Re: Interaction between user and kernel space

[Christophe Lucas <clucas@xxxxxxxxxxxxx>]

Thomas Petazzoni (thomas.petazzoni@xxxxxxxx) wrote:
> Hello,
> 
> Christophe Lucas wrote:
> 
> >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
> 
> Apparently, V4L2 allows user-space programs to «negotiate» the format of 
> the frames to be exchanged. I understand that this is useful to 
> negotiate whether you want a RGB image or YUV image or whatever, but how 
> can this help in decompressing a specific frame format ? I mean, the 
> userspace program negotiate with the pwc driver. The pwc kernel driver 
> can only capture compressed frames. Who will make the decompression ? 
> The userspace program itself ?
> 
> (Of course, I may have completely misunderstood the possibilities of 
> V4L2. Don't hesitate to tell me if I did).

I can give you one example: programs based on sn9c102 driver. userspace
programs negociate between Bayer image or sn9c kind of picture. And
decompression is made in userspace.

Some projects like :
	http://sn-webcam.sourceforge.net
	http://stolk.org/sonic-snap/

Have a nice day,

	~Christophe

PS: I think this thread begin to be HS.

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