Remote teaching and seminars with OBS

A scene from my department job talk

Background

Like most grad students entering the job market this year, I’ve had to wrestle with the transition to giving talks remotely. Personally, I have some trouble focusing on virtual seminars since the format tends to be fairly static: mostly still slides with perhaps a camera window to the side. To avoid this, I’ve spent a fair amount of time (read: procrastinating) trying to put together a setup that allows me to move around and interact with my materials a bit more. Below, I outline an approach that’s worked reasonably well for me.

Since I’m not teaching this semester, I’ve mostly focused on how to adapt an academic seminar to a remote setting, but I would use a variation of this for remote teaching given the opportunity.

I set out to replicate three particular aspects of in-person seminars/teaching:

  1. The ability to easily handwrite equations/graphs on a blackboard,
  2. The ability to draw attention to certain parts of a slide or blackboard, whether by laser pointer or physically pointing, and
  3. The ability to move and gesture while speaking.

For all of this, I’m indebted to the work of others who took time to experiment with different methods for remote teaching/seminars and create guides. In particular,

Hardware

Needed harware:

  • A computer (obviously): a relatively recent Mac would work best, but isn’t required (My main desktop runs Linux)
  • A good camera
  • A tablet with stylus (iPad with Apple Pencil)
  • A green screen and some way to hold it up
  • A second monitor is a big plus

I can’t overstate the importance of a good camera. If you have a reasonably modern digital camera, there’s a good chance it can send a video feed over usb to a computer. I use a Nikon D5500 that I normally use for bird photography, but you almost certainly have a pretty good webcam already available to you: a smart phone. Prior to rigging up my Nikon, I simply used my smartphone on a cheap gooseneck clamp using a free app called Droidcam. A wider angle lens is a big plus here to give yourself more room to move around without having to stand too far back.

Even with a good camera, you need to be extremely well lit to get a good image (and to get a good green screen effect). I use three lamps each with some cheap 1500 lumen LED bulbs.

For the microphone, so long as you don’t use your laptop’s built in-mic, I don’t think the microphone is that important. The inline mic in most earbuds works reasonably well, but it might be worth spending a little bit on the mic. I use a Blue Yeti which works well enough (as a condenser mic, it works reasonably well even sitting a bit back from it), but if I had to do it again, I probably would have gotten a cheap lav mic.

Of course, to put yourself in the same scene with slides, there’s not much substitute for a proper green screen. I got a cheap one on Amazon for under $20, but be aware that the cheap screens come folded and need steam-ironing to remove the creases. Ideally, you’ll have a wall behind you to mount it, but otherwise you’ll need some kind of stand (which will add some expense).

Lastly, you’ll need some way to write easily. For me, that means an iPad with the Apple Pencil. You will also need some way to get the video feed from the tablet into your computer.

Finally, it’s extremely useful (though not necessary) to have at least one extra monitor so you can have the chat window and participants’ videos visible separately.

Room setup

A very messy desk set up for presenting

I sit on a bar stool about 1.5 meters back from my camera in the left third of the camera’s field of view. This leaves most of the camera’s field of view as empty green screen that I can fill with the slides and gesture over. In the image below showing the OBS setup, the red box is the extent of the area I can gesture in. My camera lens is fairly wide (28mm full-frame equivalent, roughly an 80 degree field of view). If you’re using a narrower camera angle—most smart phones are probably closer to 60 degrees—you’d have to sit farther back from the camera to get a similar effect. If you’re considering buying a webcam, look for one with a wider field of view.

Since I’m sitting so far back from my desk, I also use a small table for my iPad, and I adjust my microphone to be as close as possible.

Where I sit

Software

Needed software

  • OBS
  • Virtual Cam Extension for OBS (Windows, Mac, Linux)
  • PDF software of choice on for the tablet (I use Readdle Documents on the iPad)
  • Some way to get the video feed from the tablet to the computer (see below)

OBS setup

OBS Scene arrangement

Since many others have given excellent tutorials on how to use OBS (see Luke Stein’s tutorial linked above), I’ll skip the details of the setup and jump straight to the scene arrangement.

My primary scene in OBS has three sources:

  1. Webcam input, with Chroma Key (green screen) filter applied, and with the image reflected (so I can more easily see where I’m “pointing”)
  2. Flat color as a background (black worked best for me)
  3. Video input from my iPad (see below)

In order to make better use of the space in the OBS canvas, I also adjusted the aspect ratio of my beamer slides to be a bit more square (12x10 worked will for me). This can be accomplished using the beamerposter package:

\usepackage[orientation=landscape,size=custom,width=12,height=10,scale=0.5,debug]{beamerposter}

Video input from tablet

The biggest challenge of all this was finding a way to mirror my iPad’s display to my desktop so OBS could use it. If you have a relatively recent Mac, this is easy since recent Macs and iPads by default support a system called Sidecar that allows you to use your iPad as a second screen (with touch support) for your Mac.

Since my main desktop isn’t a Mac, I settled on using Apple’s Airplay protocol to wirelessly mirror my iPad display to my desktop; however, this isn’t supported by default (Airplay is meant to mirror to a device like an AppleTV). Fortunately, with appropriate software, a regular computer can become an Airplay receiver. On Linux, this can be accomplished with an open source tool called UxPlay. I know similar software exists for Windows, but all options I saw were paid software, so I’m hesitant to recommend one in particular without trying them first.

Zoom setup

Finally, we just need to get everything into Zoom. There’s two ways to do this, each with it’s own advantages.

Webcam

The most straightforward method is to simply use the OBS virtual cam extension (link above). Within Zoom, I’d recommend specifically “spotlighting” your camera so the view doesn’t switch to another person’s camera when they speak.

Besides simplicity, this method is pretty much sure to work even if you’re not using Zoom (say, Skype or Blackboard Collaborate)—so long as whatever system you’re using supports a webcam.

The main issue I had with this method is that Zoom’s compression can make the slide text difficult to read at times unless the internet connection for everyone is absolutely perfect.

This method also has the advantage that it’s likely to work with other software such as Skype or Blackboard Collaborate.

Screen sharing

I eventually settled on using the Screen Share feature with the “optimize for video” setting enabled.

First, I create a window with the OBS canvas output (right click on the OBS canvas -> Fullscreen projector). I then share this window with Zoom. Once screen sharing, I then disable my webcam in zoom to avoid duplicate images.

This method mostly fixes the blurry text issue. Unfortunately, the video feed can lag the audio a bit which can be distracting for the viewers. This lag is somewhat unpredictable; in one of my practice talks it was apparently up to a second, and in my final department talk it wasn’t much of an issue at all. Your mileage may vary.

I haven’t tested this method with non-Zoom conference software, but I wouldn’t expect it to work well there. It seems like most software uses a compression optimized for relatively static scenes for screen sharing, so movement would likely appear very choppy to viewers. It only works in Zoom because of Zoom’s “optimize for video option” for screen sharing.

The final result

The final result

Overall, the whole setup is a bit of a house of cards, but it mostly replicated what I felt were the most important aspects of in-person talks.

Although I haven’t had a chance to use this for teaching yet, I expect things would work similarly well, either using a note-taking app on the iPad for a pure “chalk-and-talk” sort of lecture or using a hybrid approach mixing slides with handwriting.

Update: Some extra considerations

One thing I forgot to mention: before trying any of this in an actual talk, it’s very important to test it out with other people. You can’t see exactly how Zoom or whatever software you’re using compresses the video, so it’s important to check with other people whether the material you’re showing is legible to others.

Also, as I mentioned a bit before, the exact way Zoom handles video can be a bit unpredictable, so it’s good to be prepared with a backup option in case things unexpectedly go wrong. In my case, I have a backup “Scene Collection” in OBS that is a more traditional arrangement of the slides with a smaller camera overlay in the corner, and in an emergency I can switch to that in about a minute.

Avatar
Gary Baker

I’m an economic theory grad student at UW–Madison. I am currently (Spring 2021) on the job market.