Jannis Pohlmann Personal website


I am an open source enthusiast, student and musician from Lübeck, Germany. In my free time I enjoy hacking on Xfce and Lunar Linux. I've been a member of both teams since about 2005. Besides developing software, I love to listen to and play music (Guitar, Bass and Drums) and hang out with friends.

Contact me via jannis@xfce.org. My public PGP key is 0x354AFBA6. You can download it from here.

My CV is also available for download.

Tag - pulseaudio

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Thursday, December 8 2011

Looking for new maintainers for some of my projects

I am looking for a new maintainer for some of the open source projects I started over the last couple of years. Due to taking a full-time position as a software engineer, I will have less spare time to hack in the near future than I had while being a student. I will continue contributing to Xfce but I would like to focus on core development (thunar, tumbler, garcon etc.). As a consequence, I am looking for people interested in maintaining the following projects:

Most of these are smaller projects but some of them (like thunar-media-tags-plugin and xfce4-mixer) have many users. xfce4-mixer is particularly interesting, I think. It’s code base is of medium size and it lacks integration with notification daemons, key bindings for muting and altering the volume of a selected channel. Also, the per-channel widgets could be arranged in better ways than they are right now. PulseAudio support has been requested several times but that is an entirely different story. xfce4-mixer is mainly intended as a mixer for GStreamer. A PulseAudio mixer would better be written from scratch. But if anyone is up for the task - why not!

If you are interested in maintaining any of the above (yes, you are free to rename jptemplate to something that does not carry my initials!), please let me know in a comment or send a mail to xfce4-dev@xfce.org! 

(You will need knowledge of C, GLib and GTK+ for the Xfce projects and VIM script for jptemplate. But in particular panel plugins are really simple, so the code base should be easy to understand even for a GTK+ newbie who is willing to read API manuals.)

Wednesday, December 24 2008

Topics raised at UDS

Ok, this post is long overdue and has been around as a draft for more than a week now, so here it is. As readers of this weblog already know, I was at the Ubuntu Developer Summit from December 8th to 12th. We had quite a few discussions on topics I'm interested in outside the scope of the official sessions held at UDS. Let me just list them here in random order:


Arnaud Quette told me about Buildbot which can be used to test your repository for compilation errors on various systems. I suppose it can be a real time saver if you want your project to compile on a variety of distributions and UNIX flavors and want immediate response as to whether compilation is going to succeed on these. That way you don't have to wait for packagers and users to report compilation errors back to you and don't have to enter that typical ping pong developer-reporter dialog. Buildbot not only catches compilation errors but is also capable of sending notification emails and provides detailed information about the compile log and so on. It's implemented based on a server/client concept where each client tests compilation on one system and the server collects data from the clients. By using virtualization you can set up server and clients on the same machine. This would be very nice to have for Xfce but I suppose it would require another dedicated server just for running all these compilations. If anyone is interested in looking in to that, I'd be happy to establish contact to someone from Buildbot to provide you with more information. As a funny coincidence, Frédéric Péters recently announced build.gnome.org which is a great example of Buildbot usage.

Thunar and GIO

I talked to Christian Kellner about GIO/GVfs a bit in order to get information on how remote/virtual filesystems work. One thing I've thought about is how to allow for a list of user-defined remote/virtual filesystems which show up in the side pane of Thunar. There are different approaches to that. One is to use bookmarks which seems to be what, according to Christian, Nautilus does right now. While this seems to work quite well it seems to confuse users a bit. Personally, I'd like to see them separated from bookmarks. There has been a proposal for Nautilus to make the side pane look better by using sections. One thing I could imagine would be to have a "Virtual Volumes" section listing the user-defined filesystems and provide some sort of GUI for creating/removing/editing these. From what I've heard there also is a third approach, which is to make remote filesystems to appear as fake volumes in HAL or DeviceKit. I'll have to look into that in order to decide what the best way to go is, I guess.

PulseAudio and GStreamer

PulseAudio and GStreamer: We discussed the limited PulseAudio backend for GStreamer in a group of up to five people and agreed that it really needs improvement (as in more tracks have to be added to the GstMixer interface) if we don't want users to be able to control PulseAudio through the mixer applications they know. PulseAudio-specific applications like pavucontrol are not really what we want them to use.

Xubuntu Remix for Netbooks

During one of the Xubuntu sessions I talked to a member of the Ubuntu Mobile team about Xfce in general, the modularity of Xfce and the dependencies it has. He seemed to be very interested in it but he was also worried about Xfce becoming less lightweight, eating up more memory and disk space. It wasn't the first time during UDS that someone mentioned LXDE and asked me about my opinion on it. Two main reasons for Xfce being lightweight always were the small number of dependencies and applications which you could call the Xfce stack. With more and more applications and libraries being added, Xfce naturally feel less lightweight, even if these applications are not considered a part of the core desktop. You always have to keep that in mind. It seems like the high modularity of Xfce compensates parts of that and is why people are interested in Xfce in the context of mobile devices. Despite being modular and somewhat lightweight, Xfce also has improved in terms of user experience lately. I think we can push this even further. Giving accessibility more attention might also be worth considering. Usability is something I don't really see in LXDE (yet). That's what I usually tell people if they ask me for my opinion on it.

Friday, December 12 2008

Limitations of the PulseAudio backend for GStreamer

I'm at the Ubuntu Developer Summit this week and Emmet Hikory just approached me with a question about the PulseAudio support in xfce4-mixer. The problem he has is that when he wants to plug in in a bluetooth headset PulseAudio might act weird and there's only one way to fix this from the user's point of view, which is to use pavucontrol or one of the other PulseAudio tools. Unfortunately those tools don't provide a good user experience. Controls are given technical names and too much of the internal technical stuff is being exposed to the user.

So, his idea is that there has to be a user-friendly way (like using xfce4-mixer) to e.g. control the bluetooth headset after it has been plugged in.

I just took a quick look at the PulseAudio code shipped with gst-plugins-good and to me it seems to be in a pretty bad shape. Unless I'm mistaken it only exposes one track through the GstMixer interface: Master. So if you have several devices capable of audio playback/recording, like a normal sound card and a bluetooth headset, you have no control over which of them is being muted, used for recording or whatever.

What I would expect is to either have a list of tracks (one for each sink - and please give them user-friendly names!) exposed through the GstMixer interface or to have a switch for choosing the sink you want to control with the Master track. Without this, no mixer application is able to provide a user-friendly way to control PulseAudio - unless it implements its own PulseAudio support.

One major reason for rewriting xfce4-mixer based on GStreamer has always been to get rid of the need to maintain our own audio system backends. The old mixer had its own backends for ALSA, OSS and BSD and it really sucked.

So I'm hoping that maybe someone steps up to implement a proper PulseAudio backend for GStreamer, with tracks for all available audio sinks and streams. I think I'd prefer tracks over a simple switch because they allow for a more fine-grained configuration of your devices. Thanks Emmet for pointing that out.