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SDP Stripping in Nx 6.1: RTSP Proxy omits rtpmap and fmtp for Generic RTSP devices

Completed
Eylon Cohen

Hi Nx Team,

We are currently migrating our system from Nx Witness v5.1 to v6.1.1.42624, and we’ve encountered a significant issue regarding the RTSP Proxy behavior (port 7001) for 3rd-party integrations.

The Setup: Our 3rd-party application consumes streams using the standard Nx RTSP format (using digest auth embedded in the url as well): rtsp://<Server_IP>:7001/<Camera_ID>

The Problem: Since the upgrade to v6.1, 3rd-party clients (VLC, ffprobe, and our internal apps) fail to decode the stream from our custom RTSP cameras. The common error is: live555 error: Unknown codec name for RTP payload type 96

Technical Analysis & Logs: We performed a side-by-side comparison of the SDP (Session Description Protocol) returned by the camera vs. the one proxied by the Nx Server:

  1. Directly from Camera: The SDP is valid and includes the necessary mapping:
    • m=video 0 RTP/AVP 96
    • a=rtpmap:96 H264/90000
    • a=fmtp:96 packetization-mode=1;sprop-parameter-sets=...
  2. Via Nx Proxy (Port 7001): The server seems to "swallow" or strip the mapping lines. The proxied SDP only contains:
    • m=video 0 RTP/AVP 96
    • a=control:trackID=0 (Crucial rtpmap and fmtp lines are missing).

Steps Taken:

  • We verified the camera's SDP is compliant using ffprobe.
  • We used the REST API v3 to explicitly set "proxyViaServer": true for the device.
  • We deleted and re-added the device to clear any metadata cache.
  • Note: Adding ?codec=h264 to the URL manually works, but this is not a viable long-term solution for our integration as we require the server to provide a standard-compliant SDP.

Questions:

  1. Is this a known behavior or a bug in the v6.1 RTSP Proxy engine regarding Generic RTSP devices?
  2. Is there a specific configuration (via API or Server settings) to disable this SDP "sanitization" and force the server to pass the original rtpmap attributes?
  3. Are there any planned patches to address SDP transparency for 3rd-party resource proxying?

Looking forward to your insights.
Thank you.

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Comments

2 comments

Date Votes
  • Ichiro
    • Network Optix team

    Hi Cohen,

    Thank you for your report.

    We have created an internal ticket for this issue, and it appears to be a potential problem. 

    Our team is currently investigating, and we will get back to you as soon as we have more information. Please also keep an eye on your inbox for any ticket notifications.

    Once a solution is confirmed, we will share an update here so everyone can apply the necessary changes. Thank you for your support and for bringing this to our attention.

    0
  • Ichiro
    • Network Optix team

    This issue has been fixed in Nx Witness v6.1.3 (released date TBC, likely 2026/July)

    0

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