[SIPForum-discussion] Silence suppression attribute basedonrfc3108

Wed Jul 8 18:28:37 UTC 2009

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
		1717.html
<https://lists.cs.columbia.edu/pipermail/sip-implementors/2006-January/0
1%0A1717.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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