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-   -   Does G.711 have silence suppression? (http://www.velocityreviews.com/forums/t232406-does-g-711-have-silence-suppression.html)

Alex 07-31-2003 07:39 PM

Does G.711 have silence suppression?
 
Hi,

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

Thanks.



Bebop 08-01-2003 06:06 AM

Re: Does G.711 have silence suppression?
 
Alex <someone@microsoft.com> wrote:

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



Yes, most codecs have the silence suppression feature.

Cybraxis 08-01-2003 07:48 AM

Re: Does G.711 have silence suppression?
 
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 further.....in fact the packetization overhead will
require more bandwidth than is needed to carry PCM on the original TDM
serial stream.

"Alex" <someone@microsoft.com> wrote in message
news:1059680503.257889@ns1-ext.dcu.ie...
> Hi,
>
> I've read that G.711 doesnt compress voice data and operates at 64kbps.
> But does this standard have silence suppression?
>
> Thanks.
>
>




SG 09-05-2003 03:39 AM

Re: Does G.711 have silence suppression?
 
Most voip device firmware will support VAD/silence deletion, otherwise,
plainly put, there's one less large reason for voip to exist.

"Alex" <someone@microsoft.com> wrote in message
news:1059680503.257889@ns1-ext.dcu.ie...
> Hi,
>
> I've read that G.711 doesnt compress voice data and operates at 64kbps.
> But does this standard have silence suppression?
>
> Thanks.
>
>
>





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