Re:Media timed events use cases and gap analysis

Chris and All,

Here are some thoughts on an approach to address the gaps identified in the
"Synchronized Event Triggering" use case [1].

As pointed out, the "Sourcing In-band Media Resource Tracks" document [2]
needs to be updated to define the creation of metadata text tracks and cues
when DASH events are found in the MPD or media containers of interest.
Given this, there is the question of how to create browser implements.

Many, if not most, browser adaptive bitrate implementations are JavaScript
based that use media source extensions. With this, it is pretty
straightforward to extend the JS player to extract the DASH events and
create metadata text tracks and cues using the HTML5 text track API [3].
Then there is the question of the cue API.

Also as pointed out, the DataCue API would be a good way to expose these
events to web applications but DataCue is not supported in browsers. This
can be addressed by implementing a DataCue JS polyfill to create a DataCue
API on top of VTTCue, which is widely supported in browsers.

I've built a proof-of-concept of this in the past using the DASH.js player
that worked across Chrome, Firefox and Safari at that time.

The approach outlined above might address what seems to be a DataCue
chicken and egg problem. Browser vendors have been reluctant to support
DataCue because of lack of applications. Applications are stymied due to
the lack of the DataCue API. With JS players and the polyfill, content
providers can address the lack of browser support and implement timed media
applications, thereby demonstrating a demand to browser vendors.

Regards,
Bob Lund

[1] https://github.com/w3c/media-and-entertainment/blob/
master/media-timed-events/use-cases-and-gap-analysis.md
[2] https://dev.w3.org/html5/html-sourcing-inband-tracks/
[3] https://www.w3.org/TR/html52/semantics-embedded-
content.html#text-track-api

> ------------------------------
> *From:* Chris Needham <chris.needham@bbc.co.uk>
> *Sent:* Friday, February 16, 2018 5:19 AM
> *To:* public-web-and-tv@w3.org
> *Subject:* Media timed events use cases and gap analysis
>
> Dear all,
>
> Following the discussion on media timed events during the last M&E IG call
> [1], I have started a document to gather use cases and requirements [2].
>
> This is just an initial draft so far, intended to provide input to the
> work on any spec changes needed.
>
> The document needs your input, so that it reflects the IG's requirements.
> One particular area that needs attention is improved use case descriptions,
> particularly from the point of view of end users or content authors, as
> some of what's currently written is technology rather than use-case driven.
>
> Please submit feedback via the GitHub issue tracker (pull requests are
> very welcome), or via this mailing list if you prefer.
>
> Kind regards,
>
> Chris (Co-chair, Media & Entertainment Interest Group)
>
> [1] https://www.w3.org/2018/02/01-me-minutes.html
> [2] https://github.com/w3c/media-and-entertainment/blob/master/m
> edia-timed-events/use-cases-and-gap-analysis.md
>
> <https://github.com/w3c/media-and-entertainment/blob/master/media-timed-events/use-cases-and-gap-analysis.md>
> w3c/media-and-entertainment
> <https://github.com/w3c/media-and-entertainment/blob/master/media-timed-events/use-cases-and-gap-analysis.md>
> github.com
> media-and-entertainment - Repository for the Media and Entertainment
> Interest Group
>
>
>
>
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Received on Thursday, 1 March 2018 16:21:08 UTC