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+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi Ltd
+ *
+ * agc.cpp - AGC/AEC control algorithm
+ */
+
+#include <algorithm>
+#include <map>
+#include <tuple>
+
+#include <libcamera/base/log.h>
+
+#include "../awb_status.h"
+#include "../device_status.h"
+#include "../histogram.h"
+#include "../lux_status.h"
+#include "../metadata.h"
+
+#include "agc.h"
+
+using namespace RPiController;
+using namespace libcamera;
+using libcamera::utils::Duration;
+using namespace std::literals::chrono_literals;
+
+LOG_DEFINE_CATEGORY(RPiAgc)
+
+#define NAME "rpi.agc"
+
+int AgcMeteringMode::read(const libcamera::YamlObject &params)
+{
+ const YamlObject &yamlWeights = params["weights"];
+
+ for (const auto &p : yamlWeights.asList()) {
+ auto value = p.get<double>();
+ if (!value)
+ return -EINVAL;
+ weights.push_back(*value);
+ }
+
+ return 0;
+}
+
+static std::tuple<int, std::string>
+readMeteringModes(std::map<std::string, AgcMeteringMode> &metering_modes,
+ const libcamera::YamlObject &params)
+{
+ std::string first;
+ int ret;
+
+ for (const auto &[key, value] : params.asDict()) {
+ AgcMeteringMode meteringMode;
+ ret = meteringMode.read(value);
+ if (ret)
+ return { ret, {} };
+
+ metering_modes[key] = std::move(meteringMode);
+ if (first.empty())
+ first = key;
+ }
+
+ return { 0, first };
+}
+
+int AgcExposureMode::read(const libcamera::YamlObject &params)
+{
+ auto value = params["shutter"].getList<double>();
+ if (!value)
+ return -EINVAL;
+ std::transform(value->begin(), value->end(), std::back_inserter(shutter),
+ [](double v) { return v * 1us; });
+
+ value = params["gain"].getList<double>();
+ if (!value)
+ return -EINVAL;
+ gain = std::move(*value);
+
+ if (shutter.size() < 2 || gain.size() < 2) {
+ LOG(RPiAgc, Error)
+ << "AgcExposureMode: must have at least two entries in exposure profile";
+ return -EINVAL;
+ }
+
+ if (shutter.size() != gain.size()) {
+ LOG(RPiAgc, Error)
+ << "AgcExposureMode: expect same number of exposure and gain entries in exposure profile";
+ return -EINVAL;
+ }
+
+ return 0;
+}
+
+static std::tuple<int, std::string>
+readExposureModes(std::map<std::string, AgcExposureMode> &exposureModes,
+ const libcamera::YamlObject &params)
+{
+ std::string first;
+ int ret;
+
+ for (const auto &[key, value] : params.asDict()) {
+ AgcExposureMode exposureMode;
+ ret = exposureMode.read(value);
+ if (ret)
+ return { ret, {} };
+
+ exposureModes[key] = std::move(exposureMode);
+ if (first.empty())
+ first = key;
+ }
+
+ return { 0, first };
+}
+
+int AgcConstraint::read(const libcamera::YamlObject &params)
+{
+ std::string boundString = params["bound"].get<std::string>("");
+ transform(boundString.begin(), boundString.end(),
+ boundString.begin(), ::toupper);
+ if (boundString != "UPPER" && boundString != "LOWER") {
+ LOG(RPiAgc, Error) << "AGC constraint type should be UPPER or LOWER";
+ return -EINVAL;
+ }
+ bound = boundString == "UPPER" ? Bound::UPPER : Bound::LOWER;
+
+ auto value = params["q_lo"].get<double>();
+ if (!value)
+ return -EINVAL;
+ qLo = *value;
+
+ value = params["q_hi"].get<double>();
+ if (!value)
+ return -EINVAL;
+ qHi = *value;
+
+ return yTarget.read(params["y_target"]);
+}
+
+static std::tuple<int, AgcConstraintMode>
+readConstraintMode(const libcamera::YamlObject &params)
+{
+ AgcConstraintMode mode;
+ int ret;
+
+ for (const auto &p : params.asList()) {
+ AgcConstraint constraint;
+ ret = constraint.read(p);
+ if (ret)
+ return { ret, {} };
+
+ mode.push_back(std::move(constraint));
+ }
+
+ return { 0, mode };
+}
+
+static std::tuple<int, std::string>
+readConstraintModes(std::map<std::string, AgcConstraintMode> &constraintModes,
+ const libcamera::YamlObject &params)
+{
+ std::string first;
+ int ret;
+
+ for (const auto &[key, value] : params.asDict()) {
+ std::tie(ret, constraintModes[key]) = readConstraintMode(value);
+ if (ret)
+ return { ret, {} };
+
+ if (first.empty())
+ first = key;
+ }
+
+ return { 0, first };
+}
+
+int AgcConfig::read(const libcamera::YamlObject &params)
+{
+ LOG(RPiAgc, Debug) << "AgcConfig";
+ int ret;
+
+ std::tie(ret, defaultMeteringMode) =
+ readMeteringModes(meteringModes, params["metering_modes"]);
+ if (ret)
+ return ret;
+ std::tie(ret, defaultExposureMode) =
+ readExposureModes(exposureModes, params["exposure_modes"]);
+ if (ret)
+ return ret;
+ std::tie(ret, defaultConstraintMode) =
+ readConstraintModes(constraintModes, params["constraint_modes"]);
+ if (ret)
+ return ret;
+
+ ret = yTarget.read(params["y_target"]);
+ if (ret)
+ return ret;
+
+ speed = params["speed"].get<double>(0.2);
+ startupFrames = params["startup_frames"].get<uint16_t>(10);
+ convergenceFrames = params["convergence_frames"].get<unsigned int>(6);
+ fastReduceThreshold = params["fast_reduce_threshold"].get<double>(0.4);
+ baseEv = params["base_ev"].get<double>(1.0);
+
+ /* Start with quite a low value as ramping up is easier than ramping down. */
+ defaultExposureTime = params["default_exposure_time"].get<double>(1000) * 1us;
+ defaultAnalogueGain = params["default_analogue_gain"].get<double>(1.0);
+
+ return 0;
+}
+
+Agc::ExposureValues::ExposureValues()
+ : shutter(0s), analogueGain(0),
+ totalExposure(0s), totalExposureNoDG(0s)
+{
+}
+
+Agc::Agc(Controller *controller)
+ : AgcAlgorithm(controller), meteringMode_(nullptr),
+ exposureMode_(nullptr), constraintMode_(nullptr),
+ frameCount_(0), lockCount_(0),
+ lastTargetExposure_(0s), ev_(1.0), flickerPeriod_(0s),
+ maxShutter_(0s), fixedShutter_(0s), fixedAnalogueGain_(0.0)
+{
+ memset(&awb_, 0, sizeof(awb_));
+ /*
+ * Setting status_.totalExposureValue_ to zero initially tells us
+ * it's not been calculated yet (i.e. Process hasn't yet run).
+ */
+ memset(&status_, 0, sizeof(status_));
+ status_.ev = ev_;
+}
+
+char const *Agc::name() const
+{
+ return NAME;
+}
+
+int Agc::read(const libcamera::YamlObject &params)
+{
+ LOG(RPiAgc, Debug) << "Agc";
+
+ int ret = config_.read(params);
+ if (ret)
+ return ret;
+
+ const Size &size = getHardwareConfig().agcZoneWeights;
+ for (auto const &modes : config_.meteringModes) {
+ if (modes.second.weights.size() != size.width * size.height) {
+ LOG(RPiAgc, Error) << "AgcMeteringMode: Incorrect number of weights";
+ return -EINVAL;
+ }
+ }
+
+ /*
+ * Set the config's defaults (which are the first ones it read) as our
+ * current modes, until someone changes them. (they're all known to
+ * exist at this point)
+ */
+ meteringModeName_ = config_.defaultMeteringMode;
+ meteringMode_ = &config_.meteringModes[meteringModeName_];
+ exposureModeName_ = config_.defaultExposureMode;
+ exposureMode_ = &config_.exposureModes[exposureModeName_];
+ constraintModeName_ = config_.defaultConstraintMode;
+ constraintMode_ = &config_.constraintModes[constraintModeName_];
+ /* Set up the "last shutter/gain" values, in case AGC starts "disabled". */
+ status_.shutterTime = config_.defaultExposureTime;
+ status_.analogueGain = config_.defaultAnalogueGain;
+ return 0;
+}
+
+void Agc::disableAuto()
+{
+ fixedShutter_ = status_.shutterTime;
+ fixedAnalogueGain_ = status_.analogueGain;
+}
+
+void Agc::enableAuto()
+{
+ fixedShutter_ = 0s;
+ fixedAnalogueGain_ = 0;
+}
+
+unsigned int Agc::getConvergenceFrames() const
+{
+ /*
+ * If shutter and gain have been explicitly set, there is no
+ * convergence to happen, so no need to drop any frames - return zero.
+ */
+ if (fixedShutter_ && fixedAnalogueGain_)
+ return 0;
+ else
+ return config_.convergenceFrames;
+}
+
+void Agc::setEv(double ev)
+{
+ ev_ = ev;
+}
+
+void Agc::setFlickerPeriod(Duration flickerPeriod)
+{
+ flickerPeriod_ = flickerPeriod;
+}
+
+void Agc::setMaxShutter(Duration maxShutter)
+{
+ maxShutter_ = maxShutter;
+}
+
+void Agc::setFixedShutter(Duration fixedShutter)
+{
+ fixedShutter_ = fixedShutter;
+ /* Set this in case someone calls disableAuto() straight after. */
+ status_.shutterTime = limitShutter(fixedShutter_);
+}
+
+void Agc::setFixedAnalogueGain(double fixedAnalogueGain)
+{
+ fixedAnalogueGain_ = fixedAnalogueGain;
+ /* Set this in case someone calls disableAuto() straight after. */
+ status_.analogueGain = limitGain(fixedAnalogueGain);
+}
+
+void Agc::setMeteringMode(std::string const &meteringModeName)
+{
+ meteringModeName_ = meteringModeName;
+}
+
+void Agc::setExposureMode(std::string const &exposureModeName)
+{
+ exposureModeName_ = exposureModeName;
+}
+
+void Agc::setConstraintMode(std::string const &constraintModeName)
+{
+ constraintModeName_ = constraintModeName;
+}
+
+void Agc::switchMode(CameraMode const &cameraMode,
+ Metadata *metadata)
+{
+ /* AGC expects the mode sensitivity always to be non-zero. */
+ ASSERT(cameraMode.sensitivity);
+
+ housekeepConfig();
+
+ /*
+ * Store the mode in the local state. We must cache the sensitivity of
+ * of the previous mode for the calculations below.
+ */
+ double lastSensitivity = mode_.sensitivity;
+ mode_ = cameraMode;
+
+ Duration fixedShutter = limitShutter(fixedShutter_);
+ if (fixedShutter && fixedAnalogueGain_) {
+ /* We're going to reset the algorithm here with these fixed values. */
+
+ fetchAwbStatus(metadata);
+ double minColourGain = std::min({ awb_.gainR, awb_.gainG, awb_.gainB, 1.0 });
+ ASSERT(minColourGain != 0.0);
+
+ /* This is the equivalent of computeTargetExposure and applyDigitalGain. */
+ target_.totalExposureNoDG = fixedShutter_ * fixedAnalogueGain_;
+ target_.totalExposure = target_.totalExposureNoDG / minColourGain;
+
+ /* Equivalent of filterExposure. This resets any "history". */
+ filtered_ = target_;
+
+ /* Equivalent of divideUpExposure. */
+ filtered_.shutter = fixedShutter;
+ filtered_.analogueGain = fixedAnalogueGain_;
+ } else if (status_.totalExposureValue) {
+ /*
+ * On a mode switch, various things could happen:
+ * - the exposure profile might change
+ * - a fixed exposure or gain might be set
+ * - the new mode's sensitivity might be different
+ * We cope with the last of these by scaling the target values. After
+ * that we just need to re-divide the exposure/gain according to the
+ * current exposure profile, which takes care of everything else.
+ */
+
+ double ratio = lastSensitivity / cameraMode.sensitivity;
+ target_.totalExposureNoDG *= ratio;
+ target_.totalExposure *= ratio;
+ filtered_.totalExposureNoDG *= ratio;
+ filtered_.totalExposure *= ratio;
+
+ divideUpExposure();
+ } else {
+ /*
+ * We come through here on startup, when at least one of the shutter
+ * or gain has not been fixed. We must still write those values out so
+ * that they will be applied immediately. We supply some arbitrary defaults
+ * for any that weren't set.
+ */
+
+ /* Equivalent of divideUpExposure. */
+ filtered_.shutter = fixedShutter ? fixedShutter : config_.defaultExposureTime;
+ filtered_.analogueGain = fixedAnalogueGain_ ? fixedAnalogueGain_ : config_.defaultAnalogueGain;
+ }
+
+ writeAndFinish(metadata, false);
+}
+
+void Agc::prepare(Metadata *imageMetadata)
+{
+ Duration totalExposureValue = status_.totalExposureValue;
+ AgcStatus delayedStatus;
+
+ if (!imageMetadata->get("agc.delayed_status", delayedStatus))
+ totalExposureValue = delayedStatus.totalExposureValue;
+
+ status_.digitalGain = 1.0;
+ fetchAwbStatus(imageMetadata); /* always fetch it so that Process knows it's been done */
+
+ if (status_.totalExposureValue) {
+ /* Process has run, so we have meaningful values. */
+ DeviceStatus deviceStatus;
+ if (imageMetadata->get("device.status", deviceStatus) == 0) {
+ Duration actualExposure = deviceStatus.shutterSpeed *
+ deviceStatus.analogueGain;
+ if (actualExposure) {
+ status_.digitalGain = totalExposureValue / actualExposure;
+ LOG(RPiAgc, Debug) << "Want total exposure " << totalExposureValue;
+ /*
+ * Never ask for a gain < 1.0, and also impose
+ * some upper limit. Make it customisable?
+ */
+ status_.digitalGain = std::max(1.0, std::min(status_.digitalGain, 4.0));
+ LOG(RPiAgc, Debug) << "Actual exposure " << actualExposure;
+ LOG(RPiAgc, Debug) << "Use digitalGain " << status_.digitalGain;
+ LOG(RPiAgc, Debug) << "Effective exposure "
+ << actualExposure * status_.digitalGain;
+ /* Decide whether AEC/AGC has converged. */
+ updateLockStatus(deviceStatus);
+ }
+ } else
+ LOG(RPiAgc, Warning) << name() << ": no device metadata";
+ imageMetadata->set("agc.status", status_);
+ }
+}
+
+void Agc::process(StatisticsPtr &stats, Metadata *imageMetadata)
+{
+ frameCount_++;
+ /*
+ * First a little bit of housekeeping, fetching up-to-date settings and
+ * configuration, that kind of thing.
+ */
+ housekeepConfig();
+ /* Get the current exposure values for the frame that's just arrived. */
+ fetchCurrentExposure(imageMetadata);
+ /* Compute the total gain we require relative to the current exposure. */
+ double gain, targetY;
+ computeGain(stats, imageMetadata, gain, targetY);
+ /* Now compute the target (final) exposure which we think we want. */
+ computeTargetExposure(gain);
+ /*
+ * Some of the exposure has to be applied as digital gain, so work out
+ * what that is. This function also tells us whether it's decided to
+ * "desaturate" the image more quickly.
+ */
+ bool desaturate = applyDigitalGain(gain, targetY);
+ /* The results have to be filtered so as not to change too rapidly. */
+ filterExposure(desaturate);
+ /*
+ * The last thing is to divide up the exposure value into a shutter time
+ * and analogue gain, according to the current exposure mode.
+ */
+ divideUpExposure();
+ /* Finally advertise what we've done. */
+ writeAndFinish(imageMetadata, desaturate);
+}
+
+void Agc::updateLockStatus(DeviceStatus const &deviceStatus)
+{
+ const double errorFactor = 0.10; /* make these customisable? */
+ const int maxLockCount = 5;
+ /* Reset "lock count" when we exceed this multiple of errorFactor */
+ const double resetMargin = 1.5;
+
+ /* Add 200us to the exposure time error to allow for line quantisation. */
+ Duration exposureError = lastDeviceStatus_.shutterSpeed * errorFactor + 200us;
+ double gainError = lastDeviceStatus_.analogueGain * errorFactor;
+ Duration targetError = lastTargetExposure_ * errorFactor;
+
+ /*
+ * Note that we don't know the exposure/gain limits of the sensor, so
+ * the values we keep requesting may be unachievable. For this reason
+ * we only insist that we're close to values in the past few frames.
+ */
+ if (deviceStatus.shutterSpeed > lastDeviceStatus_.shutterSpeed - exposureError &&
+ deviceStatus.shutterSpeed < lastDeviceStatus_.shutterSpeed + exposureError &&
+ deviceStatus.analogueGain > lastDeviceStatus_.analogueGain - gainError &&
+ deviceStatus.analogueGain < lastDeviceStatus_.analogueGain + gainError &&
+ status_.targetExposureValue > lastTargetExposure_ - targetError &&
+ status_.targetExposureValue < lastTargetExposure_ + targetError)
+ lockCount_ = std::min(lockCount_ + 1, maxLockCount);
+ else if (deviceStatus.shutterSpeed < lastDeviceStatus_.shutterSpeed - resetMargin * exposureError ||
+ deviceStatus.shutterSpeed > lastDeviceStatus_.shutterSpeed + resetMargin * exposureError ||
+ deviceStatus.analogueGain < lastDeviceStatus_.analogueGain - resetMargin * gainError ||
+ deviceStatus.analogueGain > lastDeviceStatus_.analogueGain + resetMargin * gainError ||
+ status_.targetExposureValue < lastTargetExposure_ - resetMargin * targetError ||
+ status_.targetExposureValue > lastTargetExposure_ + resetMargin * targetError)
+ lockCount_ = 0;
+
+ lastDeviceStatus_ = deviceStatus;
+ lastTargetExposure_ = status_.targetExposureValue;
+
+ LOG(RPiAgc, Debug) << "Lock count updated to " << lockCount_;
+ status_.locked = lockCount_ == maxLockCount;
+}
+
+static void copyString(std::string const &s, char *d, size_t size)
+{
+ size_t length = s.copy(d, size - 1);
+ d[length] = '\0';
+}
+
+void Agc::housekeepConfig()
+{
+ /* First fetch all the up-to-date settings, so no one else has to do it. */
+ status_.ev = ev_;
+ status_.fixedShutter = limitShutter(fixedShutter_);
+ status_.fixedAnalogueGain = fixedAnalogueGain_;
+ status_.flickerPeriod = flickerPeriod_;
+ LOG(RPiAgc, Debug) << "ev " << status_.ev << " fixedShutter "
+ << status_.fixedShutter << " fixedAnalogueGain "
+ << status_.fixedAnalogueGain;
+ /*
+ * Make sure the "mode" pointers point to the up-to-date things, if
+ * they've changed.
+ */
+ if (strcmp(meteringModeName_.c_str(), status_.meteringMode)) {
+ auto it = config_.meteringModes.find(meteringModeName_);
+ if (it == config_.meteringModes.end())
+ LOG(RPiAgc, Fatal) << "No metering mode " << meteringModeName_;
+ meteringMode_ = &it->second;
+ copyString(meteringModeName_, status_.meteringMode,
+ sizeof(status_.meteringMode));
+ }
+ if (strcmp(exposureModeName_.c_str(), status_.exposureMode)) {
+ auto it = config_.exposureModes.find(exposureModeName_);
+ if (it == config_.exposureModes.end())
+ LOG(RPiAgc, Fatal) << "No exposure profile " << exposureModeName_;
+ exposureMode_ = &it->second;
+ copyString(exposureModeName_, status_.exposureMode,
+ sizeof(status_.exposureMode));
+ }
+ if (strcmp(constraintModeName_.c_str(), status_.constraintMode)) {
+ auto it =
+ config_.constraintModes.find(constraintModeName_);
+ if (it == config_.constraintModes.end())
+ LOG(RPiAgc, Fatal) << "No constraint list " << constraintModeName_;
+ constraintMode_ = &it->second;
+ copyString(constraintModeName_, status_.constraintMode,
+ sizeof(status_.constraintMode));
+ }
+ LOG(RPiAgc, Debug) << "exposureMode "
+ << exposureModeName_ << " constraintMode "
+ << constraintModeName_ << " meteringMode "
+ << meteringModeName_;
+}
+
+void Agc::fetchCurrentExposure(Metadata *imageMetadata)
+{
+ std::unique_lock<Metadata> lock(*imageMetadata);
+ DeviceStatus *deviceStatus =
+ imageMetadata->getLocked<DeviceStatus>("device.status");
+ if (!deviceStatus)
+ LOG(RPiAgc, Fatal) << "No device metadata";
+ current_.shutter = deviceStatus->shutterSpeed;
+ current_.analogueGain = deviceStatus->analogueGain;
+ AgcStatus *agcStatus =
+ imageMetadata->getLocked<AgcStatus>("agc.status");
+ current_.totalExposure = agcStatus ? agcStatus->totalExposureValue : 0s;
+ current_.totalExposureNoDG = current_.shutter * current_.analogueGain;
+}
+
+void Agc::fetchAwbStatus(Metadata *imageMetadata)
+{
+ awb_.gainR = 1.0; /* in case not found in metadata */
+ awb_.gainG = 1.0;
+ awb_.gainB = 1.0;
+ if (imageMetadata->get("awb.status", awb_) != 0)
+ LOG(RPiAgc, Debug) << "No AWB status found";
+}
+
+static double computeInitialY(StatisticsPtr &stats, AwbStatus const &awb,
+ std::vector<double> &weights, double gain)
+{
+ constexpr uint64_t maxVal = 1 << Statistics::NormalisationFactorPow2;
+
+ ASSERT(weights.size() == stats->agcRegions.numRegions());
+
+ /*
+ * Note how the calculation below means that equal weights give you
+ * "average" metering (i.e. all pixels equally important).
+ */
+ double rSum = 0, gSum = 0, bSum = 0, pixelSum = 0;
+ for (unsigned int i = 0; i < stats->agcRegions.numRegions(); i++) {
+ auto &region = stats->agcRegions.get(i);
+ 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];
+ pixelSum += region.counted * weights[i];
+ }
+ if (pixelSum == 0.0) {
+ LOG(RPiAgc, Warning) << "computeInitialY: pixelSum is zero";
+ return 0;
+ }
+ double ySum = rSum * awb.gainR * .299 +
+ gSum * awb.gainG * .587 +
+ bSum * awb.gainB * .114;
+ return ySum / pixelSum / maxVal;
+}
+
+/*
+ * We handle extra gain through EV by adjusting our Y targets. However, you
+ * simply can't monitor histograms once they get very close to (or beyond!)
+ * saturation, so we clamp the Y targets to this value. It does mean that EV
+ * increases don't necessarily do quite what you might expect in certain
+ * (contrived) cases.
+ */
+
+static constexpr double EvGainYTargetLimit = 0.9;
+
+static double constraintComputeGain(AgcConstraint &c, const Histogram &h, double lux,
+ double evGain, double &targetY)
+{
+ targetY = c.yTarget.eval(c.yTarget.domain().clip(lux));
+ targetY = std::min(EvGainYTargetLimit, targetY * evGain);
+ double iqm = h.interQuantileMean(c.qLo, c.qHi);
+ return (targetY * h.bins()) / iqm;
+}
+
+void Agc::computeGain(StatisticsPtr &statistics, Metadata *imageMetadata,
+ double &gain, double &targetY)
+{
+ struct LuxStatus lux = {};
+ lux.lux = 400; /* default lux level to 400 in case no metadata found */
+ if (imageMetadata->get("lux.status", lux) != 0)
+ LOG(RPiAgc, Warning) << "No lux level found";
+ const Histogram &h = statistics->yHist;
+ double evGain = status_.ev * config_.baseEv;
+ /*
+ * The initial gain and target_Y come from some of the regions. After
+ * that we consider the histogram constraints.
+ */
+ targetY = config_.yTarget.eval(config_.yTarget.domain().clip(lux.lux));
+ targetY = std::min(EvGainYTargetLimit, targetY * evGain);
+
+ /*
+ * Do this calculation a few times as brightness increase can be
+ * non-linear when there are saturated regions.
+ */
+ gain = 1.0;
+ for (int i = 0; i < 8; i++) {
+ double initialY = computeInitialY(statistics, awb_, meteringMode_->weights, gain);
+ double extraGain = std::min(10.0, targetY / (initialY + .001));
+ gain *= extraGain;
+ LOG(RPiAgc, Debug) << "Initial Y " << initialY << " target " << targetY
+ << " gives gain " << gain;
+ if (extraGain < 1.01) /* close enough */
+ break;
+ }
+
+ for (auto &c : *constraintMode_) {
+ double newTargetY;
+ double newGain = constraintComputeGain(c, h, lux.lux, evGain, newTargetY);
+ LOG(RPiAgc, Debug) << "Constraint has target_Y "
+ << newTargetY << " giving gain " << newGain;
+ if (c.bound == AgcConstraint::Bound::LOWER && newGain > gain) {
+ LOG(RPiAgc, Debug) << "Lower bound constraint adopted";
+ gain = newGain;
+ targetY = newTargetY;
+ } else if (c.bound == AgcConstraint::Bound::UPPER && newGain < gain) {
+ LOG(RPiAgc, Debug) << "Upper bound constraint adopted";
+ gain = newGain;
+ targetY = newTargetY;
+ }
+ }
+ LOG(RPiAgc, Debug) << "Final gain " << gain << " (target_Y " << targetY << " ev "
+ << status_.ev << " base_ev " << config_.baseEv
+ << ")";
+}
+
+void Agc::computeTargetExposure(double gain)
+{
+ if (status_.fixedShutter && status_.fixedAnalogueGain) {
+ /*
+ * When ag and shutter are both fixed, we need to drive the
+ * total exposure so that we end up with a digital gain of at least
+ * 1/minColourGain. Otherwise we'd desaturate channels causing
+ * white to go cyan or magenta.
+ */
+ double minColourGain = std::min({ awb_.gainR, awb_.gainG, awb_.gainB, 1.0 });
+ ASSERT(minColourGain != 0.0);
+ target_.totalExposure =
+ status_.fixedShutter * status_.fixedAnalogueGain / minColourGain;
+ } else {
+ /*
+ * The statistics reflect the image without digital gain, so the final
+ * total exposure we're aiming for is:
+ */
+ target_.totalExposure = current_.totalExposureNoDG * gain;
+ /* The final target exposure is also limited to what the exposure mode allows. */
+ Duration maxShutter = status_.fixedShutter
+ ? status_.fixedShutter
+ : exposureMode_->shutter.back();
+ maxShutter = limitShutter(maxShutter);
+ Duration maxTotalExposure =
+ maxShutter *
+ (status_.fixedAnalogueGain != 0.0
+ ? status_.fixedAnalogueGain
+ : exposureMode_->gain.back());
+ target_.totalExposure = std::min(target_.totalExposure, maxTotalExposure);
+ }
+ LOG(RPiAgc, Debug) << "Target totalExposure " << target_.totalExposure;
+}
+
+bool Agc::applyDigitalGain(double gain, double targetY)
+{
+ double minColourGain = std::min({ awb_.gainR, awb_.gainG, awb_.gainB, 1.0 });
+ ASSERT(minColourGain != 0.0);
+ double dg = 1.0 / minColourGain;
+ /*
+ * I think this pipeline subtracts black level and rescales before we
+ * get the stats, so no need to worry about it.
+ */
+ LOG(RPiAgc, Debug) << "after AWB, target dg " << dg << " gain " << gain
+ << " target_Y " << targetY;
+ /*
+ * Finally, if we're trying to reduce exposure but the target_Y is
+ * "close" to 1.0, then the gain computed for that constraint will be
+ * only slightly less than one, because the measured Y can never be
+ * larger than 1.0. When this happens, demand a large digital gain so
+ * that the exposure can be reduced, de-saturating the image much more
+ * quickly (and we then approach the correct value more quickly from
+ * below).
+ */
+ bool desaturate = targetY > config_.fastReduceThreshold &&
+ gain < sqrt(targetY);
+ if (desaturate)
+ dg /= config_.fastReduceThreshold;
+ LOG(RPiAgc, Debug) << "Digital gain " << dg << " desaturate? " << desaturate;
+ target_.totalExposureNoDG = target_.totalExposure / dg;
+ LOG(RPiAgc, Debug) << "Target totalExposureNoDG " << target_.totalExposureNoDG;
+ return desaturate;
+}
+
+void Agc::filterExposure(bool desaturate)
+{
+ double speed = config_.speed;
+ /*
+ * AGC adapts instantly if both shutter and gain are directly specified
+ * or we're in the startup phase.
+ */
+ if ((status_.fixedShutter && status_.fixedAnalogueGain) ||
+ frameCount_ <= config_.startupFrames)
+ speed = 1.0;
+ if (!filtered_.totalExposure) {
+ filtered_.totalExposure = target_.totalExposure;
+ filtered_.totalExposureNoDG = target_.totalExposureNoDG;
+ } else {
+ /*
+ * If close to the result go faster, to save making so many
+ * micro-adjustments on the way. (Make this customisable?)
+ */
+ if (filtered_.totalExposure < 1.2 * target_.totalExposure &&
+ filtered_.totalExposure > 0.8 * target_.totalExposure)
+ speed = sqrt(speed);
+ filtered_.totalExposure = speed * target_.totalExposure +
+ filtered_.totalExposure * (1.0 - speed);
+ /*
+ * When desaturing, take a big jump down in totalExposureNoDG,
+ * which we'll hide with digital gain.
+ */
+ if (desaturate)
+ filtered_.totalExposureNoDG =
+ target_.totalExposureNoDG;
+ else
+ filtered_.totalExposureNoDG =
+ speed * target_.totalExposureNoDG +
+ filtered_.totalExposureNoDG * (1.0 - speed);
+ }
+ /*
+ * We can't let the totalExposureNoDG exposure deviate too far below the
+ * total exposure, as there might not be enough digital gain available
+ * in the ISP to hide it (which will cause nasty oscillation).
+ */
+ if (filtered_.totalExposureNoDG <
+ filtered_.totalExposure * config_.fastReduceThreshold)
+ filtered_.totalExposureNoDG = filtered_.totalExposure * config_.fastReduceThreshold;
+ LOG(RPiAgc, Debug) << "After filtering, totalExposure " << filtered_.totalExposure
+ << " no dg " << filtered_.totalExposureNoDG;
+}
+
+void Agc::divideUpExposure()
+{
+ /*
+ * Sending the fixed shutter/gain cases through the same code may seem
+ * unnecessary, but it will make more sense when extend this to cover
+ * variable aperture.
+ */
+ Duration exposureValue = filtered_.totalExposureNoDG;
+ Duration shutterTime;
+ double analogueGain;
+ shutterTime = status_.fixedShutter ? status_.fixedShutter
+ : exposureMode_->shutter[0];
+ shutterTime = limitShutter(shutterTime);
+ analogueGain = status_.fixedAnalogueGain != 0.0 ? status_.fixedAnalogueGain
+ : exposureMode_->gain[0];
+ analogueGain = limitGain(analogueGain);
+ if (shutterTime * analogueGain < exposureValue) {
+ for (unsigned int stage = 1;
+ stage < exposureMode_->gain.size(); stage++) {
+ if (!status_.fixedShutter) {
+ Duration stageShutter =
+ limitShutter(exposureMode_->shutter[stage]);
+ if (stageShutter * analogueGain >= exposureValue) {
+ shutterTime = exposureValue / analogueGain;
+ break;
+ }
+ shutterTime = stageShutter;
+ }
+ if (status_.fixedAnalogueGain == 0.0) {
+ if (exposureMode_->gain[stage] * shutterTime >= exposureValue) {
+ analogueGain = exposureValue / shutterTime;
+ break;
+ }
+ analogueGain = exposureMode_->gain[stage];
+ analogueGain = limitGain(analogueGain);
+ }
+ }
+ }
+ LOG(RPiAgc, Debug) << "Divided up shutter and gain are " << shutterTime << " and "
+ << analogueGain;
+ /*
+ * Finally adjust shutter time for flicker avoidance (require both
+ * shutter and gain not to be fixed).
+ */
+ if (!status_.fixedShutter && !status_.fixedAnalogueGain &&
+ status_.flickerPeriod) {
+ int flickerPeriods = shutterTime / status_.flickerPeriod;
+ if (flickerPeriods) {
+ Duration newShutterTime = flickerPeriods * status_.flickerPeriod;
+ analogueGain *= shutterTime / newShutterTime;
+ /*
+ * We should still not allow the ag to go over the
+ * largest value in the exposure mode. Note that this
+ * may force more of the total exposure into the digital
+ * gain as a side-effect.
+ */
+ analogueGain = std::min(analogueGain, exposureMode_->gain.back());
+ analogueGain = limitGain(analogueGain);
+ shutterTime = newShutterTime;
+ }
+ LOG(RPiAgc, Debug) << "After flicker avoidance, shutter "
+ << shutterTime << " gain " << analogueGain;
+ }
+ filtered_.shutter = shutterTime;
+ filtered_.analogueGain = analogueGain;
+}
+
+void Agc::writeAndFinish(Metadata *imageMetadata, bool desaturate)
+{
+ status_.totalExposureValue = filtered_.totalExposure;
+ status_.targetExposureValue = desaturate ? 0s : target_.totalExposureNoDG;
+ status_.shutterTime = filtered_.shutter;
+ status_.analogueGain = filtered_.analogueGain;
+ /*
+ * Write to metadata as well, in case anyone wants to update the camera
+ * immediately.
+ */
+ imageMetadata->set("agc.status", status_);
+ LOG(RPiAgc, Debug) << "Output written, total exposure requested is "
+ << filtered_.totalExposure;
+ LOG(RPiAgc, Debug) << "Camera exposure update: shutter time " << filtered_.shutter
+ << " analogue gain " << filtered_.analogueGain;
+}
+
+Duration Agc::limitShutter(Duration shutter)
+{
+ /*
+ * shutter == 0 is a special case for fixed shutter values, and must pass
+ * through unchanged
+ */
+ if (!shutter)
+ return shutter;
+
+ shutter = std::clamp(shutter, mode_.minShutter, maxShutter_);
+ return shutter;
+}
+
+double Agc::limitGain(double gain) const
+{
+ /*
+ * Only limit the lower bounds of the gain value to what the sensor limits.
+ * The upper bound on analogue gain will be made up with additional digital
+ * gain applied by the ISP.
+ *
+ * gain == 0.0 is a special case for fixed shutter values, and must pass
+ * through unchanged
+ */
+ if (!gain)
+ return gain;
+
+ gain = std::max(gain, mode_.minAnalogueGain);
+ return gain;
+}
+
+/* Register algorithm with the system. */
+static Algorithm *create(Controller *controller)
+{
+ return (Algorithm *)new Agc(controller);
+}
+static RegisterAlgorithm reg(NAME, &create);
generated by cgit v1.2.1 (git 2.18.0) at 2024-05-20 06:02:59 +0000