[libcamera-devel] ScalerCrop control and camera modes

[Naushir Patuck]

Hi Jacopo,


On Wed, 11 Jan 2023 at 15:55, Jacopo Mondi via libcamera-devel <
libcamera-devel at lists.libcamera.org> wrote:

> Hi David
>
> On Wed, Jan 11, 2023 at 01:27:31PM +0000, David Plowman via
> libcamera-devel wrote:
> > Hi everyone
> >
> > A little question about what happens to the ScalerCrop control when we
> > switch between camera modes (i.e. call configure). Paying particular
> > attention to the case when the two camera modes have different sensor
> > crops (and therefore a different FoV), should the ScalerCrop be
> > preserved or not?
>
> How is a Control "preserved" between streaming sessions ?
>
> Are you wondering if the ScalerCrop set by an application during a
> streaming session should be retained by the pipeline handler after a
> [stop - configure] sequence and re-applied at start() time without
> application's intervention ?
>
> If that's the case, are there other controls preserved between
> reconfigurations or do you have any in mind ?
>

Most controls destined for the IPA currently preserve value between
reconfigurations.  For example, ExposureTime, AnalogueGain, Brightness,
Contrast, ColourGains, etc. all apply the same settings regardless of
mode.  In
fact, I cannot think of a control (apart from ScalerCrop) that is not
preserved
between reconfigurations!

Regards,
Naush


> >
> > I think we could go either way.
> >
> > If the ScalerCrop is preserved that's fine, but you have to handle the
> > case where the previous ScalerCrop is not entirely available in the
> > new mode. You also have to consider how an application would reset the
> > ScalerCrop so as to switch from a mode with a limited FoV to one with
> > a larger FoV.
> >
> > If the ScalerCrop isn't preserved that's fine too, but you have to
> > consider how an application would preserve the ScalerCrop if it wanted
> > to.
> >
> > In many respects I don't think there's much difference, applications
> > would (sometimes) have to specify the ScalerCrop they want when they
> > call start. But which do we think is the most desirable behaviour? On
> > the Pi, by not having thought about it, we are implementing the second
> > alternative (ScalerCrop not preserved).
> >
> > Thoughts?
> >
> > Thanks!
> > David
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.libcamera.org/pipermail/libcamera-devel/attachments/20230111/35e1facd/attachment.htm>