[libcamera-devel] [PATCH v3] gstreamer: Implement element EOS handling

[Umang Jain]

Hi Jalso,

Thank you for the patch.

On 11/14/23 5:48 PM, Jaslo Ziska via libcamera-devel wrote:
> This commit implements EOS handling for events sent to the libcamerasrc
> element by the send_event method (which can happen when pressing
> Ctrl-C while running gst-launch-1.0 -e, see below). EOS events from
> downstream elements returning GST_FLOW_EOS are not considered here.
>
> To archive this add a function for the send_event method which handles
> the GST_EVENT_EOS event. This function will set an atomic to the
> received event and push this EOS event to all source pads in the running
> task.
>
> Also set the GST_ELEMENT_FLAG_SOURCE flag to identify libcamerasrc as a
> source element which enables it to receive EOS events sent to the
> (pipeline) bin containing it.
> This in turn enables libcamerasrc to for example receive EOS events from
> gst-launch-1.0 when using the -e flag.
>
> Bug: https://bugs.libcamera.org/show_bug.cgi?id=91
> Signed-off-by: Jaslo Ziska <jaslo at ziska.de>
> Acked-by: Nicolas Dufresne <nicolas.dufresne at collabora.com>

I will test this on my RPi 4b and merge this today.

Reviewed-by: Umang Jain <umang.jain at ideasonboard.com>


> ---
> Thanks for all the advise on v2 everyone!
>
> In this revision I explain which EOS events are handled in the commit message a little bit more and link to the bug report.
>
> As recommended, g_autoptr is now used. I decided to declare g_autoptr(event) outside of the if-statement for now, I was not sure what the consensus on this is at the moment.
>
> Regards,
>
> Jaslo
>
>   src/gstreamer/gstlibcamerasrc.cpp | 36 ++++++++++++++++++++++++++++++-
>   1 file changed, 35 insertions(+), 1 deletion(-)
>
> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
> index 63d99571..767017db 100644
> --- a/src/gstreamer/gstlibcamerasrc.cpp
> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> @@ -9,7 +9,6 @@
>   /**
>    * \todo The following is a list of items that needs implementation in the GStreamer plugin
>    *  - Implement GstElement::send_event
> - *    + Allowing application to send EOS
>    *    + Allowing application to use FLUSH/FLUSH_STOP
>    *    + Prevent the main thread from accessing streaming thread
>    *  - Implement renegotiation (even if slow)
> @@ -29,6 +28,7 @@
>
>   #include "gstlibcamerasrc.h"
>
> +#include <atomic>
>   #include <queue>
>   #include <vector>
>
> @@ -144,6 +144,8 @@ struct _GstLibcameraSrc {
>   	gchar *camera_name;
>   	controls::AfModeEnum auto_focus_mode = controls::AfModeManual;
>
> +	std::atomic<GstEvent *> pending_eos;
> +
>   	GstLibcameraSrcState *state;
>   	GstLibcameraAllocator *allocator;
>   	GstFlowCombiner *flow_combiner;
> @@ -397,6 +399,14 @@ gst_libcamera_src_task_run(gpointer user_data)
>
>   	bool doResume = false;
>
> +	g_autoptr(GstEvent) event = self->pending_eos.exchange(nullptr);
> +	if (event) {
> +		for (GstPad *srcpad : state->srcpads_)
> +			gst_pad_push_event(srcpad, gst_event_ref(event));
> +
> +		return;
> +	}
> +
>   	/*
>   	 * Create and queue one request. If no buffers are available the
>   	 * function returns -ENOBUFS, which we ignore here as that's not a
> @@ -747,6 +757,27 @@ gst_libcamera_src_change_state(GstElement *element, GstStateChange transition)
>   	return ret;
>   }
>
> +static gboolean
> +gst_libcamera_src_send_event(GstElement *element, GstEvent *event)
> +{
> +	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
> +	gboolean ret = FALSE;
> +
> +	switch (GST_EVENT_TYPE(event)) {
> +	case GST_EVENT_EOS: {
> +		g_autoptr(GstEvent) oldEvent = self->pending_eos.exchange(event);
> +
> +		ret = TRUE;
> +		break;
> +	}
> +	default:
> +		gst_event_unref(event);
> +		break;
> +	}
> +
> +	return ret;
> +}
> +
>   static void
>   gst_libcamera_src_finalize(GObject *object)
>   {
> @@ -779,6 +810,8 @@ gst_libcamera_src_init(GstLibcameraSrc *self)
>   	state->srcpads_.push_back(gst_pad_new_from_template(templ, "src"));
>   	gst_element_add_pad(GST_ELEMENT(self), state->srcpads_.back());
>
> +	GST_OBJECT_FLAG_SET(self, GST_ELEMENT_FLAG_SOURCE);
> +
>   	/* C-style friend. */
>   	state->src_ = self;
>   	self->state = state;
> @@ -844,6 +877,7 @@ gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>   	element_class->request_new_pad = gst_libcamera_src_request_new_pad;
>   	element_class->release_pad = gst_libcamera_src_release_pad;
>   	element_class->change_state = gst_libcamera_src_change_state;
> +	element_class->send_event = gst_libcamera_src_send_event;
>
>   	gst_element_class_set_metadata(element_class,
>   				       "libcamera Source", "Source/Video",
> --
> 2.42.1