[PATCH 05/10] ipa: ipu3: Parse and store Agc stats

[Stefan Klug]

Hi Daniel,

Thanks for the patch.

On Fri, Mar 22, 2024 at 01:14:46PM +0000, Daniel Scally wrote:
> In preparation for switching to a derivation of MeanLuminanceAgc, add
> a function to parse and store the statistics for easy retrieval in an
> overriding estimateLuminance() function.
> 
> Signed-off-by: Daniel Scally <dan.scally at ideasonboard.com>
> ---
>  src/ipa/ipu3/algorithms/agc.cpp | 33 +++++++++++++++++++++++++++++++++
>  src/ipa/ipu3/algorithms/agc.h   |  8 ++++++++
>  2 files changed, 41 insertions(+)
> 
> diff --git a/src/ipa/ipu3/algorithms/agc.cpp b/src/ipa/ipu3/algorithms/agc.cpp
> index 606a237a..ee9a42cf 100644
> --- a/src/ipa/ipu3/algorithms/agc.cpp
> +++ b/src/ipa/ipu3/algorithms/agc.cpp
> @@ -142,6 +142,39 @@ double Agc::measureBrightness(const ipu3_uapi_stats_3a *stats,
>  	return Histogram(Span<uint32_t>(hist)).interQuantileMean(0.98, 1.0);
>  }
>  
> +void Agc::parseStatistics(const ipu3_uapi_stats_3a *stats,
> +			  const ipu3_uapi_grid_config &grid)
> +{
> +	uint32_t hist[knumHistogramBins] = { 0 };
> +
> +	reds_.clear();
> +	greens_.clear();
> +	blues_.clear();
> +
> +	for (unsigned int cellY = 0; cellY < grid.height; cellY++) {
> +		for (unsigned int cellX = 0; cellX < grid.width; cellX++) {
> +			uint32_t cellPosition = cellY * stride_ + cellX;
> +
> +			const ipu3_uapi_awb_set_item *cell =
> +				reinterpret_cast<const ipu3_uapi_awb_set_item *>(
> +					&stats->awb_raw_buffer.meta_data[cellPosition]);
> +
> +			reds_.push_back(cell->R_avg);
> +			greens_.push_back((cell->Gr_avg + cell->Gb_avg) / 2);
> +			blues_.push_back(cell->B_avg);
> +
> +			/*
> +			 * Store the average green value to estimate the
> +			 * brightness. Even the overexposed pixels are
> +			 * taken into account.
> +			 */
> +			hist[(cell->Gr_avg + cell->Gb_avg) / 2]++;

Why are only the greens taken into account?  Ahh its just a copy of
existing code, that gets removed in patch 7/10. Still should that be
changed to hist[r*0.299 + (gr + gb) / 2 * 0.587 + b * 0.114]++ ?

Or am I missing something here?

> +		}
> +	}
> +
> +	hist_ = Histogram(Span<uint32_t>(hist));
> +}
> +
>  /**
>   * \brief Apply a filter on the exposure value to limit the speed of changes
>   * \param[in] exposureValue The target exposure from the AGC algorithm
> diff --git a/src/ipa/ipu3/algorithms/agc.h b/src/ipa/ipu3/algorithms/agc.h
> index 9d6e3ff1..7ed0ef7a 100644
> --- a/src/ipa/ipu3/algorithms/agc.h
> +++ b/src/ipa/ipu3/algorithms/agc.h
> @@ -13,6 +13,8 @@
>  
>  #include <libcamera/geometry.h>
>  
> +#include "libipa/histogram.h"
> +
>  #include "algorithm.h"
>  
>  namespace libcamera {
> @@ -43,6 +45,8 @@ private:
>  				 const ipu3_uapi_grid_config &grid,
>  				 const ipu3_uapi_stats_3a *stats,
>  				 double gain);
> +	void parseStatistics(const ipu3_uapi_stats_3a *stats,
> +			     const ipu3_uapi_grid_config &grid);
>  
>  	uint64_t frameCount_;
>  
> @@ -55,6 +59,10 @@ private:
>  	utils::Duration filteredExposure_;
>  
>  	uint32_t stride_;
> +	std::vector<uint8_t> reds_;
> +	std::vector<uint8_t> blues_;
> +	std::vector<uint8_t> greens_;
> +	Histogram hist_;
>  };
>  
>  } /* namespace ipa::ipu3::algorithms */
> -- 
> 2.34.1
>