gstreamer: Add GstVideoMeta support

GStreamer video-info calculated stride and offset may differ from
those used by the camera.

For stride and offset mismatch, this patch adds video meta to buffer
if downstream supports VideoMeta through allocation query. Otherwise,
create a internal VideoPool using the caps, and copy video frame to
this system memory.

Signed-off-by: Hou Qi <qi.hou@nxp.com>
Reviewed-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Tested-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>

src/gstreamer/gstlibcamerapool.cpp

@@ -134,8 +134,20 @@ gst_libcamera_pool_class_init(GstLibcameraPoolClass *klass)
 						     G_TYPE_NONE, 0);
 }
 
+static void
+gst_libcamera_buffer_add_video_meta(GstBuffer *buffer, GstVideoInfo *info)
+{
+	GstVideoMeta *vmeta;
+	vmeta = gst_buffer_add_video_meta_full(buffer, GST_VIDEO_FRAME_FLAG_NONE,
+					       GST_VIDEO_INFO_FORMAT(info), GST_VIDEO_INFO_WIDTH(info),
+					       GST_VIDEO_INFO_HEIGHT(info), GST_VIDEO_INFO_N_PLANES(info),
+					       info->offset, info->stride);
+	GST_META_FLAGS(vmeta) = (GstMetaFlags)(GST_META_FLAGS(vmeta) | GST_META_FLAG_POOLED);
+}
+
 GstLibcameraPool *
-gst_libcamera_pool_new(GstLibcameraAllocator *allocator, Stream *stream)
+gst_libcamera_pool_new(GstLibcameraAllocator *allocator, Stream *stream,
+		       GstVideoInfo *info)
 {
 	auto *pool = GST_LIBCAMERA_POOL(g_object_new(GST_TYPE_LIBCAMERA_POOL, nullptr));
 
@@ -145,6 +157,7 @@ gst_libcamera_pool_new(GstLibcameraAllocator *allocator, Stream *stream)
 	gsize pool_size = gst_libcamera_allocator_get_pool_size(allocator, stream);
 	for (gsize i = 0; i < pool_size; i++) {
 		GstBuffer *buffer = gst_buffer_new();
+		gst_libcamera_buffer_add_video_meta(buffer, info);
 		pool->queue->push_back(buffer);
 	}