[libcamera-devel] [PATCH 13/13] ipa: ipu3: agc: Remove unused variables

[Kieran Bingham]

Quoting Jean-Michel Hautbois (2021-10-13 16:41:25)
> We currently control the exposure value by the shutter speed and the
> analogue gain. We can't use the digital gain to have more than the
> maximum exposure value calculated because we are not controlling it.

Do you mean, because we are not setting the digital gain in the ISP?


> Remove unused code associated with this digital gain.

If it's unused, I'm happy to see it go, and the code simplified ;-)

Unless you think we should be adding the plumbing to allow setting the
digital gain on the ISP:

Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>

> Signed-off-by: Jean-Michel Hautbois <jeanmichel.hautbois at ideasonboard.com>
> ---
>  src/ipa/ipu3/algorithms/agc.cpp | 19 +++----------------
>  src/ipa/ipu3/algorithms/agc.h   |  2 --
>  2 files changed, 3 insertions(+), 18 deletions(-)
> 
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index 81eaf436..0177bb92 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -46,8 +46,7 @@ static constexpr double kEvGainTarget = 0.5;
>  Agc::Agc()
>         : frameCount_(0), lastFrame_(0), iqMean_(0.0), lineDuration_(0s),
>           minExposureLines_(0), maxExposureLines_(0), filteredExposure_(0s),
> -         filteredExposureNoDg_(0s), currentExposure_(0s),
> -         currentExposureNoDg_(0s), prevExposureValue(0s)
> +         currentExposure_(0s), prevExposureValue(0s)
>  {
>  }
>  
> @@ -96,7 +95,6 @@ void Agc::filterExposure()
>         if (filteredExposure_ == 0s) {
>                 /* DG stands for digital gain.*/
>                 filteredExposure_ = currentExposure_;
> -               filteredExposureNoDg_ = currentExposureNoDg_;
>         } else {
>                 /*
>                  * If we are close to the desired result, go faster to avoid making
> @@ -109,18 +107,8 @@ void Agc::filterExposure()
>  
>                 filteredExposure_ = speed * currentExposure_ +
>                                 filteredExposure_ * (1.0 - speed);
> -               filteredExposureNoDg_ = speed * currentExposureNoDg_ +
> -                               filteredExposureNoDg_ * (1.0 - speed);
>         }
> -       /*
> -        * We can't let the no_dg exposure deviate too far below the
> -        * total exposure, as there might not be enough digital gain available
> -        * in the ISP to hide it (which will cause nasty oscillation).
> -        */
> -       double fastReduceThreshold = 0.4;
> -       if (filteredExposureNoDg_ <
> -           filteredExposure_ * fastReduceThreshold)
> -               filteredExposureNoDg_ = filteredExposure_ * fastReduceThreshold;
> +
>         LOG(IPU3Agc, Debug) << "After filtering, total_exposure " << filteredExposure_;
>  }
>  
> @@ -136,8 +124,7 @@ void Agc::lockExposureGain(uint32_t &exposure, double &analogueGain)
>  
>         /* extracted from Rpi::Agc::computeTargetExposure */
>         Duration currentShutter = exposure * lineDuration_;
> -       currentExposureNoDg_ = currentShutter * analogueGain;
> -       LOG(IPU3Agc, Debug) << "Actual total exposure " << currentExposureNoDg_
> +       LOG(IPU3Agc, Debug) << "Actual total exposure " << currentShutter * analogueGain
>                                 << " Shutter speed " << currentShutter
>                                 << " Gain " << analogueGain
>                                 << " Needed ev gain " << evGain;
> diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
> index 32817c4f..5b34c013 100644
> --- a/src/ipa/ipu3/algorithms/agc.h
> +++ b/src/ipa/ipu3/algorithms/agc.h
> @@ -48,9 +48,7 @@ private:
>         uint32_t maxExposureLines_;
>  
>         Duration filteredExposure_;
> -       Duration filteredExposureNoDg_;
>         Duration currentExposure_;
> -       Duration currentExposureNoDg_;
>         Duration prevExposureValue;
>  
>         uint32_t stride_;
> -- 
> 2.30.2
>