[libcamera-devel] reporting of gain and analogue gain

[Kieran Bingham]

Hi David,

On 07/10/2020 15:41, David Plowman wrote:
> Hi everyone
> 
> Whilst doing some maintenance on the Raspberry Pi AGC I noticed a bit
> of an oversight - we have no way to report the total gain being
> applied to an image. We have controls to report:
> 
> * the exposure time of the sensor
> * the analogue gain applied in the sensor
> * red and blue colour gains applied by the AWB
> 
> but nothing for any (global) digital gain demanded by the AGC. The
> consequence is that when I capture a jpeg I always report an ISO value
> based purely on the analogue gain which may be incorrect (when a
> higher gain is required than the sensor allows then we make up the
> difference with digital gain).
> 
> Any thoughts on this? Obviously there could be a digital gain control...

I assume the IPA would be then responsible for setting this? Is it
read-only?

Would we expect an application to be able to control both the analogue
gain and the digital gain manually? (When AGC is disabled I guess?)

Or would they only see an overall 'gain' control?

I'm suspecting that indeed, it would be exposed as a separate control,
because it will expose a feature that the ISP is capable of delivering.

> 
> Best regards
> David
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> 

-- 
Regards
--
Kieran