Dear Twitch developer, thenks for your nice API project, by the way after developing WP APi plugin for dozens of platforms including Soundcloud, Beatport, Youtube, Facebook, Google Maps, Vimeo and more, I can say for sure your API documentation is one of the worst ever.
At the moment, after trying to setup a very simple video player (just because I want to control play and pause via API) I just lost hours to find out that the video ID is NOT the id you have from the embed code or of the URL, but it needs a random v or c at the beginning.
I just found it out from this post
while in the documentation (Embedding Twitch | Twitch Developers) there is no trace of that. I guess if is a collection, you use c, if is a video you use v, by the way probably using the discovery API method you know it but from a normal embed URL is not clear.
[specification] I’m not talking about the src parameter, that one says about the V, i’m talking about the video ID parameter, which also doesn’t makes much sanse to have a letter before the ID, because this means that the IDs needs to have a different value between the public ID and the API id. 
I strongly recommend to produce a more clear documentation.
Thanks