Note by @fastfinge

@jscholes @andrew @klittle667 But in exchange, it means you can't just use the audio description that already exists when you're airing shows from the US and Canada, because we don't master our AD that way. It also explains to me why, when Canadian TV channels import Audio Description from the UK, the mix is an utter and total mess. I thought you guys were just really bad at that. One UK show I watch, for example, has all program audio on the left channel, and all audio description on the right channel. It's the worst of all possible worlds!