Subject: [Wish] Is there a way for client to communicate intended resolution and frame rate with WHIP?

From: Ying Yin <[email-masked]>
Date: Wed, 23 Mar 2022 14:01:26 -0400

Hello,

With WHIP, is there a standard way for the client to indicate the intended
broadcast resolution and framerate? WebRTC could temporarily adapt down
resolution and framerate, and it could start at a lower resolution than the
intended one. If the server side is transcoding and providing multiple
output resolutions, they don't necessarily want to adjust the set of
broadcast output resolutions as the ingestion changes resolutions. I
suppose there could be solutions such as setting the intended
resolution and frame rate as parameters in the url. Just wondering if this
has been considered and if there is a standard way.

Thanks,
Ying

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From: James Hurley <[email-masked]>
Date: Thu, 24 Mar 2022 16:30:07 +0100

+1 this would be very useful to see codified.

On Wed, Mar 23, 2022 at 7:01 PM Ying Yin <yingyin=
[email-masked]> wrote:

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From: Sergio Garcia Murillo <[email-masked]>
Date: Thu, 24 Mar 2022 18:46:16 +0100

Hi Ying,

I understand that you would be interested in this feature when webrt is not
use end to end, and you need some kind of ABR/protocol adaption server side
(for example for using mpeg dash/lhs on the viewing side).

I am not sure that the client should be allowed to specify the output
fps/resulutions and that should be a server side policy.

However, allowing the client to specify the source fps/resolution is an
interesting functionality.

 I don't think that there is a way to specify it on the SDP (also, due to
webrtc nature, it could be posible to chsnge the source in the middle of a
publication.

You could extract that information from the VLA header extension (
https://webrtc.googlesource.com/src/+/refs/heads/main/docs/native-code/rtp-hdrext/video-layers-allocation00).
It is not standard yet (I hope google bring it to the IETF soon) but it is
widely adopted.

Best regards
Sergio