[Asterisk-Users] ilbc high bandwidth

[Steve Kann]

Roy Sigurd Karlsbakk wrote:

>> Good day all
>> We have 2 asterisk servers connected to each other via IAX2 using ilbc.
>> Each call we make goes up to 25kbit and each one there after 25kbit as
>> well
>
>
> bit rate is 13333bps, giving 1667 bytes/sec
> packetization is 20ms, giving 34 bytes per packet

Actually, iLBC in asterisk uses 30ms frames..

> IAX header is 4 bytes
> UDP header is 8 bytes
> IP header is 20 bytes

you're also forgetting the ethernet, PPP, or other low-level overhead..

> this means one packet is 34+4+8+20=66 bytes
> 50 packets per second gives 3300 bytes/per second, meaning 26400bps
>
>> Is there a way to bring it down?
>
>
> yes
> hack asterisk to use a lower packetization value

Or use trunk mode, which can do this for single calls (try setting 
trunkfreq to 60), and also significantly reduces overhead for multiple 
calls..

-SteveK