[Bug 26738] "ISO Common Encryption EME Stream Format and Initialization Data" should be extended for MPEG-2 TS CENC

https://www.w3.org/Bugs/Public/show_bug.cgi?id=26738

--- Comment #5 from Bob Lund <b.lund@cablelabs.com> ---
(In reply to David Dorwin from comment #4)
> (In reply to Bob Lund from comment #3)
> > David, the CENC MPEG-2 TS carries concatenated PSSH boxes identical to
> > the BMFF case.  23001-9 section 5.2.1 says:
> > 
> > 5.2.1    General
> > 
> > A CETS PSSH packet carries the complete payload of a `pssh` box, as
> > defined in ISO/IEC 23001-7. Each packet uses private syntax and carries a
> > `pssh` box along with an MD5 hash for integrity.
> 
> Thanks. Questions about the above text:
> * "payload of a... box" seems a bit ambiguous as to whether it is the entire
> box or something within it.

It is the entire contents of the PSSH. The 'cets_pssh_packet' contains a
'pssh_box()' field defined in  23001-9 section 5.2.3 as "pssh_box: complete
`pssh` box, as defined in ISO/IEC 23001-7".

> * The spec only supports one PSSH box per packet? Can there be multiple CETS
> PSSH packets to support multiple System IDs?

Yes, PSSH for each system is carried in a separate PID.

> * Would the `pssh` box be stripped from the packet and provided in the
> "encrypted" event? (Answers to the above questions may add complexity here.)

The UA would provide the contents of the 'cets_pssh_packet.pssh_box()' field,
i.e. the exact same PSSH box contents , as in the CENC ISO BMFF case.

> * Why does the packet have a private syntax?

The packet syntax is not "private". It is defined in ISO/IEC 23001-9 which is
available under exactly the same terms as CENC ISO BMFF ISO/IEV 23001-7. 

> How is the user agent supposed to know how to parse it?

By purchasing the spec. Here is the link:
http://www.iso.org/iso/catalogue_detail.htm?csnumber=63440

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Received on Monday, 8 September 2014 16:56:14 UTC