CMCD is a new standard that allows player clients to report some state to the CDN to allow the CDN to improve delivery performance (see https://cdn.cta.tech/cta/media/media/resources/standards/pdfs/cta-5004-final.pdf).

Implementing this with ExoPlayer is currently difficult as the necessary information needs to be available on the playback thread at the point where the request is generated. This issue is tracking two things:

1. Making sure the necessary hooks are available to forward all required information to the chunk sources that generate the requests.
2. Providing an opt-in implementation of CMCD.