Re: In-band track metadata attribute

On Thu, Mar 20, 2014 at 4:04 AM, Bob Lund <B.Lund@cablelabs.com> wrote:
>
>
> From: <Clift>, Graham <Graham.Clift@am.sony.com>
> Date: Wednesday, March 19, 2014 at 10:43 AM
> To: Bob Lund <b.lund@cablelabs.com>
> Cc: Jon Piesing <jon.piesing@philips.com>, "public-inbandtracks@w3.org"
> <public-inbandtracks@w3.org>, Silvia Pfeiffer <silviapfeiffer1@gmail.com>,
> Eric Winkelman <E.Winkelman@cablelabs.com>, Brendan Long
> <B.Long@cablelabs.com>
>
> Subject: Re: In-band track metadata attribute
>
>
> On Mar 19, 2014 8:56 AM, Bob Lund <B.Lund@CableLabs.com> wrote:
>>
>>
>>
>> From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
>> Date: Tuesday, March 18, 2014 at 12:52 AM
>> To: Bob Lund <b.lund@cablelabs.com>
>> Cc: Eric Winkelman <E.Winkelman@cablelabs.com>, Brendan Long
>> <B.Long@cablelabs.com>, "public-inbandtracks@w3.org"
>> <public-inbandtracks@w3.org>
>> Subject: Re: In-band track metadata attribute
>> Resent-From: <public-inbandtracks@w3.org>
>> Resent-Date: Tuesday, March 18, 2014 at 12:53 AM
>>
>>> So, a PMT just describes what streams are available, similar to how the
>>> skeleton describes streams in Ogg? If so, then there is no need to expose
>>> that anywhere, since it's already inherently available to the JS developer
>>> through the tracks that are available.
>>
>>
>> SCTE-54 and  ATSC-65 specify metadata (descriptors) that appear at the
>> MPEG-2 TS program level (the so-called outer loop). These would not be
>> exposed via @kind or @inBandMetadataTrackDispatchType and would require a
>> special text track or HTMLMediaElement attribute. I am not aware of
>> use-cases where Web applications need these descriptors but am doing more
>> investigation. Perhaps other CG members, especially outside North America,
>> could do the same.
>
> Are you referring to, for example, content_advisory_descriptor and the like?
>
> yes
>
>
> Would a solution to this be to create a textTrack for the complete PMT
> contents as well as parsing the PMT contents to create additional tracks
> identified in the ES descriptor loops?
>
> Yes, but ES descriptor info is already exposed by the inBandMeta.... Attribute
> and the proposed @kind expansion.
>
> The CL mapping spec original intent was to create a track for the PMT with
> the id set to video/mp2ts_description. Has that intent changed in the
> current proposals coming from CG?
>
> A PMT track is one of the alternatives in the Wiki. It is not one of the
> submitted bugs. The question is are there use cases that require program
> level descriptors.

We should only describe something in the HTML spec that is relevant to
ALL MPEG-2 or MP4 formats. SCTE-54 and ATSC-65 seem to have specific
extensions. It would be better their mapping into HTML (if at all
required) was specified somewhere more appropriate. That's what the
DataCue is there for, IMO.

Regards,
Silvia.

Received on Monday, 24 March 2014 03:46:30 UTC