Re: Using WebVTT metadata tracks and missing API

Hi Silvia,

Le 30/10/2013 10:03, Silvia Pfeiffer a écrit :
>
> Your example settings seem a prime example for what data cues are all
> about. You should put them into a JSON in a cue - that will make the
> parsing even simpler.
I had not thought about that option. Will look into and let you know.

> There are bugs in the bug tracker for some of the header fields that
> you're after. Let's work on these and see what else we are missing
> after that.
Ok.

>
> BTW: We need to keep the connection between the video and the VTT
> resource to a minimum - in particular I object to adding the mime type
> of the media resource, or the codec, or codec paramters to the vtt
> file header. The VTT file needs to be able to be used with different
> encodings of the same video file through the <track> element, which
> can relate to different <source> elements.
>
> So, the following header fields that you are using are actually
> harmful: baseMediaFile, MPEG-4-streamType,
> MPEG-4-objectTypeIndication, sampleRate, numChannels,
> MPEG-4-DecoderSpecificInfo . Please don't start exposing such
> information in a VTT file. This information must not be made part of a
> VTT file - it is far too easy to get out of sync with an actual video
> file and is already out of sync with a different encoding of the same
> video file. The VTT file is not a companion file to a specific media
> resource. If you need to expose such information in a file, I
> recommend writing a separate file, e.g. video_metadata.xml.
You misunderstood me. The information is not duplicated in the VTT file, 
it is *only* in the VTT file. In this example, I assume that some 
audio/video/other data carried in some original media container (say 
mp4) is not supported but the browser's demultiplexing stack and thus 
not exposed to JS API via a VideoTrack or AudioTrack interface. So to 
work around that limitation, I'm thinking about using WebVTT to expose 
the data (or a reference to the data). In the example, I'm putting the 
information that was initially in the MP4 file in the WebVTT file: some 
in the header (from MP4 header to VTT header), some in the cue data 
(from MP4 samples to VTT cues).

Hope this is clearer,
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/

Received on Monday, 11 November 2013 09:50:20 UTC