[libcamera-devel] [PATCH 1/1] libcamera: controls: Add DigitalGain control

[Kieran Bingham]

Hi David,

On 27/10/2020 14:12, David Plowman wrote:
> This control reports the global digital gain applied by the pipeline
> as a whole, after capturing a raw image from the sensor.
> 
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> ---
>  src/libcamera/control_ids.yaml | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> index c8874fa9..e6362c74 100644
> --- a/src/libcamera/control_ids.yaml
> +++ b/src/libcamera/control_ids.yaml
> @@ -530,4 +530,15 @@ controls:
>          This control is only present when the pipeline supports scaling. Its
>          maximum valid value is given by the properties::ScalerCropMaximum
>          property, and the two can be used to implement digital zoom.
> +
> +  - DigitalGain:
> +      type: float
> +      description: |
> +        Global digital gain value applied to the image during all the
> +        processing steps after capturing the image from the sensor. Any raw
> +        images, therefore, will not include this gain, but the final images
> +        output by the imaging pipeline as a whole will include it.
> +
> +        This control is intended to report the value used by the image
> +        processing pipeline.


If this is a per-stream thing anyway, I guess it will then be up to
pipeline handlers to set this to the appropriate value for each stream
when it completes. The fact that this value would not be applicable to a
RAW stream makes me think it certainly should be a per-stream metadata
style value.


I'd hope this could be handled by a common helper in that instance so it
doesn't get left out of some pipeline handlers, but included in some,
and become inconsistent. Not yet sure how we can handle that, but that
will be a core issue anyway.


I wonder if we should mark this somehow as read-only, at least until we
determine that someone needs to set it.

We could introduce a control property between type: and description:
  read-only: true


Otherwise, I see no objections currently. I think we're just waiting on
top-level thoughts from Laurent. (And perhaps per-stream controls, but
that brings it's own questions )

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>


>  ...
> 

-- 
Regards
--
Kieran