[SIPForum-discussion] VAD and CNG

isshed isshed.sip at gmail.com
Thu Sep 29 05:04:33 UTC 2011

  VAD is voice activity detection whenever it detects the silence it
notifies the CNG module then CNG module generate the comfort Noise packets
(SID) and because these CNG packets are not natural so depending upon the
background noise DTX i.e discontinuos Transmission module notifies the CNG
module to incorporate some changes in  the SID packets.


On Wed, Sep 28, 2011 at 7:28 PM, Raghul Prasanna <raghul82 at yahoo.co.uk>wrote:

>   Hello all,
> If we turn on VAD, RTP wont be sent during silence period saving bandwidth.
> How does it know that there is no speech, when there is background noise?
> Say if somehow the device recognised silence, who will generate CNG is
> generated locally by the other end at regular intervals? Please explain.
> Thanks
> Prasanna
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