[Asterisk-Dev] Increasing reliability on lossy connections (iLBC, etc.)

[John Todd]

At 1:22 PM -0600 1/12/05, Michael Giagnocavo wrote:
>
>>The better solution would be to implement iLBC's packet concealment
>>methods, and then use that codec for your IAX2 trunking.  I am
>>currently under the impression (someone correct me if I'm wrong!
>>It's been a while since this was discussed...) that the iLBC code in
>>* is not completely implemented due to timing issues, so that iLBC's
>>great packet concealment methods are unused.
>>
>>Sending packets twice is... a frightening hack.
>>
>>JT
>
>Yes, but that won't work at all with my IAX2 hardphones since they don't
>support iLBC :S. I'm just wondering if resending would work, as hackish as
>it is. And... will iLBC handle 8% packet loss gracefully? Apart from the
>packet loss, the lines will do G711 fine (even sending duplicates).
>
>-Michael

If you have an Asterisk server at both ends (one in North 
America/Europe/wherever, one in Central America) then you can just 
convert from iLBC to G.711 at the "far end".  However, if you're 
talking about problems with the last mile, then yes, the awful hack 
seems like the only method you might have.  Doesn't make it any less 
of a frightening hack.  :-)

Yes, iLBC handles losses of that large reasonably well; looks to be 
an MOS of around 3 at 8% loss rate.  Look at the graph on the main 
page...

http://www.ilbcfreeware.org/

I assume you're using IAXy's?  It's kind of a crime that something 
that talks IAX doesn't have iLBC; they work so well together... but I 
suppose there is a cost/processing power limit, and iLBC requires 
some horsepower.  Maybe pony-power; it's only a single channel...



To put us back on the -dev charter here: there was discussion some 
months ago about throwing out the receive-based timing mechanisms and 
using system clock or the USB Zap-like timers for packet tx/rx 
timers.  I was under the impression that these patches would allow 
the use of the iLBC loss-suppression features.  Did anyone ever start 
working on that, or complete it?  It's Yet Another Worthy Project.

JT