linux-kernel - Re: camera application for testing (was Re: v4l subdevs without big device)

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Date:	Wed, 22 Jun 2016 00:32:46 +0200
From:	Pavel Machek <pavel@....cz>
To:	Sakari Ailus <sakari.ailus@....fi>
Cc:	Hans Verkuil <hverkuil@...all.nl>, pali.rohar@...il.com,
	sre@...nel.org, kernel list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
	linux-omap@...r.kernel.org, tony@...mide.com, khilman@...nel.org,
	aaro.koskinen@....fi, ivo.g.dimitrov.75@...il.com,
	patrikbachan@...il.com, serge@...lyn.com, tuukkat76@...il.com,
	mchehab@....samsung.com, linux-media@...r.kernel.org,
	laurent.pinchart@...asonboard.com
Subject: Re: camera application for testing (was Re: v4l subdevs without big
 device)

Hi!

> > What is reasonable camera application for testing?
> > 
> > N900 looks like a low-end digital camera. I have now have the hardware
> > working (can set focus to X cm using command line), but that's not
> > going to be useful for taking photos.
> 
> I guess you already knew about omap3camd; it's proprietary but from purely
> practical point of view it'd be an option to support taking photos on the
> N900. That would not be extensible any way, the best possible functionality
> is limited what the daemon implements.
> 
> I'm just mentioning the option of implementing wrapper for the omap3camd so
> that it can work with upsteam APIs, I don't propose that however.
> 
> > 
> > In particular, who is going to do computation neccessary for
> > autofocus, whitebalance and exposure/gain?
> 
> I think libv4l itself has algorithms to control at least some of these. It
> relies on the image data so the CPU time consumption will be high.
> 
> AFAIR Laurent has also worked on implementing some algorithms that use the
> histogram and some of the statistics. Add him to cc list.

Ok, so I played a bit... and have something working. I modified
fcam-dev to work with the current kernel, and removed most
functionality in the process. Then I re-did sharpness and autogain
computations in software, and it seems to work somehow... but its
rather slow. (But good news is that's because code is stupid; the
computations should be fast enough.)

In particular, it takes cca 10 seconds to take a picture. I guess
there's a room for improvement :-).

> > There's http://fcam.garage.maemo.org/gettingStarted.html that should
> > work on maemo, but a) it is not in Debian, b) it has non-trivial
> > dependencies and c) will be a lot of fun to get working...
> > 
> > (and d), will not be too useful, anyway, due to 1sec shutter lag:
> 
> I believe this will be shorter nowadays. I don't remember the exact
> technical solution which the text below refers to but I'm pretty sure it'll
> be better with the current upstream. API-wise, there's work to be done there
> (to port FCAM to upsteram APIs) but it's a possibility.

So far I have really horrible hacks.

Best regards,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html