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<div id="org-div-home-and-up">
<a accesskey="h" href="."> UP </a>
|
<a accesskey="H" href="https://github.com/brettviren/pygst-tutorial-org"> HOME </a>
</div><div id="content">
<h1 class="title">Python GStreamer Tutorial</h1>
<div id="table-of-contents">
<h2>Table of Contents</h2>
<div id="text-table-of-contents">
<ul>
<li><a href="#sec-1">1. Meta</a></li>
<li><a href="#sec-2">2. Introduction</a>
<ul>
<li><a href="#sec-2-1">2.1. Command Line</a></li>
</ul>
</li>
<li><a href="#sec-3">3. Playbin</a>
<ul>
<li><a href="#sec-3-1">3.1. Audio with Playbin</a></li>
<li><a href="#sec-3-2">3.2. Adding Video</a></li>
</ul>
</li>
<li><a href="#sec-4">4. Pipeline</a>
<ul>
<li><a href="#sec-4-1">4.1. Pipeline Audio Player</a></li>
<li><a href="#sec-4-2">4.2. Adding Video to the Pipeline</a></li>
</ul>
</li>
<li><a href="#sec-5">5. Src, sink, pad … oh my!</a></li>
<li><a href="#sec-6">6. Seeking</a></li>
<li><a href="#sec-7">7. Capabilities</a></li>
<li><a href="#sec-8">8. Videomixer</a></li>
<li><a href="#sec-9">9. Webcam Viewer</a></li>
</ul>
</div>
</div>
<p>
This tutorial aims at giving a brief introduction to the GStreamer 1.0 multimedia framework using its Python bindings.
</p>
<div id="outline-container-sec-1" class="outline-2">
<h2 id="sec-1"><span class="section-number-2">1</span> Meta</h2>
<div class="outline-text-2" id="text-1">
<p>
<a id="sec:meta" name="sec:meta"></a>
</p>
<p>
A GStreamer application is built as a directed, acyclic graph. In the figures these graphs are illustrated with the convention:
</p>
<ul class="org-ul">
<li>right solid line rectangles indicate basic GStreamer <i>elements</i>
</li>
<li>rounded solid line rectangles to indicate GStreamer <i>bins</i> (and <i>pipelines</i>) subclasses of <i>elements</i>.
</li>
<li>rounded dashed line rectangles to indicate <i>pads</i>
</li>
</ul>
If you are reading this from a web browser that supports JavaScript you can use some of the built-in features for navigating the document. Click on the "HELP" link or type "<tt>?</tt>" for instructions on how to use this feature.
</div>
</div>
<div id="outline-container-sec-2" class="outline-2">
<h2 id="sec-2"><span class="section-number-2">2</span> Introduction</h2>
<div class="outline-text-2" id="text-2">
<p>
<a id="sec:intro" name="sec:intro"></a>
</p>
<p>
This tutorial is meant to be a quick way to get to know more about GStreamer but it'll take some time to write it though because we don't know it ourselves … yet. We're usually using GNU/Linux and GTK in the examples but we try to keep the GUI code to an absolute minimum so it should not get in the way. Just remember that GStreamer depends heavily on Glib so you must make sure that the <a href="https://lazka.github.io/pgi-docs/#GLib-2.0/structs/MainLoop.html">Glib Mainloop</a> is running if you want to catch events on the bus. We take for granted that you are at least a fairly descent Python coder. For problems related to the Python language we redirect you over to <a href="http://python.org/doc">Online Python docs</a>.
</p>
<p>
There are also some example coding distributed with the PyGST source which you may browse at the <a href="http://cgit.freedesktop.org/gstreamer/gst-python/tree/examples">gst-python git repository</a>. Reference documents for GStreamer and the rest of the ecosystem it relies on are available at <a href="https://lazka.github.io/pgi-docs/#Gst-1.0">lazka's GitHub site</a>. The main <a href="http://gstreamer.freedesktop.org/">GStreamer</a> site has <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/">Reference Manual</a>, <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/faq/">FAQ</a>, <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/">Applications Development Manual</a> and <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/pwg/">Plugin Writer's Guide</a>. This tutorial targets the GStreamer 1.0 API which all v1.x releases should follow. The Novacut project has a <a href="https://wiki.ubuntu.com/Novacut/GStreamer1.0">guide to porting</a> Python applications from the prior 0.1 API to 1.0.
Finally, GStreamer provides the <a href="http://docs.gstreamer.com/display/GstSDK/">GstSDK documentation</a> which includes substantial C programming tutorials.
</p>
<p>
As you may see this tutorial is far from done and we are always looking for new people to join this project. If you want to write a chapter, fix the examples, provide alternatives or otherwise improve this document please do so. It is suggested to <a href="https://github.com/brettviren/pygst-tutorial-org/">clone the repository on GitHub</a> and issue a pull request. Note, the original source of this document was <a href="http://developer.berlios.de/projects/pygstdocs/">here</a> but is now dead.
</p>
</div>
<div id="outline-container-sec-2-1" class="outline-3">
<h3 id="sec-2-1"><span class="section-number-3">2.1</span> Command Line</h3>
<div class="outline-text-3" id="text-2-1">
<p>
<a id="subsec:cli" name="subsec:cli"></a>
</p>
<p>
Before getting started with Python some of the command line interface (CLI) programs that come with GStreamer are explored. Besides being generally useful they can help you find and try out what you need in a very fast and convenient way without writing a bit of code. With <a href="http://docs.gstreamer.com/display/GstSDK/gst-inspect"><code>gst-inspect</code></a> you can track highlevel elements which are shipped with the various plugins packages.
</p>
<div class="org-src-container">
<pre class="src src-sh">man gst-inspect-1.0
</pre>
</div>
<p>
If you are looking for an element but you don't know its name you can use it with grep. Getting the elements that handles ie mp3 is done like this:
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-inspect-1.0 | grep mp3 | sort | head -3
</pre>
</div>
<pre class="example">
flump3dec: flump3dec: Fluendo MP3 Decoder (liboil build)
lame: lamemp3enc: L.A.M.E. mp3 encoder
libav: avdec_mp3adufloat: libav ADU (Application Data Unit) MP3 (MPEG audio layer 3) decoder
</pre>
<p>
The <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-playbin.html"><code>playbin</code></a> element is an autoplugger which usually plays anything you throw at it, if you have the appropriate plugins installed.
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-inspect-1.0 playbin > gst-inspect-playbin.txt
</pre>
</div>
<p>
Browse example output <a href="./gst-inspect-playbin.txt">here</a>.
</p>
<p>
You can also run pipelines directly in a terminal with <a href="http://docs.gstreamer.com/display/GstSDK/gst-launch"><code>gst-launch</code></a>:
</p>
<div class="org-src-container">
<pre class="src src-sh">man gst-launch-1.0
</pre>
</div>
<p>
For playing a file with playbin:
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 playbin <span style="color: #8b2252;">\</span>
<span style="color: #a0522d;">uri</span>=http://docs.gstreamer.com/media/sintel_trailer-480p.webm
</pre>
</div>
<p>
It's also possible to link elements together with "!":
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 audiotestsrc ! alsasink
</pre>
</div>
<p>
You may also make different streams in the pipeline:
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 audiotestsrc ! alsasink videotestsrc ! xvimagesink
</pre>
</div>
<p>
Or, you can make a single frame JPEG
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 videotestsrc num-buffers=1 ! jpegenc ! <span style="color: #8b2252;">\</span>
filesink <span style="color: #a0522d;">location</span>=videotestsrc-frame.jpg
</pre>
</div>
<div class="figure">
<p><img src="./videotestsrc-frame.jpg" alt="videotestsrc-frame.jpg" />
</p>
</div>
<p>
If you are using the "name" property you may use the same element more than once. Just put a "." after its name, eg with oggmux here.
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 audiotestsrc ! vorbisenc ! oggmux <span style="color: #a0522d;">name</span>=mux ! <span style="color: #8b2252;">\</span>
filesink <span style="color: #a0522d;">location</span>=file.ogg videotestsrc ! theoraenc ! mux.
</pre>
</div>
<p>
In the next chapter we will show you more examples with Playbin.
</p>
</div>
</div>
</div>
<div id="outline-container-sec-3" class="outline-2">
<h2 id="sec-3"><span class="section-number-2">3</span> Playbin</h2>
<div class="outline-text-2" id="text-3">
<p>
<a id="sec:playbin" name="sec:playbin"></a>
</p>
<p>
The <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-playbin.html"><code>playbin</code></a> element was exercised from the command line in section <a href="#subsec:cli">2.1</a> and in this section it will be used from Python. It is a high-level, automatic audio and video player. You create a <code>playbin</code> object with:
</p>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst
Gst.init(<span style="color: #008b8b;">None</span>)
<span style="color: #b22222;"># </span><span style="color: #b22222;">...</span>
<span style="color: #a0522d;">my_playbin</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"playbin"</span>, <span style="color: #008b8b;">None</span>)
<span style="color: #a020f0;">assert</span> my_playbin
<span style="color: #a020f0;">print</span> my_playbin
</pre>
</div>
<pre class="example">
<__main__.GstPlayBin object at 0x7f2604238aa0 (GstPlayBin at 0x17e6480)>
</pre>
<p>
To get information about a playbin run:
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-inspect-0.10 playbin
</pre>
</div>
<p>
This figure shows how playbin is built internally. The "optional stuff" are things that could be platform specific or things that you may set with properties.
</p>
<div class="figure">
<p><img src="playbin-block.svg" alt="playbin-block.svg" width="100%" />
</p>
</div>
<p>
The "<b>uri</b>" property should take any possible protocol supported by your GStreamer plugins. One nice feature is that you may switch the sinks out for your own bins as shown below. Playbin always tries to set up the best possible pipeline for your specific environment so if you don't need any special features that are not implemented in playbin, it should in most cases just work "out of the box". Ok, time for a few examples.
</p>
</div>
<div id="outline-container-sec-3-1" class="outline-3">
<h3 id="sec-3-1"><span class="section-number-3">3.1</span> Audio with Playbin</h3>
<div class="outline-text-3" id="text-3-1">
<p>
<a id="subsec:playbinaudio" name="subsec:playbinaudio"></a>
</p>
<p>
This first example is just a simple audio player, insert a file with absolute path and it'll play. It's code is listed below. You can run it like:
</p>
<div class="org-src-container">
<pre class="src src-sh">python playbin-example-audio.py
</pre>
</div>
<p>
It will open a small window with a text entry. Enter the full path to some audio file and click "Start".
</p>
<a href="playbin-example-audio.py">playbin-example-audio.py</a>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #b22222;">#</span><span style="color: #b22222;">!/usr/bin/env python</span>
<span style="color: #a020f0;">import</span> os
<span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst, GObject, Gtk
<span style="color: #a020f0;">class</span> <span style="color: #228b22;">GTK_Main</span>(<span style="color: #483d8b;">object</span>):
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">__init__</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a0522d;">window</span> = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title(<span style="color: #8b2252;">"Audio-Player"</span>)
window.set_default_size(300, -1)
window.connect(<span style="color: #8b2252;">"destroy"</span>, Gtk.main_quit, <span style="color: #8b2252;">"WM destroy"</span>)
<span style="color: #a0522d;">vbox</span> = Gtk.VBox()
window.add(vbox)
<span style="color: #a020f0;">self</span>.entry = Gtk.Entry()
vbox.pack_start(<span style="color: #a020f0;">self</span>.entry, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">True</span>, 0)
<span style="color: #a020f0;">self</span>.button = Gtk.Button(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">self</span>.button.connect(<span style="color: #8b2252;">"clicked"</span>, <span style="color: #a020f0;">self</span>.start_stop)
vbox.add(<span style="color: #a020f0;">self</span>.button)
window.show_all()
<span style="color: #a020f0;">self</span>.player = Gst.ElementFactory.make(<span style="color: #8b2252;">"playbin"</span>, <span style="color: #8b2252;">"player"</span>)
<span style="color: #a0522d;">fakesink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"fakesink"</span>, <span style="color: #8b2252;">"fakesink"</span>)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"video-sink"</span>, fakesink)
<span style="color: #a0522d;">bus</span> = <span style="color: #a020f0;">self</span>.player.get_bus()
bus.add_signal_watch()
bus.connect(<span style="color: #8b2252;">"message"</span>, <span style="color: #a020f0;">self</span>.on_message)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">start_stop</span>(<span style="color: #a020f0;">self</span>, w):
<span style="color: #a020f0;">if</span> <span style="color: #a020f0;">self</span>.button.get_label() == <span style="color: #8b2252;">"Start"</span>:
<span style="color: #a0522d;">filepath</span> = <span style="color: #a020f0;">self</span>.entry.get_text().strip()
<span style="color: #a020f0;">if</span> os.path.isfile(filepath):
<span style="color: #a0522d;">filepath</span> = os.path.realpath(filepath)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Stop"</span>)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"uri"</span>, <span style="color: #8b2252;">"file://"</span> + filepath)
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.PLAYING)
<span style="color: #a020f0;">else</span>:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a0522d;">t</span> = message.<span style="color: #483d8b;">type</span>
<span style="color: #a020f0;">if</span> t == Gst.MessageType.EOS:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">elif</span> t == Gst.MessageType.ERROR:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a0522d;">err</span>, debug = message.parse_error()
<span style="color: #a020f0;">print</span> <span style="color: #8b2252;">"Error: %s"</span> % err, debug
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
Gst.init(<span style="color: #008b8b;">None</span>)
GTK_Main()
GObject.threads_init()
Gtk.main()
</pre>
</div>
</div>
</div>
<div id="outline-container-sec-3-2" class="outline-3">
<h3 id="sec-3-2"><span class="section-number-3">3.2</span> Adding Video</h3>
<div class="outline-text-3" id="text-3-2">
<p>
<a id="subsec:playbinvideo" name="subsec:playbinvideo"></a>
</p>
<p>
A <code>playbin</code> plugs both audio and video streams automagically and the <code>videosink</code> has been switched out to a <code>fakesink</code> element which is GStreamer's answer to directing output to <code>/dev/null</code>. If you want to enable video playback just comment out the following lines:
</p>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #a0522d;">fakesink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"fakesink"</span>, <span style="color: #8b2252;">"fakesink"</span>)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"video-sink"</span>, fakesink)
</pre>
</div>
<p>
If you want to show the video output in a specified window you'll have to use the <a href="https://lazka.github.io/pgi-docs/#Gst-1.0/classes/Bus.html#Gst.Bus.enable_sync_message_emission"><code>enable_sync_message_emission()</code></a> method on the bus. Here is an example with the video window embedded in the program.
</p>
<a href="playbin-example-video.py">playbin-example-video.py</a>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #b22222;">#</span><span style="color: #b22222;">!/usr/bin/env python</span>
<span style="color: #a020f0;">import</span> sys, os
<span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst, GObject, Gtk
<span style="color: #b22222;"># </span><span style="color: #b22222;">Needed for window.get_xid(), xvimagesink.set_window_handle(), respectively:</span>
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> GdkX11, GstVideo
<span style="color: #a020f0;">class</span> <span style="color: #228b22;">GTK_Main</span>(<span style="color: #483d8b;">object</span>):
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">__init__</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a0522d;">window</span> = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title(<span style="color: #8b2252;">"Video-Player"</span>)
window.set_default_size(500, 400)
window.connect(<span style="color: #8b2252;">"destroy"</span>, Gtk.main_quit, <span style="color: #8b2252;">"WM destroy"</span>)
<span style="color: #a0522d;">vbox</span> = Gtk.VBox()
window.add(vbox)
<span style="color: #a0522d;">hbox</span> = Gtk.HBox()
vbox.pack_start(hbox, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">False</span>, 0)
<span style="color: #a020f0;">self</span>.entry = Gtk.Entry()
hbox.add(<span style="color: #a020f0;">self</span>.entry)
<span style="color: #a020f0;">self</span>.button = Gtk.Button(<span style="color: #8b2252;">"Start"</span>)
hbox.pack_start(<span style="color: #a020f0;">self</span>.button, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">False</span>, 0)
<span style="color: #a020f0;">self</span>.button.connect(<span style="color: #8b2252;">"clicked"</span>, <span style="color: #a020f0;">self</span>.start_stop)
<span style="color: #a020f0;">self</span>.movie_window = Gtk.DrawingArea()
vbox.add(<span style="color: #a020f0;">self</span>.movie_window)
window.show_all()
<span style="color: #a020f0;">self</span>.player = Gst.ElementFactory.make(<span style="color: #8b2252;">"playbin"</span>, <span style="color: #8b2252;">"player"</span>)
<span style="color: #a0522d;">bus</span> = <span style="color: #a020f0;">self</span>.player.get_bus()
bus.add_signal_watch()
bus.enable_sync_message_emission()
bus.connect(<span style="color: #8b2252;">"message"</span>, <span style="color: #a020f0;">self</span>.on_message)
bus.connect(<span style="color: #8b2252;">"sync-message::element"</span>, <span style="color: #a020f0;">self</span>.on_sync_message)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">start_stop</span>(<span style="color: #a020f0;">self</span>, w):
<span style="color: #a020f0;">if</span> <span style="color: #a020f0;">self</span>.button.get_label() == <span style="color: #8b2252;">"Start"</span>:
<span style="color: #a0522d;">filepath</span> = <span style="color: #a020f0;">self</span>.entry.get_text().strip()
<span style="color: #a020f0;">if</span> os.path.isfile(filepath):
<span style="color: #a0522d;">filepath</span> = os.path.realpath(filepath)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Stop"</span>)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"uri"</span>, <span style="color: #8b2252;">"file://"</span> + filepath)
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.PLAYING)
<span style="color: #a020f0;">else</span>:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a0522d;">t</span> = message.<span style="color: #483d8b;">type</span>
<span style="color: #a020f0;">if</span> t == Gst.MessageType.EOS:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">elif</span> t == Gst.MessageType.ERROR:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a0522d;">err</span>, debug = message.parse_error()
<span style="color: #a020f0;">print</span> <span style="color: #8b2252;">"Error: %s"</span> % err, debug
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_sync_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a020f0;">if</span> message.get_structure().get_name() == <span style="color: #8b2252;">'prepare-window-handle'</span>:
imagesink = message.src
imagesink.set_property(<span style="color: #8b2252;">"force-aspect-ratio"</span>, <span style="color: #008b8b;">True</span>)
imagesink.set_window_handle(<span style="color: #a020f0;">self</span>.movie_window.get_property(<span style="color: #8b2252;">'window'</span>).get_xid())
GObject.threads_init()
Gst.init(<span style="color: #008b8b;">None</span>)
GTK_Main()
Gtk.main()
</pre>
</div>
<p>
And just to make things a little more complicated you can switch the <code>playbin</code>'s video sink to a <a href="https://lazka.github.io/pgi-docs/#Gst-1.0/classes/Bin.html"><code>Gst.Bin</code></a> with a <a href="https://lazka.github.io/pgi-docs/#Gst-1.0/classes/GhostPad.html"><code>Gst.GhostPad</code></a> on it. Here's an example with a <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gst-plugins-base-plugins/html/gst-plugins-base-plugins-timeoverlay.html"><code>timeoverlay</code></a>.
</p>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #483d8b;">bin</span> = Gst.Bin.new(<span style="color: #8b2252;">"my-bin"</span>)
<span style="color: #a0522d;">timeoverlay</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"timeoverlay"</span>)
<span style="color: #483d8b;">bin</span>.add(timeoverlay)
<span style="color: #a0522d;">pad</span> = timeoverlay.get_static_pad(<span style="color: #8b2252;">"video_sink"</span>)
<span style="color: #a0522d;">ghostpad</span> = Gst.GhostPad.new(<span style="color: #8b2252;">"sink"</span>, pad)
<span style="color: #483d8b;">bin</span>.add_pad(ghostpad)
<span style="color: #a0522d;">videosink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"autovideosink"</span>)
<span style="color: #483d8b;">bin</span>.add(videosink)
timeoverlay.link(videosink)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"video-sink"</span>, <span style="color: #483d8b;">bin</span>)
</pre>
</div>
<p>
Add that code to the example above and you'll get a <code>timeoverlay</code> too. We'll talk more about <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/manual/html/section-pads-ghost.html">"ghost pads"</a> later.
</p>
<p>
Here now adds a CLI example which plays music. It can be run it with:
</p>
<div class="org-src-container">
<pre class="src src-sh">python cliplayer.py /path/to/file1.mp3 /path/to/file2.ogg
</pre>
</div>
<a href="playbin-example-cliplayer.py">playbin-example-cliplayer.py</a>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #b22222;">#</span><span style="color: #b22222;">!/usr/bin/env python</span>
<span style="color: #a020f0;">import</span> sys, os, time, thread
<span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst, GLib, GObject
<span style="color: #a020f0;">class</span> <span style="color: #228b22;">CLI_Main</span>(<span style="color: #483d8b;">object</span>):
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">__init__</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a020f0;">self</span>.player = Gst.ElementFactory.make(<span style="color: #8b2252;">"playbin"</span>, <span style="color: #8b2252;">"player"</span>)
<span style="color: #a0522d;">fakesink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"fakesink"</span>, <span style="color: #8b2252;">"fakesink"</span>)
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"video-sink"</span>, fakesink)
<span style="color: #a0522d;">bus</span> = <span style="color: #a020f0;">self</span>.player.get_bus()
bus.add_signal_watch()
bus.connect(<span style="color: #8b2252;">"message"</span>, <span style="color: #a020f0;">self</span>.on_message)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a0522d;">t</span> = message.<span style="color: #483d8b;">type</span>
<span style="color: #a020f0;">if</span> t == Gst.MessageType.EOS:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.playmode = <span style="color: #008b8b;">False</span>
<span style="color: #a020f0;">elif</span> t == Gst.MessageType.ERROR:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a0522d;">err</span>, debug = message.parse_error()
<span style="color: #a020f0;">print</span> <span style="color: #8b2252;">"Error: %s"</span> % err, debug
<span style="color: #a020f0;">self</span>.playmode = <span style="color: #008b8b;">False</span>
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">start</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a020f0;">for</span> filepath <span style="color: #a020f0;">in</span> sys.argv[1:]:
<span style="color: #a020f0;">if</span> os.path.isfile(filepath):
filepath = os.path.realpath(filepath)
<span style="color: #a020f0;">self</span>.playmode = <span style="color: #008b8b;">True</span>
<span style="color: #a020f0;">self</span>.player.set_property(<span style="color: #8b2252;">"uri"</span>, <span style="color: #8b2252;">"file://"</span> + filepath)
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.PLAYING)
<span style="color: #a020f0;">while</span> <span style="color: #a020f0;">self</span>.playmode:
time.sleep(1)
time.sleep(1)
loop.<span style="color: #008b8b;">quit</span>()
GObject.threads_init()
Gst.init(<span style="color: #008b8b;">None</span>)
mainclass = CLI_Main()
thread.start_new_thread(mainclass.start, ())
loop = GLib.MainLoop()
loop.run()
</pre>
</div>
<p>
A <code>playbin</code> implements a <a href="https://lazka.github.io/pgi-docs/#Gst-1.0/classes/Pipeline.html"><code>Gst.Pipeline</code></a> element and that's what the next chapter is going to tell you more about.
</p>
</div>
</div>
</div>
<div id="outline-container-sec-4" class="outline-2">
<h2 id="sec-4"><span class="section-number-2">4</span> Pipeline</h2>
<div class="outline-text-2" id="text-4">
<p>
<a id="sec:pipeline" name="sec:pipeline"></a>
</p>
<p>
A <a href="https://lazka.github.io/pgi-docs/#Gst-1.0/classes/Pipeline.html"><code>Gst.Pipeline</code></a> is a top-level bin with its own bus and clock. If your program only contains one <i>bin</i>-like object, this is what you're looking for. You create a pipeline object with:
</p>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #a0522d;">my_pipeline</span> = Gst.Pipeline.new(<span style="color: #8b2252;">"my-pipeline"</span>)
</pre>
</div>
<p>
A pipeline is a "container" where you can put other objects and when everything is in place and the file to play is specified you set the pipeline's state to <a href="http://gstreamer.freedesktop.org/data/doc/gstreamer/head/gstreamer/html/GstBin.html#GstBin.notes"><code>Gst.State.PLAYING</code></a> and there should be multimedia coming out of it.
</p>
</div>
<div id="outline-container-sec-4-1" class="outline-3">
<h3 id="sec-4-1"><span class="section-number-3">4.1</span> Pipeline Audio Player</h3>
<div class="outline-text-3" id="text-4-1">
<p>
The first example here starts with the audio player from section <a href="#sec:playbin">3</a> and switches the <code>playbin</code> for the <code>mad</code> decoding pipeline that is capable of handling MP3 streams. Before coding it in Python it can be tested using <code>gst-launch</code>.
</p>
<div class="org-src-container">
<pre class="src src-sh">gst-launch-1.0 filesrc <span style="color: #a0522d;">location</span>=file.mp3 ! mad ! audioconvert ! alsasink
</pre>
</div>
<p>
Conceptually this pipeline looks like:
</p>
<div class="figure">
<p><img src="pipeline-block.svg" alt="pipeline-block.svg" width="100%" />
</p>
</div>
<p>
Done in Python this would look like <code>pipeline-example.py</code>:
</p>
<a href="pipeline-example.py">pipeline-example.py</a>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #b22222;">#</span><span style="color: #b22222;">!/usr/bin/env python</span>
<span style="color: #a020f0;">import</span> sys, os
<span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst, GObject, Gtk
<span style="color: #a020f0;">class</span> <span style="color: #228b22;">GTK_Main</span>(<span style="color: #483d8b;">object</span>):
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">__init__</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a0522d;">window</span> = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title(<span style="color: #8b2252;">"MP3-Player"</span>)
window.set_default_size(400, 200)
window.connect(<span style="color: #8b2252;">"destroy"</span>, Gtk.main_quit, <span style="color: #8b2252;">"WM destroy"</span>)
<span style="color: #a0522d;">vbox</span> = Gtk.VBox()
window.add(vbox)
<span style="color: #a020f0;">self</span>.entry = Gtk.Entry()
vbox.pack_start(<span style="color: #a020f0;">self</span>.entry, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">True</span>, 0)
<span style="color: #a020f0;">self</span>.button = Gtk.Button(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">self</span>.button.connect(<span style="color: #8b2252;">"clicked"</span>, <span style="color: #a020f0;">self</span>.start_stop)
vbox.add(<span style="color: #a020f0;">self</span>.button)
window.show_all()
<span style="color: #a020f0;">self</span>.player = Gst.Pipeline.new(<span style="color: #8b2252;">"player"</span>)
<span style="color: #a0522d;">source</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"filesrc"</span>, <span style="color: #8b2252;">"file-source"</span>)
<span style="color: #a0522d;">decoder</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"mad"</span>, <span style="color: #8b2252;">"mp3-decoder"</span>)
<span style="color: #a0522d;">conv</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"audioconvert"</span>, <span style="color: #8b2252;">"converter"</span>)
<span style="color: #a0522d;">sink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"alsasink"</span>, <span style="color: #8b2252;">"alsa-output"</span>)
<span style="color: #a020f0;">self</span>.player.add(source)
<span style="color: #a020f0;">self</span>.player.add(decoder)
<span style="color: #a020f0;">self</span>.player.add(conv)
<span style="color: #a020f0;">self</span>.player.add(sink)
source.link(decoder)
decoder.link(conv)
conv.link(sink)
<span style="color: #a0522d;">bus</span> = <span style="color: #a020f0;">self</span>.player.get_bus()
bus.add_signal_watch()
bus.connect(<span style="color: #8b2252;">"message"</span>, <span style="color: #a020f0;">self</span>.on_message)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">start_stop</span>(<span style="color: #a020f0;">self</span>, w):
<span style="color: #a020f0;">if</span> <span style="color: #a020f0;">self</span>.button.get_label() == <span style="color: #8b2252;">"Start"</span>:
<span style="color: #a0522d;">filepath</span> = <span style="color: #a020f0;">self</span>.entry.get_text().strip()
<span style="color: #a020f0;">if</span> os.path.isfile(filepath):
<span style="color: #a0522d;">filepath</span> = os.path.realpath(filepath)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Stop"</span>)
<span style="color: #a020f0;">self</span>.player.get_by_name(<span style="color: #8b2252;">"file-source"</span>).set_property(<span style="color: #8b2252;">"location"</span>, filepath)
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.PLAYING)
<span style="color: #a020f0;">else</span>:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a0522d;">t</span> = message.<span style="color: #483d8b;">type</span>
<span style="color: #a020f0;">if</span> t == Gst.MessageType.EOS:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">elif</span> t == Gst.MessageType.ERROR:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a0522d;">err</span>, debug = message.parse_error()
<span style="color: #a020f0;">print</span> <span style="color: #8b2252;">"Error: %s"</span> % err, debug
Gst.init(<span style="color: #008b8b;">None</span>)
GTK_Main()
GObject.threads_init()
Gtk.main()
</pre>
</div>
</div>
</div>
<div id="outline-container-sec-4-2" class="outline-3">
<h3 id="sec-4-2"><span class="section-number-3">4.2</span> Adding Video to the Pipeline</h3>
<div class="outline-text-3" id="text-4-2">
<p>
The next example is playing MPEG2 videos. Some demuxers, such as <code>mpegdemux</code>, uses dynamic pads which are created at runtime and therefor you can't link between the demuxer and the next element in the pipeline before the pad has been created at runtime. Watch out for the <code>demuxer_callback()</code> method below.
</p>
<div class="figure">
<p><img src="pipeline-branch-block.svg" alt="pipeline-branch-block.svg" width="100%" />
</p>
</div>
<a href="pipeline-branch-example.py">pipeline-branch-example.py</a>
<div class="org-src-container">
<pre class="src src-python"><span style="color: #b22222;">#</span><span style="color: #b22222;">!/usr/bin/env python</span>
<span style="color: #a020f0;">import</span> os
<span style="color: #a020f0;">import</span> gi
gi.require_version(<span style="color: #8b2252;">'Gst'</span>, <span style="color: #8b2252;">'1.0'</span>)
<span style="color: #a020f0;">from</span> gi.repository <span style="color: #a020f0;">import</span> Gst, GObject, Gtk
<span style="color: #a020f0;">class</span> <span style="color: #228b22;">GTK_Main</span>(<span style="color: #483d8b;">object</span>):
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">__init__</span>(<span style="color: #a020f0;">self</span>):
<span style="color: #a0522d;">window</span> = Gtk.Window(Gtk.WindowType.TOPLEVEL)
window.set_title(<span style="color: #8b2252;">"Mpeg2-Player"</span>)
window.set_default_size(500, 400)
window.connect(<span style="color: #8b2252;">"destroy"</span>, Gtk.main_quit, <span style="color: #8b2252;">"WM destroy"</span>)
<span style="color: #a0522d;">vbox</span> = Gtk.VBox()
window.add(vbox)
<span style="color: #a0522d;">hbox</span> = Gtk.HBox()
vbox.pack_start(hbox, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">False</span>, 0)
<span style="color: #a020f0;">self</span>.entry = Gtk.Entry()
hbox.add(<span style="color: #a020f0;">self</span>.entry)
<span style="color: #a020f0;">self</span>.button = Gtk.Button(<span style="color: #8b2252;">"Start"</span>)
hbox.pack_start(<span style="color: #a020f0;">self</span>.button, <span style="color: #008b8b;">False</span>, <span style="color: #008b8b;">False</span>, 0)
<span style="color: #a020f0;">self</span>.button.connect(<span style="color: #8b2252;">"clicked"</span>, <span style="color: #a020f0;">self</span>.start_stop)
<span style="color: #a020f0;">self</span>.movie_window = Gtk.DrawingArea()
vbox.add(<span style="color: #a020f0;">self</span>.movie_window)
window.show_all()
<span style="color: #a020f0;">self</span>.player = Gst.Pipeline.new(<span style="color: #8b2252;">"player"</span>)
<span style="color: #a0522d;">source</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"filesrc"</span>, <span style="color: #8b2252;">"file-source"</span>)
<span style="color: #a0522d;">demuxer</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"mpegpsdemux"</span>, <span style="color: #8b2252;">"demuxer"</span>)
demuxer.connect(<span style="color: #8b2252;">"pad-added"</span>, <span style="color: #a020f0;">self</span>.demuxer_callback)
<span style="color: #a020f0;">self</span>.video_decoder = Gst.ElementFactory.make(<span style="color: #8b2252;">"mpeg2dec"</span>, <span style="color: #8b2252;">"video-decoder"</span>)
<span style="color: #a020f0;">self</span>.audio_decoder = Gst.ElementFactory.make(<span style="color: #8b2252;">"mad"</span>, <span style="color: #8b2252;">"audio-decoder"</span>)
<span style="color: #a0522d;">audioconv</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"audioconvert"</span>, <span style="color: #8b2252;">"converter"</span>)
<span style="color: #a0522d;">audiosink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"autoaudiosink"</span>, <span style="color: #8b2252;">"audio-output"</span>)
<span style="color: #a0522d;">videosink</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"autovideosink"</span>, <span style="color: #8b2252;">"video-output"</span>)
<span style="color: #a020f0;">self</span>.queuea = Gst.ElementFactory.make(<span style="color: #8b2252;">"queue"</span>, <span style="color: #8b2252;">"queuea"</span>)
<span style="color: #a020f0;">self</span>.queuev = Gst.ElementFactory.make(<span style="color: #8b2252;">"queue"</span>, <span style="color: #8b2252;">"queuev"</span>)
<span style="color: #a0522d;">colorspace</span> = Gst.ElementFactory.make(<span style="color: #8b2252;">"videoconvert"</span>, <span style="color: #8b2252;">"colorspace"</span>)
<span style="color: #a020f0;">self</span>.player.add(source)
<span style="color: #a020f0;">self</span>.player.add(demuxer)
<span style="color: #a020f0;">self</span>.player.add(<span style="color: #a020f0;">self</span>.video_decoder)
<span style="color: #a020f0;">self</span>.player.add(<span style="color: #a020f0;">self</span>.audio_decoder)
<span style="color: #a020f0;">self</span>.player.add(audioconv)
<span style="color: #a020f0;">self</span>.player.add(audiosink)
<span style="color: #a020f0;">self</span>.player.add(videosink)
<span style="color: #a020f0;">self</span>.player.add(<span style="color: #a020f0;">self</span>.queuea)
<span style="color: #a020f0;">self</span>.player.add(<span style="color: #a020f0;">self</span>.queuev)
<span style="color: #a020f0;">self</span>.player.add(colorspace)
source.link(demuxer)
<span style="color: #a020f0;">self</span>.queuev.link(<span style="color: #a020f0;">self</span>.video_decoder)
<span style="color: #a020f0;">self</span>.video_decoder.link(colorspace)
colorspace.link(videosink)
<span style="color: #a020f0;">self</span>.queuea.link(<span style="color: #a020f0;">self</span>.audio_decoder)
<span style="color: #a020f0;">self</span>.audio_decoder.link(audioconv)
audioconv.link(audiosink)
<span style="color: #a0522d;">bus</span> = <span style="color: #a020f0;">self</span>.player.get_bus()
bus.add_signal_watch()
bus.enable_sync_message_emission()
bus.connect(<span style="color: #8b2252;">"message"</span>, <span style="color: #a020f0;">self</span>.on_message)
bus.connect(<span style="color: #8b2252;">"sync-message::element"</span>, <span style="color: #a020f0;">self</span>.on_sync_message)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">start_stop</span>(<span style="color: #a020f0;">self</span>, w):
<span style="color: #a020f0;">if</span> <span style="color: #a020f0;">self</span>.button.get_label() == <span style="color: #8b2252;">"Start"</span>:
<span style="color: #a0522d;">filepath</span> = <span style="color: #a020f0;">self</span>.entry.get_text().strip()
<span style="color: #a020f0;">if</span> os.path.isfile(filepath):
<span style="color: #a0522d;">filepath</span> = os.path.realpath(filepath)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Stop"</span>)
<span style="color: #a020f0;">self</span>.player.get_by_name(<span style="color: #8b2252;">"file-source"</span>).set_property(<span style="color: #8b2252;">"location"</span>, filepath)
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.PLAYING)
<span style="color: #a020f0;">else</span>:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a0522d;">t</span> = message.<span style="color: #483d8b;">type</span>
<span style="color: #a020f0;">if</span> t == Gst.MessageType.EOS:
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">elif</span> t == Gst.MessageType.ERROR:
<span style="color: #a0522d;">err</span>, debug = message.parse_error()
<span style="color: #a020f0;">print</span> <span style="color: #8b2252;">"Error: %s"</span> % err, debug
<span style="color: #a020f0;">self</span>.player.set_state(Gst.State.NULL)
<span style="color: #a020f0;">self</span>.button.set_label(<span style="color: #8b2252;">"Start"</span>)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">on_sync_message</span>(<span style="color: #a020f0;">self</span>, bus, message):
<span style="color: #a020f0;">if</span> message.get_structure().get_name() == <span style="color: #8b2252;">'prepare-window-handle'</span>:
imagesink = message.src
imagesink.set_property(<span style="color: #8b2252;">"force-aspect-ratio"</span>, <span style="color: #008b8b;">True</span>)
xid = <span style="color: #a020f0;">self</span>.movie_window.get_property(<span style="color: #8b2252;">'window'</span>).get_xid()
imagesink.set_window_handle(xid)
<span style="color: #a020f0;">def</span> <span style="color: #0000ff;">demuxer_callback</span>(<span style="color: #a020f0;">self</span>, demuxer, pad):
<span style="color: #a020f0;">if</span> pad.get_property(<span style="color: #8b2252;">"template"</span>).name_template == <span style="color: #8b2252;">"video_%02d"</span>:
qv_pad = <span style="color: #a020f0;">self</span>.queuev.get_pad(<span style="color: #8b2252;">"sink"</span>)
pad.link(qv_pad)
<span style="color: #a020f0;">elif</span> pad.get_property(<span style="color: #8b2252;">"template"</span>).name_template == <span style="color: #8b2252;">"audio_%02d"</span>:
qa_pad = <span style="color: #a020f0;">self</span>.queuea.get_pad(<span style="color: #8b2252;">"sink"</span>)
pad.link(qa_pad)