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Re: Tech Discussions on the Multitrack Media (issue-152)

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Sat, 12 Feb 2011 08:18:51 +1100
Message-ID: <AANLkTimWYqRDXu3=xnrm7eT_P6W08NGP8A9iYqhv6gv4@mail.gmail.com>
To: Mark Watson <watsonm@netflix.com>
Cc: public-html <public-html@w3.org>
On Sat, Feb 12, 2011 at 8:07 AM, Mark Watson <watsonm@netflix.com> wrote:
>
> On Feb 10, 2011, at 3:08 PM, Silvia Pfeiffer wrote:
>
>> Hi Mark,
>>
>> On Fri, Feb 11, 2011 at 12:47 AM, Mark Watson <watsonm@netflix.com> wrote:
>>
>>
>>> The distinction between TextTrack and MediaTrack in the API under option (1)
>>> seems strange to me. Text is just another kind of media, so shouldn't the
>>> kind for each track be ( Audio | Video | Text ) rather than ( Media | Text )
>>> where Media = ( Audio | Video ) ? [This is how it is framed in option 3,
>>> albeit up one level].
>>
>> That is indeed one of the key questions we will have to answer: do we
>> treat media tracks differently from text tracks. One the one hand they
>> can all abstractly be regarded as "some time-aligned data for a
>> video". On the other hand, the current specification of <track> does
>> not allow child elements and the TimedTrack API is very specifically
>> targeted at text tracks: the concept of text cues does not make sense
>> for media tracks. Therefore it was necessary to introduce MediaTrack
>> as an additional API. But indeed one of the questions we need to
>> answer is whether that is a good idea or not.
>>
>
> Would it be possible to define a MediaTrack class for the common stuff and re-define the existing TextTrack class to inherit from that (adding the cues stuff) ?. Or is it too late to make that kind of change to the TextTrack ?


That is another option that we should experiment with.


>>> If I read rightly this condition is not met in
>>> (3), (4) and (6) right ?
>>
>> That's not quite right. The JavaScript API is still the same for both
>> in-band and external media tracks in most of these cases.
>>
>> In case (3) we have AudioTrack and VideoTrack, which apply equally to
>> in-band and external media tracks.
>
> Ah, ok - so is it a general assumption that whatever kind of objects are created according to the markup proposal, the same kind of objects are also added to the tracks list for in-band tracks (as is specified for text tracks) ?


Yes, that is indeed what the document implies. The browser would take
care of adding the in-band and external tracks to the correct list of
objects, just as is prescribed for TextTracks right now.


> I was wondering whether it made sense for in-band tracks to result in a complete HTMLMediaElement object being created in the tracks list: it seems you just need a much more limited object like TextTrack, with just the kind/label/language and mode.


That is a concern of options (6) and (7) I suppose.


Silvia.


>
> ...Mark
>
Received on Friday, 11 February 2011 21:19:44 UTC

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