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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.

  • Can you attach or link to one of them? – Gyan Oct 17 '15 at 12:12
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    Do you mean, 20 MB for a 5 minute video is what you have or your desired output. If the latter is the case, just use a highly efficient codec such as H264 or VP9; if you already have a 5 minute video with a size of 20 MB, that's already pretty good – I don't see how you could further reduce the size significantly without noticable quality loss. – MoritzLost Oct 17 '15 at 15:04
  • @MoritzLost Thanks for the comment. That's the current, larger size. I agree it's already quite small, just looking for optimizations if possible. – Rogare Oct 17 '15 at 15:39
  • @Mulvya Not right now unfortunately, but you can just picture subtitles appearing over a white background. Each word fades in one at a time, and then the sentence remains for a few seconds before it disappears and the next begins. Most of the screen is just white space. – Rogare Oct 17 '15 at 15:40
  • Assuming 96 kbps for the audio, that's about 500 kbps for the video stream. For the type of content you describe, x264 with veryslow preset and a high-ish CRF may get you there. – Gyan Oct 17 '15 at 15:48
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(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.
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