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

[Jacopo Mondi]

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)

Thanks
   j

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