Seemingly every conference due to take place this year has either been cancelled or will be run virtually due to the COVID-19 pandemic. Many organisers have decided that running entirely live virtual programmes causes more trouble than it’s worth (e.g. due to unforseeable IT and internet issues disrupting the schedule), and so are asking their presenters to prerecord their talks, which are then broadcast “live” on the day.

I recently “presented” two virtual prerecorded talks at the ISMB conference using Open Broadcast Software Studio (OBS Studio), a free open-source software package most commonly used by live-streamers on Twitch and Youtube. It is super simple to use and achieves a professional output, with video overlaying a presentation slide deck/poster PDF. This blog is a “how-to” on getting started with OBS for conference talks/poster presentations.

Step 1. Download the appropriate OBS Studio client for your operating system from obsproject.com [This guide will be written from the perspective of the Windows download & Windows software, e.g. full Microsoft Powerpoint]

Step 2. Prepare your presentation or poster for streaming. The key thing here is that either document appears in its own window, which allows us to use OBS’ “window capture” feature later.
(a) Poster: Open your poster as a PDF in its own window using Adobe Acrobat
(b) Presentation: This is slightly more involved; instead of Powerpoint displaying your presentation full-screen, what you want is for it to be displayed in a separate window. The way to do this in full Microsoft Powerpoint is to go to the “Slide Show” tab, and select “Set Up Slide Show”. In this new window, change the radio button from “Presented by a speaker (full screen)” to “Browsed by an individual (window)”. Finally, click “From Beginning” in the Slide Show tab to cause the presentation to pop-up in its own window.

Step 3: Configuring OBS to display your front camera over a poster/slide deck.
(a) Open OBS Studio. It will look like this:

(b) Add the powerpoint/poster source. In the bottom-left corner of the Sources box, click the “+” button and select “Window Capture“. Rename as appropriate, e.g. “Conference Slides”.

In the next pop-up, use the Window drop-down menu to select the appropriate “POWERPNT.EXE” window. If you’re presenting a poster, this will be your Adobe window.

Now resize the presentation by clicking and dragging the red box diagonally to the bottom-right and clicking and dragging the box to re-center it. The aim is to get the white Powerpoint slide background to fit snuggly in the OBS black box.

(c) To overlay your front camera, we need to add a new source. Click the “+” button at the bottom-left of the Sources box and this time click Video Capture Device. Rename the input “Front Camera” or whatever you fancy. *Ensure your camera is not being used by any other application, or it won’t show up properly!* If the camera is being displayed in the OBS window, click OK to the next menu accepting all the defaults. Otherwise click the “Device” drop-down and select the correct camera input.

Now resize your front camera in the same way as the slide deck/poster. First click it to ensure you’ve got the camera window selected, then click and drag the red corner box diagonally downwards. Reposition the camera wherever you want it to display relative to your presentation by clicking and dragging.

(d) You’re almost there! You can check that the audio feed is coming from the correct microphone by right-clicking the Mix/Aux text in the Audio Mixer box and selecting “Properties”. Another drop-down allows you to specify which input audio device should be used.

Step 4: Present!
Click the “Start Recording” button the bottom-right corner of the OBS Studio window, and click back to your powerpoint presentation/PDF window. Now present your heart out to your webcam, clicking forward your slides/scroll down the poster as needed. OBS will capture it all. When you’ve finished, switch back across to the OBS window and click “Stop Recording”. The file will be saved in the Videos folder, unless otherwise specified in the OBS settings.

Step 5: Remuxing! Your video will be saved in .mkv format, which doesn’t play nicely with most video editting software. Thankfully, OBS Studio provides an option to “remux” .mkv files to .mp4 files, which are far more widely used! Go to the OBS Studio window, click File, and then “Remux Recordings”.

In this next window, click the white ellipsis to browse for the .mkv files you want to convert to .mp4 files. Then click remux and let OBS work its magic.

Step 6: Editting. You’ll have some disruption at the start and end of your video caused by tabbing back and forth to OBS Studio. You can make your submission seem even more professional by trimming this out. I did this in Windows by opening the Photos app > New Video > Import the .mp4 file > Use the trim function > Save video in high definition.

This has shown me just how easy it is to get started with content creation, be it for streaming, demo videos, or prerecorded presentations. You can make your presentation look even more professional by designing an institution/branded “screen” for your presentation slides and video to sit inside. We’ve been doing this for Oxford University Scientific Society talk recordings, see below!