cafe_ccic: possible reason why gqcam is not working

cafe_ccic: possible reason why gqcam is not working

[Németh Márton]

Dear Jonathan,

I read in your documentation found at linux-2.6.27/Documentation/video4linux/cafe_ccic, and
found that you mention that "gqcam" is not working together with cafe_ccic.

I have done some investigation of the gqcam 0.9.1-4 found in Debian system. I wanted
to use gqcam with a different webcam and found out the following things:

 - gqcam currently only supports video4linux 1, and it uses the following
   ioctls: VIDIOCSPICT, VIDIOCSWIN, VIDIOCGCAP, VIDIOCGWIN and VIDIOCGPICT.

 - gqcam only supports read() method of getting the frames.

 - gqcam currently has a limitation that it allocates a static buffer size of
   640*480*3 bytes. This is defined in gqcam.h, struct Camera, field rawbuffer.

As I came across with this buffer limitation, I created a simple patch which at least
can warn the user about this problem instead of getting segmentation fault. The
patch available at http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=502350 .

I hope this helps you to track down why gqcam is not working with cafe_ccic.

Regards,

	Márton Németh

Re: cafe_ccic: possible reason why gqcam is not working

[Jonathan Corbet]

On Thu, 23 Oct 2008 11:17:39 +0200
Németh Márton <nm127@freemail.hu> wrote:

>  - gqcam currently only supports video4linux 1, and it uses the
> following ioctls: VIDIOCSPICT, VIDIOCSWIN, VIDIOCGCAP, VIDIOCGWIN and
> VIDIOCGPICT.

...and that, of course, is the problem.  The V4L1 emulation in the
kernel cannot do a perfect job of things.  This application really
needs to be dragged forward to V4L2 if it is to work well with
contemporary video drivers.

Thanks,

jon