[SIPForum-discussion] Silence suppression attribute basedonrfc3108

Wed Jul 8 14:28:28 UTC 2009

Hi,

RFC 4856 (it obsoletes RFC 3555) defines the Media Type registrations of
Payload formats for RTP AV profile.
It includes the OPTIONAL PARAMETERS for those media types, including the
ones you seem to be looking for.
As described in this document, if the "annexb" parameter is omitted, "yes"
is implied.
For G723, if the "annexa" parameter is omitted, "yes" also is implied.

Regards,

Herve

-----Message d'origine-----
De : discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] De la part de Manpreet Singh
Envoyé : lundi 6 juillet 2009 06:05
À : John Atkinson; Anuradha Prakashkumar; discussion at sipforum.org
Objet : Re: [SIPForum-discussion] Silence suppression attribute
basedonrfc3108

Not sure if its still clear. 3389 talks about paylaod defition for CN.
Its not touching the case where silencesuppression attribute is there or
not. May be I am missing the text in the RFC so if someone can point me
to exact excerpt, would be helpful. But my question is still not
answered well in these rfcs. 3389 does say one needs to define the
payload type to support CN. Absence of this doesn't mean no CN but RTP
can still handle it via non-continous sequence numbers.

The question really was if G729A or any other codec where Silence
suppression is not ON by default, absence of silencesuppression attrbute
in SDP means ON or OFF?  Ofcourse if one says ON then the SDP needs to
define CN payload. But would that mean abesence of silencesuppression
attribute means no VAD?

Thnx  

-----Original Message-----
From: John Atkinson [mailto:johnat at nortel.com] 
Sent: Wednesday, July 01, 2009 8:24 PM
To: Anuradha Prakashkumar; Manpreet Singh; discussion at sipforum.org
Subject: RE: [SIPForum-discussion] Silence suppression attribute based
onrfc3108

read RFC 3555 for 729AnnexB use  and 723annexA use  

and, as mentioned below, see rfc 3389 for codecs such as 711 and 726-32
that don't have their own vad/cng/dtx algorithms

-----Original Message-----
From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Prakashkumar,
Anuradha WIPRO (External:WBNG:WIPRO)
Sent: Wednesday, July 01, 2009 12:52 AM
To: msingh at ibasis.net; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Silence suppression attribute based
onrfc3108

RFC 3389? Have you checked? It talks lots about VAD and Noise level
comfort. Also I could somewhere read it as endpoint implementation
dependent. Will let you know if I get something more.

________________________________

From: Manpreet Singh [mailto:msingh at ibasis.net]
Sent: Wednesday, July 01, 2009 9:34 AM
To: Anuradha Prakash kumar (WT01 - Telecom Equipment);
discussion at sipforum.org
Subject: RE: [SIPForum-discussion] Silence suppression attribute based
on rfc3108

Anuradha

Thanks for the URL. Although it does say default is ON, its not writen
in any spec. Is there a reference to spec you can point me to? Alteast
3108 doesnt talk about this and I am not sure where they are taking that
reference.

thnx

________________________________

From: anuradha.kumar1 at wipro.com [mailto:anuradha.kumar1 at wipro.com]
Sent: Tuesday, June 30, 2009 11:54 PM
To: Manpreet Singh; discussion at sipforum.org
Subject: RE: [SIPForum-discussion] Silence suppression attribute based
on rfc3108

Hello Manpreet,

I had a chance to look at this. VAD or silence suppression is used to
save bandwidth in a case where the originating and terminating parties
do not speak but still the background voice gets played which is
unnecessary. 

Now coming to your question whenever not indicated silence suppression
or Voice Activity Detection is set to ON. I guess we can verify this as
well by monitoring it by network analyzers like wire shark. Please refer
to the URL
https://lists.cs.columbia.edu/pipermail/sip-implementors/2006-January/01
1717.html

Regards,

Anu  

________________________________

From: discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] On Behalf Of Manpreet Singh
Sent: Tuesday, June 30, 2009 9:06 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Silence suppression attribute based on
rfc3108

Hi

If the silence suppression attribute is not present in SDP, whats the
default behaviour? Would the absence mean ON or OFF for a certain media
type?

thnx

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