Re: Embedding the track kind in WebVTT files

David,

I wanted to tell the advantages of mentioning the type of SUBTITLE, in Http
Live Streaming playlist.
We can have a multiple subtitle support for a single hls playlist. For good
bandwidth (bitrate) we can have TTML with animations and for lower
bandwidths (bitrates) we can use normal webSRT or webVTT as they wont
support animations.
If hls choses only audio for lower bandwidth (bitrate), we can use only
webVTT just for normal texts display.

Highest bandwidth with animation support.
#EXT-X-MEDIA:TYPE=SUBTITLES,subtitle_type:TTML:GROUP-ID="subs",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",URI="subtitles/eng/prog_index.m3u8

Average bandwidth with webvtt support.
#EXT-X-MEDIA:TYPE=SUBTITLES,subtitle_type:WEBVTT:GROUP-ID="subs",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",URI="subtitles/eng/prog_index.m3u8

lowest bandwidth with websrt/webvtt support (just for text display).
#EXT-X-MEDIA:TYPE=SUBTITLES,subtitle_type:WEBSRT:GROUP-ID="subs",NAME="English",DEFAULT=YES,AUTOSELECT=YES,FORCED=NO,LANGUAGE="en",URI="subtitles/eng/prog_index.m3u8

This content will help in smooth playback of video with subtitle. Please
let me know the comments if you have.

I don't know with whom I can discuss this about adding the changes in HTTP
Live Streaming spec for these SUBTITLE changes.

Thanks and Regards,
Sunil

Warm Regards,

Sunil Deshpande
Bangalore


On Thu, Sep 12, 2013 at 10:41 PM, David Singer <singer@apple.com> wrote:

> Yes, this is a good idea.  We've suggested it before.  Not least there is
> the case where the captioning is done by a  separate 'house' from the
> HTML5, and the HTML authors want some clue as to what's in the file.  I
> agree, they should be able to over-ride.  Self-describing files are a Good
> Thing, I think.
>
>
> On Sep 12, 2013, at 2:30 , Cyril Concolato <
> cyril.concolato@telecom-paristech.fr> wrote:
>
> > Hi all,
> >
> > WebVTT files are/will be used in environments where there might not be
> an HTML page pointing to it. Some examples are:
> > - WebVTT content embedded and multiplexed with video and audio in an MP4
> file
> > - Plain text WebVTT files referenced by an adaptive streaming manifest
> (DASH MPD, HLS playlist, ...)
> >
> > All embedding environments typically enable marking a track with a
> language (e.g. an audio track) but not all can carry the kind types
> (subtitles, captions, metadata). In order to avoid losing that information
> in those environments, I think the WebVTT file should declare its kind.
> Also, when producing WebVTT files, it should be possible to indicate the
> language, kind or even label in the file itself, to avoid mistakes.
> >
> > I would like to propose to define standard WebVTT metadata headers, as
> follows:
> > - WebVTT metadata header name: kind
> > - WebVTT metadata header value: as defined by kind attribute of the
> track element in the HTML 5 specification
> >
> > - WebVTT metadata header name: language
> > - WebVTT metadata header value: as defined by srclang attribute of the
> track element in the HTML 5 specification
> >
> > - WebVTT metadata header name: label
> > - WebVTT metadata header value: as defined by label attribute of the
> track element in the HTML 5 specification
> >
> > Note that some people are already using non standard name/values for
> that (e.g.
> http://wiki.webmproject.org/webm-metadata/temporal-metadata/webvtt-metadata
> )
> >
> > Of course, this introduce redundancy when the embedding environment also
> sets those attributes and might be problematic if the values differ.
> Resolving conflicts should be specified by the embedding environment. In
> HTML, the information in the HTML page should probably have precedence, to
> be able to use a caption track as metadata, if the HTML author wants to.
> >
> > Comments ?
> >
> > Regards,
> > Cyril
> >
> > --
> > Cyril Concolato
> > Maître de Conférences/Associate Professor
> > Groupe Multimedia/Multimedia Group
> > Telecom ParisTech
> > 46 rue Barrault
> > 75 013 Paris, France
> > http://concolato.wp.mines-telecom.fr/
> >
> >
>
> David Singer
> Multimedia and Software Standards, Apple Inc.
>
>
>