[Asterisk-Users] Asterisk and Cisco 7960 problems persist (for me, anyway)

[Rich Adamson]

> It seems that each time I get a new checkout of * from CVS my Cisco 7960 
> works worse than before. I know this stuff's in flux, so I mention this 
> in case it's news.  Anyone else having trouble?  What I'm seeing (er, 
> hearing) is really choppy audio. The previous version I had installed 
> had fairly frequent audio dropouts (not present when I make the same 
> calls through the same * box using a TDM400P interface).

Brian,

Are you having the choppy audio only on iax2 links or on other calls as
well?

There was an issue with erratic iax2 timestamps which caused the Cisco
phones to effectively drop any sip packet that had uneven timestamps
causing extremely choppy audio. The choppy audio (as I seen it) was
only in one direction (from the iax2 source with the erratic timestamps
towards to 7960 phone).

If your issue is not associated with iax2, then be aware the Cisco v6.x
code changed DSP firmware internally, and any sip/rtp packets arriving with
uneven timestamps (within the rtp pkts) will be dropped and cause the
choppy audio. You should be able to see the timestamps with ethereal.
The timestamp difference between successive pkts should be exactly
160 milliseconds; if its anything else, the phone will drop the pkt.
(Not sure if that is a real Cisco bug or a planned change, but it
certainly has a hugh negative impact on voice quality.)

I'm running CVS-HEAD-05/02/04 with no problems today.

Rich