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Dash-Industry-Forum / Guidelines-TimingModel

DASH-IF implementation guidelines: the DASH timing model
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5.2.9.2. Availability #9

Closed irajs closed 4 years ago

irajs commented 4 years ago

[V5 Call 8/14] There is not term like "availability window" defined in MPEG DASH spec. Instead "Segment availability times" is a defined term.

We need to either use "segment availability times" or

  1. mention this is a new term introduced by IOP.
  2. define the relationship between above to terms and show how "availability window" is derived from "Segment availability times".
irajs commented 4 years ago

Changed the text as the following:

A [=media segment=] is available when an HTTP request to acquire the [=media segment=] can be started and successfully performed to completion by a client. During playback of a [=dynamic MPD=], new [=media segments=] continuously become [=available=] and stop being [=available=] with the passage of time. [[!MPEGDASH]] defines the segment availability times of a segment as the duration in wall-clock time in which that segment is available.

An availability window is a time span on the [=MPD timeline=] that determines which [=media segments=] can be expected to be [=available=]. Each [=representation=] has its own [=availability window=]. Consequently, [=availability window=] at each moment is defined by the union of [=segment availability times=] of all available segments at that moment.

sandersaares commented 4 years ago

"Availability window" is an important term and introducing it is not an accident. This term positions availability in a way more suitable for easy understanding by readers.

I believe this matches the August changes by Iraj, where the term is kept but better related to DASH terminology. I am further iterating on the wording right now.

I will close this issue since the August changes already addressed this topic. Comments on any later iterations can be reviewed separately.