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

[David Plowman]

Morning all

Can I give this one its little weekly nudge? Thanks  :)

Best regards
David

On Mon, 16 Nov 2020 at 10:18, David Plowman
<david.plowman at raspberrypi.com> wrote:
>
> Hi again
>
> Can I give this discussion another little metaphorical shove, please? Thanks!
>
> Best regards
> David
>
> On Mon, 9 Nov 2020 at 07:53, David Plowman <david.plowman at raspberrypi.com> wrote:
>>
>> 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
>>>