- From: Steve Morris via GitHub <sysbot+gh@w3.org>
- Date: Wed, 09 Nov 2016 09:44:00 +0000
- To: public-tvcontrol@w3.org
While I we may be able to use EME in a system that's using CI or CI+ for descrambling, I'm not sure that EME is a good fit with the way that embedded conditional access systems operate.. My reading of the EME spec is that all keys must be passed to the CDM via the MediaKeySession interface (see the definition of "Key" in section 2 of the EME spec). While some of this may be feasible in a CI-based environment, this is not possible with any of the embedded CA systems that I'm aware of for digital TV: in those cases, the library provided by the CA vendor (the equivalent of the CDM) expects to directly acquire the ECM messages containing the keys, using hardware resources that it has requested from the software that it's linked against. There are several reasons for this; security being one of them but performance being another. Different CA systems will need different information from the stream at different times in order to operate correctly, and managing this via an update() call to a MediaKeySession will be problematic. In most cases, the CA library will directly set up the section filters it needs to extract the relevant data, based on the PMT and Condtional Access Table carried in an MPEG-2 transport stream. While we could ignore embedded CA systems, that will exclude a lot of devices and potential uses. This may be an area where it's best for the spec to be mostly silent: different CA systems have different requirements, and so it is probably best left to the user agent to decide how a given CA system is integrated. -- GitHub Notification of comment by stevem-tw Please view or discuss this issue at https://github.com/w3c/tvcontrol-api/issues/17#issuecomment-259372545 using your GitHub account
Received on Wednesday, 9 November 2016 09:44:06 UTC