
Element Implementation:
No loopfunc(), must be chain-based or not configured yet
Has change_state() function
Pads:
SINK: 'sink'
Implementation:
Has chainfunc(): 0x4001cde8
Has default eosfunc() gst_pad_eos_func()
Pad Template: 'sink'
Capabilities:
'audiosink_sink':
MIME type: 'audio/raw':
format: Integer: 16
depth: List:
Integer: 8
Integer: 16
rate: Integer range: 8000 - 48000
channels: Integer range: 1 - 2
Element Arguments:
GstAudioSink::mute: Boolean
GstAudioSink::format: Enum (default 16)
(8): 8 Bits
(16): 16 Bits
GstAudioSink::channels: Enum (default 2)
(1): Mono
(2): Stereo
GstAudioSink::frequency: Integer
</screen>
<para>
To query the information about a plugin, you would do:
</para>
<screen>
gstreamer-inspect gstelements
</screen>
</sect1>
<sect1>
<title><command>gstmediaplay</command></title>
<para>
A sample media player.
</para>
</sect1>
</chapter>