support autofocus / autogain in libv4l2

[Mauro Carvalho Chehab]

Em Tue, 25 Apr 2017 00:07:01 +0200
Pavel Machek <pavel at ucw.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