[libcamera-devel] [PATCH v1] gstreamer: Provide framerate support for libcamerasrc.

[Rishikesh Donadkar]

This patch aims to add framerate support to libcamerasrc in the 
direction gstreamer->libcamera.

Add a field of the type ControlList to GstLibcameraSrcState.
Get the framerate from the caps and convert it to FrameDuration.
Set the FrameDurationLimits control in the initControls_ and pass
the initControls_ at the time of starting camera.

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
Signed-off-by: Rishikesh Donadkar <rishikeshdonadkar at gmail.com>

---
Tested the patch with 3 different framerates with the help of the
fpsdisplaysink element.

https://paste.debian.net/1251951/

https://paste.debian.net/1251952/

https://paste.debian.net/1251953/
---
 src/gstreamer/gstlibcamera-utils.cpp | 18 ++++++++++++++++++
 src/gstreamer/gstlibcamera-utils.h   |  3 +++
 src/gstreamer/gstlibcamerasrc.cpp    |  7 ++++++-
 3 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
index 5a21a391..7d8519da 100644
--- a/src/gstreamer/gstlibcamera-utils.cpp
+++ b/src/gstreamer/gstlibcamera-utils.cpp
@@ -8,6 +8,7 @@
 
 #include "gstlibcamera-utils.h"
 
+#include <libcamera/control_ids.h>
 #include <libcamera/formats.h>
 
 using namespace libcamera;
@@ -236,6 +237,23 @@ gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,
 	stream_cfg.size.height = height;
 }
 
+void
+gst_libcamera_configure_controls_from_caps(ControlList &controls, [[maybe_unused]] GstCaps *caps)
+{
+	/* read framerate from caps - convert to integer and set to frame_time. */
+	GstStructure *s = gst_caps_get_structure(caps, 0);
+	gint fps_n = -1, fps_d = -1;
+	if (gst_structure_has_field(s, "framerate"))
+		gst_structure_get_fraction(s, "framerate", &fps_n, &fps_d);
+
+	if (fps_n < 0 || fps_d < 0)
+		return;
+
+	gdouble frame_duration = static_cast<double>(fps_d) / static_cast<double>(fps_n) * 1000000.0;
+	controls.set(controls::FrameDurationLimits,
+		     Span<const int64_t, 2>({ static_cast<int64_t>(frame_duration), static_cast<int64_t>(frame_duration) }));
+}
+
 #if !GST_CHECK_VERSION(1, 17, 1)
 gboolean
 gst_task_resume(GstTask *task)
diff --git a/src/gstreamer/gstlibcamera-utils.h b/src/gstreamer/gstlibcamera-utils.h
index 164189a2..1f737e84 100644
--- a/src/gstreamer/gstlibcamera-utils.h
+++ b/src/gstreamer/gstlibcamera-utils.h
@@ -9,6 +9,7 @@
 #pragma once
 
 #include <libcamera/camera_manager.h>
+#include <libcamera/controls.h>
 #include <libcamera/stream.h>
 
 #include <gst/gst.h>
@@ -18,6 +19,8 @@ GstCaps *gst_libcamera_stream_formats_to_caps(const libcamera::StreamFormats &fo
 GstCaps *gst_libcamera_stream_configuration_to_caps(const libcamera::StreamConfiguration &stream_cfg);
 void gst_libcamera_configure_stream_from_caps(libcamera::StreamConfiguration &stream_cfg,
 					      GstCaps *caps);
+void gst_libcamera_configure_controls_from_caps(libcamera::ControlList &controls, GstCaps *caps);
+
 #if !GST_CHECK_VERSION(1, 17, 1)
 gboolean gst_task_resume(GstTask *task);
 #endif
diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
index 16d70fea..d1080271 100644
--- a/src/gstreamer/gstlibcamerasrc.cpp
+++ b/src/gstreamer/gstlibcamerasrc.cpp
@@ -131,6 +131,7 @@ struct GstLibcameraSrcState {
 	std::queue<std::unique_ptr<RequestWrap>> completedRequests_
 		LIBCAMERA_TSA_GUARDED_BY(lock_);
 
+	ControlList initControls_;
 	guint group_id_;
 
 	int queueRequest();
@@ -496,6 +497,7 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
 		/* 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;
@@ -504,6 +506,7 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
 		/* Fixate caps and configure the stream. */
 		caps = gst_caps_make_writable(caps);
 		gst_libcamera_configure_stream_from_caps(stream_cfg, caps);
+		gst_libcamera_configure_controls_from_caps(state->initControls_, caps);
 	}
 
 	if (flow_ret != GST_FLOW_OK)
@@ -524,6 +527,7 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
 		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;
@@ -566,7 +570,7 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
 		gst_flow_combiner_add_pad(self->flow_combiner, srcpad);
 	}
 
-	ret = state->cam_->start();
+	ret = state->cam_->start(&state->initControls_);
 	if (ret) {
 		GST_ELEMENT_ERROR(self, RESOURCE, SETTINGS,
 				  ("Failed to start the camera: %s", g_strerror(-ret)),
@@ -576,6 +580,7 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
 	}
 
 done:
+	state->initControls_.clear();
 	switch (flow_ret) {
 	case GST_FLOW_NOT_NEGOTIATED:
 		GST_ELEMENT_FLOW_ERROR(self, flow_ret);
-- 
2.25.1