My workplace is a school adapting to the pandemic. We need a tool on Windows that will let teachers record their voices while they show the screen, either showing a slide presentation or showing how to use an application.

The tools we have available require too many complicated steps to use, so aren't accessible to all teachers, and create a huge file size that are hard for students with slow internet to download.

At the moment, the file size is ~20 GB for a presentation of 40 slides, where technically it only needs to store 40 pictures plus audio. We get disk space problems after 30 minutes of recording.

We need something that will optimize the file size, for instance, if a slide doesn't change in minute, it doesn't need to save thousands of frames of footage, but should continue to save the audio.

At the moment we use Powerpoint 2016 for the presentation or VLC to record the screen, which needs even more steps to capture audio as well.

The actual saving steps for VLC with audio are even more complex, requiring selecting codecs, etc. which is far too complicated for most of my co-workers, even with a picture guide to follow along with.

What software can allow teachers to easily make screen recordings and creates small file sizes?

  • Just another off-topic question: it seems like you can't afford more disk space. And 20 GB doesn't seem to be a lot where I live. I have thrown away a few 500 GB disks recently, simply because nobody wanted to have them. If I have some disks around again, would it help sending them to you? Commented Aug 31, 2020 at 6:17
  • I think you are misunderstanding my need for low file size. I'm working in a region of the United States where a lot of people don't have running water, electricity, let alone internet. Water literally comes around on a big truck. Some students are spending the whole week in hot car in parking lots with wifi so they can access on-line classes. If a screen recording is 500 GB+, it could use up a student's monthly data cap quickly. I'm saying I need to screen record my 20 GB slide show with a voice-over, without it becoming 500 GB.
    – Village
    Commented Aug 31, 2020 at 12:19
  • Oh. I didn't know such regions exist in the US. Sorry. I still hope my answer gives you the results you need. If not, let me know as well. At least for the Powerpoint presentation, there should be an even more lightweight solution by just recording audio and delivering the presentation as is. Commented Aug 31, 2020 at 14:42
  • A good search term could be "slidecast". That seems to be the term that mixes slideshow and podcast, i.e. it saves the slides separate from the audio. I have no concrete recommendation, though. Commented Sep 25, 2020 at 14:24

1 Answer 1


I recommend OBS Studio. While it is probably used mainly for streaming, it can also record the screen to disk.

For your requirements:

  • it works on Windows (Windows 8 or higher). I use it on Windows.
  • it can record your screen
  • it can record audio
  • it compresses to MP4, H264 Codec, which produces small file sizes

The initial setup may take some time, but it will be saved, so all subsequent recordings are much easier.

One time setup

  1. download and install OSB Studio

  2. create a profile. Profiles define the resolution and hotkeys you work with. I create one named FHD for a full HD recording.


  3. Go to settings


  4. Define the resolution you want to work with. Here I choose 1920x1080 for FullHD. Ideally choose the same resultions to no scaling is required.

    Output resolution

  5. Create a new scene collection. That's just a name. I use different names for different purposes like private versus commercial projects. You might only need one scene collection. I'll name it SR Demo here.

    Scene collection

  6. By default, there's one scene called Scene. That's probably sufficient for you at the beginning.

  7. Add a source by clicking the + Icon, choose Display Capture

    Display Capture

  8. Select the screen that you want to record.

    Screen selection

  9. Add an audio capture source

    Audio source

  10. Select the audio device that shall be used, likely a microphone

    Audio device

  11. Go to settings


  12. For ease of use, assign a hotkey to "Start recording" and "Stop recording". This makes it possible to use OBS without having it in front. Otherwise you'll always see a bit of OBS at the beginning and the end of the recording. If you want to avoid video editing, a hotkey is a good idea. Note that you can use the same hotkey for starting and stopping, which is convenient.

    Hotkey assignment

  13. Set up the output format for recording. Here's what I use:

    Recording format

    You might prefer Average bitrate (ABR). Note that you also set up the output path in this dialog.

  14. Start the presentation in full screen mode.

  15. Press the hotkey to start recording.

  16. Press the hotkey to stop recording. Make sure you don't close OBS too early before it finishes processing of the video.

Next time recording

  1. Start OBS

  2. Start the presentation in full screen mode.

  3. Press the hotkey to start recording.

  4. Press the hotkey to stop recording.

If that ain't simple ...


I have recorded 45 seconds in Full HD with ABR, which gave me a 8 MB file. For 2 hours, that's an estimated 1.3 GB file size. I hope it suits your needs.

  • For a 40 slides PowerPoint presentation, wouldn't it be better to set some really low FPS? I've tried reducing FPS of your 8 MB video with ffmpeg, at 1 FPS if became 2.74 MB, at 0.2 FPS (ffmpeg -i OBSDemo.mp4 -filter:v fps=0.2 OBSdemo_02fps.mp4) it became 1.36 MB (and looked rather disorienting because of jerky scrolling and mouse movement, but that won't be a problem for a set of slides with no moving parts).
    – Headcrab
    Commented Sep 1, 2020 at 11:25
  • @Headcrab: yes. I was choosing a higher frame rate for the screencast. For a presentation, lower values will result in smaller file size. The presentation should not use animations or transition effects then Commented Sep 1, 2020 at 11:38
  • Wow, a downvote? What for? Commented Sep 6, 2020 at 8:12
  • I still find these file sizes enormous for a slideshow. Since not much is changing on the screen, shouldn't the video codec be able to keep the size small? What file format / codec is used here?
    – kutschkem
    Commented Sep 25, 2020 at 13:43
  • @kutschkem: the Codec is H.264. As mentioned by @ Headcrab, the frame rate can be set to 1 fps or even lower. What's really needed is a slidecast, a mixture of slideshare and podcast.Unfortunately, I can not recommend one of them. Commented Sep 25, 2020 at 14:21

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