Prior to our technology uplift here is how we got a video feed to the rostrum.
Master feed is from OBS Studio. We installed the NDI Tools package and add on for OBS Studio. Now OBS studio can send an NDI feed. All our buildings have been uplifted to Gbit networking. We placed a computer on the stand that is wired to the network and running NDI Tools Studio Monitor
https://ndi.tv/tools/ The monitor output goes through a HDMI splitter to a projector (optional) and two other monitors on rostrum.
This eliminates all the composite video feeds which do not support HD graphical elements such as videos / ppt presentations in any kind of reasonable resolution.
Post technology uplift. We have an HDMI input and output as well as audio injector on podium. The current plan is to take the video HDMI output from the building distribution system and feed a HDMI splitter to then send program video to the two rostrum monitors.
The SP wants to show a video. We will have a dedicated computer running OBS Studio in the video closet that is attached to the network. The videos are pre-setup as scenes in OBS Studio. Again this computer will output NDI video via the installation of NDI tools. On the stand we will have an Apple TV4K that has TV Stream Monitor for NDI software. The HDMI output from the Apple TV is sent to an HDMI splitter. One branch goes to the projector. The other branch goes to the HDMI input on the podium. Because of how the church AV system is programmed in order to get audio via HDMI to the audio processor we would need the rostrum HDMI channel selected on the Extron presentation switcher. (We are extracting the video from the CP video output to send to an external production switcher.) We cannot do this since we need the switcher set to DP input and consequently we would be blocking the HDMI based audio input. The solution is to run an audio cable from the projector audio output to the podium mounted audio input. (The projector is acting as an HDMI audio de-embedder) The audio then appears to the audio processor as one of the inputs for the main mix. (This probably will make more sense to those with the new Extron/QSC based systems)
The short version is that the church provided a dedicated HDMI feed from and to the podium. Using NDI and the building network we have a third HDMI feed to the podium.