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[Bug 24951] New: Use a simple string to identify the initData format instead of a MIME/content type

From: <bugzilla@jessica.w3.org>
Date: Wed, 05 Mar 2014 23:46:51 +0000
To: public-html-media@w3.org
Message-ID: <bug-24951-5436@http.www.w3.org/Bugs/Public/>
https://www.w3.org/Bugs/Public/show_bug.cgi?id=24951

            Bug ID: 24951
           Summary: Use a simple string to identify the initData format
                    instead of a MIME/content type
           Product: HTML WG
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Encrypted Media Extensions
          Assignee: adrianba@microsoft.com
          Reporter: ddorwin@google.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org,
                    singer@apple.com

The spec currently uses a |contentType| parameter and attribute to tell the CDM
and application, respectively, how to interpret the corresponding |initData|.
The spec says, "The contentType attribute contains the MIME type of the media
data specific to the event."

The proposal is to replace |contentType| and the MIME type string it contains
with something like |initDataFormat| or |initDataType|, which would contain a
simple string that exactly defines the format of the Initialization Data
contained in |initData|.

Examples include "webm" and "cenc". These strings would be documented in the
existing Container Guidelines.

The new value would directly replace the createSession() parameter and
MediaKeyNeededEvent (needkey event) attribute. We would need to discuss changes
to isTypeSupported() further since both the format/protection system and
contentType are useful. (The isTypeSupported() signature is already being
discussed in bug 24873.)

Benefits of this change include:
* Eliminate ambiguity in the meaning of isTypeSupported() responses for "mp4"
MIME types - this provides no indication of the protection scheme (see bug
17673).
* Allows simplification of the definition of Initialization Data for CENC (see
bug 17673).
* Eliminates the superfluous "audio/" and "video/" and additional checks in
clients and applications.
* No ambiguity around whether codecs, etc. may also be included in
|contentType|.


This bug tracks the proposal in
http://lists.w3.org/Archives/Public/public-html-media/2014Jan/0037.html
(originall
http://lists.w3.org/Archives/Public/public-html-media/2014Jan/0008.html). There
has also been some discussion starting with
https://www.w3.org/Bugs/Public/show_bug.cgi?id=17673#c37.

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Received on Wednesday, 5 March 2014 23:46:52 UTC

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