Re: Proposal from HbbTV

On Thu, Sep 25, 2014 at 6:56 AM, Alexander Adolf
<alexander.adolf@condition-alpha.com> wrote:
> Dear Silvia,
>
> On 2014-09-24, at 22:32 , Jon Piesing <Jon.Piesing@tpvision.com> wrote:
>
>>> If a text track never exposes any cues, we shouldn't expose its existence to browsers. That's like saying: hey, I have some data, but I won't give it to you. Or if we apply that logic to an audio or video stream: it's like announcing that a video stream exists, but not rendering it. Such tracks are not relevant to this specification.
>>
>> What about text tracks that are rendered by the (native) media player and where HTML would like to be able to enable/disable them in the same way as video & audio?
>> [...]
>
> Our (though unstated) assumption is that a browser in a TV set (which is what we are targeting) will be able to render subtitles and captions tracks. Hence, the following would display the video with some flavour subtitles:
>
> <video>
>   <source src=’http://mycdn.de/video.mp4’ type=’video/mp4’>
>   <track kind=’subtitles’ srclang=’de’ label=’German for the English’
>    src=’http://mycdn.de/subtitles_de.ttml’ />
>   <track kind=’subtitles’ srclang=’de’ label=’German for the hard of hearing’
>    src=’http://mycdn.de/subtitles_de2.ttml’ />
>   <track kind=’captions’ srclang=’en’
>    src=’http://mycdn.de/subtitles_hearing_impaired.ttml’ />
> </video>

Just a note on this: this is markup for external text tracks. This is
definitely not how in-band tracks will be exposed.

What you probably mean instead is that these inband tracks will be
part of the media element's list of textTracks just like such external
text tracks:

interface HTMLMediaElement : HTMLElement {
...
  readonly attribute TextTrackList textTracks;
...
}

see http://www.w3.org/html/wg/drafts/html/master/dom.html#htmlelement .

For external tracks like the above you're going to have to define a
parser that is part of Web browsers and thus exposing TextTrackCues
will not be the difficult part.

Best Regards,
Silvia.


> At the JS level, selecting the track would have the side effect of the platform rendering it; just like for video and audio. In the above example, the script's choice of text track would likely be based on the user's impairment type and language preferences.
>
> In such an environment, we thought that selecting/unselecting a text track would be sufficient, and couldn't think of anything interesting that could be done with a cue.
>
> Cheers,
>
>   --alexander

Received on Sunday, 12 October 2014 07:27:13 UTC