Let's assume we have an encrypted stream (SmoothStreaming + Playready) and a custom receiver build on googlecast/cast-custom-receiver.
I can see that device tries to get the license from the LA_URL (license acquisition URL) - extracted from stream PlayReady ProtectionHeader.
I wonder is there a way to override this behaviour? I want receiver to delegate license acquisition to sender - iOS app in my case.
When you are setting up a Host, you can pass a licenseUrl (see here), I think if that is present, it will be used for license acquisition.
You can achieve this by modifying the Media Player Library. The only thing that needs to be done - exposing challenge, key system, init data & sessionId though prepareLicenseRequest()
.
< this.c.prepareLicenseRequest && !this.c.prepareLicenseRequest() || this.gb()
---
> this.c.prepareLicenseRequest && !this.c.prepareLicenseRequest(this.ef, Df[this.vc], this.qb, this.hf) || this.gb()
Please verify the variable names cause they can be different (they can be found in webkitAddKey()
call later in the media_player.js code).
In your receiver just define the your own prepareLicenseRequest
implementation:
window.mediaHost.prepareLicenseRequest = function(challenge,keySystem, initData, sessionId) {
debug('drm', 'prepareLicenseRequest');
window.initData = initData;
window.sessionId = sessionId;
window.keySystem = keySystem;
var base64challenge = window.btoa(pack(challenge));
window.messageBus.broadcast(base64challenge); // TODO send only to initiator
return false // receiver will stop not request license by itself
}
When license acquired by sender it can send it back via the same channel. In this case receiver needs to add the license to the env:
window.messageBus.onMessage = function(event) {
var base64key = event['data'];
var key = unpack(window.atob(base64key));
window.mediaElement.webkitAddKey(window.keySystem, new Uint8Array(unpack(unbase64)), window.initData, window.sessionId);
window.mediaElement.play();
}
window.messageBus
in this case is a custom channel (urn:x-cast:me.trnl.cast.key
)
That's it. It works for us and it's quite fast.