[libcamera-devel] [PATCH v3 1/2] libcamera: Add a SensorSensitivity property

[Naushir Patuck]

Hi Jacopo.

On Fri, 20 May 2022 at 09:43, Jacopo Mondi <jacopo at jmondi.org> wrote:

> Hi,
>
> On Thu, Apr 21, 2022 at 04:11:16PM +0100, Naushir Patuck via
> libcamera-devel wrote:
> > The SensorSensitivity property is a scaling factor that describes how
> sensitive
> > the selected sensor mode is compared to other readout modes of the same
> sensor.
> > For example, a binned mode might have twice the sensitivity of the full
> > resolution mode, meaning you would get double the signal level for the
> same
> > exposure and gains.
> >
> > Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> > Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> > ---
> >  src/libcamera/property_ids.yaml | 12 ++++++++++++
> >  1 file changed, 12 insertions(+)
> >
> > diff --git a/src/libcamera/property_ids.yaml
> b/src/libcamera/property_ids.yaml
> > index 12ecbce5eed4..11b7ebdc3105 100644
> > --- a/src/libcamera/property_ids.yaml
> > +++ b/src/libcamera/property_ids.yaml
> > @@ -678,6 +678,18 @@ controls:
> >          \todo Turn this property into a "maximum control value" for the
> >          ScalerCrop control once "dynamic" controls have been
> implemented.
> >
> > +  - SensorSensitivity:
> > +      type: float
> > +      description: |
> > +        The relative sensitivity of the chosen sensor mode.
> > +
> > +        Some sensors have readout modes with different sensitivities.
> For example,
> > +        a binned camera mode might, with the same exposure and gains,
> produce
> > +        twice the signal level of the full resolution readout. This
> would be
> > +        signalled by the binned mode, when it is chosen, indicating a
> value here
> > +        that is twice that of the full resolution mode. This value will
> be valid
> > +        after the configure method has returned successfully.
>
> Sorry, I should have payed much more attention during the review.
>
> The sensitivity depends on the mode applied to the sensor, and as the
> description suggests changes at Camera::configure() time.
>
> Libcamera properties are immutable and they should not depend on the
> current configuration but they should stay constant during the whole
> lieftime of the Camera.
>
> This should rather be a Control, even if I understand it cannot be
> changed by the user. Do we maybe need to reconsider Properties'
> immutability (Laurent in cc for opinions)
>

ScalerCropMaximum is an existing mutable property as well.  Like
SensorSensitivity, it is mutable in the sense it is mode specific, but
does not change after a Configure() call.

Regards,
Naush



>
> Thanks
>    j
>
> > +
> >    #
> ----------------------------------------------------------------------------
> >    # Draft properties section
> >
> > --
> > 2.25.1
> >
>
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