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

[Phil Cluff <[e-mail]>]

Thanks Roger, that makes complete sense.

I think this is fine as a SHOULD for sure. I think it'd be good to have
this advice / example in the spec, as redundant streams in general have (in
my opinion) always been a little unloved from that perspective.

Thanks again!

On Fri, Apr 16, 2021 at 5:22 PM Roger Pantos <[e-mail]> wrote:

> Hello Phil. Audio and text tracks can be steered to particular pathways
> the same way they are today: by defining per-pathway Rendition Groups and
> making sure each Variant Stream on a particular pathway specifies the
> Rendition Group for that pathway:
>
> #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio-0-A",NAME="en
> (Main)",DEFAULT=YES,LANGUAGE="en",URI="audio-0.m3u8
> <https://primary-cdn.com/audio-0.m3u8>"
> #EXT-X-MEDIA:TYPE=AUDIO,GROUP-ID="audio-0-B",NAME="en
> (Main)",DEFAULT=YES,LANGUAGE="en",URI="https://
> <https://backup-cdn.com/audio-0.m3u8>
> backup.example.com/content/videos/video12/audio-0.m3u8"
>
>
> #EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="avc1.640028”,AUDIO="audio-0-A”,PATHWAY-ID="CDN-A"
> low/audio-video.m3u8
>
>
> #EXT-X-STREAM-INF:BANDWIDTH=1280000,CODECS="avc1.640028",AUDIO="audio-0-B",PATHWAY-ID="CDN-B"
> https://backup.example.com/content/videos/video12/low/audio-video.m3u8
>
> I’d be willing to add some advice along those lines to the spec, perhaps
> as a SHOULD. But at the moment I’m not inclined to require it, in order to
> give content providers maximum flexibility.
>
>
> Roger.
>
> On Apr 16, 2021, at 2:14 AM, Phil Cluff <[e-mail]> wrote:
>
> 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]
>
>
>

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