pipeline: ipa: raspberrypi: Refactor and move the Raspberry Pi code

Split the Raspberry Pi pipeline handler and IPA source code into common
and VC4/BCM2835 specific file structures.

For the pipeline handler, the common code files now live in
src/libcamera/pipeline/rpi/common/
and the VC4-specific files in src/libcamera/pipeline/rpi/vc4/.

For the IPA, the common code files now live in
src/ipa/rpi/{cam_helper,controller}/
and the vc4 specific files in src/ipa/rpi/vc4/. With this change, the
camera tuning files are now installed under share/libcamera/ipa/rpi/vc4/.

To build the pipeline and IPA, the meson configuration options have now
changed from "raspberrypi" to "rpi/vc4":

meson setup build -Dipas=rpi/vc4 -Dpipelines=rpi/vc4

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo.mondi@ideasonboard.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 0 insertions, 922 deletions

diff --git a/src/ipa/raspberrypi/controller/rpi/agc.cpp b/src/ipa/raspberrypi/controller/rpi/agc.cpp
deleted file mode 100644
index e6fb7b8d..00000000
--- a/src/ipa/raspberrypi/controller/rpi/agc.cpp
+++ /dev/null
@@ -1,922 +0,0 @@
-/* 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);