A "video poster presentation" sounds like a logical impossibility, but now that conferences are online, they seem to be a thing. What makes one effective? How is this different from a recorded conference talk? What makes for good content?
First, this answer isn't based on experience of creating such things, but just on general principles. I assume that you want an audience to actually watch the video to the end and that what you have to say isn't so earth shatteringly novel and important that they naturally will. But also, I assume that what you want to say has value in itself, though more for some than others.
First, I think you have about 15 seconds at the start of the presentation to answer the viewers question "Should I continue with this or not?" But the answer has to be obvious from the presentation, rather than just saying outright "This is why you should watch." If you aren't immediately compelling, people will hit the "next" button. It isn't like a class where students are forced to sit and watch.
The last 15 seconds are probably also very important so that people have a succinct message to carry away - make it memorable.
Talking heads are boring. A video has an advantage over a live talk, of course, since interested watchers can hit rewind if they miss a point, but still, do something to avoid the talking head issue. An overly pedantic presentation will probably also induce watchers to move on.
I assume that the most interested people will have some way to contact you after the presentation so that you can get follow up. The format suggested by walkar in a comment sounds like it might be very good, so that people can ask questions after viewing and possibly get some synergy going. But I also assume you don't have control over format.
I'd suggest, actually, that you take some inspiration from an early science oriented TV show intended for children: Watch Mr. Wizard. It was a half hour of simple science done live. The wikipedia article points to some similar things that this show inspired. Some of the shows are available on [YouTube[(https://www.youtube.com/results?search_query=Mr.+Wizard). And note that by using another person, in this case a youngster, as an assistant, Don Herbert avoids the talking head problem. You can have a "conversation" with an assistant that you can't have with the audience.
Background: I'm an old guy with hearing problems. I don't watch TV or depend on video much. When I do, I'm looking for visual impact and am quick to move on if the presentation starts out too slowly or gets boring. On the other hand, I'm interested in lots of things. If you catch me early, I might stick around. I don't need to take notes anymore, so won't, but a clear message about the key insight (the last few seconds) will stick with me and make you memorable.
Oh, and I never missed an episode of Mr. Wizard.
Online poster presentations are displayed on a small screen. Usually the user interface makes it hard or impossible to zoom and scroll. Therefore, poster graphical design does not work. Instead, large fonts and a much smaller number of images should be used. Essentially, the poster should look like a slide instead of a poster.