Picture slideshow with subtitles over Whatsapp

There are several problems, if you want to make a picture slideshow, which shall be transmitted through Whatsapp:

  • You need a Whatsapp compatible video format.
  • Pictures may have different formats / resolutions.
  • Smart-phone displays have wide screens.
  • Whatsapp's upper bound of a video's file size is 16MB.
  • How to make subtitles?

In what follows, you will find my quick and dirty solution. Note that you need Linux with GNU parallel, ImageMagick, and ffmpeg installed.

find . -type f | parallel "convert {} -resize 1280x720 -auto-orient -background 'rgb(0,0,0)' -gravity center -extent 1280x720 {/.}_1.jpg"

This command line finds all pictures in current directory (and subdirectories) and converts them to a 16:9 format (1280x720) with black margins, if necessary. No files are replaced, but rather new files are generated that end with _1.jpg.

ffmpeg -framerate 0.5 -pattern_type glob -i '*_1.jpg' -vf subtitles=subtitles.srt -c:v libx264 -c:a aac -r 30 -pix_fmt yuv420p out.mp4

Ffmpeg makes a video out.mp4, which shows each picture for two seconds (30 FPS) and uses File subtitle.srt for subtitles. This file shall have following pattern:

1
00:00:00,00 --> 00:00:04,00
Happy birthday..

2
00:00:04,00 --> 00:00:06,00
...to you!

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