W3C home > Mailing lists > Public > public-html-media@w3.org > September 2016

[encrypted-media] Early detection of output protection status

From: mwatson2 via GitHub <sysbot+gh@w3.org>
Date: Wed, 07 Sep 2016 15:24:40 +0000
To: public-html-media@w3.org
Message-ID: <issues.opened-175532345-1473261878-sysbot+gh@w3.org>
mwatson2 has just created a new issue for 
https://github.com/w3c/encrypted-media:

== Early detection of output protection status ==
At any given time, Output Protection (HDCP etc.) may be inapplicable 
(internal displays), not engaged or engaged at various different 
security levels. The type of video content that may be provided, 
specifically the resolution, may be dependent on the Output Protection
 status.

In EME, this may be implemented by providing separate keys for each 
resolution and a license which specifies the Output Protection 
requirements for each key. The CDM is responsible for enforcing these 
license restrictions, including restricting video resolution according
 to the license conditions.

A problem with the EME API is that the information about Output 
Protection status, in the form of the status of each key, is not 
available until after the license is provided.

Unless the CDM supports downscaling, the consequence is one of the 
following:
- only low resolution video can be downloaded before the license has 
been provided. The presentation begins at low quality.
- downloading of video data cannot begin before the license has been 
provided. The presentation takes longer to start because of this.
- high resolution data downloaded before the license has been provided
 may need to be discarded once the license has been provided and key 
status determined. The presentation takes longer to start in these 
cases and data is downloaded unnecessarily.

Since downscaling is not widely supported, this feature requests asks 
for a mechanism to discover output protection status before the 
license is provided, without a round trip to the server.

Please view or discuss this issue at 
https://github.com/w3c/encrypted-media/issues/311 using your GitHub 
account
Received on Wednesday, 7 September 2016 15:24:47 UTC

This archive was generated by hypermail 2.3.1 : Wednesday, 7 September 2016 15:24:47 UTC