[libcamera-devel] [RFC PATCH v2] gstreamer: Factor out _pad_push_stream_start from _task_enter

[paul.elder at ideasonboard.com]

Hi Vedant,

On Mon, Aug 02, 2021 at 12:21:44AM +0530, Vedant Paranjape wrote:
> This patch creates gst_libcamera_pad_push_stream_start function to
> create stream id and to push the stream start.
> 
> Update functional code in gst_libcamera_src_task_enter(), which creates
> stream id and pushes the stream start with the refactored
> function gst_libcamera_pad_push_stream_start().

The code looks better than before, but I'm not quite seeing the
rationale. Why is this change important? Perhaps you told me before, but
the "why" is what should be in the commit message, so that reviewers can
see. To some extent, the "what" isn't as important, since the reviewer
can simply read the patch (though it is useful when the patch is long
and complex).


Paul

> 
> Signed-off-by: Vedant Paranjape <vedantparanjape160201 at gmail.com>
> ---
>  src/gstreamer/gstlibcamerapad.cpp | 19 +++++++++++++++++++
>  src/gstreamer/gstlibcamerapad.h   |  2 ++
>  src/gstreamer/gstlibcamerasrc.cpp |  7 +------
>  3 files changed, 22 insertions(+), 6 deletions(-)
> 
> diff --git a/src/gstreamer/gstlibcamerapad.cpp b/src/gstreamer/gstlibcamerapad.cpp
> index c00e81c8..d4211050 100644
> --- a/src/gstreamer/gstlibcamerapad.cpp
> +++ b/src/gstreamer/gstlibcamerapad.cpp
> @@ -20,6 +20,7 @@ struct _GstLibcameraPad {
>  	GstLibcameraPool *pool;
>  	GQueue pending_buffers;
>  	GstClockTime latency;
> +	gint stream_id_num;
>  };
>  
>  enum {
> @@ -81,6 +82,7 @@ static void
>  gst_libcamera_pad_init(GstLibcameraPad *self)
>  {
>  	GST_PAD_QUERYFUNC(self) = gst_libcamera_pad_query;
> +	self->stream_id_num = 0;
>  }
>  
>  static GType
> @@ -155,6 +157,23 @@ gst_libcamera_pad_get_stream(GstPad *pad)
>  	return nullptr;
>  }
>  
> +void
> +gst_libcamera_pad_push_stream_start(GstPad *pad, const guint group_id)
> +{
> +	auto *self = GST_LIBCAMERA_PAD(pad);	
> +	{
> +		GLibLocker lock(GST_OBJECT(self));
> +		self->stream_id_num++;
> +	}
> +
> +	g_autoptr(GstElement) element = gst_pad_get_parent_element(pad);
> +	g_autofree gchar *stream_id_intermediate = g_strdup_printf("%i%i", group_id, self->stream_id_num);
> +	g_autofree gchar *stream_id = gst_pad_create_stream_id(pad, element, stream_id_intermediate);
> +	GstEvent *event = gst_event_new_stream_start(stream_id);
> +	gst_event_set_group_id(event, group_id);
> +	gst_pad_push_event(pad, event);
> +}
> +
>  void
>  gst_libcamera_pad_queue_buffer(GstPad *pad, GstBuffer *buffer)
>  {
> diff --git a/src/gstreamer/gstlibcamerapad.h b/src/gstreamer/gstlibcamerapad.h
> index 779f2d13..7693374f 100644
> --- a/src/gstreamer/gstlibcamerapad.h
> +++ b/src/gstreamer/gstlibcamerapad.h
> @@ -26,6 +26,8 @@ void gst_libcamera_pad_set_pool(GstPad *pad, GstLibcameraPool *pool);
>  
>  libcamera::Stream *gst_libcamera_pad_get_stream(GstPad *pad);
>  
> +void gst_libcamera_pad_push_stream_start(GstPad *pad, const guint group_id);
> +
>  void gst_libcamera_pad_queue_buffer(GstPad *pad, GstBuffer *buffer);
>  
>  GstFlowReturn gst_libcamera_pad_push_pending(GstPad *pad);
> diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
> index b18f1efb..bb8ea07a 100644
> --- a/src/gstreamer/gstlibcamerasrc.cpp
> +++ b/src/gstreamer/gstlibcamerasrc.cpp
> @@ -361,15 +361,10 @@ gst_libcamera_src_task_enter(GstTask *task, [[maybe_unused]] GThread *thread,
>  
>  	GST_DEBUG_OBJECT(self, "Streaming thread has started");
>  
> -	gint stream_id_num = 0;
>  	StreamRoles roles;
>  	for (GstPad *srcpad : state->srcpads_) {
>  		/* Create stream-id and push stream-start. */
> -		g_autofree gchar *stream_id_intermediate = g_strdup_printf("%i%i", state->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, state->group_id_);
> -		gst_pad_push_event(srcpad, event);
> +		gst_libcamera_pad_push_stream_start(srcpad, state->group_id_);
>  
>  		/* Collect the streams roles for the next iteration. */
>  		roles.push_back(gst_libcamera_pad_get_role(srcpad));
> -- 
> 2.25.1
>