[libcamera-devel] [RFC PATCH 0/1] IPU3 AWB gains correction

[Cao, Bingbu]

Hi, JM,

For BNR parameters WB gain factor for the three channels [Ggr, Ggb, Gb, Gr].
Their precision is U3.13 and the range is (0, 8) and the actual gain is
Gx + 1, it is typically Gx = 1.

Pout = {Pin * (1 + Gx)}.

So that means for wb_gains.Ggr/gb/g/r = 0.5, the actual gain is 1.5.

It seems not correct to changing ratio from 8192 to 4096 as its
precision is U3.13.  I am not familiar with ipa implementation in
libcamera, not sure other details.


________________________
BRs,  
Bingbu Cao 

> -----Original Message-----
> From: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> Sent: Thursday, June 16, 2022 5:12 PM
> To: libcamera-devel at lists.libcamera.org
> Cc: Cao, Bingbu <bingbu.cao at intel.com>; sakari.ailus at linux.intel.com;
> Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> Subject: [RFC PATCH 0/1] IPU3 AWB gains correction
> 
> Hi there,
> 
> Bingbu, Sakari, I cc'ed you because this patch is not aligned with the
> current documentation in the intel-ipu3.h file, could you have a look
> please ?
> 
> The part which worries me is that the green gains should be 0 for the
> white balance to be correct which is not stated in the documentation at
> all.
> 
> In order to demonstrate it I captured two frames, [1] is the actual SGo2
> image quality, and [2] with this patch applied.
> 
> [1]: https://pasteboard.co/hUcL4U6eyyAH.png
> [2]: https://pasteboard.co/2XIbkkL8kitl.png
> 
> There is a very clear benefit, that's why I submit this RFC as I think it
> needs to be clarified :-).
> 
> Thanks !
> JM
> 
> Jean-Michel Hautbois (1):
>   ipa: ipu3: awb: Correct the coefficient factor
> 
>  src/ipa/ipu3/algorithms/awb.cpp | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> --
> 2.34.1