Re: HTML WG Note publication of sourcing in-band media resources

On Mon, May 19, 2014 at 7:22 PM, Philip Jägenstedt <philipj@opera.com> wrote:
> On Mon, May 19, 2014 at 2:46 AM, Silvia Pfeiffer
> <silviapfeiffer1@gmail.com> wrote:
>>
>> On Fri, May 16, 2014 at 8:30 AM, Jerry Smith (WINDOWS)
>> <jdsmith@microsoft.com> wrote:
>> > The Introduction section of the In-Band Media Resource document implies that subtitles could be a subset of captions and share a single in-band track.  Is there any known example that actually does this?
>> >
>> > Jerry
>>
>> I've been told that there are some ISO BMFF files that have both 'SDH'
>> and 'Subtitle' kinds associated with a single timed text track, so
>> yes.
>
> I think the bit that Jerry referred to is "it is possible that a media
> container may encapsulate a subtitle and a caption track in a single
> in-band track to save space. In HTML, these tracks will be exposed as
> two TextTrack objects."

Yes, that's what I replied to. 'SDH' are subtitles for the deaf and
hard of hearing and contain extra cues that describe noises and sound
effects on top of those cues that are only for 'subtitles'.

> If such a track in ISO BMFF is to be exposed as two tracks, is there a
> way to distinguish which cues should be excluded from the subtitles
> track? Having two identical tracks is obviously not useful.

Agreed. I don't actually have that spec, but I was told that there is
a distinction.

> How do existing media players handle such files?

No idea. But there are MPEG experts on this list.

> Finally, does ISO BMFF have SDH (subtitles for the deaf or
> hard-of-hearing) as a separate flag from the subtitle and captions
> kinds, or is possible to assign an arbitrary number of kinds to a
> track? Either way it doesn't sound like it maps 1:1 to the HTML track
> kinds.

That's what I tried to say: since the ISO BMFF 'SDH' track contains
both 'SDH' and 'subtitles' cues, it should be mapped to both a
@kind='captions' track and also a @kind='subtitles' track where the
cues that are marked to be for SDH only are removed.

That's how I understood the relationship.

Silvia.

Received on Monday, 19 May 2014 11:30:29 UTC