[libcamera-devel] ScalerCrop control and camera modes

[David Plowman]

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?

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