Re: [Hls-interest] Streaming Video Alliance Comments on HLS Content Steering Proposals

[Phil Cluff <[e-mail]>]

Thanks Roger and the Apple team for looking at this approach, it's really
appreciated! I also really appreciate that this finally formalises the
expected player behaviour for redundant streams.

I think there is something missing though, specifically, in the current
implementation I don't think it works for un-muxed audio and video, and
text tracks, since PATHWAY-ID can only be defined on #EXT-X-STREAM-INF,
#EXT-X-I-FRAME-STREAM-INF.

I think we also need to be able to define PATHWAY-ID on #EXT-X-MEDIA so
that we do things like this for redundant alternate audio or text tracks:

#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio-0",NAME="en
(Main)",DEFAULT=YES,AUTOSELECT=YES,LANGUAGE="en",URI="
https://primary-cdn.com/audio-0.m3u8",PATHWAY-ID="1"
#EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio-0",NAME="en
(Main)",DEFAULT=YES,AUTOSELECT=YES,LANGUAGE="en",URI="
https://backup-cdn.com/audio-0.m3u8",PATHWAY-ID="2"

And the same for text tracks:

#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs-1",CHARACTERISTICS="public.accessibility.transcribes-spoken-dialog",NAME="English",AUTOSELECT=YES,DEFAULT=YES,FORCED=NO,LANGUAGE="en",URI="
https://primary-cdn.com/subs-1.m3u8",PATHWAY-ID="1"
#EXT-X-MEDIA:TYPE=SUBTITLES,GROUP-ID="subs-1",CHARACTERISTICS="public.accessibility.transcribes-spoken-dialog",NAME="English",AUTOSELECT=YES,DEFAULT=YES,FORCED=NO,LANGUAGE="en",URI="
https://backup-cdn.com/subs-1.m3u8",PATHWAY-ID="2"

I think this might require some minor changes under 4.3.4.1.1. Rendition
Groups in the HLS spec to clarify that entries in a group are not
duplicates when their PATHWAY-ID does not match.

Let me know if I've missed something as always!

Thanks again!


On Fri, Apr 16, 2021 at 12:23 AM Law, Will <wilaw=
[e-mail]> wrote:

> Well a big public thank you to Roger and the team at Apple for their open
> mindedness and willingness to take feedback around this, even to the degree
> that it represented a large rewrite of the feature. I think you have a
> genuinely simpler and thus more robust product as a result. We look forward
> to supporting you in taking it to production. It’s also encouraging for
> list members who put time & effort in to preparing feedback, to know that
> it is given due consideration. So thanks all around.
>
>
>
> In speaking with Kirk this afternoon, it would be really useful to have an
> additional optional reserved parameter of
>
>
>
> _HLS_lastSteerTime=<timestamp>
>
>
>
> in which the player passes to the steering server the last wall-clock time
> at which it executed a steering action.
>
>
>
> Why would this be useful? Primarily, it allows the decoupling of the check
> frequency from the steering execution frequency. Delivery problems can
> happen quickly  - within 30s in some cases. Having a 5 minute check-in
> interval means that a player can be banging its head against a poorly
> performing server for many minutes before it moves away. Users have proven
> inability to absorb such failures for more than 20s or so. We could address
> this problem by having the player call the steering server every 20s.
> However we don’t want the QoE churn that might come if the player switches
> at 20s intervals. It would be nice solution then if the player has the
> option of checking in frequently but the steering server could then
> intelligently steer some players who had been stable for a while,
> immediately, while for others it could wait for some churn-avoiding
> threshold before steering them. This new timestamp query arg would enable
> this optimized behavior and it would allow the steering server to remain
> stateless in its operation.
>
>
>
> Cheers
>
> Will
>
>
>
>
>
> *From: *Roger Pantos <rpantos=[e-mail]>
> *Date: *Thursday, April 15, 2021 at 3:29 PM
> *To: *"[e-mail]" <[e-mail]>
> *Subject: *Re: [Hls-interest] Streaming Video Alliance Comments on HLS
> Content Steering Proposals
>
>
>
> Okay folks, we’ve done a number of audits and we think that simple
> annotation of redundant streams will work well enough for content steering.
> I’ve updated the spec to reflect that, and bumped the spec version to
> 1.2b1.
>
>
>
> We left an opening in 1.2 that will allow us to introduce new Pathways
> through the steering manifest if there’s a demand for that in the future.
>
>
>
> As always, thanks to everyone for their thoughtful contributions!
>
>
> --
> Hls-interest mailing list
> [e-mail]
> https://www.ietf.org/mailman/listinfo/hls-interest
>


-- 
Phil Cluff | Product Lead | [phone] | [e-mail]