Re: Wiki update

My apologies for the delayed response. Great discussion.
I have entered this in bugzilla for further tracking:  https://www.w3.org/Bugs/Public/show_bug.cgi?id=27509

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

JP


From: Giuseppe Pascale <giuseppep@opera.com<mailto:giuseppep@opera.com>>
Date: Monday, November 3, 2014 at 3:04 AM
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com<mailto:silviapfeiffer1@gmail..com>>
Cc: Cyril Concolato <cyril.concolato@telecom-paristech.fr<mailto:cyril.concolato@telecom-paristech.fr>>, "Abello, Jean-Pierre" <Jeanpierre.Abello@nielsen.com<mailto:Jeanpierre.Abello@nielsen.com>>, Bob Lund <b.lund@cablelabs.com<mailto:b.lund@cablelabs.com>>, Eric Carlson <eric.carlson@apple.com<mailto:eric.carlson@apple.com>>, "public-inbandtracks@w3.org<mailto:public-inbandtracks@w3.org>" <public-inbandtracks@w3.org<mailto:public-inbandtracks@w3.org>>
Subject: Re: Wiki update

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 Sun, Nov 2, 2014 at 9:30 PM, Silvia Pfeiffer <silviapfeiffer1@gmail.com<mailto:silviapfeiffer1@gmail.com>> wrote:

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:
>>>>
>>>> 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.

I'll have a go at it later.

Cheers,
Silvia.