[Asterisk-Users] Distortion/crackling/skipping problems on outgoing calls -- please help!!!

[Rich Adamson]

> So, can no one give me any suggestions? Perhaps I can elaborate upon 
> further testing and attempts to debug this tremendously frustrating problem.
> 
> My softphone (typically IAXComm, but same results connecting via SIP on 
> Xten Xlite)  is installed on a P4 1.6 w/ 256 megs of RAM and an 
> integrated sound chipset (Intel/AC97). I've had some problems with this 
> chipset in Linux, and it doesn't support hardware mixing, so I've had to 
> attempt to get dmix and ALSA running in an acceptable fashion; needless 
> to say, I still have problems, and I don't know if this is related.
> 
> I can record and playback my own voice and other audio (podcasts, Net 
> radio, and music) fine with this headset (some cheap, Chinese $15 
> headset). However, when it comes to receiving decoded audio on the other 
> end of a VoIP conversation, it sounds "scratchy," distorted, crackly, 
> whatever you want to call it. It's not the clarity so much as it is the 
> other things I just mentioned. It's very hard ot put into words, but I'm 
> hoping *someone* can associate with my problem.
> 
> To make sure it wasn't my Asterisk box that was mucking things up, I 
> connected directly with my softphone to my outgoing VoIP terminators, 
> voipjet and Voxee. Sure enough, it sounded *exactly* the same as it does 
> going through my * box on the LAN and then out through the public Net to 
> voipjet and/or Voxee. Thus, I know it is my side of the equation that is 
> mucking things up, but I cannot for the life of me pinpoint exactly 
> *WHERE* this is taking place.
> 
> Actually, I also unplugged my headphones and plugged back in the 
> speakers, and it sounded roughly the same, but it's harder to tell 
> because they're not surrounding your ears, quality isn't as clear, and 
> ambient noise can be more easily heard and is distracting.
> 
> I'm thinking, at this point, that it's my sound card that's messing 
> things up, or its configuration or something. However, can anyone 
> explain *why* non-VoIP-conversations sound perfect on my speakers and 
> headset, while VoIP calls sound very bad?

If I were to try to diagnose the above, I'd be using Ethereal to 
capture the voip packets coming from your itsp's, and analyzing 
that captured data to look for unusual things.

If your itsp connections are sip based, ethereal has a utility to 
analyze/summarize some of this for you. If those connections are iax
based, then you will need to analyze the packets yourself looking
for unusual things.

Analyzing the packets (either sip or iax) can consume a lot of time,
but you really need to ensure those packets are arriving in a consistent
manner, timestamps contained within the packets are consecutive and
proper, packets are not arriving out of order, etc. At the same time
that you're capturing those packets, use the facilities within asterisk
to summarize what it thinks is going on (eg, 'iax2 show netstats'),
so _that_ data can be correlated to the info derived from the packet
captures.

If this is a small soho * system, then run ethereal right on the same
asterisk system capturing the data as it arrives at the system. Doing
so will help identify any issues that you might have involving your
local lan, broadband issues, etc, etc.

Assuming the problem that you've described is consistent and happens
on a regular basis, you don't need to collect and analyze megabytes 
of packet captures. Just collect a short duration sample that is 
assured to contain the representative packets associated with the
bad audio (maybe five or ten seconds worth). If the analysis does
not indicate a problem at that point, then at least you know the
problem is internal to asterisk, etc.

If you don't feel you have the skills or knowledge to do that
analysis, then hire someone that can.

Both your original post and the followup post contain a ton of 
adjectives and adverbs describing a technical problem, but contain 
little (or no) technical data (such as the results from above or 
results from various * show commands) that would allow anyone to 
comment on your problem. So, doubtful anyone is ever going to reply
to such postings with anything helpful.