[Bug 17673] 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

--- Comment #58 from David Dorwin <ddorwin@google.com> ---
(In reply to Jerry Smith from comment #57)
> Changes made in https://dvcs.w3.org/hg/html-media/rev/5e4403d01787.

Comments on the changes:

1) "Common Encryption files may contain one or more protection system specific
header ('pssh') boxes, each for a different SystemID."
  - This makes it sound like a PSSH box can only appear once per SystemID.
  - I believe you mean that they are unique within a series at each location
where a PSSH is necessary.
  - For interoperability and consistency, we may want to note that a PSSH box
for all SystemIDs should be present wherever their are any PSSH boxes.

2) The second paragraph of section 3 seems to specifically address embedded
keys. Is that right? Is this the *only* use of PSSH boxes in a 'moof'? Embedded
keys are not currently covered by the main EME spec text.
2a) "Each ‘moof’/’pssh’ must protect the contained keys with a SystemID
specific method." How can a 'moof' protect the keys?
2b) The last sentence explains why one might use sample groups. I believe this
is the only such text in the spec and should be removed. (This would be
valuable in a "Using EME with Common Encryption" primer, but I don't think it
belongs in the spec/registry.

3) The third paragraph seems orthogonal to EME and like a DASH-specific usage
of a generic EME capability (see also below). I think it should be removed. (Is
it really CENC that specifies this or is it DASH?)

4) "The application may parse out 'pssh' boxes which do not correspond to the
selected key system, and may not use the InitData from the file at all and
instead use initData from another source (e.g. the XML element described
above).
  - The first part is fine, but I'm not sure we need to specify it."
  - The second part is (or should be) covered by the spec and applies to all
init data types. I don't think we need to specify this here.
  - As above, I think we should remove the XML reference.

5) Is there a formal reference for CENC 2nd edition? Is it just "ISO/IEC DIS
23001-7 2nd Edition" for now?

6) nit: s/boxes(s)/box(es)/

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Received on Wednesday, 28 May 2014 21:05:04 UTC