Re: EME support for CENC with AES-CBC?

Some questions to help frame the discussion:
Why would one use CBC instead of CTR? What would be gained that would
justify the additional complexity to CDMs and/or adding another
(non-)interoperability dimension?

Joe, why do you say the Apple CDM is an obvious candidate?

David

On Tue, Jun 17, 2014 at 9:25 AM, Joe Steele <steele@adobe.com> wrote:

> The obvious candidate CDM to support this would be the Apple CDM support
> announced at the recent WWDC. Although Adobe could support this as well.
> Agreed about the “capabilities” field. This is a good area to think about.
>
> Joe
>
> On Jun 17, 2014, at 7:35 AM, Mark Watson <watsonm@netflix.com> wrote:
>
> I think this is a bridge to cross when we have a CDM that plans to support
> the new encryption mode. Seems like a prime candidate for the
> "capabilities" field proposed for isTypeSupported and that it could be
> addressed by defining a capability value in the byte stream format
> specification at some later date.
>
> [Btw, we should probably define a high level format for the capability
> field so that it is possible to mix standardized capabilities with
> keysystem-specific ones].
>
> ...Mark
>
>
> On Mon, Jun 16, 2014 at 6:03 PM, David Dorwin <ddorwin@google.com> wrote:
>
>> Are you specifically interested in just CBC or is there something else in
>> the amendment? (For what it's worth, it does not appear that amendment has
>> been published.)
>>
>> The ISO Common Encryption EME Stream Format and Initialization Data
>> <https://dvcs.w3.org/hg/html-media/raw-file/default/encrypted-media/cenc-format.html#stream-format> spec
>> is based on ISO/IEC 23001-7:2012 the AES-128 CTR encryption it specifies.
>>
>>
>>
>> On Mon, Jun 16, 2014 at 5:20 PM, Jerry Smith (WINDOWS) <
>> jdsmith@microsoft.com> wrote:
>>
>>> It would seem that when new encryption types are added to CENC, then
>>> these will need to be supported by CENC compatible CDMs.  If we agree on
>>> that, then the current model for IsTypeSupported() should be sufficient.
>>>
>>> Jerry
>>>
>>> -----Original Message-----
>>> From: Joe Steele [mailto:steele@adobe.com]
>>> Sent: Monday, June 16, 2014 1:57 PM
>>> To: <public-html-media@w3.org>
>>> Subject: EME support for CENC with AES-CBC?
>>>
>>> I am curious whether this group intends to say anything about support
>>> for the AES-CBC encryption mode for ISOBMFF with CENC. I have been
>>> reviewing the amendments to the CENC spec, specifically "Part 7: Common
>>> encryption format for ISO base media file format, AMENDMENT 1: AES-CBC-128
>>> and key rotation". I am wondering how CDMs should expect to handle this -
>>> or if it is called out via isTypeSupported().
>>>
>>> This may have been discussed and I just cannot find the references to it.
>>>
>>> Joe
>>>
>>>
>>
>
>