Re: [Rum] Codec requirements in draft-rosen-rue-01

Richard Shockey <> Tue, 27 August 2019 22:34 UTC

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Date: Tue, 27 Aug 2019 18:34:00 -0400
From: Richard Shockey <>
To: Adam Roach <>, Brian Rosen <>, Paul Kyzivat <>
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Thread-Topic: [Rum] Codec requirements in draft-rosen-rue-01
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Subject: Re: [Rum] Codec requirements in draft-rosen-rue-01
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+1 to Adam's excellent comments. 

Richard Shockey

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On 8/27/19, 5:57 PM, "Rum on behalf of Adam Roach" < on behalf of> wrote:

    I certainly have thoughts. The executive summary is that I personally 
    believe RUM should specify Opus as the one audio codec MTI, and match 
    RFC 7742's "Non-Browser" requirements for the video codec MTI. Rationale 
     From an interop perspective, the important thing is that any given 
    profile has (at least) one MTI video codec and (at least) one MTI audio 
    codec. I know there is a strong desire -- one that I share -- that these 
    endpoints can talk to/be implemented in web browsers without the need 
    for media transcoding.
    For audio: WebRTC selected G.711 and Opus as both MTI; the former 
    because it works without transcoding to landline PSTN destinations, and 
    the latter because it sounds much, much better. RUM could make the same 
    decision; or it could decide to move away from a codec that is as old as 
    I am and opt to designate Opus as the only MTI. Given that RUM 
    inherently needs to deploy into audio/video environments, backwards 
    compatibility with the PSTN seems to be unnecessary baggage.
    For video: While specifying either VP8 or H.264 would be sufficient for 
    system interop, and for interop with compliant WebRTC endpoints, I'd 
    really prefer not to re-live the WebRTC video codec wars. Concretely, 
    what I would propose is that RUM indicate that the video codec 
    requirements are defined to be identical to those defined for "WebRTC 
    Non-Browsers" in Section 5 of RFC 7742. It should be made clear that RUM 
    endpoints *are* *not* WebRTC Non-Browsers per se; merely that they 
    comply with the same video codec requirements as WebRTC Non-Browsers.
    On 8/27/19 2:34 PM, Brian Rosen wrote:
    > Well, we certainly want interoperability, and I think we can only get that with MTI codecs.
    > I think we really are talking about a WebRTC-compatible endpoint, but we want interoperability with a WebRTC browser endpoint.
    > Not sure how to say this.  Maybe Adam can help.
    > Brian
    >> On Aug 12, 2019, at 4:20 PM, Paul Kyzivat <> wrote:
    >> draft-rosen-rue-01 changes the video codec requirements. It now simply references webrtc RFC7742.
    >> RFC7742 distinguishes three types of endpoints: "WebRTC browser", "WebRTC non-browser", and "WebRTC-compatible endpoint". AFAIK it assumes that each end is one of these.
    >> Is the expectation here that both the RUE and the provider comply with one of these? In particular, that the provider may simply be a "WebRTC-compatible endpoint? Notably:
    >>    "WebRTC-compatible endpoints" are free to implement any video codecs
    >>    they see fit.  This follows logically from the definition of "WebRTC-
    >>    compatible endpoint".  It is, of course, advisable to implement at
    >>    least one of the video codecs that is mandated for WebRTC browsers,
    >>    and implementors are encouraged to do so.
    >> Similarly, the audio requirements have been changed to reference webrtc RFC7874. That one doesn't have the distinction between "WebRTC browser", "WebRTC non-browser", and "WebRTC-compatible endpoint". It applies the same requirements to all. In particular, it requires OPUS support. I don't know why it doesn't make the same endpoint distinctions as for video.
    >> I think simply referencing these documents isn't sufficient. Seems like we need a more nuanced specification of what is required, though we may still reference these docs with qualifications.
    >> 	Thanks,
    >> 	Paul
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