[SIPForum-discussion] Query regarding RTP/AVP Media Profiles

[erol turac]

a-line in the sdp is an optional field and fmtp is a a-line attribute which
points any specific media attribute.
for example, you can use fmtp as a media attribute to negotiate media
parameters for dtmf.

annex-b is just a variation of G729 codec with Voice Activity Detection and
Comfort Noise Generation support.
The interoperability between G729 B variations ;


G.729 Annex-B and G.729A Annex-B

G.729 Annex-B and G.729 Annex-B

G.729A Annex-B and G.729A Annex-B
If initial invite is only support G729 Annexb, you should response it 1 of
the codecs above.


your sdp seems fine. You can try to remove t38 parameter from the initial
invite. This causes problem for many products in the market.

Rgrds,






On 9/3/07, Matthew Pragnell <Matthew.Pragnell at tnzi.com> wrote:
>
>  Hi,
>
>
>
> I wonder if anyone can help me.
>
>
>
> I have a fault which is affecting our IP Call Control platform. I receive
> an INVITE, in the SDP, the codec list specifies g729 variants (Media
> Description, name and address (m): audio 32206 RTP/AVP 18 18 18 18 0 8 96).
> I think that the reason it is hanging in our IP call element is because
> there is some missing media attribute information in the SDP for example
> (a=fmtp:18 annexb=no). This specifies which variant of G729 to use.
>
>
>
> SDP
>
> v=0
>
> o=msx-mitry-2 2147483647 1 IN IP4 x.x.x.x
>
> s=sip call
>
> c=IN IP4 84.103.233.85
>
> t=0 0
>
> m=audio 35864 RTP/AVP 18 18 18 18 0 8 96
>
> a=rtpmap:96 telephone-event/8000
>
> a=sendrecv
>
> a=ptime:20
>
> a=rtpmap:8 PCMA/8000
>
> a=rtpmap:0 PCMU/8000
>
> a=rtpmap:18 G729B/8000
>
> a=rtpmap:18 G729AB/8000
>
> a=rtpmap:18 G729A/8000
>
> a=rtpmap:18 G729/8000
>
> m=image 35866 udptl t38
>
> a=T38FaxRateManagement:transferredTCF
>
> a=T38FaxUdpEC:t38UDPRedundancy
>
> a=T38MaxBitRate:14400
>
> a=T38FaxVersion:0
>
>
>
> Can someone confirm if this is correct and add any additional information
> which would be helpful.
>
>
>
> Thanks
>
>
>
> Matt Pragnell
> UK Network Support Engineer
>
> T
>
> +44 207 628 9833
>
>  F
>
> +44 207 628 5262
>
> M
>
> +44 77 9542 6125
>
> E
>
> matthew.pragnell at tnzi.com <steve.burgess at tnzi.com>
>
> W
>
> www.tnzi.com
>
> TNZUK Suite, C/O IX Europe
> 101, Finsbury Pavement,
> London, EC2A 1RS, UK
>
>
>
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-- 
Erol Turaç
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