Re: [Hls-interest] Availability Duration of Partial Segments

Hello Vijay, You’re right that we should clarify this in the spec. In the meantime:

> On Apr 15, 2021, at 8:21 AM, Vijay Jayaraman <Vijay.Jayaraman=40wowza.com@dmarc.ietf.org> wrote:
> 
> Hi All,
>  
> I have a question related to LLHLS ( 6.2.2. Live Playlists - https://tools.ietf.org/html/draft-pantos-hls-rfc8216bis-07#section-6.2.2 <https://tools.ietf.org/html/draft-pantos-hls-rfc8216bis-07#section-6.2.2> )
>  
> The spec states the following about part *tags* in the playlist.
> EXT-X-PART tags SHOULD be removed from the Playlist after they are
>    greater than three Target Durations from the end of the Playlist.
>  
> The spec states the following about the availability duration of media *segments*.
> The Availability Duration of a Media Segment is the duration of the
>    segment plus the duration of the longest-duration Playlist
>    distributed by the server containing that segment.  If the server
>    removes a Media Segment URI from a Playlist that contains an EXT-
>    X-ENDLIST tag, clients MUST be able to download the corresponding
>    Media Segment until the time of removal plus the segment's
>    Availability Duration.
>  
> I couldn’t find specific information on the Availability Duration of *Partial Segments*.
> When not using BYTERANGE for partial segments, what is the Availability duration of the partial segments?

I would follow the lead of the caching advice in Appendix B.1:

      Successful responses to blocking Media segment requests should be
      cached for six Target Durations. 

and keep Partial Segments available for at least 6 target durations on the origin.

> When using BYTERANGE for partial segments, does the Availability Duration of Media Segments apply to Partial Segments as well?

Well, in most cases keeping a Media Segment available means that byte range requests against that segment are available too. But if your origin is peculiar in that it can make whole-resource requests available for longer than range requests against those resources, I would keep the range requests available for at least six target durations as well.

regards,

Roger Pantos
Apple Inc.

> Thanks,
> -Vijay
>  
> Vijay Jayaraman
> Staff Software Engineer
> Wowza Media Systems | The solution you start with, the partner you scale with.
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