Lots of fun with w3cam and friends

[Nick Holloway]

jfm@softgallery.com (J-F Mammet) writes:
> w3cam runs as nobody, so do a chmod 777 /dev/video and will be ok.
> However I only get a blank image with it. Any idea ??

I think this is due to the auto-exposure getting reset (at least that
is what it looks like).

When you restart gqcam, with the camera pointing outside, you can see
the auto-exposure.  The picture starts off white, and adjusts so you
see a reasonable picture.

With 0.4.1, you could see that every other time, the picture would reset
to white, and recalibrate.  This meant that you could get vidcat to grab
a usable picture once after gqcam had run.  The next time it would come
out white.

With 0.4.3, the reset appears to happen every time.  So, when used
indoors, you get a picture (from the default exposure), but outside you
get just white.

With single frame captures, I don't think just using the last exposure
will be valid.  I think waiting until the auto-exposure has settled down
before grabbing the frame would be valid.

I don't know if you can always tell the difference between a single frame
grab, and a stream grab.  It appears that "vidcat" uses capture_frame,
and "gqcam" doesn't, but I don't know if this is universally true.

Secondly, my attempts to look at the values from GetExposure in
capture_frame didn't reveal the values changing with time.

-- 
 `O O'  | Nick.Holloway@alfie.demon.co.uk
// ^ \\ | http://www.alfie.demon.co.uk/
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