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答复: [Bug 17673] New: Define Initialization Data for implementations that choose to support the ISO Base Media File Format

From: Sunyang (Eric) <eric.sun@huawei.com>
Date: Tue, 3 Jul 2012 09:01:31 +0000
To: "bugzilla@jessica.w3.org" <bugzilla@jessica.w3.org>, "public-html-media@w3.org" <public-html-media@w3.org>
Message-ID: <9254B5E6361B1648AFC00BA447E6E8C32AEB6AA5@szxeml545-mbx.china.huawei.com>
Should we define a format specification for every container?
Or we can define a common requirement for all format?

-----邮件原件-----
发件人: bugzilla@jessica.w3.org [mailto:bugzilla@jessica.w3.org] 
发送时间: 2012年7月3日 7:40
收件人: public-html-media@w3.org
主题: [Bug 17673] New: Define Initialization Data for implementations that choose to support the ISO Base Media File Format

https://www.w3.org/Bugs/Public/show_bug.cgi?id=17673


           Summary: Define Initialization Data for implementations that
                    choose to support the ISO Base Media File Format
           Product: HTML WG
           Version: unspecified
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P3
         Component: Encrypted Media Extensions
        AssignedTo: adrianba@microsoft.com
        ReportedBy: ddorwin@google.com
         QAContact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-media@w3.org


v0.1 of the proposal says "Initialization Data is... container-specific data" 
[1]. To help ensure implementations that choose to support a given format are
interoperable and provide examples for the reader, we should define
Initialization Data along with its use and behavior for common formats. This is
similar to how the Media Source proposal has provided guidance for containers
[2].

This bug tracks this task for ISO/IEC 14496-12, the ISO Base Media File Format
(ISO BMFF) [3].

Below is a non-exhaustive list of items to address:
* Files should use ISO/IEC 23001-7, Common Encryption (CENC) [4].
* What are the contents of initData? Likely one of the following:
  - All Protection System Specific Header (PSSH) boxes in the file
  - A single Protection System Specific Header (PSSH) box
    * Note: If a key system has not been specified, the user agent won't know
which to select.
  - Key ID(s)
* Does the first initData result in a license containing all the keys that
might be necessary for the entire file/stream?
* If there are multiple keys used, should a needkey event be fired for each?
* What are the contents of the needkey event when an encrypted block is
encountered and no key is available [5]? Is it the same initData or
key-specific information?
* How does Clear Key work?
  - Must there be a PSSH for Clear Key?
  - How are keys and key IDs correlated?


[1]
http://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-media/encrypted-media.html#initialization-data

[2]
http://dvcs.w3.org/hg/html-media/raw-file/tip/media-source/media-source.html#byte-stream-formats

[3]
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=51533

[4]
http://www.iso.org/iso/iso_catalogue/catalogue_tc/catalogue_detail.htm?csnumber=60397

[5]
http://dvcs.w3.org/hg/html-media/raw-file/tip/encrypted-media/encrypted-media.html#algorithms-enrypted-block


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Received on Tuesday, 3 July 2012 09:02:52 UTC

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