[libcamera-devel] [PATCH v2 5/6] src: ipa: raspberrypi: Estimate the colour temerature if starting with fixed colour gains

[Laurent Pinchart]

Hi David,

Thank you for the patch.

On Mon, Dec 07, 2020 at 06:01:20PM +0000, David Plowman wrote:
> When the AWB is started from "cold" with fixed colour gains, we try to
> estimate the colour temperature this corresponds to (if a calibrated
> CT curve was supplied). When fixed colour gains are set after the AWB
> has been running, we leave the CT estimate alone, as the one we have
> is probably sensible.
> 
> This estimated colour is passed out in the metadata for other
> algorithms - notably ALSC - to use.
> 
> Signed-off-by: David Plowman <david.plowman at raspberrypi.com>
> ---
>  src/ipa/raspberrypi/controller/rpi/alsc.cpp |  6 +++++-
>  src/ipa/raspberrypi/controller/rpi/awb.cpp  | 14 ++++++++++++++
>  src/ipa/raspberrypi/controller/rpi/awb.hpp  |  1 +
>  3 files changed, 20 insertions(+), 1 deletion(-)
> 
> diff --git a/src/ipa/raspberrypi/controller/rpi/alsc.cpp b/src/ipa/raspberrypi/controller/rpi/alsc.cpp
> index 183a0c95..c354c985 100644
> --- a/src/ipa/raspberrypi/controller/rpi/alsc.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/alsc.cpp
> @@ -146,6 +146,7 @@ void Alsc::Read(boost::property_tree::ptree const &params)
>  	config_.threshold = params.get<double>("threshold", 1e-3);
>  }
>  
> +static double get_ct(Metadata *metadata, double default_ct);
>  static void get_cal_table(double ct,
>  			  std::vector<AlscCalibration> const &calibrations,
>  			  double cal_table[XY]);
> @@ -210,6 +211,9 @@ void Alsc::SwitchMode(CameraMode const &camera_mode,
>  	// change.
>  	bool reset_tables = first_time_ || compare_modes(camera_mode_, camera_mode);
>  
> +	// Believe the colour temperature from the AWB, if there is one.
> +	ct_ = get_ct(metadata, ct_);
> +
>  	// Ensure the other thread isn't running while we do this.
>  	waitForAysncThread();
>  
> @@ -254,7 +258,7 @@ void Alsc::fetchAsyncResults()
>  	memcpy(sync_results_, async_results_, sizeof(sync_results_));
>  }
>  
> -static double get_ct(Metadata *metadata, double default_ct)
> +double get_ct(Metadata *metadata, double default_ct)

Is this needed, does the compiler complain otherwise ? And on a side
note, we could also move the function up to avoid forward declarations,
but that doesn't have to be part of this patch.

>  {
>  	AwbStatus awb_status;
>  	awb_status.temperature_K = default_ct; // in case nothing found
> diff --git a/src/ipa/raspberrypi/controller/rpi/awb.cpp b/src/ipa/raspberrypi/controller/rpi/awb.cpp
> index 6b359ac5..2266c07b 100644
> --- a/src/ipa/raspberrypi/controller/rpi/awb.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/awb.cpp
> @@ -19,6 +19,9 @@ using namespace RPiController;
>  
>  const double Awb::RGB::INVALID = -1.0;
>  
> +// todo - the locking in this algorithm needs some tidying up as has been done
> +// elsewhere (ALSC and AGC).
> +
>  void AwbMode::Read(boost::property_tree::ptree const &params)
>  {
>  	ct_lo = params.get<double>("lo");
> @@ -121,6 +124,7 @@ Awb::Awb(Controller *controller)
>  	async_abort_ = async_start_ = async_started_ = async_finished_ = false;
>  	mode_ = nullptr;
>  	manual_r_ = manual_b_ = 0.0;
> +	first_switch_mode_ = true;
>  	async_thread_ = std::thread(std::bind(&Awb::asyncFunc, this));
>  }
>  
> @@ -201,9 +205,19 @@ void Awb::SwitchMode([[maybe_unused]] CameraMode const &camera_mode,
>  		prev_sync_results_.gain_r = manual_r_;
>  		prev_sync_results_.gain_g = 1.0;
>  		prev_sync_results_.gain_b = manual_b_;
> +		// If we're starting up for the first time, try and
> +		// "dead reckon" the corresponding colour temperature.
> +		if (first_switch_mode_ && config_.bayes) {
> +			Pwl ct_r_inverse = std::move(config_.ct_r.Inverse());
> +			Pwl ct_b_inverse = std::move(config_.ct_b.Inverse());

I think you can drop std::move(), as Naush mentioned return value
optimization will take care of this (and std::move() can actually
prevent RVO in some cases).

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +			double ct_r = ct_r_inverse.Eval(ct_r_inverse.Domain().Clip(1 / manual_r_));
> +			double ct_b = ct_b_inverse.Eval(ct_b_inverse.Domain().Clip(1 / manual_b_));
> +			prev_sync_results_.temperature_K = (ct_r + ct_b) / 2;
> +		}
>  		sync_results_ = prev_sync_results_;
>  	}
>  	metadata->Set("awb.status", prev_sync_results_);
> +	first_switch_mode_ = false;
>  }
>  
>  void Awb::fetchAsyncResults()
> diff --git a/src/ipa/raspberrypi/controller/rpi/awb.hpp b/src/ipa/raspberrypi/controller/rpi/awb.hpp
> index d86b9598..8525af32 100644
> --- a/src/ipa/raspberrypi/controller/rpi/awb.hpp
> +++ b/src/ipa/raspberrypi/controller/rpi/awb.hpp
> @@ -159,6 +159,7 @@ private:
>  	double manual_r_;
>  	// manual b setting
>  	double manual_b_;
> +	bool first_switch_mode_; // is this the first call to SwitchMode?
>  };
>  
>  static inline Awb::RGB operator+(Awb::RGB const &a, Awb::RGB const &b)

-- 
Regards,

Laurent Pinchart