Re: [Wish] WG Last Call for draft-ietf-wish-whip

PRs 95 and 96 look good.

On PR 98:

WebRTC conferencing servers commonly send an Offer to receive simulcast, which includes the maximum number of streams that the server can support. In WHIP, it does not seem like the ingester can send an Offer to receive to the encoder. So I guess that the encoder has to look at the Answer to understand the ingester limitations (e.g. encoder asked to send 3 streams, ingester answered with 2)?

With respect to SVC, the issue is really what the decoder can handle. For example, software decoders for VP8, VP9 and AV1 can typically decode any legal encoding, and H.264/AVC software decoders can commonly handle temporal scalability. 

Hardware decoders and transcoders are a different story; they can lack of support for reference scaling, which prevents decoding spatial scalability (or even changing resolution without a key frame). 

So I might say “decoder specific” rather than “codec specific”. 

> On Mar 8, 2023, at 07:22, Sean Turner <sean@sn3rd.com> wrote:
> 
> Sergio: Thanks for the work here.
> Bernard: Would really appreciate the review so that we can get the new I-D in before Monday’s submission deadline.
> 
> Cheers,
> spt
> 
>> On Mar 8, 2023, at 09:06, Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com> wrote:
>> 
>> Hi Bernard,
>> 
>> I have created 3 PRs addressing your feedback:
>> 
>> https://github.com/wish-wg/webrtc-http-ingest-protocol/pulls
>> 
>> Could you review them and let me know if you are happy with the changes?  I plan to submit a new draft by the end of the week.
>> 
>> Best regards
>> Sergio
>> 
>> 
>> On Tue, Feb 28, 2023 at 9:09 PM Bernard Aboba <bernard.aboba@gmail.com> wrote:
>> Comments below.
>> 
>>>> On Feb 28, 2023, at 05:48, Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com> wrote:
>>> 
>>> 
>>> 
>>> Hi Bernard,
>>> 
>>> Thank you very much for your feedback, comments below inline.
>>> 
>>>> On Fri, Feb 24, 2023 at 10:56 PM Bernard Aboba <bernard.aboba@gmail.com> wrote:
>>> Here is my (belated) review. 
>>> 
>>> Section 1
>>> 
>>> “ While WebRTC has been very successful in a wide range of scenarios,
>>>   its adoption in the broadcasting/streaming industry is lagging 
>>>   behind.”
>>> 
>>> [BA] I recently saw a survey indicating that WHIP is now the second most implemented ingestion protocol, second only to RTMP.  So while this sentence may have been correct at one time, it seems out of date now.  Can we delete this sentence? 
>>> 
>>> Also, overall Section 1 seems like it could be shortened considerably by highlighting the major points. Here is my suggestion: 
>>> 
>>> 
>>> I am ok with changing the introduction, will review your text and propose a PR with your changes.
>> 
>> [BA] Sounds good.
>> 
>>> 
>>> Section 2
>>> 
>>> I do not see a definition of “track”.  I think this is important to clarify. 
>>> 
>>> I already had a PR related to that adding a reference to RFC8830.
>>> 
>>> https://github.com/wish-wg/webrtc-http-ingest-protocol/pull/95
>>> 
>>> Do you think it would be enough?
>> 
>> [BA] I would also add a definition for “track”.
>> 
>>> Yes, this is definitely possible, see me comment about using track as defined in RFC8830. Given that stereo and surround sound are SDP negotiated, do you think that we need to include any further clarification apart of the track one?
>> 
>> [BA] I think that’s all that is needed.
>> 
>>> I agree with you, should we remove the reference to SVC completely and only leave simulcast support in that section?
>> 
>> [BA] That would make sense. Only thing to worry about might be ingestors that can’t handle reference scaling (e.g. spatial modes) but that’s an edge case that might be not be encountered in practice.
>> 
>>> 
>>> Best regards
>>> Sergio
>> -- 
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> 