Opencv GStreamer pipeline doesn't work on Raspberry Pi 4 - c++

Question

I'm trying to open UDP stream video in Raspberry Pi using this pipeline:
VideoCapture video("udpsrc port=5600 ! application/x-rtp,payload=96,encoding-name=H264 !"
"rtpjitterbuffer mode=1 ! rtph264depay ! h264parse ! decodebin ! videoconvert ! appsink emit-signals=true sync=false max-buffers=2 drop=true", cv::CAP_GSTREAMER);
// Exit if video is not opened
if(!video.isOpened())
{
cout << "Could not read video file" << endl;
return 1;
}
However, video.isOpened() return false and I couldn't be able to open with this code. This works on loopback test and another Ubuntu 18.04 PC but RPi 4 (Buster OS) couldn't run it. Also following lines can run upcoming gstream video:
gst-launch-1.0 udpsrc port=5600 caps='application/x-rtp, media=(string)video, clock-rate=(int)90000, encoding-name=(string)H264' ! rtph264depay ! h264parse ! avdec_h264 ! autovideosink fps-update-interval=1000 sync=false
Furthermore specific code stack (e.g. [video_udp.cpp][1]) can easily handle video but also it's hard to use with opencv.
NOTE: OpenCV version is 4.2.0-pre

Answer 1

The problem is about using GStreamer library as a plugin of OpenCV. OpenCV doesn't throw exception even you build source code without GStreamer support. (In default, GStreamer library was directly found by Ubuntu, conversely Raspberry Pi 4 couldn't find it.)
Firstly I check build information of OpenCV with std::cout<<cv::getBuildInformation(); in Ubuntu 18.04 machine and found that:
GStreamer: YES (1.14.5)
Also I just check this on Raspberry Pi 4 side and build information was:
GStreamer:NO
Before the build OpenCV I just compare GStreamer plugins with gst-inspect-1.0 command for both of them and I just install some missing plugins like gstreamer1.0-tools . Also I wasn't know the problem, before the checking build information, so I installed some other GStreamer plugins that currently I don't remember.
Lastly, I build system by adding -D WITH_GSTREAMER=ON flag. And now it works well.
I'll edit answer if the problem related to missing plugins those are installed later. For this, I'll check this issue with clean Buster OS image.