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

[David Plowman]

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
>>
>>
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