[libcamera-devel] [PATCH v6] gstreamer: Added virtual functions needed to support request pads

[paul.elder at ideasonboard.com]

Hi Vedant,

On Sat, Jun 19, 2021 at 12:02:18AM +0530, Vedant Paranjape wrote:
> This patch adds support for using request pads in libcamerasrc Gst
> Element. It allows a user to request multiple streams if the platform
> supports multistream output using libcamera.
> 
> This was tested on Raspberry Pi 4B+ with a camera connected to CSI port.
> It can be tested by running the following command
> 
> gst-launch-1.0 libcamerasrc camera-name="<camera-name-here>" name=src src.src ! queue ! videoconvert ! autovideosink src.src_0 ! queue ! videoconvert ! autovideosink
> 
> Signed-off-by: Vedant Paranjape <vedantparanjape160201 at gmail.com>

Reviewed-by: Paul Elder <paul.elder at ideasonboard.com>

> ---
>  src/gstreamer/gstlibcamerasrc.cpp | 53 ++++++++++++++++++++++++++++++-
>  1 file changed, 52 insertions(+), 1 deletion(-)
> 
> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
> index ccc61590..ea53c2b5 100644
> --- a/src/gstreamer/gstlibcamerasrc.cpp
> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> @@ -361,10 +361,12 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>  	GST_DEBUG_OBJECT(self, "Streaming thread has started");
>  
>  	guint group_id = gst_util_group_id_next();
> +	gint stream_id_num = 0;
>  	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);
> +		g_autofree gchar *stream_id_intermediate = g_strdup_printf("%i%i", group_id, stream_id_num++);
> +		g_autofree gchar *stream_id = gst_pad_create_stream_id(srcpad, GST_ELEMENT(self), stream_id_intermediate);
>  		GstEvent *event = gst_event_new_stream_start(stream_id);
>  		gst_event_set_group_id(event, group_id);
>  		gst_pad_push_event(srcpad, event);
> @@ -640,6 +642,53 @@ gst_libcamera_src_init(GstLibcameraSrc *self)
>  	self->state = state;
>  }
>  
> +static GstPad *
> +gst_libcamera_src_request_new_pad(GstElement *element, GstPadTemplate *templ,
> +				  const gchar *name, [[maybe_unused]] const GstCaps *caps)
> +{
> +	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
> +	g_autoptr(GstPad) pad = NULL;
> +
> +	GST_DEBUG_OBJECT(self, "new request pad created");
> +
> +	pad = gst_pad_new_from_template(templ, name);
> +	g_object_ref_sink(pad);
> +
> +	if (gst_element_add_pad(element, pad)) {
> +		GLibLocker lock(GST_OBJECT(self));
> +		self->state->srcpads_.push_back(reinterpret_cast<GstPad *>(g_object_ref(pad)));
> +	} else {
> +		GST_ELEMENT_ERROR(element, STREAM, FAILED,
> +				  ("Internal data stream error."),
> +				  ("Could not add pad to element"));
> +		return NULL;
> +	}
> +
> +	return reinterpret_cast<GstPad *>(g_steal_pointer(&pad));
> +}
> +
> +static void
> +gst_libcamera_src_release_pad(GstElement *element, GstPad *pad)
> +{
> +	GstLibcameraSrc *self = GST_LIBCAMERA_SRC(element);
> +
> +	GST_DEBUG_OBJECT(self, "Pad %" GST_PTR_FORMAT " being released", pad);
> +
> +	{
> +		GLibLocker lock(GST_OBJECT(self));
> +		std::vector<GstPad *> &pads = self->state->srcpads_;
> +		auto begin_iterator = pads.begin();
> +		auto end_iterator = pads.end();
> +		auto pad_iterator = std::find(begin_iterator, end_iterator, pad);
> +
> +		if (pad_iterator != end_iterator) {
> +			g_object_unref(*pad_iterator);
> +			pads.erase(pad_iterator);
> +		}
> +	}
> +	gst_element_remove_pad(element, pad);
> +}
> +
>  static void
>  gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>  {
> @@ -650,6 +699,8 @@ gst_libcamera_src_class_init(GstLibcameraSrcClass *klass)
>  	object_class->get_property = gst_libcamera_src_get_property;
>  	object_class->finalize = gst_libcamera_src_finalize;
>  
> +	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;
>  
>  	gst_element_class_set_metadata(element_class,
> -- 
> 2.25.1
>