[libcamera-devel] [PATCH] ipa: raspberrypi: Normalise region sums to 16-bits
Kieran Bingham
kieran.bingham at ideasonboard.com
Tue Jan 31 15:19:15 CET 2023
Quoting Naushir Patuck (2023-01-31 13:46:46)
> The VC4 ISP uses a pipeline bit-depth of 13-bits. The AGC algorithm needs to
> know this bit-depth when computing the Y value for the image.
>
> Instead of hardcoding the VC4 bit-depth in the AGC source code, normalise all
> region sums to 16-bits when filling the Statistics structure. AWB and ALSC are
> agnostic about pipeline depth, so do not need changing.
>
> Signed-off-by: Naushir Patuck <naush at raspberrypi.com>
> Reviewed-by: David Plowman <david.plowman at raspberrypi.com>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
> ---
> src/ipa/raspberrypi/controller/rpi/agc.cpp | 11 +++++------
> src/ipa/raspberrypi/raspberrypi.cpp | 18 ++++++++++++------
> src/ipa/raspberrypi/statistics.h | 6 ++++++
> 3 files changed, 23 insertions(+), 12 deletions(-)
>
> diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> index 868c30f03d66..ea0c82b5c4c8 100644
> --- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
> +++ b/src/ipa/raspberrypi/controller/rpi/agc.cpp
> @@ -28,8 +28,6 @@ LOG_DEFINE_CATEGORY(RPiAgc)
>
> #define NAME "rpi.agc"
>
> -static constexpr unsigned int PipelineBits = 13; /* seems to be a 13-bit pipeline */
> -
> int AgcMeteringMode::read(const libcamera::YamlObject ¶ms)
> {
> const YamlObject &yamlWeights = params["weights"];
> @@ -586,6 +584,7 @@ void Agc::fetchAwbStatus(Metadata *imageMetadata)
> static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
> double weights[], double gain)
> {
> + constexpr unsigned int maxVal = 1 << Statistics::NormalisationFactorPow2;
> /*
> * Note how the calculation below means that equal weights give you
> * "average" metering (i.e. all pixels equally important).
> @@ -593,9 +592,9 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
> double rSum = 0, gSum = 0, bSum = 0, pixelSum = 0;
> for (unsigned int i = 0; i < stats->agcRegions.numRegions(); i++) {
> auto ®ion = stats->agcRegions.get(i);
> - double rAcc = std::min<double>(region.val.rSum * gain, ((1 << PipelineBits) - 1) * region.counted);
> - double gAcc = std::min<double>(region.val.gSum * gain, ((1 << PipelineBits) - 1) * region.counted);
> - double bAcc = std::min<double>(region.val.bSum * gain, ((1 << PipelineBits) - 1) * region.counted);
> + double rAcc = std::min<double>(region.val.rSum * gain, (maxVal - 1) * region.counted);
> + double gAcc = std::min<double>(region.val.gSum * gain, (maxVal - 1) * region.counted);
> + double bAcc = std::min<double>(region.val.bSum * gain, (maxVal - 1) * region.counted);
> rSum += rAcc * weights[i];
> gSum += gAcc * weights[i];
> bSum += bAcc * weights[i];
> @@ -608,7 +607,7 @@ static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
> double ySum = rSum * awb.gainR * .299 +
> gSum * awb.gainG * .587 +
> bSum * awb.gainB * .114;
> - return ySum / pixelSum / (1 << PipelineBits);
> + return ySum / pixelSum / maxVal;
> }
>
> /*
> diff --git a/src/ipa/raspberrypi/raspberrypi.cpp b/src/ipa/raspberrypi/raspberrypi.cpp
> index cff079bbafb3..1cf7649c3303 100644
> --- a/src/ipa/raspberrypi/raspberrypi.cpp
> +++ b/src/ipa/raspberrypi/raspberrypi.cpp
> @@ -1154,11 +1154,17 @@ RPiController::StatisticsPtr IPARPi::fillStatistics(bcm2835_isp_stats *stats) co
> /* RGB histograms are not used, so do not populate them. */
> statistics->yHist = std::move(RPiController::Histogram(stats->hist[0].g_hist, NUM_HISTOGRAM_BINS));
>
> + /*
> + * All region sums are based on a 13-bit pipeline bit-depth. Normalise
> + * this to 16-bits for the AGC/AWB/ALSC algorithms.
> + */
> + constexpr unsigned int scale = Statistics::NormalisationFactorPow2 - 13;
> +
> statistics->awbRegions.init({ DEFAULT_AWB_REGIONS_X, DEFAULT_AWB_REGIONS_Y });
> for (i = 0; i < statistics->awbRegions.numRegions(); i++)
> - statistics->awbRegions.set(i, { { stats->awb_stats[i].r_sum,
> - stats->awb_stats[i].g_sum,
> - stats->awb_stats[i].b_sum },
> + statistics->awbRegions.set(i, { { stats->awb_stats[i].r_sum << scale,
> + stats->awb_stats[i].g_sum << scale,
> + stats->awb_stats[i].b_sum << scale },
> stats->awb_stats[i].counted,
> stats->awb_stats[i].notcounted });
>
> @@ -1168,9 +1174,9 @@ RPiController::StatisticsPtr IPARPi::fillStatistics(bcm2835_isp_stats *stats) co
> */
> statistics->agcRegions.init(15);
> for (i = 0; i < statistics->agcRegions.numRegions(); i++)
> - statistics->agcRegions.set(i, { { stats->agc_stats[i].r_sum,
> - stats->agc_stats[i].g_sum,
> - stats->agc_stats[i].b_sum },
> + statistics->agcRegions.set(i, { { stats->agc_stats[i].r_sum << scale,
> + stats->agc_stats[i].g_sum << scale,
> + stats->agc_stats[i].b_sum << scale },
> stats->agc_stats[i].counted,
> stats->awb_stats[i].notcounted });
>
> diff --git a/src/ipa/raspberrypi/statistics.h b/src/ipa/raspberrypi/statistics.h
> index affb7272c963..22a72c94a90d 100644
> --- a/src/ipa/raspberrypi/statistics.h
> +++ b/src/ipa/raspberrypi/statistics.h
> @@ -30,6 +30,12 @@ using RgbyRegions = RegionStats<RgbySums>;
> using FocusRegions = RegionStats<uint64_t>;
>
> struct Statistics {
> + /*
> + * All histogram and region based statistics are scaled to a maximum
> + * value given by (1 << NormalisationFactorPow2) - 1.
> + */
> + static constexpr unsigned int NormalisationFactorPow2 = 16;
> +
> /*
> * Positioning of the AGC statistics gathering in the pipeline:
> * Pre-WB correction or post-WB correction.
> --
> 2.25.1
>
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