[Bug 27509] New: Add mappings for HLS

https://www.w3.org/Bugs/Public/show_bug.cgi?id=27509

            Bug ID: 27509
           Summary: Add mappings for HLS
           Product: HTML WG
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Sourcing In-band Media Resource Tracks
          Assignee: silviapfeiffer1@gmail.com
          Reporter: Jp.abello@nielsen.com
        QA Contact: public-html-bugzilla@w3.org
                CC: mike@w3.org, public-html-admin@w3.org

Created attachment 1556
  --> https://www.w3.org/Bugs/Public/attachment.cgi?id=1556&action=edit
Silvia's diagram

The discussion below was started on public-inbandtracks@w3.org on Oct 27.

I also share concerns about allowing non-“standard" mappings in the webapp. 
In addition, wouldn’t UA native mappings consume much less CPU and memory? 
This still matters on resource constrained devices such as Smart TVs.

JP

> From: Giuseppe Pascale <giuseppep@opera.com>
> Date: Monday, November 3, 2014 at 3:04 AM
>
> there might be devices/specs (e.g. HbbTV) where dash is supported natively 
> and NOT via MSE, hence a "standard" mapping may still be useful, to avoid 
> people come up with their own.
>

> On Mon, Nov 3, 2014 at 10:33 AM, Silvia Pfeiffer <silviapfeiffer1@gmail.com> wrote:
>> On Mon, Nov 3, 2014 at 10:33 AM, Silvia Pfeiffer
>>> <silviapfeiffer1@gmail.com> wrote:
>>>> On Mon, Nov 3, 2014 at 9:12 AM, Cyril Concolato
>>>> <cyril.concolato@telecom-paristech.fr> wrote:
>>>> Le 02/11/2014 21:30, Silvia Pfeiffer a écrit :
>>>> On 3 Nov 2014 03:42, "Cyril Concolato"
>>>> <cyril.concolato@telecom-paristech.fr
>>>> <mailto:cyril.concolato@telecom-paristech.fr>> wrote:
>>>>>
>>>>> Hi Bob, Silvia,
>>>>>
>>>>> Le 02/11/2014 16:57, Bob Lund a écrit :
>>>>>>
>>>>>>
>>>>>> On 11/2/14, 3:45 AM, "Silvia Pfeiffer" <silviapfeiffer1@gmail.com
>>>>>> <mailto:silviapfeiffer1@gmail.com>> wrote:
>>>>>>
>>>>>>> On Wed, Oct 29, 2014 at 8:48 AM, Cyril Concolato
>>>>>>> <cyril.concolato@telecom-paristech.fr
>>>>>>> <mailto:cyril.concolato@telecom-paristech.fr>> wrote:
>>>>>>>>
>>>>>>>>> Le 28/10/2014 05:02, Abello, Jean-Pierre a écrit :
>>>>>>>>> It would be awesome if the spec could also define mappings for HLS.
>>>>>>>>
>>>>>>>> Yes, I do think HLS is another format that we should target. It
>>>>>>>> has some commonalities with existing formats that we target: DASH 
>>>>>>>> for the use of manifests and adaptative streaming aspects; and 
>>>>>>>> MPEG-2 TS as a segment format. The basics of exposing tracks 
>>>>>>>> from TS should be reusable. It might need some tweaking compared 
>>>>>>>> to what we started specifying, for instance to expose ID3 Tag 
>>>>>>>> PES streams.
>>>>>>>>
>>>>>>>> In an informal discussion with Eric (in copy), I discovered 
>>>>>>>> that WebKit already exposes them using some API, see:
>>>>>>>>
>>>>>>>>
>>>>>>>> http://trac.webkit.org/browser/trunk/LayoutTests/http/tests/media/track-i
>>>>>>>> n-band-hls-metadata.html
>>>>>>>
>>>>>>> For the record: I do have some reservations about adding DASH and HLS
>>>>>>> support, since browsers do not typically support these formats
>>>>>>> natively.
>>>>>
>>>>> [CC] I've heard that Webkit/GTK has some native support for DASH, but I
>>>>> couldn't verify it. I would expect that in the future some browsers have
>>>>> native support for DASH or HLS. But I agree with you that support for
>>>>> DASH/HLS is different from direct support for TS/MP4/OGG...
>>>>>
>>>>>>> Actually, HLS is supported in Safari, so it has some excuse,
>>>>>>> but DASH is only supported via Media Source Extensions. I have been
>>>>>>> worried about that a bit.
>>>>>>
>>>>>> There has been text added to the spec for DASH using MSE. MSE behavior
>>>>>> is that the UA sources tracks based on information in Initialization
>>>>>> Segments. The application may specify default track attributes for
>>>>>> those tracks, which the UA will use if those same  attributes are not
>>>>>> sourced from Initialization Segment data. It seems useful to me for
>>>>>> the sourcing spec to describe this.
>>>>>>
>>>>>> On a related note, I plan to submit an MSE bug so that it references
>>>>>> the sourcing spec for sourcing tracks as described above.
>>>>>
>>>>> What about adding a diagram like this one to the introduction:
>>>>> http://concolato.wp.mines-telecom.fr/files/2014/11/inband-sourcing.png
>>>>> and maybe indicating that some implementations may use one path or the
>>>>> other.
>>>>>
>>>>
>>>> Adding a diagram like this is useful, but I don't understand the one you
>>>> made. In particular, all the media format parsing is happening in the UAs
>>>> and not in an app.
>>>> 
>>> In the diagram, I meant to say that: Browser+MSE+HTML Media+Other API is the
>>> UA. Maybe that's not obvious. Can you suggest any change here?
>>> Then I tried to carry to options in this diagram:
>>> - when processing DASH (or HLS), the manifest is fetched and parsed by the
>>> Web App, and then media data is fetched using XHR (other APIs) and passed to
>>> the MSE part of the Browser. When it goes in the MSE API part in the
>>> diagram, this is meant to say that some parsing is done (eg. MPD, or ISOBMFF
>>> sidx ...) and then some part is done in the browser (in the MSE part).
>>> - it is perfectly possible to process media in the Web app, it's exactly
>>> what I do in mp4box.js. Other projects such as [2] do it for TS.
>>> 
>> 
>> OK. It might be better to paint individual paths (parallel paths) for
>> each of these different paths that a media resource can go through
>> from being picked up by the browser all the way to rendering. Then
>> identify what APIs are being used.
>> 
>> I'm not very good at drawing - do you want to try this?
> 
> After all, I gave it a try, see attached.
> 
> The red arrows are what we are defining. I've tried to explain the
> different paths through the UA APIs.
> 
> Hope that makes sense?
> 
> Cheers,
> Silvia.

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Received on Thursday, 4 December 2014 04:05:39 UTC