Unable to view RTSP(UDP) streaming over OpenVPN

[qussungtn]

Dear all,

I am able to view RTSP streaming over TCP (by choosing "use RTSP over TCP" from Demuxers)
But it is not possible to view RTSP streaming over UDP.
I checked Wireshark and confirmed that UDP packets are coming.
I believe that open VPN configuration is okay because I could get udp packets properly.

In the same local network without VPN connection, there was no issue with viewing RTSP streaming over UDP.
I compared the UDP packet from both cases (VPN, local network).
Both the UDP packet looks almost the same (ports numbers are different).

I cannot understand why only RTSP over TCP is working in a VPN connection.
I searched for the information a lot but I couldn't figure it out.

Can you give an advice on this issue?

best regards
Seongsu