Looking at the recommendation of NDI SDK we should keep the orignal behavior :

• Create the receiver (list) when plugin initialize.
• Retrieve the list of found sources when populating the dialog
• Find a way to "force update / refresh" the list of Source detected that does NOT add delay in opening the dialog box.

Ultimately this goes back to some discussions from couple months ago : #1088

Here is what it says about this in the NDI SDK:

It is important to understand that mDNS discovery might take some time to locate all network sources. This means that an ‘early’ return to NDIlib_find_get_current_sources might not include all the sources on the network; these will be added (or removed) as additional or new sources are discovered. It commonly takes a few seconds to discover all sources on a network. https://docs.ndi.video/all/developing-with-ndi/sdk/ndi-find

Waiting is the proper thing to do, otherwise the user will waste time trying to track down connectivity issues including firewalls, when really it was just a matter of waiting.

Also, timing tests have shown that the wait function only waits the full wait time when no new ones were found. On a typical launch of the properties dialog, the wait times were 1ms, 6ms and then 1000ms for the last one.

We could reduce the time down to 500ms, but they say a few seconds is needed. I could also add a refresh source list button and do the proper wait. In any event, I think a lot of problems people are having with the firewall is that we are not waiting long enough for the sources to show up.
Please let me know how to proceed with getting this change in place.

I agree we should allow for some "extra time" whenever possible, but this cannot be at the expense of the UI loading.

Also referring to the documentation :
"For applications that wish to list the current sources in a user interface menu, the recommended approach would be to create an NDIlib_find_instance_t instance when your user interface is opened and then – each time you wish to display the current list of available sources – call NDIlib_find_get_current_sources."

Which is why maintaining the list in "ndi_find" at the plugin level (and not at the source) would make sense.

we can either have a "recurring" check for new source ( in background ), or this to be triggered for "extra check of new source" at different times (a function like "refresh source discovery" ?)

Delaying the UI display because we look for source will impact the user experience and make it look "sluggish". Which is why the "refresh source list" or "detect sources" button would be a preferred option overall.

Suggestion for now :

• implement ndi source finder at plugin level (load with plugin load, destroy at plugin unload)
• Have a function to "refresh the list" that can be called a different places of the plugin.
• Find a good place to call this refresh / wait on sources (even better if this is in the background) > for now we can keep it when launching the dialog box for lack of a better location.

Another option is to spin off a thread to do the waiting and update the properties list. This way the dialog is not delayed, but when or if the user has decided to select a source, the list will be complete. Adding a refresh button would merely spin off the same thread. The thread would end as soon as a complete list is received.

Another option is to spin off a thread to do the waiting and update the properties list. This way the dialog is not delayed, but when or if the user has decided to select a source, the list will be complete. Adding a refresh button would merely spin off the same thread. The thread would end as soon as a complete list is received.

This would be a good option IMHO.

This way:

• list of available source is updated at regular interval
• No delay in the UI

I updated the PR to spin off a thread to wait for all the sources to be located. A new class was created called NDIFinder which has one public method called getNDISourceList. The method will return a list immediately if the list it has is less than 5 seconds old. Otherwise, a thread is created where it waits for all NDI sources to show up, waiting at most 1 second. When no new sources show up, a callback provided in the getNDISourceList call, is called with the list NDI names.

Tested on OBS31.0.3 on MacOS 15.4 / Windows 11 / Ubuntu 24.04 - no issues - assumed good.