I'm a newbie... so take that into account when considering the following
In OBS, within a given Scene are sources.. you can have multiple sources, and enable/disable them individually
In OBS, the source list has implications in terms of order. The sources higher up with be 'on top' of other sources
So you could simply have you "Image" source higher up in Source list, so that when Image source turned on, would be atop the video image (covering entirely if so configured)
- be aware, in that scenario, I think the underlying video would still be rendered/processed (ie CPU & GPU load..)
I suspect there are better ways... hopefully if you confirm this is the type of thing you are looking for, someone more knowledgeable than I will possibly advise if there is a better way to do this.
*if* you are CPU/GPU constrained, you could then (either Studio Mode or separate scene) resize the video to minimize it and associated resource consumption (not sure can be hidden altogether to eliminate ALL overhead of processing... ?? sorry not a aspect of OBS I've played with)
I my case, I have separate scenes, and then I resize the 'Source' as desired with per Scene. I don't use Studio Mode (no need in my usage pattern). Each scene I re-frame/re-position the video according to my needs. I have a PowerPoint window to one side of the canvas... and if the Text content in the PPT page is limited, I'll shift the text box to the side, and enlarge the video 'frame'. I then switch scenes leaving the PPT on the screen/canvas (usually, unless full frame pre-recorded video to play) [PPTx is lowest in my Source list] and then switch scenes which have different sources ... live video feed and pre-recorded videos {pre-recorded for COVID-19 safety/physical distancing reasons to not have them be live as well}
I hope this gives you some ideas and helps
