[libcamera-devel] [PATCH 0/1] DigitalGain control

[David Plowman]

Hi everyone

Can I give this patch a little prod, see how folks would like to move
forward on this one?

Thanks!
David

On Tue, 27 Oct 2020 at 14:12, David Plowman <david.plowman at raspberrypi.com>
wrote:

> Hi everyone
>
> I wanted to raise a topic on which there was already some discussion a
> few weeks back, prompted by my noticing a gap in the metadata that we
> provide with images.
>
> My observation was that I couldn't correctly set the ISO value in my
> JPEG files because we don't report how much digital gain has been
> supplied by the image processing pipeline. To address this problem, it
> seemed as good a way as any actually to include a proposal for a new
> DigitalGain control (see the associated patch). Nevertheless, I think
> there's a discussion to be had first. Notably:
>
> * Should we let the pipeline report a single global "digital gain"
>   value or, given that different gains may be applied to the colour
>   channels, should we report three gain values instead?
>
> * In the Pi world I'd like this to be a read-only control, i.e. you
>   can't force the pipeline digital gain to a particular value, as our
>   AGC doesn't work like that. But there may be platforms that do allow
>   you to set the digital gain.
>
> * You could imagine this being "per-stream". I think it's another case
>   of "practically everyone will just want a single value", though
>   technically you might be able to imagine some platform and use-cases
>   where different outputs might reflect different digital gains.
>
> * There's a question about digital gain being applied by the sensor
>   itself, but I'm inclined to view that as a separate topic. The issue
>   at hand, at least for me, is being able to distinguish the gain
>   applied by the sensor, and which we see in the raw frames, from that
>   applied by the ISP, which appears in the JPEGs.
>
> You may have other comments too - so everyone's thoughts would be much
> appreciated.
>
> Thanks!
> David
>
> David Plowman (1):
>   libcamera: controls: Add DigitalGain control
>
>  src/libcamera/control_ids.yaml | 11 +++++++++++
>  1 file changed, 11 insertions(+)
>
> --
> 2.20.1
>
>
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