On Friday 28 September 2007 14:13:37 Bertrik Sikken wrote: > Hi all, > > A couple of years ago I worked on getting some webcams working > with Linux. To be honest, I was unpleasantly surprised. > There seems to be a lack of direction on how webcams > are even supposed to be supported. > > The problem is that many USB webcams send raw 'bayer' sensor > data in a compressed form to the PC in order to get reasonable > frames-per-second over a full-speed (12 Mb/s) USB connection > AFAIK, the linux kernel developers decided that is was no longer > allowed to do decompression and bayer format conversion in the kernel. > > This leaves a huge gap between kernel drivers that simply > stream raw or compressed bayer data (or other proprietary > format) and applications that expect to received simple > RGB frames from the v4l(2) device file. > > Many webcam drivers are consequently maintained out of the > official kernel and *DO* include decompression and bayer > conversion to at least get webcams into a workable state. > (Examples, there are many more: > * Philips PWC driver: http://www.saillard.org/linux/pwc/ > * Various other drivers: http://www.linux-projects.org > * Spca driver: http://mxhaard.free.fr/spca5xx.html ) > > Some ideas: > * create a user-space library for webcams that reads the compressed > data from a v4l(2) device file, decompresses and unbayers it, > then exposes it through a standard API to applications. > * as above, instead of library, use gstreamer plug-ins (each compressed > webcam format would have its own plugin, with perhaps a single plugin > for unbayering). > * bypass the kernel drivers entirely and use libusb to talk to the > webcams. A problem is that (AFAIK) libusb does not support isochronous > USB transfers and many cameras use this transfer mode. > > Any thoughts on how to improve Linux webcam support? Hello Bertrik, you may want to have a look at the V4L extension project: http://thierry.merle.free.fr/v4l2_extension/general.html There's also a mailing list. BR Luca
