[Sugar-devel] [ASLO] webcam images and control

[Benjamin M. Schwartz]

Aleksey Lim wrote:
> On Thu, Feb 25, 2010 at 03:39:26PM +0100, Emmanuel Di Folco wrote:
>> I would like to be able to :
>> - control the gain or integration time of the camera (mode Photo, not  
>> video) in order not to saturate (this is obviously feasible, since  
>> the images taken during the day are not saturated !)
>> - eventually restrict the size of the screen window that is  
>> considered by the 'automatic gain adjustment algorithm' (where I  
>> would insert the moon)

The automatic gain adjustment is performed in hardware, not software.  In
the standard mode, the CPU has no control over the camera's gain/exposure
time.  It may be possible to put the camera into a "manual" mode, where
the CPU can control gain and other parameters, but I do not know how to do
this.

The best person to ask is Jonathan Corbet, who wrote the camera's driver.
 However, the camera's interface has proven difficult to work with and
poorly documented, so many advanced functions have not been implemented in
the driver.  On the XO-1.5, even basic camera functionality is still not
working correctly.

>> - gather the raw images, not the JPG compressed ones.

I did manage to do this on the XO-1.  You can try the instructions from:
http://lists.laptop.org/pipermail/devel/2008-February/011029.html

This code also controls the "integration time" by acquiring many images
and averaging them.

--Ben

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