Re: [splices] Using Two Separate Devices to Start a Conversation proposal

"Shekh-Yusef, Rifaat (Rifaat)" <> Tue, 07 June 2011 02:02 UTC

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From: "Shekh-Yusef, Rifaat (Rifaat)" <>
To: Paul Kyzivat <>, "" <>
Date: Mon, 6 Jun 2011 22:02:52 -0400
Thread-Topic: [splices] Using Two Separate Devices to Start a Conversation proposal
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Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal
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Hi All,

Very interesting discussion.

What I had in mind is what Peter described below, but you guys came up with very interesting new ideas that can be used to address this scenario.
The scenario is technically an interesting and challenging one, but I tend to agree with Paul that it is not really a use case that will likely be used and maybe we should spend our time addressing other more likely to be used uses case.


From: [] On Behalf Of Paul Kyzivat []
Sent: Monday, June 06, 2011 7:45 PM
Subject: Re: [splices] Using Two Separate Devices to Start a Conversation proposal

I suspect asymmetric rtp *won't* work a lot of the time, for many
reasons, whether we think they are reasonable or not.

Maybe this is just an unreasonable use case. I can't really imagine
wanting to do this. If I have a handset, or headset, with a mic, it
probably has a "speaker" too, and it would seem weird using the mic and
not its speaker too. And when they are separate there is likely to be
problems with echos.


On 6/6/2011 7:27 PM, Peter Musgrave wrote:
> Hi all,
> My assumptions were that:
> - Alice's desk phone is doing the media aggregation and creating a
> reINVITE for Bob with a=sendrecv and asymmetric media:
>    * media is sent from Bob to Alice desk phone
>    * media is sent from Alice Computer to Bob
> As far as Bob knows this is a dialog only with Alice's deskphone. Bob
> does not have to support SPLICES or do anything special.
> Bob must handle asymmetric RTP from Alice.
> Ok?
> I agree that requiring media relay does become a bad idea when the
> relaying element is e.g a cellphone.
> Do we think that having asymmetric RTP will be ok? A lot of
> implementation have worked toward symmetric RTP (and some will only play
> RTP arriving from the place they are sending to! [1 implementation at
> SIPIT28, 3 at SIPIT27 - so maybe not worth worrying about]). Are there
> any issues with ZRTP or use of ICE? [I am not an ICE expert so I can't
> recall if symmetric RTP was baked into ICE, umm "frozen in" to ICE maybe?]
> Regards,
> Peter
> On Mon, Jun 6, 2011 at 5:45 PM, Alan Johnston <
> <>> wrote:
>     But isn't the INVITE Join received at Alice's Desk Phone?  If so, then
>     a normal Join will result in Alice's Desk Phone performing mixing of
>     audio streams from Alice's PC, Alice's Desk Phone, and Bob.  I thought
>     what was desired (and shown by Rifaat's flow) was that Alice's Desk
>     phone did not mix the media, but instead inserted/spliced the media
>     from Alice's PC into the dialog with Bob, resulting in a re-INVITE to
>     Bob with two m= lines.
>     - Alan -
>     On Mon, Jun 6, 2011 at 4:15 PM, Worley, Dale R (Dale)
>     < <>> wrote:
>      > No, surely it is an ordinary join.  At the far UA, there are two
>     incoming dialogs, each with one audio m= line.  The only oddity is
>     that one dialog is recvonly (at the far UA), and so is never sent
>     media.  The other dialog is sendonly (at the far UA) and so never
>     provides audio to the mixing, but is only sent the result of the
>     mixing.  The effect is that the far UA's input audio is sent only to
>     the second dialog, and the far UA's output audio is driven only by
>     the first dialog.
>      >
>      > Dale
>      >
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