GStreamer and Python GI

Let’s take a brief look at how to get a Python-gi-based GStreamer program working. Here’s the basic template:

#!/usr/bin/env python3
# Example 1

import gi
gi.require_version("Gst", "1.0")
from gi.repository import Gst
Gst.init(None)


def main():
    print("Using Gst: {}.{}.{}.{}".format(*Gst.version()))

    registry = Gst.Registry.get()
    plugins = registry.get_plugin_list()

    for plugin in plugins:
        print("{}: {}".format(plugin.get_name(), plugin.get_version()))

if __name__ == "__main__":
    main()

You can run this puppy by saving it to a file and running:

$ python3 example_1.py

There’s some fun stuff going on here, even if there’s no pretty output.

import gi

Firstly, we’re importing the gi module, which is the GObject Introspection implementation for python. Suffice it to say that this is where the bindings for our GStreamer magic live – you can always check out more about GObject and the Introspection support over at the GNOME project.

gi.require_version("Gst", "1.0")

Then, we’re requiring the version of “Gst” to be “1.0”. Why? Because we want to target the latest and greatest GStreamer software, based on the 1.0 APIs, and if you happen to have the previous 0.10 software installed, the repository could inadvertently load it instead of the 1.0 libraries, and the 0.10 series does not play nice with the gobject introspection system.

Gst.init(None)

Next, we’re initalizing the GStreamer libraries.

Once we get inside main(), we’re printing out the version of the GStreamer libraries that we’re working with.

print("Using Gst: {}.{}.{}.{}".format(*Gst.version()))

Finally, we’re taking a look at the Registry, which is where GStreamer keeps track of all of the various plugins that provide functionality in the system. If you have need of a particular minimum version of a certain plugin, then you can use the Registry to make sure that your users have that version installed.

registry = Gst.Registry.get()
plugins = registry.get_plugin_list()

for plugin in plugins:
    print("{}: {}".format(plugin.get_name(), plugin.get_version()))