This week I am in Cambridge getting to know my colleagues at Collabora Multimedia and attending both the ELC and the GStreamer Conference, which were co-locating.
ELC was interesting. There were a lot of talks dealing with user interface and multimedia issues, and I was pleasantly surprised to find out several presenters mentioning Qt, usually in conjunction with MeeGo. I remember that four or five years ago Qt was relatively unknown, at least in the free software events I used to attend. Nowadays this is clearly not the case: a presenter from Alcatel had a lecture where he compared the available solutions for embedded Linux products. It was a nice presentation, covering all the different SoC architectures as well as the frameworks and toolkits. When he reached the toolkit section there was a big chart with 7 or 8 different solutions, and Qt was clearly a contender for the top position.

The GStreamer conference was a pleasant surprise for me as well, as I was not expecting that many developers. There were at least 150 people there from different projects and companies, and the quality of the presentations was great. I was very pleased to meet another Brazilian developer, Luciana Fujii from Holoscopio. She presented about Landell, a GStreamer-based recording and streaming solution that was used for the last FISL conference in Brazil. It looks very interesting and could possibly help us solve some of the challenges related to recording and streaming content for the next Desktop Summit. On-the-fly camera switching and titling are possible, as well as recording and streaming using different settings. It is Python-based and seems very simple to operate.

I also met several other developers working with GStreamer either professionally or in their pet projects. One I found particularly interesting to watch in action was Stefan Kost’s Buzztard: a pretty impressive music composition environment. I recommend a visit to the site: it can work with both samples and generated sounds, has a built-in sequencer/tracker and can even work with legacy Buzz Windows plugins. For some songs Stefan told me that the internal GStreamer pipeline created by Buzz uses up to 500 elements! (mixers, effects, sound generators…) And it all runs at real time: in his machine this was using 25% of the CPU, but of these only 5% were really being used to play the track, as the rest was mostly consumed by the GUI.

Finally, I collected some initial feedback about the current QtGStreamer implementation and possible use cases. I think we are in the right track so far, and I hope we can see the results of this work pretty soon in the form of applications as cool as the ones I have seen in this conference.

For the past couple of weeks I have been working on a very cool project, one started and lead by one of our brilliant KDE hackers-that-came-from-GSoC, George Kiagiadakis (gkiagia). I remember that the project got my attention when it was first announced. But I was very busy at that time, and could only follow it from a distance, until now.

As the title of this post reveals, I am talking about QtGStreamer, the Qt-style bindings for the GStreamer multimedia framework.

The project has been progressing during the past year, mostly because it is used in George’s kcall. The structure of the bindings is very flexible, as it follows the powerful pipeline model that is the strength of GStreamer’s design without falling into the trap of trying to map the GStreamer API 1:1. This gives us something that is friendly to the Qt/KDE developer, but at the same time allows things that are very difficult (or impossible) to do with the multimedia APIs we have currently, like displaying a webcam and transcoding the video at the same time with a few lines of code, or streaming audio/video from a remote location transparently.

Even if QtGStreamer is already functional for simple applications it is of course not complete. There is still a lot of work to be done. So as part of my job with Collabora Multimedia I have been assigned to help it reach a feature-complete status. This does not mean the whole GStreamer API will be wrapped: we are aiming for something that is directed specifically to application developers, and I hope it will allow us to help developers code better multimedia experiences for both Qt, MeeGo and KDE users.

My work on the project started recently, and there is still much I have to learn. Luckily George has been around to mentor me, and Collabora Multimedia has a LOT of expertise in GStreamer, of course. I spent the first few weeks doing a full review of the existing GStreamer bindings for all languages, and identifying the missing pieces that we needed to provide. Oh, and making stupid mistakes as well 🙂 You can follow the development of course at the current QGStreamer repository, and don’t be shy if you think you can help, or have a specific request. At this time it is important for us to identify the use cases we have not envisioned for QtGStreamer and do our best to provide an easy API to make them possible, so your input is much appreciated.

I plan to blog regularly about the status of this project. For now, I will already answer the inevitable initial questions:

a) No, it is not meant to replace Phonon. Different use cases, different priorities.
b) No, we could not make this work as part of the Phonon-gstreamer backend. Although the Phonon-gstreamer backend could possibly be ported to QtGStreamer in the future, if there is interest in doing it.
c) No, this does not conflict with the QtMobility/MultimediaKit API. Again, the use case is different, and they might interoperate in the future.

My work on this project is being sponsored by Nokia/MeeGo. As you might know, GStreamer is the official media framework for the MeeGo project, much like Qt is the official developer API. So this project aims to provide the link between those two powerful elements in the MeeGo ecosystem. I will keep you posted about our development, and thanks for reading so far!