[PATCH] gstreamer: Add GstVideoMeta support

[Hou Qi]

This change is to provide correct stride and offset for downstream
plugin who needs GstVideoMeta when camera is connected to waylandsink
or others.

Without GstVideoMeta, waylandsink uses video-info calculated stride and
offset to create wlbuffer. The calculated stride is 4 aligned with width.
While camera stride got from driver reported bytesperline maybe the
same size with width. There will be mismatch between camera output
buffer and wlbuffer if camera generated size is not 4 aligned for
multi-plane formats such as NV12 and NV16. It causes display abnormal.
---
 src/gstreamer/gstlibcamerasrc.cpp | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/src/gstreamer/gstlibcamerasrc.cpp b/src/gstreamer/gstlibcamerasrc.cpp
index 912a8d55..c357dda1 100644
--- a/src/gstreamer/gstlibcamerasrc.cpp
+++ b/src/gstreamer/gstlibcamerasrc.cpp
@@ -285,10 +285,30 @@ int GstLibcameraSrcState::processRequest()
 	GstFlowReturn ret = GST_FLOW_OK;
 	gst_flow_combiner_reset(src_->flow_combiner);
 
-	for (GstPad *srcpad : srcpads_) {
+	for (gsize i = 0; i < srcpads_.size(); i++) {
+		GstPad *srcpad = srcpads_[i];
 		Stream *stream = gst_libcamera_pad_get_stream(srcpad);
 		GstBuffer *buffer = wrap->detachBuffer(stream);
+		StreamConfiguration &stream_cfg = src_->state->config_->at(i);
+		GstVideoInfo info;
+		g_autoptr(GstCaps) caps = gst_pad_get_current_caps(srcpad);
 
+		if (!gst_video_info_from_caps(&info, caps)) {
+			GST_WARNING("Failed to create video info");
+		} else {
+			guint k, stride;
+			gsize offset = 0;
+			for (k = 0; k < GST_VIDEO_INFO_N_PLANES(&info); k++) {
+				stride = gst_video_format_info_extrapolate_stride(info.finfo, k, stream_cfg.stride);
+				info.stride[k] = stride;
+				info.offset[k] = offset;
+				offset += stride * GST_VIDEO_FORMAT_INFO_SCALE_HEIGHT(info.finfo, k, GST_VIDEO_INFO_HEIGHT(&info));
+			}
+			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);
+		}
 		FrameBuffer *fb = gst_libcamera_buffer_get_frame_buffer(buffer);
 
 		if (GST_CLOCK_TIME_IS_VALID(wrap->pts_)) {
-- 
2.34.1