[maemo-developers] N900 camera control - focus movement, white balance, auto-focus calcs, etc.

[From: Simon Pickering]

Hello everyone,

I'm looking into how to use the camera on the N900 when it is released,
I would like to be able to write some code in Python if at all possible,
but I guess I can move my app back to C if needs must.

Anyway, the camera will need to be focused, so I have been trawling
through the kernel code and gstreamer source to try and work out how to
do this, but I thought I may as well just ask as it may save me some
time.

I see there are ioctls for the ad5820 focus piezo controller which could
be used (though I've not looked to see if there's a dev entry for that
device yet), and Qole pointed out that the /dev/video0 device reports
that it has v4l2 extended controls, including the ability to move the
focus (though no mention of autofocus there afaict).

I understand I should be able to adjust the focus through a gstreamer
element such as camerabin or the photography interfaces, but ideally I'd
like to do this from Python. Is v4l2camsrc linked to these btw?

The other option (which means I don't have to wrap one of the gstreamer
elements for Python) is to use the v4l2 extended control command ioctls
directly on the /dev/video0 device. I'm assuming that should be possible
anyway, certainly the Python part looks pretty straight forward (see
e.g. FMRadio.py).

While we're on the subject, I see some header files for what I presume
is a Ti binary blob named isp_*.h. isp_af.h contains header information
for autofocus functionality afaict. Is this functionality exposed to
userspace anywhere?

Looking through the package list, I came across a libgdigicam, might
this be involved...?

Anyway I'm going to keep experimenting with the above, but thought I'd
see if anyone else has any bright ideas.

Cheers,


Simon