src/ipa/raspberrypi/cam_helper.hpp


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/* SPDX-License-Identifier: BSD-2-Clause */
/*
 * Copyright (C) 2019, Raspberry Pi (Trading) Limited
 *
 * cam_helper.hpp - helper class providing camera information
 */
#pragma once

#include <memory>
#include <string>

#include <libcamera/base/span.h>
#include <libcamera/base/utils.h>

#include "camera_mode.h"
#include "controller/controller.hpp"
#include "controller/metadata.hpp"
#include "md_parser.hpp"

#include "libcamera/internal/v4l2_videodevice.h"

namespace RPiController {

// The CamHelper class provides a number of facilities that anyone trying
// to drive a camera will need to know, but which are not provided by the
// standard driver framework. Specifically, it provides:
//
// A "CameraMode" structure to describe extra information about the chosen
// mode of the driver. For example, how it is cropped from the full sensor
// area, how it is scaled, whether pixels are averaged compared to the full
// resolution.
//
// The ability to convert between number of lines of exposure and actual
// exposure time, and to convert between the sensor's gain codes and actual
// gains.
//
// A function to return the number of frames of delay between updating exposure,
// analogue gain and vblanking, and for the changes to take effect. For many
// sensors these take the values 2, 1 and 2 respectively, but sensors that are
// different will need to over-ride the default function provided.
//
// A function to query if the sensor outputs embedded data that can be parsed.
//
// A function to return the sensitivity of a given camera mode.
//
// A parser to parse the embedded data buffers provided by some sensors (for
// example, the imx219 does; the ov5647 doesn't). This allows us to know for
// sure the exposure and gain of the frame we're looking at. CamHelper
// provides functions for converting analogue gains to and from the sensor's
// native gain codes.
//
// Finally, a set of functions that determine how to handle the vagaries of
// different camera modules on start-up or when switching modes. Some
// modules may produce one or more frames that are not yet correctly exposed,
// or where the metadata may be suspect. We have the following functions:
// HideFramesStartup(): Tell the pipeline handler not to return this many
//     frames at start-up. This can also be used to hide initial frames
//     while the AGC and other algorithms are sorting themselves out.
// HideFramesModeSwitch(): Tell the pipeline handler not to return this
//     many frames after a mode switch (other than start-up). Some sensors
//     may produce innvalid frames after a mode switch; others may not.
// MistrustFramesStartup(): At start-up a sensor may return frames for
//    which we should not run any control algorithms (for example, metadata
//    may be invalid).
// MistrustFramesModeSwitch(): The number of frames, after a mode switch
//    (other than start-up), for which control algorithms should not run
//    (for example, metadata may be unreliable).

class CamHelper
{
public:
	static CamHelper *Create(std::string const &cam_name);
	CamHelper(std::unique_ptr<MdParser> parser, unsigned int frameIntegrationDiff);
	virtual ~CamHelper();
	void SetCameraMode(const CameraMode &mode);
	virtual void Prepare(libcamera::Span<const uint8_t> buffer,
			     Metadata &metadata);
	virtual void Process(StatisticsPtr &stats, Metadata &metadata);
	virtual uint32_t ExposureLines(libcamera::utils::Duration exposure) const;
	virtual libcamera::utils::Duration Exposure(uint32_t exposure_lines) const;
	virtual uint32_t GetVBlanking(libcamera::utils::Duration &exposure,
				      libcamera::utils::Duration minFrameDuration,
				      libcamera::utils::Duration maxFrameDuration) const;
	virtual uint32_t GainCode(double gain) const = 0;
	virtual double Gain(uint32_t gain_code) const = 0;
	virtual void GetDelays(int &exposure_delay, int &gain_delay,
			       int &vblank_delay) const;
	virtual bool SensorEmbeddedDataPresent() const;
	virtual double GetModeSensitivity(const CameraMode &mode) const;
	virtual unsigned int HideFramesStartup() const;
	virtual unsigned int HideFramesModeSwitch() const;
	virtual unsigned int MistrustFramesStartup() const;
	virtual unsigned int MistrustFramesModeSwitch() const;

protected:
	void parseEmbeddedData(libcamera::Span<const uint8_t> buffer,
			       Metadata &metadata);
	virtual void PopulateMetadata(const MdParser::RegisterMap &registers,
				      Metadata &metadata) const;

	std::unique_ptr<MdParser> parser_;
	CameraMode mode_;

private:
	bool initialized_;
	/*
	 * Smallest difference between the frame length and integration time,
	 * in units of lines.
	 */
	unsigned int frameIntegrationDiff_;
};

// This is for registering camera helpers with the system, so that the
// CamHelper::Create function picks them up automatically.

typedef CamHelper *(*CamHelperCreateFunc)();
struct RegisterCamHelper
{
	RegisterCamHelper(char const *cam_name,
			  CamHelperCreateFunc create_func);
};

} // namespace RPi