New Playback Requirement: Event Message Processing

[haudiobe]

8.20 Event Message Processing
CTA WAVE content may contain event messages of relevance for the application.
The first version of this specification does not define a test for this.

[haudiobe]

(19/11/06 DPCTF)

• W3C work does some work on this
• DASH-IF (see published information) + MPEG developed (see CDAM.1) an Event Processing Model as well (more or less completed)
• dash.js has a polyfill that will do the work (preferably make this polyfill library independent of dash.js)
  We start from the DASH-IF/MPEG model for playback requirements (Thomas)

For making the tests complete, we need

• Content Requirements for Event messages in CTA WAVE Content Specification - at this stage no difference CMAF, only guidelines and recommendations. Would be good to have a specific normative section in Content Specification (augmented with recommendations and guidelines) => 2020 spec.
• Need Test cases and test material for this purpose
  (John)

[haudiobe]

An initial proposal is provided here, but needs more work:
https://1drv.ms/w/s!AiNJEPgowJnWgos-u32ftrH96QvscQ?e=vPuxHh

[jpiesing]

#76 makes the point that some of the streams should have events in them as a matter of principle.

[dsilhavy]

dash.js uses the IsoBoxer library to check for EMSG boxes: https://github.com/madebyhiro/codem-isoboxer

Workflow is as simple as we check for EMSG after segments have been downloaded. Event handling is done in a separate class (EventController). We support version 1 and 2 events. This logic could be reused if required, although decoupling of other dash.js parts is required.

[jpiesing]

As far as I can tell. MSE implementations and browsers don't do anything with emsg boxes & should ignore them. If this is correct then there's nothing for WAVE to test here.

[dsilhavy]

I think Iraj and DASH-IF are working on this in the context of MSE v2. I agree that currently nothing can be tested here with MSE v1

[haudiobe]

At this stage this is implemented as a javascript library. No test are needed. It would be reasonable to refer to

1. processing model
2. Javascript library that can be used as a reference that includes
   a) IsoBoxer library to check for EMSG boxes: https://github.com/madebyhiro/codem-isoboxer
   b) https://github.com/Dash-Industry-Forum/dash.js/blob/development/src/streaming/controllers/EventController.js

Propose to add the above informative description.

[gitwjr]

@jpiesing noted that we decided to test to confirm event messaging does not break anything.
Part of RFP: Change to test content generation scripts. Need to add event message to some content and do simple tests to see if anything breaks.
11/22/2022: No resolution.

[gitwjr]

Included in latest contract. Close.