Re: support autofocus / autogain in libv4l2

From: Pavel Machek <pavel@ucw.cz>
To: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: pali.rohar@gmail.com, sre@kernel.org,
	kernel list <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linux-omap@vger.kernel.org, tony@atomide.com, khilman@kernel.org,
	aaro.koskinen@iki.fi, ivo.g.dimitrov.75@gmail.com,
	patrikbachan@gmail.com, serge@hallyn.com, abcloriens@gmail.com,
	Sakari Ailus <sakari.ailus@iki.fi>,
	Sakari Ailus <sakari.ailus@linux.intel.com>,
	linux-media@vger.kernel.org, hdegoede@redhat.com
Subject: Re: support autofocus / autogain in libv4l2
Date: Tue, 25 Apr 2017 10:20:41 +0200	[thread overview]
Message-ID: <20170425082041.GB30380@amd> (raw)
In-Reply-To: <20170424225731.7532e368@vento.lan>

[-- Attachment #1: Type: text/plain, Size: 1919 bytes --]

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.

That would be too slow :-(.

> 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).

I do have mplayer working, but that one is not linked against libv4l2
:-(.

> > 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).

Is 16bit bayer a recent development? I can't see it in

commit 374806e868f5a7a48ecffde4c6a1abfcfa5ccd65
Author: Hans Verkuil <hans.verkuil@cisco.com>
Date:   Fri Apr 22 09:31:57 2016 +0200

> > 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.

And settings are persistent, so I can enable autogain, then lauch
something like xawtv, and it will automatically get autogain? Ok,
good.

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

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 181 bytes --]