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The video4linux user-space: libv4l2, applications and a server - Brandon Philips


Brandon Philips is a Linux developer for Novell's SuSE Labs and has been involved with the video4linux community for almost a year working to fix up Kernel bugs as they arise and writing additions to the spec.


With the merging of the gspca driver sans in-Kernel decompression in 2.6.27 it has become necessary to start working with upstream application developers to ensure that they can support the proliferation of new frame and compression formats. Earlier this month Hans de Geode started this work and created libv4l2: a low level wrapper around existing V4L IOCTLs. Having a user space library sitting between applications and the Kernel opens up the possibility for doing a fairly simple V4L server that can allow sharing of frames between multiple applications: like sound servers ALSA dmix or PulseAudio.

The talk will quickly cover three important topics about the V4L user space:

  • Give an update on how libv4l2 support is progressing and where work is needed.
  • Present a video4linux frame server design and possibly demo. A frame server will allow multiple application to use a V4L device at the same time. For example you can take photos with Cheese while chatting on Skype. Even more critically this is needed for user space autofocus daemons. Many modern webcams simply leave the task of auto-focusing up to software.
  • Discuss the need for a GNOME/KDE control panel for adjusting camera properties. No application I have seen currently implements a UI to adjust all the controls cameras present. Also a desktop level control panel (and tray icon like the volume control) will help move from the one camera one application paradigm too.