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Re: HTML5 Last Call May 2011 & DASH/Adaptive Streaming

From: Mark Watson <watsonm@netflix.com>
Date: Tue, 15 Feb 2011 22:10:33 -0800
To: Glenn Adams <glenn@skynav.com>
CC: Philippe Le Hegaret <plh@w3.org>, "Ali C. Begen (abegen)" <abegen@cisco.com>, Silvia Pfeiffer <silviapfeiffer1@gmail.com>, Jean-Claude Dufourd <jean-claude.dufourd@telecom-paristech.fr>, "Richard Maunder (rmaunder)" <rmaunder@cisco.com>, "public-web-and-tv@w3.org" <public-web-and-tv@w3.org>
Message-ID: <F0C8A93F-88A3-4A5B-90D2-6FA805343190@netflix.com>
What I think would be useful, though, would be to specify that *if* DASH (say) is supported by an HTML5 video implementation *then* is should be done in a specific way.

Otherwise we have the prospect of multiple different implementations supporting different things.

For the examples you give below, it is at least clear what you support if you support a certain version of ECMAScript, say.

For DASH used in HTML5 a minimal set of things that should be nailed down are:
- that a URL for a DASH manifest can be provided in the @src or <source> element
- what error should be reported if the manifest is invalid, or if the media it points to cannot be found
- how to label DASH tracks so that the different kinds of track map to the Multi-Track API (or whatever is agreed for ISSUE-152) and a single way to do the mapping
- what event to use to report automatic bitrate changes

This is pretty basic stuff, but it would help if everyone that does it, does it the same way.


On Feb 15, 2011, at 5:33 PM, Glenn Adams wrote:

For that matter, HTML5 does not require a UA to support either the HTML syntax of HTML5 or the XML syntax of HTML5. A compliant HTML5 UA could support neither (albeit with little utility).

HTML5 does *not* specify:

 *   which top-level document types must be supported
 *   which version of ECMAScript must be supported
 *   which version/modules of CSS must be supported
 *   which version/modules of DOM must be supported
 *   which URI schemes (protocols) must be supported
 *   which non-streaming media types must be supported
 *   which streaming media types must be supported

HTML5 is a technology framework specification that requires other specifications (profiles) to fill in these gaps. In the context of certain TV standardization activities, such work to define one or more profiles is already underway.

N.B. I am not criticizing HTML5 for not making such choices. In fact, I think the editor and group has taken the best approach in that regard.


On Tue, Feb 15, 2011 at 5:59 PM, Philippe Le Hegaret <plh@w3.org<mailto:plh@w3.org>> wrote:
On Tue, 2011-02-15 at 18:40 -0500, Ali C. Begen (abegen) wrote:
> I think folks need to agree on the container format not the codec type. A good container format will be good for several codecs that exist today and will yet to come.

My understanding is that the IP issues surrounding the codec types are
also surrounding the container formats and the streaming technologies.
So, I'd be surprised if any agreement was reached within the HTML
Working Group on those topics. I can't imagine a different conclusion
that the H.264/Theora discussion at this point. In any case, as Glenn
alluded to, HTML has been technology neutral since the beginning. Unless
I'm mistaken, we don't require implementations to support a specific
image format.

Received on Wednesday, 16 February 2011 06:11:16 UTC

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