答复: [EME] specification question: key Sytem selection

Hi Mark,

 

I think Eric’s question is that it’s not clear how UA get to know the key
systems supported by the file.

 

Here is my understanding: UA can get the information of key systems from the
HTMLSourceElement.keySystem (which is mentioned explicitly in the draft)  or
from the metadata in the file (which is not mentioned in the draft
explicitly, maybe we need some words to explain it).

 

How UA get initData is not clear too.  See example 7.2.2 “other content
decryption module”, the app get initData from key needed event before
calling generateKeyRequest. So it seems that UA can get the initData from
the file and set the MediaKeyNeededEvent.initData. Some clarifying words may
be needed also.

 

Btw, can MediaKeyNeededEvent.keySystem contain multiple supported key
systems, so app can select preferred one from them?

 

 

Best Regards,

 

Haojun Zhou

Email: zhouhaojun@huawei.com

Huawei Nanjing R&D Center, 101 Software Avenue, Yuhuatai District, Nanjing,
Jiangsu, PRC.

 

 

 

发件人: Mark Watson [mailto:watsonm@netflix.com] 
发送时间: 2012年7月1日 11:43
收件人: Sunyang (Eric)
抄送: public-html-media@w3.org
主题: Re: [EME] specification question: key Sytem selection

 

The key system is selected with the call to generateKeyRequest(). If that
keysystem is not supported (by the browser, or by the file) then the call
will fail and the app can try a different keysystem. 

 

Note that all three of the app, the file and the browser may support
multiple keysystems. Only a keysystem in the intersection of these three
sets may be used. There may still be more than one. The app needs to choose
its favorite from that set, as there may be commercial implications of the
choice for the app. The way we chose to implement that was by allowing the
app to attempt generateKeyRequest with different key systems, in preference
order, until one succeeded. That seems actable given that the set of
keysystems in the intersection I describe above is likely to be very small
(coming up with an example where there are 3, say, is already a challenge).

 

…Mark

 

On Jun 29, 2012, at 8:30 PM, Sunyang (Eric) wrote:





After reading the specification, I have a question on Key System selection.

 

If media element’s source attribute has a keySystem attribute then we use
this as selected keySystem, this is OK.

If no selected KeySystem, the specification says “jump to Key Presence”

 

The question is :

 

At “jump to Key Presence” is a else if of “selected key system”, so here
we have no idea about key system,

We may need let app or CDM to analyze the initData to find the KeySystem,
but I have not seen any text for

Analyzing initData here, or I miss something?

 

So where we select the Key System if no selected key system in media
element?

 

 

  _____  

孙扬
华为技术有限公司 Huawei Technologies Co., Ltd.
<image001.jpg>

Phone: +86 25 56622934
Fax: +86 25 56624081
Mobile: +86 13851889004
Email: eric.sun@huawei.com
地址：南京市雨花区软件大道101号 华为南京基地 邮编：210012
Huawei Technologies Co., Ltd.
No 101,Software Avenue, Yuhua District,Nanjing 518129, P.R.China
http://www.huawei.com

  _____  

本邮件及其附件含有华为公司的保密信息，仅限于发送给上面地址中列出的个人或群
组。禁
止任何其他人以任何形式使用（包括但不限于全部或部分地泄露、复制、或散发）本邮
件中
的信息。如果您错收了本邮件，请您立即电话或邮件通知发件人并删除本邮件！
This e-mail and its attachments contain confidential information from
HUAWEI, which 
is intended only for the person or entity whose address is listed above. Any
use of the 
information contained herein in any way (including, but not limited to,
total or partial 
disclosure, reproduction, or dissemination) by persons other than the
intended 
recipient(s) is prohibited. If you receive this e-mail in error, please
notify the sender by 
phone or email immediately and delete it!