Camera knobs and dials...

[Robert Tinker]

Dear Jim:

Thanks much.
To give some idea of why these controls could be important for kids, 
see the attached.

Bob



At 10:41 AM -0400 10/3/06, jg at laptop.org wrote:
>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>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


-- 
Dr. Robert Tinker, president

The Concord Consortium
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