[libcamera-devel] [PATCH v5 04/10] ipa: Add common contrast based AF implementation
Daniel Semkowicz
dse at thaumatec.com
Fri Mar 24 15:29:02 CET 2023
Create a new class with contrast based Auto Focus implementation
using hill climbing algorithm. This common implementation is independent
of platform specific code. This way, each platform can just implement
contrast calculation and run the AF control loop basing on this class.
This implementation is based on the code that was common for IPU3
and RPi AF algorithms.
Signed-off-by: Daniel Semkowicz <dse at thaumatec.com>
---
.../libipa/algorithms/af_hill_climbing.cpp | 379 ++++++++++++++++++
src/ipa/libipa/algorithms/af_hill_climbing.h | 91 +++++
src/ipa/libipa/algorithms/meson.build | 2 +
3 files changed, 472 insertions(+)
create mode 100644 src/ipa/libipa/algorithms/af_hill_climbing.cpp
create mode 100644 src/ipa/libipa/algorithms/af_hill_climbing.h
diff --git a/src/ipa/libipa/algorithms/af_hill_climbing.cpp b/src/ipa/libipa/algorithms/af_hill_climbing.cpp
new file mode 100644
index 00000000..6ee090eb
--- /dev/null
+++ b/src/ipa/libipa/algorithms/af_hill_climbing.cpp
@@ -0,0 +1,379 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Red Hat
+ * Copyright (C) 2022, Ideas On Board
+ * Copyright (C) 2023, Theobroma Systems
+ *
+ * af_hill_climbing.cpp - AF contrast based hill climbing common algorithm
+ */
+
+#include "af_hill_climbing.h"
+
+#include "libcamera/internal/yaml_parser.h"
+
+/**
+ * \file af_hill_climbing.h
+ * \brief AF contrast based hill climbing common algorithm
+ */
+
+namespace libcamera {
+
+namespace ipa::algorithms {
+
+LOG_DEFINE_CATEGORY(Af)
+
+/**
+ * \class AfHillClimbing
+ * \brief Contrast based hill climbing auto focus control algorithm
+ * implementation
+ *
+ * Control part of the auto focus algorithm. It calculates the lens position
+ * based on the contrast measure supplied by the platform-specific
+ * implementation. This way it is independent from the platform.
+ *
+ * Platform layer that use this algorithm should call process() function
+ * for each each frame and set the lens to the calculated position.
+ *
+ * Focus search is divided into two phases:
+ * 1. coarse search,
+ * 2. fine search.
+ *
+ * In the first phase, the lens is moved with bigger steps to quickly find
+ * a rough position for the best focus. Then, based on the outcome of coarse
+ * search, the second phase is executed. Lens is moved with smaller steps
+ * in a limited range within the rough position to find the exact position
+ * for best focus.
+ *
+ * Tuning file parameters:
+ * - **coarse-search-step:** The value by which the lens position will change
+ * in one step in the *coarse search* phase. Unit is lens specific.
+ * - **fine-search-step:** The value by which the lens position will change
+ * in one step in the *fine search* phase. Unit is lens specific.
+ * - **fine-search-range:** Search range in the *fine search* phase, expressed
+ * as a percentage of the coarse search result. Valid values are
+ * in the [0, 100] interval. Value 5 means 5%. If coarse search stopped
+ * at value 200, the fine search range will be [190, 210].
+ * - **max-variance-change:** ratio of contrast variance change in the
+ * *continuous mode* needed for triggering the focus change. When the variance
+ * change exceeds this value, focus search will be triggered. Valid values are
+ * in the [0.0, 1.0] interval.
+ * .
+ *
+ * \todo Search range in the *fine search* phase should depend on the lens
+ * movement range rather than coarse search result.
+ * \todo Implement setRange.
+ * \todo Implement setSpeed.
+ * \todo Implement setMeteringMode.
+ * \todo Implement setWindows.
+ * \todo Implement the AfPauseDeferred mode.
+ */
+
+/**
+ * \brief Initialize the AfHillClimbing with tuning data
+ * \param[in] tuningData The tuning data for the algorithm
+ *
+ * This method should be called in the libcamera::ipa::Algorithm::init()
+ * method of the platform layer.
+ *
+ * \return 0 if successful, an error code otherwise
+ */
+int AfHillClimbing::init(const YamlObject &tuningData)
+{
+ coarseSearchStep_ = tuningData["coarse-search-step"].get<uint32_t>(30);
+ fineSearchStep_ = tuningData["fine-search-step"].get<uint32_t>(1);
+ fineRange_ = tuningData["fine-search-range"].get<uint32_t>(5);
+ fineRange_ /= 100;
+ maxChange_ = tuningData["max-variance-change"].get<double>(0.5);
+
+ LOG(Af, Debug) << "coarseSearchStep_: " << coarseSearchStep_
+ << ", fineSearchStep_: " << fineSearchStep_
+ << ", fineRange_: " << fineRange_
+ << ", maxChange_: " << maxChange_;
+
+ return 0;
+}
+
+/**
+ * \brief Configure the AfHillClimbing with sensor and lens information
+ * \param[in] minFocusPosition Minimum position supported by camera lens
+ * \param[in] maxFocusPosition Maximum position supported by camera lens
+ *
+ * This method should be called in the libcamera::ipa::Algorithm::configure()
+ * method of the platform layer.
+ */
+void AfHillClimbing::configure(int32_t minFocusPosition,
+ int32_t maxFocusPosition)
+{
+ minLensPosition_ = minFocusPosition;
+ maxLensPosition_ = maxFocusPosition;
+}
+
+/**
+ * \brief Run the auto focus algorithm loop
+ * \param[in] currentContrast New value of contrast measured for current frame
+ *
+ * This method should be called in the libcamera::ipa::Algorithm::process()
+ * method of the platform layer for each frame.
+ *
+ * Contrast value supplied in the \p currentContrast parameter can be platform
+ * specific. The only requirement is the contrast value must increase with
+ * the increasing image focus. Contrast value must be highest when image is in
+ * focus.
+ *
+ * \return New lens position calculated by the AF algorithm
+ */
+int32_t AfHillClimbing::process(double currentContrast)
+{
+ currentContrast_ = currentContrast;
+
+ if (shouldSkipFrame())
+ return lensPosition_;
+
+ switch (mode_) {
+ case controls::AfModeManual:
+ /* Nothing to process. */
+ break;
+ case controls::AfModeAuto:
+ processAutoMode();
+ break;
+ case controls::AfModeContinuous:
+ processContinuousMode();
+ break;
+ }
+
+ return lensPosition_;
+}
+
+void AfHillClimbing::processAutoMode()
+{
+ if (state_ == controls::AfStateScanning) {
+ afCoarseScan();
+ afFineScan();
+ }
+}
+
+void AfHillClimbing::processContinuousMode()
+{
+ /* If we are in a paused state, we won't process the stats. */
+ if (pauseState_ == controls::AfPauseStatePaused)
+ return;
+
+ if (state_ == controls::AfStateScanning) {
+ afCoarseScan();
+ afFineScan();
+ return;
+ }
+
+ /*
+ * AF scan can be started at any moment in AfModeContinuous,
+ * except when the state is already AfStateScanning.
+ */
+ if (afIsOutOfFocus())
+ afReset();
+}
+
+/**
+ * \brief Request AF to skip n frames
+ * \param[in] n Number of frames to be skipped
+ *
+ * For the requested number of frames, the AF calculation will be skipped
+ * and lens position will not change. The platform layer still needs to
+ * call process() function for each frame during this time.
+ * This function can be used by the platform layer if the hardware needs more
+ * time for some operations.
+ *
+ * The number of the requested frames (\p n) will be applied only if \p n has
+ * higher value than the number of frames already requested to be skipped.
+ * For example, if *setFramesToSkip(5)* was already called for the current
+ * frame, then calling *setFramesToSkip(3)* will not override the previous
+ * request and 5 frames will be skipped.
+ */
+void AfHillClimbing::setFramesToSkip(uint32_t n)
+{
+ if (n > framesToSkip_)
+ framesToSkip_ = n;
+}
+
+void AfHillClimbing::setMode(controls::AfModeEnum mode)
+{
+ if (mode == mode_)
+ return;
+
+ LOG(Af, Debug) << "Switched AF mode from " << mode_ << " to " << mode;
+ mode_ = mode;
+
+ state_ = controls::AfStateIdle;
+ pauseState_ = controls::AfPauseStateRunning;
+
+ if (mode_ == controls::AfModeContinuous)
+ afReset();
+}
+
+void AfHillClimbing::setRange([[maybe_unused]] controls::AfRangeEnum range)
+{
+ LOG(Af, Error) << __FUNCTION__ << " not implemented!";
+}
+
+void AfHillClimbing::setSpeed([[maybe_unused]] controls::AfSpeedEnum speed)
+{
+ LOG(Af, Error) << __FUNCTION__ << " not implemented!";
+}
+
+void AfHillClimbing::setMeteringMode([[maybe_unused]] controls::AfMeteringEnum metering)
+{
+ LOG(Af, Error) << __FUNCTION__ << " not implemented!";
+}
+
+void AfHillClimbing::setWindows([[maybe_unused]] Span<const Rectangle> windows)
+{
+ LOG(Af, Error) << __FUNCTION__ << " not implemented!";
+}
+
+void AfHillClimbing::setTrigger(controls::AfTriggerEnum trigger)
+{
+ if (mode_ != controls::AfModeAuto) {
+ LOG(Af, Warning)
+ << __FUNCTION__ << " not valid in mode " << mode_;
+ return;
+ }
+
+ LOG(Af, Debug) << "Trigger called with " << trigger;
+
+ if (trigger == controls::AfTriggerStart)
+ afReset();
+ else
+ state_ = controls::AfStateIdle;
+}
+
+void AfHillClimbing::setPause(controls::AfPauseEnum pause)
+{
+ if (mode_ != controls::AfModeContinuous) {
+ LOG(Af, Warning)
+ << __FUNCTION__ << " not valid in mode " << mode_;
+ return;
+ }
+
+ switch (pause) {
+ case controls::AfPauseImmediate:
+ pauseState_ = controls::AfPauseStatePaused;
+ break;
+ case controls::AfPauseDeferred:
+ LOG(Af, Warning) << "AfPauseDeferred is not supported!";
+ break;
+ case controls::AfPauseResume:
+ pauseState_ = controls::AfPauseStateRunning;
+ break;
+ }
+}
+
+void AfHillClimbing::setLensPosition(float lensPosition)
+{
+ if (mode_ != controls::AfModeManual) {
+ LOG(Af, Warning)
+ << __FUNCTION__ << " not valid in mode " << mode_;
+ return;
+ }
+
+ lensPosition_ = static_cast<int32_t>(lensPosition);
+
+ LOG(Af, Debug) << "Requesting lens position " << lensPosition_;
+}
+
+void AfHillClimbing::afCoarseScan()
+{
+ if (coarseCompleted_)
+ return;
+
+ if (afScan(coarseSearchStep_)) {
+ coarseCompleted_ = true;
+ maxContrast_ = 0;
+ const auto diff = static_cast<int32_t>(
+ std::abs(lensPosition_) * fineRange_);
+ lensPosition_ = std::max(lensPosition_ - diff, minLensPosition_);
+ maxStep_ = std::min(lensPosition_ + diff, maxLensPosition_);
+ }
+}
+
+void AfHillClimbing::afFineScan()
+{
+ if (!coarseCompleted_)
+ return;
+
+ if (afScan(fineSearchStep_)) {
+ LOG(Af, Debug) << "AF found the best focus position!";
+ state_ = controls::AfStateFocused;
+ }
+}
+
+bool AfHillClimbing::afScan(uint32_t steps)
+{
+ if (lensPosition_ + static_cast<int32_t>(steps) > maxStep_) {
+ /* If the max step is reached, move lens to the position. */
+ lensPosition_ = bestPosition_;
+ return true;
+ } else {
+ /*
+ * Find the maximum of the variance by estimating its
+ * derivative. If the direction changes, it means we have passed
+ * a maximum one step before.
+ */
+ if ((currentContrast_ - maxContrast_) >= -(maxContrast_ * 0.1)) {
+ /*
+ * Positive and zero derivative:
+ * The variance is still increasing. The focus could be
+ * increased for the next comparison. Also, the max
+ * variance and previous focus value are updated.
+ */
+ bestPosition_ = lensPosition_;
+ lensPosition_ += static_cast<int32_t>(steps);
+ maxContrast_ = currentContrast_;
+ } else {
+ /*
+ * Negative derivative:
+ * The variance starts to decrease which means the maximum
+ * variance is found. Set focus step to previous good one
+ * then return immediately.
+ */
+ lensPosition_ = bestPosition_;
+ return true;
+ }
+ }
+
+ LOG(Af, Debug) << "Previous step is " << bestPosition_
+ << ", Current step is " << lensPosition_;
+ return false;
+}
+
+void AfHillClimbing::afReset()
+{
+ LOG(Af, Debug) << "Reset AF parameters";
+ lensPosition_ = minLensPosition_;
+ maxStep_ = maxLensPosition_;
+ state_ = controls::AfStateScanning;
+ coarseCompleted_ = false;
+ maxContrast_ = 0.0;
+ setFramesToSkip(1);
+}
+
+bool AfHillClimbing::afIsOutOfFocus() const
+{
+ const double diff_var = std::abs(currentContrast_ - maxContrast_);
+ const double var_ratio = diff_var / maxContrast_;
+ LOG(Af, Debug) << "Variance change rate: " << var_ratio
+ << ", Current lens step: " << lensPosition_;
+ return var_ratio > maxChange_;
+}
+
+bool AfHillClimbing::shouldSkipFrame()
+{
+ if (framesToSkip_ > 0) {
+ framesToSkip_--;
+ return true;
+ }
+
+ return false;
+}
+
+} /* namespace ipa::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/libipa/algorithms/af_hill_climbing.h b/src/ipa/libipa/algorithms/af_hill_climbing.h
new file mode 100644
index 00000000..47d2bbec
--- /dev/null
+++ b/src/ipa/libipa/algorithms/af_hill_climbing.h
@@ -0,0 +1,91 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+/*
+ * Copyright (C) 2021, Red Hat
+ * Copyright (C) 2022, Ideas On Board
+ * Copyright (C) 2023, Theobroma Systems
+ *
+ * af_hill_climbing.h - AF contrast based hill climbing common algorithm
+ */
+
+#pragma once
+
+#include <libcamera/base/log.h>
+
+#include "af.h"
+
+namespace libcamera {
+
+class YamlObject;
+
+namespace ipa::algorithms {
+
+LOG_DECLARE_CATEGORY(Af)
+
+class AfHillClimbing : public Af
+{
+public:
+ int init(const YamlObject &tuningData);
+ void configure(int32_t minFocusPosition, int32_t maxFocusPosition);
+ int32_t process(double currentContrast);
+ void setFramesToSkip(uint32_t n);
+
+ controls::AfStateEnum state() final { return state_; }
+ controls::AfPauseStateEnum pauseState() final { return pauseState_; }
+
+private:
+ void setMode(controls::AfModeEnum mode) final;
+ void setRange(controls::AfRangeEnum range) final;
+ void setSpeed(controls::AfSpeedEnum speed) final;
+ void setMeteringMode(controls::AfMeteringEnum metering) final;
+ void setWindows(Span<const Rectangle> windows) final;
+ void setTrigger(controls::AfTriggerEnum trigger) final;
+ void setPause(controls::AfPauseEnum pause) final;
+ void setLensPosition(float lensPosition) final;
+
+ void processAutoMode();
+ void processContinuousMode();
+ void afCoarseScan();
+ void afFineScan();
+ bool afScan(uint32_t steps);
+ void afReset();
+ [[nodiscard]] bool afIsOutOfFocus() const;
+ bool shouldSkipFrame();
+
+ controls::AfModeEnum mode_ = controls::AfModeManual;
+ controls::AfStateEnum state_ = controls::AfStateIdle;
+ controls::AfPauseStateEnum pauseState_ = controls::AfPauseStateRunning;
+
+ /* Current focus lens position. */
+ int32_t lensPosition_ = 0;
+ /* Local optimum focus lens position during scanning. */
+ int32_t bestPosition_ = 0;
+
+ /* Current AF statistic contrast. */
+ double currentContrast_ = 0;
+ /* It is used to determine the derivative during scanning */
+ double maxContrast_ = 0;
+ /* The designated maximum range of focus scanning. */
+ int32_t maxStep_ = 0;
+ /* If the coarse scan completes, it is set to true. */
+ bool coarseCompleted_ = false;
+
+ uint32_t framesToSkip_ = 0;
+
+ /* Position limits of the focus lens. */
+ int32_t minLensPosition_;
+ int32_t maxLensPosition_;
+
+ /* Minimum position step for searching appropriate focus. */
+ uint32_t coarseSearchStep_;
+ uint32_t fineSearchStep_;
+
+ /* Fine scan range 0 < fineRange_ < 1. */
+ double fineRange_;
+
+ /* Max ratio of variance change, 0.0 < maxChange_ < 1.0. */
+ double maxChange_;
+};
+
+} /* namespace ipa::algorithms */
+
+} /* namespace libcamera */
diff --git a/src/ipa/libipa/algorithms/meson.build b/src/ipa/libipa/algorithms/meson.build
index 3df4798f..20e437fc 100644
--- a/src/ipa/libipa/algorithms/meson.build
+++ b/src/ipa/libipa/algorithms/meson.build
@@ -2,8 +2,10 @@
libipa_algorithms_headers = files([
'af.h',
+ 'af_hill_climbing.h',
])
libipa_algorithms_sources = files([
'af.cpp',
+ 'af_hill_climbing.cpp',
])
--
2.39.2
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