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Dash-Industry-Forum / Guidelines-TimingModel

DASH-IF implementation guidelines: the DASH timing model
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5.2. Timing model #12

Closed irajs closed 4 years ago

irajs commented 5 years ago

This document presents an interoperable view of DASH presentation timing and segment addressing. This interpretation is considerably narrower than afforded by [MPEGDASH], constraining services to a specific set of reasonably flexible behaviors that are highly interoperable with modern client platforms. Services conforming to this document SHALL use this timing model. TO:

This document defines a constrained DASH presentation timing and related segment addressing. The allowed options are considerably narrower than the ones afforded by [MPEGDASH], constraining services to a specific set of reasonably flexible behaviors that are highly interoperable with modern client platforms. Services conforming to this document SHALL use this timing model.

Change: real time to "wall clock time", and defined wall clock time.

Note: In addition to mapping the MPD timeline to real time, a dynamic MPD can be updated during the presentation. Updates may add new periods and remove or modify existing ones, though some restrictions apply. See § 5.2.7.5 MPD updates. TO: Note: In addition to mapping the MPD timeline to real time, a dynamic MPD can be updated during the presentation. Updates may add new periods and remove or modify existing ones, including adding new segments with progress in time, though some restrictions apply. See § 5.2.7.5 MPD updates.

The zero point on the MPD timeline of a dynamic MPD is mapped to the point in real time indicated by MPD@availabilityStartTime. This value SHALL NOT change between MPD updates. To The anchor (reference point in time) on the MPD timeline of a dynamic MPD is mapped to the point in real time indicated by MPD@availabilityStartTime. This value is fixed for the entire sessions, i.e. the anchor doesn't changed with MPD updates.

(Move the SHALL statement to MPD update session: This value SHALL NOT change between MPD updates.)

  1. Representations within a period are grouped in adaptation sets, which associate related representations and decorate them with metadata. To:
  2. For the enabling the client dynamically switching between different bitrates, Representations within a period are grouped in adaptation sets, which associate related representations and decorate them with metadata.
haudiobe commented 5 years ago

How does this relate to Dash-Industry-Forum/DASH-IF-IOP#358 ?

sandersaares commented 5 years ago

zero point VS time zero - we should analyze if there is a difference (esp. in usages elsewhere in text)

Services conforming to this document SHALL use this timing model.

To what exactly? Reference from central point. Purpose is to avoid impression you can pick and choose.

haudiobe commented 5 years ago

(v5 editing: 08/07/2019) 1) Use wall-clock time 2) We use time zero instead of anchor 3) We need a central section that reference what sections/features need to be implemented. Sections itself are just putting requirements when implementing this feature. 4) Iraj will look at Dash-Industry-Forum/DASH-IF-IOP#358 and will combine

irajs commented 5 years ago

Combined proposed text here, Dash-Industry-Forum/DASH-IF-IOP#358 and the existing text. Also changed the introduction and added a section on conformance requirement to make clear the purpose of this chapter vs the conformance requirements coming from MPEG DASH and CMAF.

sandersaares commented 4 years ago

The proposed text was merged, so I think this issue can be closed. Please correct me if I am wrong.