RTSP encoded Stream storage - Using OpenCV/C++

I hope all are doing great.

I am trying to do the RTSP video streaming display as well as storage. as shown in the following figure.

The below Gstreamer pipeline is working fine for the following two task.

1. Capture, decode and display.

2. Capture & store the same stream into a file (without any decoding operation).

   gst-launch-1.0 -e rtspsrc location=rtsp://admin:888888@192.168.5.21:5001/udp/av0_0 ! rtph264depay ! h264parse ! tee name=t ! queue ! omxh264dec ! videoconvert ! queue ! autovideosink sync=false async=false t. ! queue ! mp4mux ! filesink location=out.mp4

Now, In order to process the frames, I have to perform the above similar task in the C++/OpenCV programming,

1. Capture the RTSP encoded video stream, decode and process it.
2. Capture & Store the incoming encoded RTSP video stream into the file without performing decoding operation on it using openCV/C++ programming.

The first task is doable using the OpenCV code shown below.

VideoCapture cap("rtspsrc location=rtsp://admin:888888@192.168.5.21:5001/udp/av0_0 ! rtph264depay ! h264parse ! omxh264dec ! videoconvert ! appsink sync=false async=false",cv::CAP_GSTREAMER);

cap.read(img);
process(img);

• Problem I have tried a couple of ways to do the second task but I could not able to do it.

I have tried the following code that can store the video stream in a file but not able to play stored output.mp4 file due to the wrong storage frames.

cv::VideoCapture cap ("-e rtspsrc location=rtsp://admin:888888@192.168.5.21:5001/udp/av0_0 ! rtph264depay ! h264parse ! tee name=t ! queue ! omxh264dec ! videoconvert ! queue ! appsink t. ! queue  ! filesink location=out.mp4");

cap.read(img);
process(img);
cv::imshow(img);

It would be greatly appreciated if anyone can guide me to do the second task (capture and store the Input encoded stream to a file).