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

[Cao, Bingbu]

Laurent and JM,

Give me some time, let me confirm with our algo team.

________________________
BRs,  
Bingbu Cao 

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> Sent: Friday, June 17, 2022 4:08 PM
> To: Cao, Bingbu <bingbu.cao at intel.com>
> Cc: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>;
> libcamera-devel at lists.libcamera.org; sakari.ailus at linux.intel.com
> Subject: Re: [libcamera-devel] [RFC PATCH 0/1] IPU3 AWB gains correction
> 
> Hi Bingbu,
> 
> Thank you very much for your quick reply.
> 
> On Fri, Jun 17, 2022 at 06:58:36AM +0000, Cao, Bingbu via libcamera-devel
> wrote:
> > 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.
> 
> Just to make sure my understanding is correct, does this mean the
> following ?
> 
> wb_gains.gr = 0    -> actual gain = 1.0
> wb_gains.gr = 4096 -> actual gain = 1.5
> wb_gains.gr = 8192 -> actual gain = 2.0
> 
> > 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.
> >
> > > -----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(-)
> 
> --
> Regards,
> 
> Laurent Pinchart