Laszlo Pandy

Jono Bacon asked me to hold a session on GStreamer and a session on Cairo for the Ubuntu Opportunistic Developer Week.

My GStreamer session went well. The IRC log is available online. I went through my slides which explained how to do a few simple things in Python. I used playbin2 to implement audio/video playback with pausing, seeking and position queries to update the slider. I was impressed how simple the code is; only 120 lines of Python.

I was less impressed with my Cairo session. Unlike with GStreamer, I couldn’t think up a clear use case that I could explain the solution to in under one hour. Instead I went through the very simple cairo API and showed how to use it with GTK or with PDF, PNG and SVG file formats. The IRC log and the code as online for this session as well. I did not make any slides.

Jokosher

This week Michael and I also released a new version of Jokosher. It is available on the download page on Launchpad even though the Jokosher website has not been updated yet.

Little has changed in this release so when we get around to changing the website there won’t be an announcement or anything. The reason for making this release was to get a bug fix out for a blocker which prevented Jokosher from running at all with newer versions of GTK. We wanted to get this done soon so it could be in the Ubuntu Lucid release, and the packaged version wouldn’t be broken. We also threw in a few other bug fixes while we were at it.

Many Jokosher users have been inquiring about support for JACK for some time. Since 0.9 we have had support for using a custom playback pipeline, but you could only use ALSA for recording. After removing the DBus code which we used to retrieve device information from ALSA we can now use whatever recording backend is supported by Gstreamer.

Since we removed our ALSA specific code, we now use the GstPropertyProbe interface on the “device” property to retrieve the list of devices. Currently this only works with ALSA, but if you are using Gstreamer from CVS the patches of mine that were recently committed make it work with PulseAudio as well. JACK does not support the “device” property at all, since the JACK control panel is used to select devices.

As an added bonus, removing the ALSA specific code will make it substantially easier to make Jokosher work on Windows. None of our developers are doing a Windows port,  but if you are interested you are certainly welcome to try it out and see if it works.

This code is not yet merged into the main branch, but you can get it from the custom-audio-src branch in Launchpad and give JACK a try.

After all these years of using it, learning about it, raving about it, and complaining about it, I can finally say I have contributed to Gstreamer. Specifically my contribution was four patches improving the ability to retrieve device information from the PulseAudio elements.

It feels great.