external_libcamera/src/gstreamer/gstlibcamerasrc.cpp

/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
 * Copyright (C) 2019, Collabora Ltd.
 *     Author: Nicolas Dufresne <nicolas.dufresne@collabora.com>
 *
 * gstlibcamerasrc.cpp - GStreamer Capture Element
 */

/**
 * \todo libcamera UVC drivers picks the lowest possible resolution first, this
 * should be fixed so that we get a decent resolution and framerate for the
 * role by default.
 */

#include "gstlibcamerasrc.h"

#include <vector>

#include <libcamera/camera.h>
#include <libcamera/camera_manager.h>

#include "gstlibcamerapad.h"
#include "gstlibcamera-utils.h"

using namespace libcamera;

GST_DEBUG_CATEGORY_STATIC(source_debug);
#define GST_CAT_DEFAULT source_debug

/* Used for C++ object with destructors. */
struct GstLibcameraSrcState {
	std::unique_ptr<CameraManager> cm_;
	std::shared_ptr<Camera> cam_;
	std::unique_ptr<CameraConfiguration> config_;
	std::vector<GstPad *> srcpads_;
};

struct _GstLibcameraSrc {
	GstElement parent;

	GRecMutex stream_lock;
	GstTask *task;

	gchar *camera_name;

	GstLibcameraSrcState *state;
};

enum {
	PROP_0,
	PROP_CAMERA_NAME
};

G_DEFINE_TYPE_WITH_CODE(GstLibcameraSrc, gst_libcamera_src, GST_TYPE_ELEMENT,
			GST_DEBUG_CATEGORY_INIT(source_debug, "libcamerasrc", 0,
						"libcamera Source"));

#define TEMPLATE_CAPS GST_STATIC_CAPS("video/x-raw; image/jpeg")

/* For the simple case, we have a src pad that is always present. */
GstStaticPadTemplate src_template = {
	"src", GST_PAD_SRC, GST_PAD_ALWAYS, TEMPLATE_CAPS
};

/* More pads can be requested in state < PAUSED */
GstStaticPadTemplate request_src_template = {
	"src_%s", GST_PAD_SRC, GST_PAD_REQUEST, TEMPLATE_CAPS
};

static bool
gst_libcamera_src_open(GstLibcameraSrc *self)
{
	std::unique_ptr<CameraManager> cm = std::make_unique<CameraManager>();
	std::shared_ptr<Camera> cam;
	gint ret = 0;

	GST_DEBUG_OBJECT(self, "Opening camera device ...");

	ret = cm->start();
	if (ret) {
		GST_ELEMENT_ERROR(self, LIBRARY, INIT,
				  ("Failed listing cameras."),
				  ("libcamera::CameraMananger::start() failed: %s", g_strerror(-ret)));
		return false;
	}

	g_autofree gchar *camera_name = nullptr;
	{
		GLibLocker lock(GST_OBJECT(self));
		if (self->camera_name)
			camera_name = g_strdup(self->camera_name);
	}

	if (camera_name) {
		cam = cm->get(self->camera_name);
		if (!cam) {
			GST_ELEMENT_ERROR(self, RESOURCE, NOT_FOUND,
					  ("Could not find a camera named '%s'.", self->camera_name),
					  ("libcamera::CameraMananger::get() returned nullptr"));
			return false;
		}
	} else {
		if (cm->cameras().empty()) {
			GST_ELEMENT_ERROR(self, RESOURCE, NOT_FOUND,
					  ("Could not find any supported camera on this system."),
					  ("libcamera::CameraMananger::cameras() is empty"));
			return false;
		}
		cam = cm->cameras()[0];
	}

	GST_INFO_OBJECT(self, "Using camera named '%s'", cam->name().c_str());

	ret = cam->acquire();
	if (ret) {
		GST_ELEMENT_ERROR(self, RESOURCE, BUSY,
				  ("Camera name '%s' is already in use.", cam->name().c_str()),
				  ("libcamera::Camera::acquire() failed: %s", g_strerror(ret)));
		return false;
	}

	/* No need to lock here, we didn't start our threads yet. */
	self->state->cm_ = std::move(cm);
	self->state->cam_ = cam;

	return true;
}

static void
gst_libcamera_src_task_run(gpointer user_data)
{
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(user_data);

	GST_DEBUG_OBJECT(self, "Streaming thread is now capturing");
}

static void
gst_libcamera_src_task_enter(GstTask *task, GThread *thread, gpointer user_data)
{
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(user_data);
	GLibRecLocker lock(&self->stream_lock);
	GstLibcameraSrcState *state = self->state;
	GstFlowReturn flow_ret = GST_FLOW_OK;
	gint ret;

	GST_DEBUG_OBJECT(self, "Streaming thread has started");

	guint group_id = gst_util_group_id_next();
	StreamRoles roles;
	for (GstPad *srcpad : state->srcpads_) {
		/* Create stream-id and push stream-start. */
		g_autofree gchar *stream_id = gst_pad_create_stream_id(srcpad, GST_ELEMENT(self), nullptr);
		GstEvent *event = gst_event_new_stream_start(stream_id);
		gst_event_set_group_id(event, group_id);
		gst_pad_push_event(srcpad, event);

		/* Collect the streams roles for the next iteration. */
		roles.push_back(gst_libcamera_pad_get_role(srcpad));
	}

	/* Generate the stream configurations, there should be one per pad. */
	state->config_ = state->cam_->generateConfiguration(roles);
	/*
	 * \todo Check if camera may increase or decrease the number of streams
	 * regardless of the number of roles.
	 */
	g_assert(state->config_->size() == state->srcpads_.size());

	for (gsize i = 0; i < state->srcpads_.size(); i++) {
		GstPad *srcpad = state->srcpads_[i];
		StreamConfiguration &stream_cfg = state->config_->at(i);

		/* Retrieve the supported caps. */
		g_autoptr(GstCaps) filter = gst_libcamera_stream_formats_to_caps(stream_cfg.formats());
		g_autoptr(GstCaps) caps = gst_pad_peer_query_caps(srcpad, filter);
		if (gst_caps_is_empty(caps)) {
			flow_ret = GST_FLOW_NOT_NEGOTIATED;
			break;
		}

		/* Fixate caps and configure the stream. */
		caps = gst_caps_make_writable(caps);
		gst_libcamera_configure_stream_from_caps(stream_cfg, caps);
	}

	if (flow_ret != GST_FLOW_OK)
		goto done;

	/* Validate the configuration. */
	if (state->config_->validate() == CameraConfiguration::Invalid) {
		flow_ret = GST_FLOW_NOT_NEGOTIATED;
		goto done;
	}

	/*
	 * Regardless if it has been modified, create clean caps and push the
	 * caps event. Downstream will decide if the caps are acceptable.
	 */
	for (gsize i = 0; i < state->srcpads_.size(); i++) {
		GstPad *srcpad = state->srcpads_[i];
		const StreamConfiguration &stream_cfg = state->config_->at(i);

		g_autoptr(GstCaps) caps = gst_libcamera_stream_configuration_to_caps(stream_cfg);
		if (!gst_pad_push_event(srcpad, gst_event_new_caps(caps))) {
			flow_ret = GST_FLOW_NOT_NEGOTIATED;
			break;
		}

		/* Send an open segment event with time format. */
		GstSegment segment;
		gst_segment_init(&segment, GST_FORMAT_TIME);
		gst_pad_push_event(srcpad, gst_event_new_segment(&segment));
	}

	ret = state->cam_->configure(state->config_.get());
	if (ret) {
		GST_ELEMENT_ERROR(self, RESOURCE, SETTINGS,
				  ("Failed to configure camera: %s", g_strerror(-ret)),
				  ("Camera::configure() failed with error code %i", ret));
		gst_task_stop(task);
		return;
	}

done:
	switch (flow_ret) {
	case GST_FLOW_NOT_NEGOTIATED:
		GST_ELEMENT_FLOW_ERROR(self, flow_ret);
		gst_task_stop(task);
		break;
	default:
		break;
	}
}

static void
gst_libcamera_src_task_leave(GstTask *task, GThread *thread, gpointer user_data)
{
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(user_data);

	GST_DEBUG_OBJECT(self, "Streaming thread is about to stop");
}

static void
gst_libcamera_src_close(GstLibcameraSrc *self)
{
	GstLibcameraSrcState *state = self->state;
	gint ret;

	ret = state->cam_->release();
	if (ret) {
		GST_ELEMENT_WARNING(self, RESOURCE, BUSY,
				    ("Camera name '%s' is still in use.", state->cam_->name().c_str()),
				    ("libcamera::Camera.release() failed: %s", g_strerror(-ret)));
	}

	state->cam_.reset();
	state->cm_->stop();
	state->cm_.reset();
}

static void
gst_libcamera_src_set_property(GObject *object, guint prop_id,
			       const GValue *value, GParamSpec *pspec)
{
	GLibLocker lock(GST_OBJECT(object));
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);

	switch (prop_id) {
	case PROP_CAMERA_NAME:
		g_free(self->camera_name);
		self->camera_name = g_value_dup_string(value);
		break;
	default:
		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
		break;
	}
}

static void
gst_libcamera_src_get_property(GObject *object, guint prop_id, GValue *value,
			       GParamSpec *pspec)
{
	GLibLocker lock(GST_OBJECT(object));
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);

	switch (prop_id) {
	case PROP_CAMERA_NAME:
		g_value_set_string(value, self->camera_name);
		break;
	default:
		G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);
		break;
	}
}

static GstStateChangeReturn
gst_libcamera_src_change_state(GstElement *element, GstStateChange transition)
{
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
	GstStateChangeReturn ret = GST_STATE_CHANGE_SUCCESS;
	GstElementClass *klass = GST_ELEMENT_CLASS(gst_libcamera_src_parent_class);

	ret = klass->change_state(element, transition);
	if (ret == GST_STATE_CHANGE_FAILURE)
		return ret;

	switch (transition) {
	case GST_STATE_CHANGE_NULL_TO_READY:
		if (!gst_libcamera_src_open(self))
			return GST_STATE_CHANGE_FAILURE;
		break;
	case GST_STATE_CHANGE_READY_TO_PAUSED:
		/* This needs to be called after pads activation.*/
		if (!gst_task_pause(self->task))
			return GST_STATE_CHANGE_FAILURE;
		ret = GST_STATE_CHANGE_NO_PREROLL;
		break;
	case GST_STATE_CHANGE_PLAYING_TO_PAUSED:
		ret = GST_STATE_CHANGE_NO_PREROLL;
		break;
	case GST_STATE_CHANGE_PAUSED_TO_READY:
		/*
		 * \todo this might require some thread unblocking in the future
		 * if the streaming thread starts doing any kind of blocking
		 * operations. If this was the case, we would need to do so
		 * before pad deactivation, so before chaining to the parent
		 * change_state function.
		 */
		gst_task_join(self->task);
		break;
	case GST_STATE_CHANGE_READY_TO_NULL:
		gst_libcamera_src_close(self);
		break;
	default:
		break;
	}

	return ret;
}

static void
gst_libcamera_src_finalize(GObject *object)
{
	GObjectClass *klass = G_OBJECT_CLASS(gst_libcamera_src_parent_class);
	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(object);

	g_rec_mutex_clear(&self->stream_lock);
	g_clear_object(&self->task);
	g_free(self->camera_name);
	delete self->state;

	return klass->finalize(object);
}

static void
gst_libcamera_src_init(GstLibcameraSrc *self)
{
	GstLibcameraSrcState *state = new GstLibcameraSrcState();
	GstPadTemplate *templ = gst_element_get_pad_template(GST_ELEMENT(self), "src");

	g_rec_mutex_init(&self->stream_lock);
	self->task = gst_task_new(gst_libcamera_src_task_run, self, nullptr);
	gst_task_set_enter_callback(self->task, gst_libcamera_src_task_enter, self, nullptr);
	gst_task_set_leave_callback(self->task, gst_libcamera_src_task_leave, self, nullptr);
	gst_task_set_lock(self->task, &self->stream_lock);

	state->srcpads_.push_back(gst_pad_new_from_template(templ, "src"));
	gst_element_add_pad(GST_ELEMENT(self), state->srcpads_[0]);
	self->state = state;
}

static void
gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
{
	GstElementClass *element_class = GST_ELEMENT_CLASS(klass);
	GObjectClass *object_class = G_OBJECT_CLASS(klass);

	object_class->set_property = gst_libcamera_src_set_property;
	object_class->get_property = gst_libcamera_src_get_property;
	object_class->finalize = gst_libcamera_src_finalize;

	element_class->change_state = gst_libcamera_src_change_state;

	gst_element_class_set_metadata(element_class,
				       "libcamera Source", "Source/Video",
				       "Linux Camera source using libcamera",
				       "Nicolas Dufresne <nicolas.dufresne@collabora.com");
	gst_element_class_add_static_pad_template_with_gtype(element_class,
							     &src_template,
							     GST_TYPE_LIBCAMERA_PAD);
	gst_element_class_add_static_pad_template_with_gtype(element_class,
							     &request_src_template,
							     GST_TYPE_LIBCAMERA_PAD);

	GParamSpec *spec = g_param_spec_string("camera-name", "Camera Name",
					       "Select by name which camera to use.", nullptr,
					       (GParamFlags)(GST_PARAM_MUTABLE_READY
							     | G_PARAM_CONSTRUCT
							     | G_PARAM_READWRITE
							     | G_PARAM_STATIC_STRINGS));
	g_object_class_install_property(object_class, PROP_CAMERA_NAME, spec);
}