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Re: [media] The specification of the MPEG DASH manifest format

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Thu, 17 Feb 2011 13:17:16 +1100
Message-ID: <AANLkTi=aK_oCVZFZiYPGcqTGZ0ZQH4QougyMUpy+MyPn@mail.gmail.com>
To: David Singer <singer@apple.com>
Cc: HTML Accessibility Task Force <public-html-a11y@w3.org>
On Thu, Feb 17, 2011 at 12:22 PM, David Singer <singer@apple.com> wrote:
>
> On Feb 17, 2011, at 8:07 , Silvia Pfeiffer wrote:
>
>> Dear all,
>>
>> as discussed in today's media subgroup call, here is the current
>> specification of the MPEG DASH manifest format, which is useful for
>> the Media Multitrack API solution (1) at
>> http://www.w3.org/WAI/PF/HTML/wiki/Media_Multitrack_Media_API :
>>
>> http://mpeg.chiariglione.org/working_documents/mpeg-b/dash/dash-dis.zip
>>
>> I personally think we would need to define a profile of it before it
>> will work with our media elements - such as enforcing that only one
>> mime type is used per manifest and that it works with the @media query
>> of our <source> elements. But I haven't actually read the spec yet. It
>> will take some time to work this out.
>
> It is, alas, a big spec.  There are...lots of options.  But we can surely help understand it.  I can pull in experts on various areas as needed.  Ask away.  There are also public lists you can join if you want more email.
>
> In general, it'll be better if the profile talks about what must *be* present and work, and be silent about other stuff.  Not sure what you mean by only one mime type per manifest, for example...


I'm concretely thinking about the following scenario:

<video controls>
  <source src="webm_manifest.mpd" type="?? - maybe video/mpd+webm" />
  <source src="mp4_manifest.mpd" type="?? - maybe video/mpd+mp4" />
</video>

mpd is what MPEG specified. The manifest file has a mime type of
video/vnd.mpeg.dash.mpd , which is not really useful for us in the
realm of the <source> elements. So, for a profile, maybe we can define
a more specific mime type, which makes more sense to our
circumstances. Also, the use of @media would influence what can be in
the manifest file, e.g. only videos below a certain screen size.

Hope this clarifies the concern I raised.

Cheers,
Silvia.
Received on Thursday, 17 February 2011 02:18:09 GMT

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