Even though I don't usually get involved with the presentation side of film and TV, a while ago, I was asked to create a presentation and playback system for a small local movie theatre. Now, there are off-the-shelf systems for this sort of thing designed to be compliant with current standard for digital cinema, but they were after something smaller (read: cheaper) which would drive their reasonably-good-but-not-great projector and do ads and trailers, as well as any non-film-based media that came in. Because they didn't really have any idea what they were going to be playing, we decided to use the open-source mplayer as the playback core of this thing, especially given that it had also to interact with MIDI-controlled lighting equipment, variable screen masking, RS-232 projector controls, the theatre's existing multipoint surround system, etc., and all the other stuff that you get in a real live movie theatre. The client didn't want to pay for all of that to be written from scratch. I didn't object: presenting video in a commercial environment has different challenges to just watching a DVD at home. Not only does mplayer play more or less anything you could care to wave in its direction, it would allow us with only slight illegality to strip video off DVDs and hold it on hard disk for better cueing and avoidance of all the irritations associated with normal DVD players - screensavers, limited pause holding, unwanted menus and transition effects. So we built this thing, worked out all the kinks with various implementations of MIDI show control, and all was entirely WTF-free - lights went up and down, video played back, and all was well. It'll send you email if the projector reports a failing lamp. Fantastic.
Our first show was from DVD. Not ideal; really we prefer uncompressed, hi-def media for screens 40 feet wide, but we were confident we'd built a system that would wring every last corpuscle of image quality out of the format. It was a documentary which included lots of dialogue in a little-known African language, and included subtitles on the disc. In French, Aramaic, and German.
Not English.
The DVD packaging promised English subs. We rescanned the IFOs again and again, even going through them in a hex editor to find only "fr, am, de" listed. Eventually, reasoning that probably only small parts of the disc were in the obscure language and a large part of the expected audience was native in that language, it wouldn't be a problem. Needless to say, we were wrong.
The WTF came out in the post-mortem.
Most vaguely technical people will have realised that DVD subtitles are created by placing a selection of bitmap images on the disc, with one of the CLUT entries designated as transparent. These bitmaps are laid over the live video by a basic keyer in the DVD playeras instructed by timing markers embedded in the video stream. And for the French, Aramaic and German subs, they were.
What we discovered was that the Production company had indeed had an English subtitled version made before they had the DVD made. The English subtitles existed as a complete second copy of the movie burned onto the disc with the subtitles actually as part of the video image itself, halving the data rate available for either and completely screwing with anyone who bothered reading the subtitle tables to find out where the subtitles were.