[Asterisk-Dev] IAX vs. IAX2 - problems and notes

[John Todd]

I've done some testing with both IAX and IAX2 between endpoints, and 
I've noticed some differences:

1) IAX2 doesn't seem to have "comfort noise", while IAX seems to have 
a steady background "hiss" which is what I'd expect on a phone

2) IAX2 has some serious sound squelching/clipping that interferes 
with call audio.  It almost appears that IAX2 is half-duplex.  If the 
other end of the line is talking, I can't break in to the 
conversation and talk over them or interrupt; I have to wait until 
they're done talking before I can be heard, unless I shout into the 
phone and create a "louder" noise.  This may be related to #1.

3) IAX2 seems to drop the audio fairly frequently in intermittent 
intervals.  If I am silent for too long, the audio from the far end 
stops, and I'm left with a silent line.  I then need to "create a 
noise" like blowing into the microphone or say "HEY!" into the 
microphone for the audio to start up again where I can hear the far 
end.  Needless to say, this is very disconcerting to myself and the 
other party.  This may be related to #1 and #2.

4) IAX2 has better sound quality, as far as clarity of the voices on 
the channel.

5) IAX2 and IAX have broken "jitter" and "lag" variables; they often 
jump up into numbers like 65123ms, which is obviously false.  This 
normally happens after a few minutes of conversation time.

6) IAX2 will often drop one side of the conversation completely. 
Normally, when I initiate the call, it is my audio channel that will 
be lost. I can hear the other end, but they cannot hear me.  We hang 
up, and try again.


My experiences with these issues are relative to my configuration, of 
course, which is normally SIP (G.711, Cisco ATA-186) -> * -> IAX -> * 
-> SIP (G.711, Cisco 79xx)  However, they are real issues for me, and 
warrant some further data from anyone else out there with the same 
problems.  If more than one person has seen the same problems, I'd 
like to talk with them about it.  I've already found one person 
(tclark) who has reported some of the symptoms, and I'd like to find 
others so that we can present a better view of the issues to Mark (or 
anyone else) who might be able to narrow them down

JT