How to drastically reduce size of very simple video? I've got a series of videos that I'm looking to drastically reduce in size. The video content is very simple: text animating on white background with a voice track on top. The text is mostly just subtitles and occasionally an image pops up, sort of like a PowerPoint/Keynote presentation, and it needs to play on iPad at Retina resolution.

In terms of size, here's an example of one of the video files:


Size: 20 MB
Dimensions: 1920 x 1080 
Duration: 5 minutes, 18 seconds
Codecs: H.264, AAC
Color profile: HD (1-1-1)
Audio channels: 2
FPS: 25


If there were a video format with variable frame rate, that would be ideal because so much of the video holds a constant frame for a second or so (like a PowerPoint/Keynote presentation). 

The reason is to reduce download size of a video-intensive app.
(This may not be considered a complete answer, no matter the Rigid policies. This may be better as a comment.)

You can try using:


H.265 video codec (very efficient — 100-second video of 1080p @60fps was just 6-7 MB even with audio, when recorded with Bandicam screen recorder, which is free).
Mono audio channel
Use a lower bit depth and bit rate for audio as well as color/video.
Take a look at how Khan Academy compresses their vids ohh, sorry, they drop the resolution
Explore the free software HandBrake. It offers variable frame rate compressions.