I'm a bit confused here, if you are talking about the flow in your image I quoted (the one using the big buck bunny public link) with the ffmpeg command in an exec node, it worked fine but that is a very small image, It seemed to work with my Lorex rtsp stream, although the HD image choked the image-output node.
My statement about not being a general solution is based on the errors/warnings thrown by the various rtsp stream reading methods.
I've come to the conclusion that this is an interaction with the stream sources (cameras, dvrs etc) and the stream URL reader. It seems if you can view the stream for a few minutes in some version of VLC, the straight from China camera makers deem that "it works".
I will try two of my Onvif rtsp URLs in this flow, I'll put a debug node on the exec stderr and see what happens and follow-up. Both are HD (720p, 1080p) so I know the image output will "choke". I can try duplicating it and running both streams at once.
Why do you think I don't like the flow? Its nice to have options, I'm here more for getting a good display from node red in a web page (dashboard or whatever), learning about other input possibilities is welcome for potential future projects, but using openCV Python bindings are pretty compelling for me at the moment.
If node red is running a single threaded event loop I'd expect problems with multiple streams, but if each exec node spawns a separate thread/process performace could be similar. Until we find a node-red image viewer with the performance similar to openCV highgui module it might be impossible to verify.
I didn't know about your big buck bunny public stream -- its great for these discussions/experiments, I had no luck with Google, but do you know of a public URL with higher resolution -- at least D1 (704x480)?
Since the AI input is resized ~300x300 (depending on the model) I've found D1 or 720p to be about the optimum, the 1080p images miss people walking by in the upper third of the frame (not really a problem for my purposes), but the 1080p images also offer an option to crop the image which can keep me off ladders to adjust the cameras (why PTZ would rock if the cameras weren't 4X+ more expensive that what I have now, PT is of course acceptable for fixed lens cameras)
