using threads and pyGST in a wx python app

Question

OK, so I am writing an app, which plays music with the pyGST bindings.

This requires the use of threads to handle playback. The bindings library handles most of the thread control for me, which is nice(and what I was looking for in them).

Now, I don't have a full grasp on this concept, so I would be eager for some references. But the way I understand it, is I have to basically inform the app that it can use multiple threads.

I gathered this from the examples on the gstreamer site, where they use this call:

gtk.gdk.threads_init()  
gtk.main()

according to here, this tells the app it can use multiple threads(more or less), which is where my above assumption came from.

That is the background. Now get this. I have placed those lines in my code, and they work fine. My app plays music rather than crashing whenever it tries. But something doesn't feel right.
In the examples that I got those lines from, they use gtk for the whole GUI, but I want to use wxWidgets, so it feels wrong calling this gtk function to do this.

Is there a wx equivalent to this? or is it ok to use this, and will it still work cross platform?

Also, I have to figure out how to kill all these threads on exit(which it does not do right now) I see how they do it in the example using a gtk method again, so again, looking for a wx equivalent.

PS: I think this(or the solution) may be related to the wx.App.MainLoop() function, but I am lost in trying to understand how this loop works, so again, good references about this would be appreciated, but I suppose not necessary as long as I have a good solution.

Answer 1

Try using this instead:

import gobject
gobject.threads_init()

I wonder how come it is not written in large print at the start of every python gstreamer plugin piece of documentation: it only took me several hours to find it.

A bit more details here.

Answer 2

I have no experience with pyGST, but the general advice for using threads and wxPython is to only update the GUI from the main thread (i.e. the thread that starts the MainLoop). See http://wiki.wxpython.org/LongRunningTasks for more information.

Answer 3

I have no experience with the python bindings, but I have had success using wxWidgets and GStreamer together on Windows. The problem is that wxWidgets runs a Windows event loop while GStreamer uses a GLib event loop. If you don't care about any of the GStreamer events, you shouldn't need to do anything. However, if you care to receive any of the GStreamer events, you will have to run your own GLib event loop (GMainLoop) in a separate thread with a separate GMainContext. Use gst_bus_create_watch to create a GST event source, add a callback to the source with g_source_set_callback, and then attach it to the main context of your GLib event loop with g_source_attach. You can then handle the GST in the callback, for example, to forward the events to the wx main event loop.