Thomas Petazzoni (thomas.petazzoni@xxxxxxxx) wrote: > Hello, > > Recently, Linus committed a patch from Alan Cox that removes the > controversial decompressors of the PWC module from the kernel. The > commit log [1] suggests to reimplement the decompression code in userspace. > > I'm wondering how this could work. Webcam drivers are supposed to offer > to userspace a V4L-compatible API, in order to work with programs such > as xawtv or gnomemeeting. If the decompression code is not made in > kernel space, how can the kernel offer a V4L-compatible API for the PWC > webcams ? Having a library called by the user programs doesn't seem to > be an option, because it would require an adaptation of all user > programs, adaptation which would specific to a particular webcam type. > > Should the compressed frame be sent to a userspace daemon which > decompress it and then sends it back to the kernel, which could offer a > V4L-compatible API ? Isn't it a bit overkilled ? Use V4L2. Perhaps this pointers could help you : http://www.mail-archive.com/linux-usb@xxxxxxxx/msg02026.html (very old) http://www.ussg.iu.edu/hypermail/linux/kernel/0408.3/2684.html http://v4l2spec.bytesex.org/spec/format.html#AEN656 > > I just wanted your opinion and ideas about this subject, just for > curiosity. I'm not saying I will try to do the horrible reverse > engineering stuff, I just want to understand how it _could_ work. But perhaps I say mistakes. I will be happy someone could clarify this point or point us on a clear answser. ~Christophe -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
