[App_rpt-users] Codec Negotiation

[Will Bashlor]

Hi List,

Ok, so I have a portable node and it works great at home but on the road
using my iPhone hotspot with Verizon it's quite jittery and doesn't sound
very good, even when I have 2 or 3 bars. I can connect to the same node
using echolink and it works fine even with 1 to 2 bars.

I'm using the hamvoip image without any codec changes and I notice it
connects to our local repeater hamvoip node with g726aal2 which makes sense
because  g726aal2 is first in [general] which I believe controls outbound
connections.

So I wanted to see what I sounded like so I connected to 40894 so I could
hear my own voice. It connected using ulaw for some reason. The only way I
could get it to change was to comment out the codecs I didn't want to use
in [general]. Apparently it doesn't negotiate how I think it does.

On ulaw and  g726aal2 it sounded pretty terrible. gsm was better but it was
still broken up. I wanted to try ilbc but codec negotiation failed which
I'm sure means that 40894 doesn't allow ilbc.

I then connected successfully to our local repeater node with ilbc and it
sounded just fine, even with one bar, but I need to test more...

Is this anyone else's experience with using hotspots?

I've modified the codec under [genera] to the below, which the way I
understand is for outgoing connections. And the codec order is the order of
attempted negotiation. I ordered them on my portable node in order of least
bandwidth to greatest.

So with that said, when I connect to my local node, which allows ilbc, why
does it negotiate to g726aal2?

And how can I setup iax.conf so it always connects using the lowest
bandwidth codec that the other side allows?

allow=ilbc
allow=gsm
allow=g726aal2
allow=ulaw

73,

Will, KE4IAJ
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