When the CDM gets a license from the license server, who (in the browser) is the responsible of the decryption the video files so that they can be played in the video player?
Because afaik (I might be wrong though), the CDM only interacts with the license server, but it doesn't have decryption capabilities.
The EME (Encrypted Media Extensions) is an interface in the browser for the working with all the different CDMs. It provides metadata which the JavaScript application can use to request a license from the DRM license server. The license acquisition is not handled by the CDM, but the EME provides a way for the JavaScript application to pass the received license to the CDM. The CDM then handles all the decryption and often also the decoding of the content. Using this workflow the decryption key as well as the decrypted content doesn't leak to the application or anywhere else as this would compromise the DRM solution.
A good overview about the whole DRM topic is covered in one of Bitmovin's tutorials.
