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I have an issue to view RTSP streaming over UDP in the open VPN connection. Our project is to integrate 360 degree IP camera in unity system. And we want to get the UDP streaming rather than TCP to reduce latency. However, we have an issue with streaming over UDP as below.

  1. In the local network

    • both TCP and UDP connection is okay. I can view the RTSP streaming over both protocol.
  2. In the openVPN

    • I could get both TCP and UDP packets from client side(unity pc)
    • But I can view RTSP streaming over only TCP.
    • When I tried to viwe RTSP streaming over UDP, I am getting "buffer deadlock prevented error". VLC plays videos but there is no contents inside.
  3. check wireshark.

    • RTSP default port number is 554 for both TCP and UDP and I set it as 554.
    • TCP source port is 554.
    • UDP souce port(RTSP server) is not 554 but random numbers in both cases (local network and via VPN).
    • I set the url in vlc as " rtsp://192.168.1.30:554".

RTSP OVER TCP - from wireshark

RTSP OVER UDP - from wireshark

4: Questions.

  • In the local network, even though UDP source port is not 554 but random ports. It was possible to view streaming over UDP. it is very weird for me because I set url with 554 port.

  • In the VPN connection, UDP source port is not 554 and causes an error(buffer deadlock prevented). I think VPN configuration is not an issue because I can receive both TCP and UDP packets.

  • I checked the meaning of "buffer deadlock prevented error" from vlc forum. "It means the decoder wants more data in before it can give data out, but at the same time, the flow control wants the decoder to output something before it allows more data in. To break the deadlock, VLC will turn then off flow control and allow data in" I think the problem is from our home network bandwidth. I set two subnet in my home network for VPN test. If streaming has no problem in the local network, it has to work also in the VPN connection.

I need your advice on this issue. best regars

Seongsu

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