Dump subtitles¶

• Dump title 1 - 6

  #! /bin/sh
  set -e
  for title in `seq 1 6`; do
      mplayer dvd://${title} -dumpstream -dumpfile title${title}.vob
  done

• Extract raw subs from vob with transcode

  #! /bin/sh
  set -e
  for title in `seq 1 6`; do
      tcextract -i title${title}.vob -x ps1 -t vob -a 0x21 > title${title}.sub
  done

• Convert to vobsub (needs VTS_0*_0.IFO from DVD)

  #! /bin/sh
  set -e
  for title in `seq 1 6`; do
      subtitle2vobsub -o itcrowd${title} -i VTS_0${title}_0.IFO -a 2 < title${title}.sub
  done

• Convert every subtitle to image

  #! /bin/sh
  set -e
  for title in `seq 1 6`; do
      mkdir -p itcrowd${title}
      vobsub2pgm -i VTS_0${title}_0.IFO -t 2 itcrowd${title} itcrowd${title}/itcrowd${title}_
      for image in itcrowd${title}/*.pgm; do
          convert ${image} ${image%.pgm}.pcx && rm ${image}
      done
  done

Decode¶

The subtitles from episode 1, 2, 3 and 5 contain base64 encoded files. It's possible to use tools like base64 from coreutils - but they can only handle text files and not images. So get 100 secretaries and let them convert each file into a text file. ;-)

I've "created" a small program which memorize every letter I've converted manually and uses this information again when it finds the same or a similar pattern. So I had two runs - one to fill the brain of this little dump OCR software and another to save the result.

If you want to start with an empty brain.db (no, you don't want that... trust me), don't pipe the output anywhere because the first run is an interactive run (full brain.db is inside the archive). After the first run, it is intelligent enough and you can convert each image in a separate file.

#! /bin/sh
set -e
BRAIN=~/brain.db
for title in 1 2 3 5; do
    for image in itcrowd${title}/*.pcx; do
        itcrowd_decoder ${BRAIN} ${image} > ${image}.txt
    done
done

Merging¶

It's important to know that some subtitles are duplicates and must be removed before we can continue by merging all files of one episode in a big text file. There are different strategies to do that... for example by looking at the timestamps. It's a possible duplicate when there is no difference between the end of the last subtitle and the start of the new one. I used a small script to do that.

#! /usr/bin/env python
dict = {}
lines = open("itcrowd6_.srtx").readlines()

i = 0
cur = ""
last_end_time = ""

for line in lines:
    if i % 4 == 0:
        cur = line
    elif i % 4 == 1:
        t = line.split()
        if t[0] == last_end_time:
            print cur

        last_end_time = t[2]

    i += 1

At the end a list of all duplicates is generated:

• itcrowd1_*.pcx.txt

  • 0125

  • 0140

  • 0236

  • 0433

  • 0494

  • 0538

• itcrowd2_*.pcx.txt

  • 0127

  • 0363

• itcrowd3_*.pcx.txt

  • 0009

• itcrowd5_*.pcx.txt

  • 0002

  • 0187

  • 0378 (needs to be replaced)

  • 0751

  • 0902

• itcrowd6_*.pcx.txt (different tool to decode that into txt files)

  • 0002

  • 0298 (needs to be replaced)

  • 0602

  • 0877

  • 1366

After we removed the duplicates and merged (e.g. with cat) the remaining ones into itcrowd${title}.txt, base64 -d can do his work (don't forget to remove MIME-Header from the beginning of the file).

EasterEgg1.jpg¶

• picture of Moss

• Exif comment: You've found an Easter Egg!

• Exif GPS-Position: Pinewood Studios (I.T. Department set)

Barber.z5¶

The second episode will bring us a text adventure ("The Barber of Sadville") for z-machine interpreters like frotz. My personal walkthrough to get 42/42 points (there are some bugs which makes it even harder):

                  .--------.
                  |        |
                  | Toilet |
                  |        |
.------.----------o----#---o---------------------------------------------.
|      |          | Toilet |                                             |
| Lift # Corridor #        #              End of Corridor                |
|      |          | Area   |                                             |
o------o----------o----#---o------------o---------o-----------o----#-----o--------.
                  |        |            | Storage | Moss's    |          | Jen's  |
                  | Toilet | Kitchen    #         #           # Entrance #        |
                  |        |            | Corner  | Desk      |          | Office |
                  o--------o------------o----#----o----- -----o----#-----o--------o
                           | Richmond's | Roy's   |           | Games    |
                           |            #         # Workbench #          |
                           | Room       | Desk    |           | Corner   |
                           o------------o---------o-----------o----------o

• Lift

  • take screwdriver

  • press button

  • wait

  • east

• Basement Corridor

  • east

• The Toilet Area

  • east

• End of Corridor

  • take spectrum

  • check keypad

  • read note

  • type 3584 on keypad

  • south

• Office Entrance

  • take zx80

  • east

• Jen's Office

  • take computer

  • switch off computer

  • switch on computer

  • west

• Office Entrance

  • south

• Games Corner

  • take xbox

  • west

• Workbench

  • take radio

  • north

• Moss's Desk

  • take commodore amiga

  • west

• Storage Corner

  • take bitstik

  • west

• Kitchen

  • east

• Storage Corner

  • west

• Kitchen

  • take pendant

  • check ceiling

  • east

• Storage Corner

  • south

• Roy's Desk

  • west

  • say I am your boss to roy

  • open red door

  • plugh

• Richmond's Room

  • check lights

  • east

• Roy's Desk

  • use computer

  • plugh

• Richmond's Room

  • check lights

  • check lights

  • check lights

  • check lights

  • check lights

  • open red door

  • east

• Roy's Desk

  • east

• Workbench

  • east

• Games Corner

  • north

• Office Entrance

  • open door

  • north

• End of the Corridor

  • west

• The Toilet Area

  • type 5982 on keypad

  • north

• Toilet

  • take two-way radio

  • switch on two-way radio

  • tune two-way radio to 159.65

  • listen to radio

EggDump¶

• bbc master mode0 image

• can be decoded by using the basic program "SOPHIE" or into an PPM by

  #! /usr/bin/env python
  data = open("EggDump").read()
  
  print "P1"
  print "640 512"
  
  def print_byte(x):
      for i in range(0, 8):
          print ((x & 0x80) >> 7)
          x = x << 1
  
  def decode_blockline(x, y, line):
      byte_pos = y * 640 + x * 8 + line
      byte = ord(data[byte_pos])
      print_byte(~byte)
  
  for y in range(0, 32):
      for line in range(0, 16):
          for x in range(0, 80):
              decode_blockline(x, y, line / 2)

SOPHIE¶

This listing was not encoded using base64 but is a listing of a small BBC Basic program. Only an emulator of an BBC machine or a real BBC machine have to be used to run it. I've tried BeebEm emulator to simulate the basic interpreter and the acorn hardware. You can load the image with the basic program and EggDump from the previous episode, type CHAIN "SOPHIE" and press ENTER to watch a picture of Roy with an easter egg and hear The IT Crowd melody.

DFS Explorer can be used to create this image. I've used the Linux freeware version. It is extreme important to set Load of EGGDUMP to FF3000 and Exec to FF7FFF and save SOPHIE as basic program (don't know how to do that in DFS Explorer without typing everything into the basic shell and using the command SAVE "SOPHIE" to save it on the disc). Combining these two steps is enough to create the image which later can be used with the CHAIN "SOPHIE" command.

More about the usage of the basic shell can be found in the official User Guide.

EasterEgg3.part.2¶

You cannot use the data before you didn't extract EasterEgg3.part.1 from episode 6. But there seems to be a problem with the generated subtitles which have to be fixed before the file can be used later.

After watching the episode again with mplayer, I've noticed that subtitle page 378 differs from the one I got from subtitleripper. Even with SubRip it wasn't possible (ok, this thing exported nothing as it should) to rip the subtitle image. Only a typing monkey could create a working version which filled the missing bytes.

Hint.tiff: Thornes box¶

The episode 6 is very different compared to the earlier episodes. No base64 encoded stuff nor text in the subtitles - only a small box in the lower right corner. If you have watched the (hidden) track 10 on the DVD, you will (maybe) know what that could mean. I tried to think a little bit about what each line could encodes and came up with following interpretation

9 bits was a little bit too much - so the lowest bit was identified as parity bit. I've tried to check it by decoding everything and it looks like the correct interpretation.

And again, I miss two bytes. Where are they gone? You can look in the generated blob at offset 1002 and see a nice message about this TIFF image and guess where one byte is missing (0x49 at the beginning of the file). The other missing byte ruins the image file directory at offset 1186 - so the missing byte must be in front of it. After some research, I noticed that subtitle2vobsub or vobsub2pgm is buggy and we can replace itcrowd6_0298.pcx and some other broken exports with a version I saw by using mplayer. This one will give us another hint what to do next (picture of an arrow pointing to the upper right).

EasterEgg3.part.1¶

The real secret of episode 6 can be found in the top right part of the screen where the Hint.tiff points to. This region can not seen on old TVs but is visible on computers or newer screens when this region is not disabled. It works quite similar to the subtitles but with an extra empty line after the begin and before the end marker.

mplayer -vf crop=1:42:719:38 ../title6.vob -vo png -nosound can be used to get the "raw" overscan images in separate files.

The overscan has many blank frames and some extra frames to learn the encoding (frame 36-290) which must be removed. After the conversion, you will get EasterEgg3.part.1 with some greetings at the beginning of the file and a checksum + file length... wait a second, am I missing a byte again or why is the checksum wrong?!?

This time the frame for offset 17708 is missing. Just insert 0x03 and everything looks fine.

You can combine both parts (without the comment at the beginning) together and get a picture of Jen with her easter egg. Take a look at it with a tool like exif to get more information out of the image - like the image unique id. Looks suspicious, or? This hex string can easily converted in a ASCII string (use an hex editor if you don't know all ASCII chars hex representation). If you done it right it should give you a smart hint for the competition - 'A: "Theobromine"'.