I work for a company that produced its own Encoders, and we had issues with CC ( We got there) we had Just under 100 developers, now they did not just focus on CC, but they focused on all the data between lines 18-29 (as well as the over all video) with in the frame as, as well as subtle changes that are constantly happening from the content owners which have a knock on effect down stream in the echo system and you constantly adjusting and trying to stay ahead and making sure you compatible with every echo system out their/TV,Tablet,Cell, ect...plus any change you make on a software encode has to be thoroughly vetted because of knock on... so the process is really rigorous & long at best... I don't right code personally and know "exactly" what what it takes to implament CC, but it was our last thing we did and it took a while, that is why I believe Netflix , Amazon,MGO and other it was the last thing implemented on there platforms.