Lecture Video Screenshots
Capture every slide from Zoom, Teams, and Panopto lecture recordings automatically.
How to use
- 1Download your lecture recording and upload it here.
- 2Set a frame count that samples roughly every 20 to 30 seconds.
- 3Choose PNG for crisp slide text, or JPEG for smaller files.
- 4Download the ZIP and drop the slides into your notes.
Choosing an interval for slides
Slide-based lectures change on a slow, irregular cadence - most lecturers spend between one and three minutes per slide. Sampling every 20 to 30 seconds is dense enough to catch every slide with a few duplicates, without producing hundreds of near-identical images.
Duplicates are not a problem in practice. Sorted by filename, identical consecutive slides sit next to each other and are quick to delete in bulk. Missing a slide entirely is much more annoying than deleting six copies of one, so err toward over-sampling.
| Lecture length | Every 20s | Every 30s | Every 60s |
|---|---|---|---|
| 50 minutes | 150 frames | 100 frames | 50 frames |
| 90 minutes | 270 frames | 180 frames | 90 frames |
| 3 hours | 540 frames | 360 frames | 180 frames |
Use PNG for slide text
This is the one case where the format recommendation flips. Slides are mostly flat colour with sharp-edged text, and that is precisely the content JPEG handles worst - its compression produces visible ringing around high-contrast edges, which makes small text harder to read.
PNG compresses flat regions extremely efficiently. A 1080p slide often lands under 100 KB as PNG, smaller than the equivalent JPEG and considerably sharper. For screen-content lectures, PNG is both the better and the more compact choice.
Platform notes
Zoom cloud recordings download as H.264 MP4 and extract without trouble. If speaker view was active, the slide area occupies only part of the frame, so you may want to crop afterwards - recording in shared-screen-only mode next time avoids this.
Microsoft Teams recordings live in OneDrive or SharePoint and need downloading rather than streaming; they are H.264 MP4 and work fine. Panopto splits primary and secondary streams, so make sure you download the screen capture stream rather than the webcam feed. Its downloads are usually MP4.
One caveat worth stating plainly: check your institution’s policy before downloading recordings. Many universities permit personal study use and prohibit redistribution, and some course materials are licensed in ways that restrict copying entirely.
FAQ
How many frames should I extract from a lecture?
Roughly one every 20 to 30 seconds. For a 50-minute lecture that is 100 to 150 frames, which catches every slide with a manageable number of duplicates.
Which format is best for slides?
PNG. Slides are flat colour with sharp text, which is exactly what JPEG compresses badly - you get ringing artifacts around letters. PNG is usually both sharper and smaller for this content.
Can I extract directly from Zoom or Panopto?
No, you need the file locally first. Both platforms offer a download option for recordings you have access to.
How do I remove duplicate slides?
Sort the extracted files by name and duplicates sit next to each other, since they were captured consecutively. Selecting and deleting runs of identical frames takes a few seconds.