Andres wrote:
[EMAIL PROTECTED] wrote:
On Tue, 3 Aug 2004, Steve Underwood wrote:
Eh? G.729 has no particular features to allow more effective packet
loss concealment. iLBC has, but at the cost of a substantially
higher bit rate. In fact G.711 is a little ahead of G.729 in the
regard, since packets are completely independant. The smoothing in
G.729 means you need the previous packet to decode the current one
properly.
For IAX2, at least, Asterisk oes not use the lost-packet-concealment
of any codec. This is because the incoming frames "clock" Asterisk.
For iLBC's lost packet concealment to work, Asterisk would have to
start calling the decoder with a NULL at the point when the missing
packet shold have arrived.
This certainly explains why we get terrible audio at 10% packet loss
between Asterisk servers between 2 end points using iLBC, but if we
use 2 SPA2000s using G.729 to commincate directly with each other (and
having the same 10% packet loss), they sound pretty good. We had been
trying to figure why iLBCs loss concealment wasn't helping much. I
was never able to explain this until now:)
Thanks.
If you have 10% packet loss G.729 should sound awful. Are you really
getting 10% packet loss in the G.729 case? If not, why does iLBC give
that? Is the higher bit rate of iLBC pushing things over your available
bandwidth limit? Seems pretty odd.
Regards,
Steve
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