gistfile1.rb

#!/usr/bin/env ruby

def video_rotation(video_path)
  `mediainfo #{video_path} | grep -i rotation`.match(/(\d+)/)
  $1.to_i
end

def video_dimensions(video_path)
  dimensions = `mediainfo #{video_path} | egrep -i 'width|height'`.scan(/([\d\s]+)pixels/)
  portrait_video?(video_path) && dimensions.reverse!
  dimensions.join('x').delete(' ')
end

def video_transform(video_path)
  {
    0   => "",
    90  => "-vf transpose=1",
    180 => "-vf hflip,vflip",
    270 => "-vf transpose=2"
  }[video_rotation(video_path)]
end

def portrait_video?(video_path)
  [90, 270].include? video_rotation(video_path)
end

def process_video(video_path)
  output = "#{File.basename(video_path, '.*')}_rotated#{File.extname(video_path)}"
  transform = video_transform(video_path)
  `ffmpeg -i #{video_path}  -metadata:s:v:0 rotate=0  #{transform}  #{output}`
end

ARGV.each do |video_path|
  process_video video_path
end