[SIPForum-discussion] Silence suppression attribute basedonrfc3108

Thu Jul 9 08:28:05 UTC 2009

Silence suppression is an option,  by the way, if nothing is précised or if
there are no attribute, silence suppression have to be removed

De : discussion-bounces at sipforum.org
[mailto:discussion-bounces at sipforum.org] De la part de Manpreet Singh
Envoyé : mercredi 8 juillet 2009 20:29
À : Spencer Dawkins; Andro
Cc : discussion at sipforum.org
Objet : Re: [SIPForum-discussion] Silence suppression attribute
basedonrfc3108

Even thi RFC is not talking about default behaviour for absence of optional
parameters like silence suppression. G729 is very clearly defined such that
absence of anneb mean anneb=yes. What does absence of silencesuppression
attribute imply?

Thnx

  _____  

From: Spencer Dawkins [mailto:spencer at wonderhamster.org] 
Sent: Wednesday, July 08, 2009 12:00 PM
To: Andro; Manpreet Singh
Cc: discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Silence suppression attribute
basedonrfc3108

this was identified as a common interworking problem in SIPconnect/1.1
discussions - there are implementations that don't realize that annexb is
enabled by default.

Spencer

----- Original Message ----- 

From: Andro <mailto:androjoker at gmail.com>  

To: Manpreet Singh <mailto:msingh at ibasis.net>  

Cc: discussion at sipforum.org 

Sent: Tuesday, July 07, 2009 10:18 AM

Subject: Re: [SIPForum-discussion] Silence suppression attribute
basedonrfc3108

Hello, 

I don't know if this answers your question, but I remember that , if annexb
support is not specified in SDP payload , it is enabled by default for g729.

Andrea

2009/7/6 Manpreet Singh <msingh at ibasis.net>

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
<https://lists.cs.columbia.edu/pipermail/sip-implementors/2006-January/01%0A
1717.html> 
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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