[Asterisk-Users] rtp sound quality?

[Bob Knight]

Rich Adamson wrote:

>pstn -> sip gw -> * -> C7960
>
>When I dial into * via the pstn, I hear the ivr menu just fine (good
>quality). I press 3000 (valid extn), and I begin to hear ringing however the 
>ring back is very very choppy.
>
>I answer the C7960, and speech is clear in both directions. Place the C7960
>extn on hold, and the MOH is very choppy. Checking 'sip show channels' indicates
>both the sip gw and C7960 are using ulaw; Both are 100 meg on local LAN. Top
>suggests all processes running less then 1 or 2 percent.
>
>The choppy sound only happens on the sip gw (Mediatrix 1204). MOH between two
>C7960's works fine. MOH via x100p works fine.
>
>Tried canreinvite=no and yes; no difference. Using a packet sniffer, I see a
>~200 millisecond delay about every 1/2 second or so (varys), but nothing within 
>the trace to hint at a layer-2 problem.
>
>Anyone have any thoughts as to why ringback and MOH are choppy but conversations
>are fine?  Anything else I can look at to isolate the issue?
>
You need to disable VAD on the 1204.
The 1204 stops xmiting RTP to * if it does not detect any acoustic energy.

* can not clock itself sending RTP packets.
It relyes on receiving RTP packets for it's timing.
Try singing along with your MOH and the choppiness should go away, or
disable VAD, or fix * RTP driver.

-- 
Bob Knight
[-w] the work option
bk at minusw.com
925-449-9163