Camera knobs and dials...

[Jim Gettys]

On Tue, 2006-10-03 at 08:31 -0600, Jonathan Corbet wrote:
> Jim Gettys <jg at laptop.org> wrote:
> 
> > To do so, they need to be
> > able to use the device in as linear a fashion (photometrically) as
> > possible: disable gain control, black point processing, color balancing,
> > etc, which from looking at the sensor spec appears to be possible from a
> > quick perusal.  Such sensors do a remarkable amount of signal processing
> > internally these days.
> > 
> > I know V4L has facilities for controlling (most of) these features, that
> > you are hooking up in the sensor driver right now.  Does V4L also have
> > facilities for completely disabling these features?  Are there any
> > features of the chip that V4L does not support?
> 
> V4L2 has a fair number of predefined controls, there's a list at:
> 
>   http://v4l2spec.bytesex.org/spec/x488.htm#CONTROL-ID
> 
> Some of them do what they want - disabling white balance, auto exposure
> control, etc.  There is also a way to add driver-specific controls for
> the ones that are missing.  So all of this can be handled.
> 
> If it seems that any of those settings should be turned into standard
> V4L2 controls, that's easy enough to make happen.
> 
> The big challenge is a story you've heard from me for a while:
> translating those controls into an appropriate set of OV7670 register
> settings.  I have come to the conclusion that those settings really
> constitute a form of opaque firmware, and, without cooperation from 
> OmniVision, they can be hard to get right.  There's a lot of registers
> simply marked "reserved" in the spec, and there are undocumented 
> ordering issues as well.  It can all be done, eventually.

OK, let's get you hooked up with OmniVision.  I expect we can get their
attention.
                                      - Jim

-- 
Jim Gettys
One Laptop Per Child