download lecture video from MIT ODL

dl.rb

if ARGV.length != 1
  puts "Give one URL as argument"
  exit
end

url = ARGV[0]
match = url.match(/\/videos\/([0-9a-f]+)/)
video_id = match[1] if match
if not video_id
  puts "Could not find video ID"
  exit
end

puts "Video id: #{video_id}"

MEDIA_URL = "https://d3tsb3m56iwvoq.cloudfront.net/transcoded/#{video_id}/video_1504127981921-c2jlwt%05d.ts"

i = 0
while true
  system("mkdir -p #{video_id}")
  url_formatted = MEDIA_URL % i
  cmd = ("wget -O #{video_id}/%05d.ts " % i) + url_formatted
  res = system(cmd)
  break if not res
  i = i + 1
  puts "downloaded #{i}"
end

ffmpeg_file_list = (0..i).map do |n|
  "file '%05d.ts'" % n
end.join("\n")

File.write("#{video_id}/list.txt", ffmpeg_file_list)

system("mkdir -p videos/")
system("ffmpeg -f concat -i #{video_id}/list.txt -vcodec copy -acodec copy videos/#{video_id}.mp4")