From fb8ad13dc3e38a1bb056c209f692af53588c7b84 Mon Sep 17 00:00:00 2001
From: Milan Zamazal <mzamazal@redhat.com>
Date: Fri, 27 Sep 2024 15:46:23 +0200
Subject: libcamera: software_isp: Move exposure+gain to an algorithm module
This is the last step to fully convert software ISP to Algorithm-based
processing.
The newly introduced frameContext.sensor parameters are set, and the
updated code moved, before calling Algorithm::process() to have the
values up-to-date in stats processing.
Resolves software ISP TODO #10.
Signed-off-by: Milan Zamazal <mzamazal@redhat.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Reviewed-by: Umang Jain <umang.jain@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
---
src/ipa/simple/algorithms/agc.cpp | 139 ++++++++++++++++++++++++++++++++++
src/ipa/simple/algorithms/agc.h | 33 ++++++++
src/ipa/simple/algorithms/meson.build | 1 +
3 files changed, 173 insertions(+)
create mode 100644 src/ipa/simple/algorithms/agc.cpp
create mode 100644 src/ipa/simple/algorithms/agc.h
(limited to 'src/ipa/simple/algorithms')
diff --git a/src/ipa/simple/algorithms/agc.cpp b/src/ipa/simple/algorithms/agc.cpp
new file mode 100644
index 00000000..783dfb8b
--- /dev/null
+++ b/src/ipa/simple/algorithms/agc.cpp
@@ -0,0 +1,139 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Red Hat Inc.
+ *
+ * Exposure and gain
+ */
+
+#include "agc.h"
+
+#include <stdint.h>
+
+#include <libcamera/base/log.h>
+
+namespace libcamera {
+
+LOG_DEFINE_CATEGORY(IPASoftExposure)
+
+namespace ipa::soft::algorithms {
+
+/*
+ * The number of bins to use for the optimal exposure calculations.
+ */
+static constexpr unsigned int kExposureBinsCount = 5;
+
+/*
+ * The exposure is optimal when the mean sample value of the histogram is
+ * in the middle of the range.
+ */
+static constexpr float kExposureOptimal = kExposureBinsCount / 2.0;
+
+/*
+ * The below value implements the hysteresis for the exposure adjustment.
+ * It is small enough to have the exposure close to the optimal, and is big
+ * enough to prevent the exposure from wobbling around the optimal value.
+ */
+static constexpr float kExposureSatisfactory = 0.2;
+
+Agc::Agc()
+{
+}
+
+void Agc::updateExposure(IPAContext &context, double exposureMSV)
+{
+ /*
+ * kExpDenominator of 10 gives ~10% increment/decrement;
+ * kExpDenominator of 5 - about ~20%
+ */
+ static constexpr uint8_t kExpDenominator = 10;
+ static constexpr uint8_t kExpNumeratorUp = kExpDenominator + 1;
+ static constexpr uint8_t kExpNumeratorDown = kExpDenominator - 1;
+
+ double next;
+ int32_t &exposure = context.activeState.agc.exposure;
+ double &again = context.activeState.agc.again;
+
+ if (exposureMSV < kExposureOptimal - kExposureSatisfactory) {
+ next = exposure * kExpNumeratorUp / kExpDenominator;
+ if (next - exposure < 1)
+ exposure += 1;
+ else
+ exposure = next;
+ if (exposure >= context.configuration.agc.exposureMax) {
+ next = again * kExpNumeratorUp / kExpDenominator;
+ if (next - again < context.configuration.agc.againMinStep)
+ again += context.configuration.agc.againMinStep;
+ else
+ again = next;
+ }
+ }
+
+ if (exposureMSV > kExposureOptimal + kExposureSatisfactory) {
+ if (exposure == context.configuration.agc.exposureMax &&
+ again > context.configuration.agc.againMin) {
+ next = again * kExpNumeratorDown / kExpDenominator;
+ if (again - next < context.configuration.agc.againMinStep)
+ again -= context.configuration.agc.againMinStep;
+ else
+ again = next;
+ } else {
+ next = exposure * kExpNumeratorDown / kExpDenominator;
+ if (exposure - next < 1)
+ exposure -= 1;
+ else
+ exposure = next;
+ }
+ }
+
+ exposure = std::clamp(exposure, context.configuration.agc.exposureMin,
+ context.configuration.agc.exposureMax);
+ again = std::clamp(again, context.configuration.agc.againMin,
+ context.configuration.agc.againMax);
+
+ LOG(IPASoftExposure, Debug)
+ << "exposureMSV " << exposureMSV
+ << " exp " << exposure << " again " << again;
+}
+
+void Agc::process(IPAContext &context,
+ [[maybe_unused]] const uint32_t frame,
+ [[maybe_unused]] IPAFrameContext &frameContext,
+ const SwIspStats *stats,
+ [[maybe_unused]] ControlList &metadata)
+{
+ /*
+ * Calculate Mean Sample Value (MSV) according to formula from:
+ * https://www.araa.asn.au/acra/acra2007/papers/paper84final.pdf
+ */
+ const auto &histogram = stats->yHistogram;
+ const unsigned int blackLevelHistIdx =
+ context.activeState.blc.level / (256 / SwIspStats::kYHistogramSize);
+ const unsigned int histogramSize =
+ SwIspStats::kYHistogramSize - blackLevelHistIdx;
+ const unsigned int yHistValsPerBin = histogramSize / kExposureBinsCount;
+ const unsigned int yHistValsPerBinMod =
+ histogramSize / (histogramSize % kExposureBinsCount + 1);
+ int exposureBins[kExposureBinsCount] = {};
+ unsigned int denom = 0;
+ unsigned int num = 0;
+
+ for (unsigned int i = 0; i < histogramSize; i++) {
+ unsigned int idx = (i - (i / yHistValsPerBinMod)) / yHistValsPerBin;
+ exposureBins[idx] += histogram[blackLevelHistIdx + i];
+ }
+
+ for (unsigned int i = 0; i < kExposureBinsCount; i++) {
+ LOG(IPASoftExposure, Debug) << i << ": " << exposureBins[i];
+ denom += exposureBins[i];
+ num += exposureBins[i] * (i + 1);
+ }
+
+ float exposureMSV = (denom == 0 ? 0 : static_cast<float>(num) / denom);
+ updateExposure(context, exposureMSV);
+}
+
+REGISTER_IPA_ALGORITHM(Agc, "Agc")
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/agc.h b/src/ipa/simple/algorithms/agc.h
new file mode 100644
index 00000000..ad5fca9f
--- /dev/null
+++ b/src/ipa/simple/algorithms/agc.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2024, Red Hat Inc.
+ *
+ * Exposure and gain
+ */
+
+#pragma once
+
+#include "algorithm.h"
+
+namespace libcamera {
+
+namespace ipa::soft::algorithms {
+
+class Agc : public Algorithm
+{
+public:
+ Agc();
+ ~Agc() = default;
+
+ void process(IPAContext &context, const uint32_t frame,
+ IPAFrameContext &frameContext,
+ const SwIspStats *stats,
+ ControlList &metadata) override;
+
+private:
+ void updateExposure(IPAContext &context, double exposureMSV);
+};
+
+} /* namespace ipa::soft::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/simple/algorithms/meson.build b/src/ipa/simple/algorithms/meson.build
index f575611e..37a2eb53 100644
--- a/src/ipa/simple/algorithms/meson.build
+++ b/src/ipa/simple/algorithms/meson.build
@@ -2,6 +2,7 @@
soft_simple_ipa_algorithms = files([
'awb.cpp',
+ 'agc.cpp',
'blc.cpp',
'lut.cpp',
])
--
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