[SIPForum-discussion] Silence suppression attribute basedonrfc3108

Wed Jul 8 16:00:20 UTC 2009

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 
  To: Manpreet Singh 
  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

    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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