KDE4 and video acquisition

[Laurent Pinchart]

Hi everybody,

with all the development effort going in KDE4 (and renaming kdemm to Phonon 
must be a sign that developers are active on the project, isn't it ? :-)), I 
thought I would rise the issue of video acquisition.

I recently wrote a Linux device driver for new generation webcams. After a few 
weeks of development and some tests with a very simple V4L2 command line 
application, I thought I would try live video streaming. Finding an 
application which would support the webcam turned out to be much more 
difficult than I would have expected. Either V4L2, MJPEG or both were not 
supported in the application, when things were not even worse. That's when I 
found out that video acquisition support in Linux is far from being perfect, 
or even easily usable at all.

Application currently have to support V4L and V4L2 with various streaming 
methods (read, mmap, ...), need to implement conversion from all possibles 
image formats that webcams generate (RGB, YUV, MJPEG, PWC, ...) and even have 
to work around driver or hardware bugs. That situation is clearly suboptimal.

As KDE developers are busy creating an architecture for the multimedia 
framework in KDE4, I was wondering if any of you have thought about webcam 
support. Everything I read about Phonon states that sound will be supported 
through various backends (GStreamer, NMM or MAS), but the video input has not 
been publicly discussed so far. With all the controls that a webcam can 
expose (brightness/contrast/hue/saturation, but also exposure time, gain, 
power line frequency setting, pan/tilt/zoom, iris, ...), the job is not 
trivial.

All constructive comments are welcome :-)

Laurent Pinchart