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[me-media-timed-events] DataCue or a more specific API for DASH and emsg events

From: Chris Needham via GitHub <sysbot+gh@w3.org>
Date: Thu, 14 Jun 2018 09:19:18 +0000
To: public-web-and-tv@w3.org
Message-ID: <issues.opened-332318505-1528967957-sysbot+gh@w3.org>
chrisn has just created a new issue for https://github.com/w3c/me-media-timed-events:

== DataCue or a more specific API for DASH and emsg events ==
Our discussion so far in the IG has focused on `DataCue`, which as defined in the current [HTML 5.3 draft](https://www.w3.org/TR/2018/WD-html53-20180426/semantics-embedded-content.html#text-tracks-exposing-inband-metadata), and is not present in the WHATWG HTML Living Standard.

In addition to the `TextTrackCue` attributes (`startTime`, `endTime`, and `id`, among others), `DataCue` is defined as having a single `data` attribute.

In addition to the message payload, `emsg` and DASH events also contain `schema` and `value` strings. `schema` is a URI that identifies the message scheme, and `value` is described as "the value for the event" in the [MPEG DASH spec](http://standards.iso.org/ittf/PubliclyAvailableStandards/c065274_ISO_IEC_23009-1_2014.zip).

In practice - e.g., for RadioVIS (image slides alongside an audio stream) in [DVB](https://www.dvb.org/resources/public/standards/a168_dvb_mpeg-dash_nov_2017.pdf) (section 9.1.7) - a combination of `schema` and `value` is used to inform applications how to interpret the message payload data.

So I have two questions:

1. Is the existing `DataCue` as currently defined what we need, or should we aim for a more specific API that also exposes the `schema` and `value` values?
2. Is there a need for an API that allows applications to tell the UA which `schema`s it wants to receive, or should the UA simply expose all `emsg` events to applications?

Please view or discuss this issue at https://github.com/w3c/me-media-timed-events/issues/2 using your GitHub account
Received on Thursday, 14 June 2018 09:19:28 UTC

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