[SIPForum-discussion] Silence suppressionattribute basedonrfc3108

Sun Jul 12 16:41:21 UTC 2009

"By default VAD is turned on "

This is different than whats been said below. Also in any case, if this assumption is made, which RFC says this? Do you have a reference? also you are talking about codecs with and without implicent VAD right?

________________________________

From: Ayyanar PK [mailto:pkayyanar at in.com] 
Sent: Saturday, July 11, 2009 11:05 PM
To: Boris Vercher
Cc: Manpreet Singh; Spencer Dawkins; Andro; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Silence suppressionattribute basedonrfc3108

As someone said earlier it is endpoint implementation . I recently used this attribute to turn off VAD when G.711 codes is used for fax communication. By default VAD is turned on and when this attribute is no more seen in SD, VAD will remain the same. 

	---------- Original message ----------
	From:Boris Vercher< boris.vercher at ilexia.com >
	Date: 09 July 09 13:58:05
	Subject: Re: [SIPForum-discussion] Silence suppressionattribute basedonrfc3108
	To: "'Manpreet Singh'" , "'Spencer Dawkins'" , "'Andro'" 

	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 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/01%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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