Does G.711 have silence suppression?

Discussion in 'VOIP' started by Alex, Jul 31, 2003.

  1. Alex

    Alex Guest


    I've read that G.711 doesnt compress voice data and operates at 64kbps.
    But does this standard have silence suppression?

    Alex, Jul 31, 2003
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  2. Alex

    Bebop Guest

    Yes, most codecs have the silence suppression feature.
    Bebop, Aug 1, 2003
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  3. Alex

    Cybraxis Guest

    The basic G.711 standard does not include a silence detector (aka VAD, voice
    activity detection). Most system level implementations of G.711 with VoIP
    use a proprietary VAD on the TDM/analog side of the 'codec'.

    G.711 appendix A and B add VAD and spectrally matched comfort noise
    generation as standards, so you should start to see them filter through in
    commercially available implementations of G.711 about now.

    To say G.711 doesn't compress voice is not accurate. Voice starts of as an
    analog signal and is typically compressed (or rather companded) to a
    PCM/G.711 64kbps stream. This carries less information that the original
    analog signal, so technically it is compressed. However if you are starting
    with a voice signal already on a digital network (T1/E1 etc) then it will
    already be PCM/G.711 companded, so going top G.711 on a packet network
    doesn't compress it any fact the packetization overhead will
    require more bandwidth than is needed to carry PCM on the original TDM
    serial stream.
    Cybraxis, Aug 1, 2003
  4. Alex

    SG Guest

    Most voip device firmware will support VAD/silence deletion, otherwise,
    plainly put, there's one less large reason for voip to exist.
    SG, Sep 5, 2003
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