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Re: [MMUSIC] M-line philosophy (Re: Wisdom sought: Prioritization of codecs)

Christer Holmberg <christer.holmberg@ericsson.com> Thu, 22 November 2012 12:35 UTC

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From: Christer Holmberg <christer.holmberg@ericsson.com>
To: Harald Alvestrand <harald@alvestrand.no>, Bernard Aboba <bernard_aboba@hotmail.com>
Thread-Topic: [MMUSIC] M-line philosophy (Re: Wisdom sought: Prioritization of codecs)
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Date: Thu, 22 Nov 2012 12:35:26 +0000
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References: <50A4AC20.5030306@alvestrand.no> <50A4AE7F.4040403@alvestrand.no>, <50A51F04.5090502@alum.mit.edu> <50A54895.7030006@nostrum.com>, <50A9BFD4.3000601@alvestrand.no> <BLU002-W219B21BE1C13A009AE59C0B93550@phx.gbl> <50AE1A2C.4040201@alvestrand.no>
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Subject: Re: [MMUSIC] M-line philosophy (Re: Wisdom sought: Prioritization of codecs)
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Hi,

>> The M-line is problematic because it binds together multiple things:
>> 
>> - A set of parameters for media transmission *in all directions* (bound to payload type)
>
>[BA] RFC 3264 Section 5.1 makes it clear that the parameters need not apply in all directions (though sendrecv is the default): 
>
>agreed. What I find more problematic / irritating is that with parameters that apply to both directions of a sendrecv stream, there's no way to specify one set that applies A->B and another set that applies  B->A.
>With sendonly / recvonly streams, this is not an issue; with parameters that apply only in one direction (such as crypto keys), it is also not an issue. But for some parameters, it is an issue.

The root to these problems is that fact that, at one point many earth spins ago, the community made a decision that with SIP/SDP you only need to indicate your receiving capabilities...

Regards,

Christer

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