Note by @fastfinge

@jscholes @andrew @klittle667 So in other words, in order to even know what the overly complicated standard is, you have to pay for the documentation. And then you actually have to implement the thing. And then, of course, the fact that there is no public open-source reference implementation means that everyone does it slightly differently, so if you want to build your own equipment to work with AD tracks, you have to account for every possible way the documentation could ever be interpreted by anyone, along with some impossible ones. And absolutely none of this infrastructure could be reused to offer multilingual dubs of programs in different audio streams. Whereas in Canada described audio is effectively just another language; you will sometimes encounter a program with four different audio streams: English, English AD, French, and French AD. And here I thought the UK was better at this than North America.