linux-kernel - Re: support autofocus / autogain in libv4l2

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Message-ID: <20170424225731.7532e368@vento.lan>
Date:   Mon, 24 Apr 2017 22:57:38 -0300
From:   Mauro Carvalho Chehab <mchehab@...pensource.com>
To:     Pavel Machek <pavel@....cz>
Cc:     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, abcloriens@...il.com,
        Sakari Ailus <sakari.ailus@....fi>,
        Sakari Ailus <sakari.ailus@...ux.intel.com>,
        linux-media@...r.kernel.org, hdegoede@...hat.com
Subject: Re: support autofocus / autogain in libv4l2

Em Tue, 25 Apr 2017 00:07:01 +0200
Pavel Machek <pavel@....cz> escreveu:

> Hi!
> 
> > Please don't add a new application under lib/. It is fine if you want
> > some testing application, if the ones there aren't enough, but please
> > place it under contrib/test/.
> > 
> > You should likely take a look at v4l2grab first, as it could have
> > almost everything you would need.  
> 
> I really need some kind of video output. v4l2grab is not useful
> there. v4l2gl might be, but I don't think I have enough dependencies.

Well, you could use some app to show the snaps that v4l2grab takes.

Yeah, compiling v4l2gl on N9 can indeed be complex. I suspect that it 
shouldn't hard to compile xawtv there (probably disabling some optional
features).

> Umm, and it looks like libv4l can not automatically convert from
> GRBG10.. and if it could, going through RGB24 would probably be too
> slow on this device :-(.

I suspect it shouldn't be hard to add support for GRBG10. It already
supports 8 and 16 bits Bayer formats, at lib/libv4lconvert/bayer.c
(to both RGB and YUV formats).

How it would preform is another question ;)

> > IMO, the above belongs to a separate processing module under
> > 	lib/libv4lconvert/processing/  
> 
> Is there an example using autogain/autowhitebalance from
> libv4lconvert?

Well, if you plug a USB camera without those controls, it should
automatically expose controls for it, as if the device had such
controls.

Thanks,
Mauro