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

[Laurent Pinchart]

Hi Bingbu,

On Mon, Jun 20, 2022 at 12:03:52PM +0000, Cao, Bingbu wrote:
> JM and Laurent,
> 
> I get some pseudo code from Algo which to calculate the gain
> settings from awb results, I hope it can help you.
> 
> --------------------------------------------------------
> 
> inline int Real2fix(unsigned N, double x)

I suppose this was meant to be

template<unsigned N>
inline int Real2fix(double x)

based on how it's called below.

> {
>       return static_cast<int>(x * (1<<N) +
> 		(x > 0 ? 0.5 : -0.5));
> }
> 
> final_b_per_g=awb_results->final_b_per_g;
> final_r_per_g=awb_results->final_r_per_g;
> 
> float max_ratio = MAX(MAX(final_b_per_g, final_r_per_g), 
> 			1.0f);
> 
> wb_gains->r = static_cast<unsigned short>(
> 	Clamp<wb_apply_min_, wb_apply_max_>(Real2fix<13>(
> 	max_ratio / final_r_per_g - 1)));
> 
> wb_gains->b = static_cast<unsigned short>(
> 	Clamp<wb_apply_min_, wb_apply_max_>(Real2fix<13>(
> 	max_ratio / final_b_per_g - 1)));
> 
> wb_gains->gr =  wb_gains->gb =  static_cast<unsigned short>(
> 	Clamp<wb_apply_min_, wb_apply_max_>(Real2fix<13>(
> 	max_ratio - 1)));

Thank you, that clarifies it.

> --------------------------------------------------------
> BTW, I checked the 2nd picture, it is better than 3, but it is a
> little pinkish.

Yes, further improvements are needed. The image is also a bit too dark
now. Still, it's much better than before :-)

> > -----Original Message-----
> > From: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> > Sent: Friday, June 17, 2022 10:40 PM
> > To: Cao, Bingbu <bingbu.cao at intel.com>; Laurent Pinchart
> > <laurent.pinchart at ideasonboard.com>
> > Cc: libcamera-devel at lists.libcamera.org; sakari.ailus at linux.intel.com
> > Subject: Re: [libcamera-devel] [RFC PATCH 0/1] IPU3 AWB gains correction
> > 
> > Thank you.
> > FYI, I tested the patch I sent with this fixed [1], and I obtain [2]
> > while it is [3] on master.
> > 
> > [1]: https://patchwork.libcamera.org/patch/16256/
> > [2]: https://pasteboard.co/sPXz45GjbpAg.png
> > [3]: https://pasteboard.co/DLfD69BzsFuu.png
> > 
> > Waiting for your confirmation ;-).
> > JM
> > 
> > On 17/06/2022 15:30, Cao, Bingbu via libcamera-devel wrote:
> > > 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