Environment:

• vMix (new beta, not tested with version 28)

• All devices configured with static IPs

• NDI Discovery Server in place

Issue:

• When adding an NDI source in vMix, the source sometimes appears as a black image. Adding the same source in the official NDI Studio Monitor on the same computer works correctly, ruling out a network configuration error.

• The issue is resolved only after restarting vMix: The source is shown correctly.

Reproduction Notes:

• Occurs mainly after the encoder is rebooted (not every time).

• NDI Source Discovery (Kane’s tool) shows that the Discovery Server is providing correct data after encoder reboot.

• Studio Monitor consistently displays the source without issue.

Since both vMix and Studio Monitor rely on the same NDI library—and Studio Monitor has no issue—I suspect the following:

Could it be that the NDI source list in vMix is not updated with new data from the discovery server when the source was already detected previously? For example, if the encoder, after reboot, decides to use a new port (or changes its IP when using DHCP).

Thank you for investigation! Best regards, Patrick

Hi,

You're right, it's easy to close and re-open Studio Monitor during testing. That's why I restarted my tests (focusing on using Studio Monitor and vMix in the same way).

And you're right again: I need to revise my statement. The issue is still present, but the behavior of vMix and Studio Monitor is exactly the same. So it’s not a specific vMix issue — rather, it seems to be something the NDI Find library doesn’t handle well.

My findings:

Using mDNS*

• If the encoder advertises its source data with a changed IP or source port, the NDI Find library never updates an earlier discovered source with the new data.

• Reconnecting to this source results in a black frame.

• NDI Source Discovery (Kane's tool) shows the correct (new) mDNS data.

Using Discovery Server*

• If the encoder advertises its source data with a changed IP or source port, the source device disappears from the NDI Find list after about a minute and never returns.

• Reconnecting to this source is no longer possible.

• NDI Source Discovery (Kane's tool) initially shows two entries with the same name. After about a minute, the older entry is removed and only the newer one remains on the Discovery Server. At the same time, NDI Find no longer reports this device.

*Because the issue only appears sometimes, I forced it by manually changing the encoder’s IP address.

It seems that NDI Find does not handle this edge case properly. I will report this to NDI support.

In my opinion, NDI Find should always update a source with its current data and report this to applications like vMix and Studio Monitor. I don’t expect already connected sources to switch automatically, but at the very least a manual reconnect should work.

Definitely not a vMix problem - but probably something to consider in OMT discovery process.

Thank you, best regards,
Patrick