emsg Media Presentation Ended Case

[technogeek00]

There is a special case called out for MPD Expiration events:

In the case in which both presentation_time_delta and event_duration are zero, then the Media Presentation is ended.

How is this event exposed via our model since version 0 vs 1 message boxes are not exposed? This might logically expose as presentation_time equal to the containing segment start time and event_duration of zero, but that same value set could also be a emsg type 1 with presentation_time equal to the segment start time and a zero event_duration

[irajs]

How about defining a pseudo messagedata for Ended Media Presentation, e.g. ///&&##!!!DashMediaPresentationIsEndedAtTheStartofThisEvent!!##&&// ?

[irajs]

@dsilhavy Does dash.js handles the case of presentation_time_delta = event_duration=0?

[irajs]

Questions during the DASH-IF's Event TF 9/2:

1. What does "Media Presentation is ended" mean?
2. What does it mean for the client and what if the MPD says otherwise?
3. Does the MPD need to be updated to show the end of the presentation?
4. Why not send the event for MPD update, and just update the MPD with the new presentation end time?

Suggest deprecating this specific feature?

[irajs]

DASH-IF's Event Task force call 11/11/2022:

MPEG's response to DASH-IF's liaison:

Regarding the question about the event duration in the MPD expiration validity event, we included

further clarification in the 5th edition AMD2 Working Draft, discouraging the use of event duration to update the media presentation duration.

Then we do not need to do any special treatment of the event duration, in this case, the DASH-IF client and the application ignore the event duration and we can close the issue.

Check the rest of IOP V5 to make sure that the reset of V5 is consistent in terms of media presentation duration update -> Live TF should clarify.

[dsilhavy]

@irajs @haudiobe : I got an action in the last IOP Call:

Regarding the question about the event duration in the MPD expiration validity event, we included further clarification in the 5th edition AMD2 Working Draft, discouraging the use of event duration to update the media presentation duration. => Daniel please check

I am not completely sure what to look for but this is what we support in dash.js at this point in terms of DASH-specific events:

• We handle urn:mpeg:dash:event:2012 with value 1. Values 2 for MPD Patch and 3 for the complete MPD are not supported

• We update the duration according to:

  if (event.calculatedPresentationTime == 0xFFFFFFFF) {//0xFF... means remaining duration unknown
     newDuration = NaN;
  } else {
     newDuration = event.calculatedPresentationTime + event.duration;
  }

  event.calculatedPresentationTime is defined as:

• For version 0 events: calculatedPresentationTime = periodStart + mediaStartTime - presentationTimeOffset + presentationTimeDelta;

• For version 1 events: calculatedPresentationTime = periodStart - presentationTimeOffset + presentationTimeDelta

I assume this needs to be removed based on what was defined in AMD2?