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diff --git a/src/ipa/raspberrypi/controller/rpi/alsc.h b/src/ipa/raspberrypi/controller/rpi/alsc.h
new file mode 100644
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+++ b/src/ipa/raspberrypi/controller/rpi/alsc.h
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+/* SPDX-License-Identifier: BSD-2-Clause */
+/*
+ * Copyright (C) 2019, Raspberry Pi (Trading) Limited
+ *
+ * alsc.h - ALSC (auto lens shading correction) control algorithm
+ */
+#pragma once
+
+#include <mutex>
+#include <condition_variable>
+#include <thread>
+
+#include "../algorithm.h"
+#include "../alsc_status.h"
+
+namespace RPiController {
+
+/* Algorithm to generate automagic LSC (Lens Shading Correction) tables. */
+
+struct AlscCalibration {
+	double ct;
+	double table[ALSC_CELLS_X * ALSC_CELLS_Y];
+};
+
+struct AlscConfig {
+	/* Only repeat the ALSC calculation every "this many" frames */
+	uint16_t framePeriod;
+	/* number of initial frames for which speed taken as 1.0 (maximum) */
+	uint16_t startupFrames;
+	/* IIR filter speed applied to algorithm results */
+	double speed;
+	double sigmaCr;
+	double sigmaCb;
+	double minCount;
+	uint16_t minG;
+	double omega;
+	uint32_t nIter;
+	double luminanceLut[ALSC_CELLS_X * ALSC_CELLS_Y];
+	double luminanceStrength;
+	std::vector<AlscCalibration> calibrationsCr;
+	std::vector<AlscCalibration> calibrationsCb;
+	double defaultCt; /* colour temperature if no metadata found */
+	double threshold; /* iteration termination threshold */
+	double lambdaBound; /* upper/lower bound for lambda from a value of 1 */
+};
+
+class Alsc : public Algorithm
+{
+public:
+	Alsc(Controller *controller = NULL);
+	~Alsc();
+	char const *name() const override;
+	void initialise() override;
+	void switchMode(CameraMode const &cameraMode, Metadata *metadata) override;
+	void read(boost::property_tree::ptree const &params) override;
+	void prepare(Metadata *imageMetadata) override;
+	void process(StatisticsPtr &stats, Metadata *imageMetadata) override;
+
+private:
+	/* configuration is read-only, and available to both threads */
+	AlscConfig config_;
+	bool firstTime_;
+	CameraMode cameraMode_;
+	double luminanceTable_[ALSC_CELLS_X * ALSC_CELLS_Y];
+	std::thread asyncThread_;
+	void asyncFunc(); /* asynchronous thread function */
+	std::mutex mutex_;
+	/* condvar for async thread to wait on */
+	std::condition_variable asyncSignal_;
+	/* condvar for synchronous thread to wait on */
+	std::condition_variable syncSignal_;
+	/* for sync thread to check  if async thread finished (requires mutex) */
+	bool asyncFinished_;
+	/* for async thread to check if it's been told to run (requires mutex) */
+	bool asyncStart_;
+	/* for async thread to check if it's been told to quit (requires mutex) */
+	bool asyncAbort_;
+
+	/*
+	 * The following are only for the synchronous thread to use:
+	 * for sync thread to note its has asked async thread to run
+	 */
+	bool asyncStarted_;
+	/* counts up to framePeriod before restarting the async thread */
+	int framePhase_;
+	/* counts up to startupFrames */
+	int frameCount_;
+	/* counts up to startupFrames for Process function */
+	int frameCount2_;
+	double syncResults_[3][ALSC_CELLS_Y][ALSC_CELLS_X];
+	double prevSyncResults_[3][ALSC_CELLS_Y][ALSC_CELLS_X];
+	void waitForAysncThread();
+	/*
+	 * The following are for the asynchronous thread to use, though the main
+	 * thread can set/reset them if the async thread is known to be idle:
+	 */
+	void restartAsync(StatisticsPtr &stats, Metadata *imageMetadata);
+	/* copy out the results from the async thread so that it can be restarted */
+	void fetchAsyncResults();
+	double ct_;
+	bcm2835_isp_stats_region statistics_[ALSC_CELLS_Y * ALSC_CELLS_X];
+	double asyncResults_[3][ALSC_CELLS_Y][ALSC_CELLS_X];
+	double asyncLambdaR_[ALSC_CELLS_X * ALSC_CELLS_Y];
+	double asyncLambdaB_[ALSC_CELLS_X * ALSC_CELLS_Y];
+	void doAlsc();
+	double lambdaR_[ALSC_CELLS_X * ALSC_CELLS_Y];
+	double lambdaB_[ALSC_CELLS_X * ALSC_CELLS_Y];
+};
+
+} /* namespace RPiController */