mvimg_convert.rb

#!/usr/bin/env ruby

# Tool to convert Google motion JPGs (MVIMG) to MP4 video files.
#
# requires exiftool utility (ie: `apt install exiftool`)
# requires exiftool gem (ie: `gem install exiftool`)
#
require 'exiftool'

files = Dir['*.jpg']

files.each do |file|
  exif = Exiftool.new(file)
  offset = exif[:micro_video_offset]
  next unless offset
  
  file_size = File.new(file).size
  start = file_size - offset

  out_file = File.basename(file, '.jpg') + '.mp4'
  puts "Writing " + out_file
  IO.copy_stream(file, out_file, file_size, start)
end