Re: MPEG-2 TS Closed Caption mapping

On Tue, May 13, 2014 at 7:34 AM, Clift, Graham <Graham.Clift@am.sony.com> wrote:
> The problem I identified related to passing a caption service of type line
> 21 as an audio or video track

If line21 captions are burnt into a video track, then exposing them as
a video track makes sense. I don't understand how they would be
exposed as an audio track.

> which then wouldn't provide an attribute of
> mode and hence no way for the application to enable them.

Audio and video tracks can also be enabled through JavaScript, so
that's not a problem.

> The latest version
> of the spec fixes that in that it only creates text tracks for caption
> services.

OK, good to know.

Cheers,
Silvia.

> Regards
>
> Graham
>
> On May 12, 2014 2:14 PM, "Ladd, Pat" <Pat_Ladd2@cable.comcast.com> wrote:
> Graham;
>
>     I took a different meaning from your question.  In
> http://rawgit.com/silviapfeiffer/HTMLSourcingInbandTracks/master/index.html
> section 3, the table in step 3 indicates that when a Caption Service
> Descriptor is signaled in a PMT a TextTrack is created with kind "captions"
> and in the case of captions digitized in the video stream, i.e. CEA708, the
> id is the PID of the video elementary stream carrying the captions.  What I
> gather from that is setting the captions TextTrack mode to showing will
> cause the captions in the video stream to be rendered.
>
> Pat...
>
> -----Original Message-----
> From: Silvia Pfeiffer [mailto:silviapfeiffer1@gmail.com]
> Sent: Sunday, May 11, 2014 12:52 PM
> To: Clift, Graham; Bob Lund
> Cc: public-inbandtracks@w3.org
> Subject: Re: MPEG-2 TS Closed Caption mapping
>
> Hi Graham,
>
> audio and video tracks can be activated the same way that text tracks are,
> except there is no browser-provided default UI, so the JS developer has to
> do that.
>
> AudioTrack has 'enabled'
> http://www.w3.org/html/wg/drafts/html/master/embedded-content.html#dom-audiotrack-enabled
> and
> VideoTrack has 'selected'
> http://www.w3.org/html/wg/drafts/html/master/embedded-content.html#dom-videotrack-selected
> .
>
> HTH.
>
> Also note that Bob has made a small change to the new spec and updated the
> caption selection part:
> http://rawgit.com/silviapfeiffer/HTMLSourcingInbandTracks/master/index.html
>
> Cheers,
> Silvia.
>
>
> On Sat, May 10, 2014 at 3:27 AM, Clift, Graham <Graham.Clift@am.sony.com>
> wrote:
>> The ‘Sourcing In-band Media Resource Tracks from Media Containers into
>> HTML’
>> spec seems to imply that CC track description will either be presented
>> to the application as a TextTrack when the captions are not line 21 or
>> as Audio/Video track when they are line 21.
>>
>>
>>
>> So the question I had is, how does the application set line 21
>> captions to showing when contained as an audio or video track?
>>
>>
>>
>> Regards
>>
>>
>>
>> Graham
>

Received on Wednesday, 14 May 2014 09:21:01 UTC