[libcamera-devel] [PATCH v4 2/2] gstreamer: Provide framerate support for libcamerasrc.

[Umang Jain]

Hi Rishi,

Thank you for the patch,

Looks the the patch is getting in shape now... :-)

On 9/12/22 3:26 PM, Rishikesh Donadkar wrote:
> Add a field of the type ControlList to GstLibcameraSrcState.
>
> Get the framerate from the caps and convert it to FrameDuration.
> Clamp the frame_duration between the min/max FrameDuration supported
> by the camera and set the FrameDurationLimits control in the initControls_
>
> Solve the complications in exposing the correct framerate due to loss in
> precision as a result of casting the frameduration to int64_t(which is
> required in libcamera to set the FrameDurationLimits control).
>
> Example -
>
> * Suppose the framerate requested is 35/1. The framerate is read form
>    the caps in the from of fraction that has a numerator and
>    denominator.
>
> * Converting to FrameDuration (in microseconds)
>      (1 * 10^6) / 35 = 28571.4286
>      int64_t frame_duration = 28571
>      (the precision here is lost.)
> * To expose the framerate in caps, Inverting the frame_duration to get
>    back the framerate and converting to Seconds.
>      double framerate = 10^6 / 28571
>      and
>      10^6/28571 which is close but not equal to 35/1 will fail the negotiation.
>
> To solve the above problem, Store the framerate requested in the peer
> element caps in a container GstStructure, to be retrieved later.
>
> Get the control::FrameDurationLimits value that was set previously,
> convert to framerate and if it is equal to the one requested, set the
> framerate in the caps, else set the framerate to whatever is obtained
> from inverting the controls::FrameDurationLimits.
>
> Pass the initControls_ at camera->start().
>
> Signed-off-by: Rishikesh Donadkar <rishikeshdonadkar at gmail.com>
> ---
>   src/gstreamer/gstlibcamera-utils.cpp | 69 ++++++++++++++++++++++++++++
>   src/gstreamer/gstlibcamera-utils.h   |  7 +++
>   src/gstreamer/gstlibcamerasrc.cpp    | 16 ++++++-
>   3 files changed, 91 insertions(+), 1 deletion(-)
>
> diff --git a/src/gstreamer/gstlibcamera-utils.cpp b/src/gstreamer/gstlibcamera-utils.cpp
> index 4df5dd6c..907ceab9 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;
> @@ -405,6 +406,74 @@ gst_libcamera_configure_stream_from_caps(StreamConfiguration &stream_cfg,
>   	}
>   }
>   
> +void gst_libcamera_get_framerate_from_caps([[maybe_unused]] GstCaps *caps,
> +					   GstStructure *container)
> +{
> +	GstStructure *s = gst_caps_get_structure(caps, 0);
> +	gint fps_n = -1, fps_d = -1;
> +
> +	if (gst_structure_has_field_typed(s, "framerate", GST_TYPE_FRACTION)) {
> +		if (!gst_structure_get_fraction(s, "framerate", &fps_n, &fps_d)) {
> +			GST_WARNING("invalid framerate in the caps.");

s/invalid/Invalid
> +			return;
> +		}
> +	}
> +
> +	if (fps_n < 0 || fps_d < 0)

should it be combined with above if block, as this seems invalid as well...

	if (!gst_structure_get_fraction(s, "framerate", &fps_n, &fps_d) &&
	    (fps_n < 0 || fps_d < 0)) {
		GST_WARNING(...);
		...
	}

> +		return;
> +
> +	gst_structure_set(container, "framerate", GST_TYPE_FRACTION, fps_n, fps_d, nullptr);
> +}
> +
> +void gst_libcamera_clamp_and_set_frameduration(ControlList &controls, const ControlInfoMap &camera_controls,
> +					       const GstStructure *container)
> +{
> +	gint fps_caps_n, fps_caps_d;
> +	const GValue *framerate = gst_structure_get_value(container, "framerate");
> +
> +	if (!gst_structure_has_field_typed(container, "framerate", GST_TYPE_FRACTION))
> +		return;
> +
> +	auto iterFrameDuration = camera_controls.find(controls::FrameDurationLimits.id());
> +	if (iterFrameDuration == camera_controls.end())

This is a serious condition to be honest, that the camera doesn't give 
FrameDurationLimits and we are trying to set framerate ....

I think we should introduce here a warning
> +		return;
> +
> +	fps_caps_n = gst_value_get_fraction_numerator(framerate);
> +	fps_caps_d = gst_value_get_fraction_denominator(framerate);
> +
> +	int64_t frame_duration = (fps_caps_d * 1000000.0) / fps_caps_n;
> +	int64_t min_frame_duration = iterFrameDuration->second.min().get<int64_t>();
> +	int64_t max_frame_duration = iterFrameDuration->second.max().get<int64_t>();
> +
> +	if (frame_duration < min_frame_duration) {
> +		frame_duration = min_frame_duration;
> +	} else if (frame_duration > max_frame_duration) {
> +		frame_duration = max_frame_duration;
> +	}
> +
> +	controls.set(controls::FrameDurationLimits,
> +		     Span<const int64_t, 2>({ frame_duration, frame_duration }));
> +}
> +
> +void gst_libcamera_framerate_to_caps(const ControlList &controls, GstCaps *caps, const GValue *container)
> +{
> +	if (!GST_VALUE_HOLDS_FRACTION(container))
> +		return;
> +
> +	GstStructure *s = gst_caps_get_structure(caps, 0);
> +	gint fps_n, fps_d, fps_caps_n, fps_caps_d;
> +
> +	fps_caps_n = gst_value_get_fraction_numerator(container);
> +	fps_caps_d = gst_value_get_fraction_denominator(container);
> +	double framerate = 1000000 / controls.get(controls::FrameDurationLimits).value()[0];
> +	gst_util_double_to_fraction(framerate, &fps_n, &fps_d);
> +
> +	if (fps_caps_n / fps_caps_d == fps_n / fps_d)
> +		gst_structure_set(s, "framerate", GST_TYPE_FRACTION, fps_caps_n, fps_caps_d, nullptr);
> +	else
> +		gst_structure_set(s, "framerate", GST_TYPE_FRACTION, fps_n, fps_d, nullptr);

I think we can even simplify all this now that we have a GValue 
container to work with.

Would it be possible to save the fraction for min/max frame_duration 
cases ( if..elseif {} in gst_libcamera_clamp_and_set_frameduration()) 
and update the container with that fraction.

... and simply use the container's framrate num/denum value here instead 
of doing all the conversion / comparision?

I think it will get simpler that way , no?
> +}
> +
>   #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..bc04b073 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 +19,12 @@ 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_get_framerate_from_caps(GstCaps *caps, GstStructure *container);
> +void gst_libcamera_clamp_and_set_frameduration(libcamera::ControlList &controls,
> +					       const libcamera::ControlInfoMap &camera_controls, const GstStructure *container);
> +void gst_libcamera_framerate_to_caps(const libcamera::ControlList &controls, GstCaps *caps,
> +				     const GValue *container);
> +
>   #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 1ee1d08a..5cdf23a1 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();
> @@ -462,6 +463,8 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>   	GstFlowReturn flow_ret = GST_FLOW_OK;
>   	gint ret;
>   
> +	GstStructure *container = gst_structure_new_empty("container");
> +
>   	GST_DEBUG_OBJECT(self, "Streaming thread has started");
>   
>   	gint stream_id_num = 0;
> @@ -496,6 +499,7 @@ 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);
> +

spurious emptry line, remove it
>   		if (gst_caps_is_empty(caps)) {
>   			flow_ret = GST_FLOW_NOT_NEGOTIATED;
>   			break;
> @@ -504,6 +508,7 @@ 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_get_framerate_from_caps(caps, container);
>   	}
>   
>   	if (flow_ret != GST_FLOW_OK)
> @@ -524,6 +529,10 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>   		return;
>   	}
>   
> +	/* Check frame duration bounds within controls::FrameDurationLimits */
> +	gst_libcamera_clamp_and_set_frameduration(state->initControls_,
> +						  state->cam_->controls(), container);
> +
>   	/*
>   	 * Regardless if it has been modified, create clean caps and push the
>   	 * caps event. Downstream will decide if the caps are acceptable.
> @@ -531,8 +540,11 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>   	for (gsize i = 0; i < state->srcpads_.size(); i++) {
>   		GstPad *srcpad = state->srcpads_[i];
>   		const StreamConfiguration &stream_cfg = state->config_->at(i);
> +		const GValue *framerate = gst_structure_get_value(container, "framerate");
>   
>   		g_autoptr(GstCaps) caps = gst_libcamera_stream_configuration_to_caps(stream_cfg);
> +		gst_libcamera_framerate_to_caps(state->initControls_, caps, framerate);
> +

It would be interesting to test on  a multistream platform and see if 
you get different framerates for each srcpad / loop iteration? Any ideas 
how should we handle ?

>   		if (!gst_pad_push_event(srcpad, gst_event_new_caps(caps))) {
>   			flow_ret = GST_FLOW_NOT_NEGOTIATED;
>   			break;
> @@ -566,7 +578,7 @@ 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 +588,8 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>   	}
>   
>   done:
> +	state->initControls_.clear();
> +	g_free(container);
>   	switch (flow_ret) {
>   	case GST_FLOW_NOT_NEGOTIATED:
>   		GST_ELEMENT_FLOW_ERROR(self, flow_ret);