Tip on recording online presentations as videos

I like to record webinars and online presentations so I can watch them offline. I use SnagIt plus a free tool called Handbrake.

I've been using Camtasia and SnagIt for years. I used Camtasia a lot for making screen recordings of presentations, but at one point they added that ability into SnagIt, which is a lot easier to use. It does some really basic editing as well.

Something helpful to know about how video encoding work: It takes a screenshot and uses that as something called a "key frame" and saves it. Then it takes successive screenshots and computes the differences and saves them instead.

For things like filming people and events live, or like what you'd see in a TV show, if the camera is still and there's motion in the scene limited to just a small part, then the differences between each frame are fairly small until the camera's angle changes, and you end up with a decent amount of compression.

For online presentations, like most webinars these days, unless the person has their face in a little bubble, the screen doesn't change AT ALL for quite a while -- dozens if not hundreds of key frames -- which means there's NO CHANGE between the key frames. Even with a headshot in a bubble, the changes from frame to frame are minimal.

I was on a webinar the other day and they had around two dozen slides and took an hour to go through them. SnagIt doesn't not optimize anything, and its videos end up quite bloated for this purpose. It tends to create videos that are around 15MB per minute, which isn't that unusual. So an hour long presentation can be around 1GB in length.

Note that MP4 has a sound track attached to it that's usually encoded as MP3, and it's highly compressed already. The audio for an hour long presentation can be only 100k or less. So we're just talking about the VIDEO part of the file here.

Anyway, most screen recording tools don't know what sort of thing they're dealing with, and they're tuned to do a good job for whatever you might throw at them.

Handbrake lets you optimize the compression, and when you have a presentation that's got several minutes of the same visual and nothing changes, it can compress most of that out since the differences are minimal. You can adjust the key-frame-rate to make use larger intervals that might compress it even further as long as there aren't any small changes in the background screen color during recording. (That's common if you're using a camera to capture a presentation. But recording a screen presentation made with something like Keynote or Powerpoint isn't likely to do that.)

So I ended up compressing this 1.2GB presentation video down to around 60 MB! Usually they're around 150M-200M with nominal screen activity. The audio is not affected.

It would be nice if someone made a compression algorithm designed for online presentations that recognizes when the slides change and make that moment a key frame, then leaves it unchanged if there's minimal changes until the next slide is recognized. It would result in really tiny videos. Unfortunately, I'm not sure that video encoders and decoders can work that way, but if they can, it would be ideal. Maybe it's something that AI can help with.

I've always thought there's a market for someone to make a tool that can analyze a presentation like this and turn it into a bunch of screenshots that change each time the slide shows a major change. That way, it becomes a series of time-based triggers rather than image compression. Using video to record presentations like this as if they're continuous action sequences is very inefficient. And, unfortunately, saving them as something like Powerpoint files is even worse than saving them as videos for some reason -- PP files are HUGE! I've never understood why.

So if you want to record webinars or presentations that are just a bunch of slides with someone talking over them (or in a bubble), use something like SnagIt or Camtasia and then use Handbrake to reprocess the video to shrink the MP4 file WAY down. You'll end up with an MP4 video that's 90% (or more) smaller than the original and it will sound the same and look nearly identical.

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