Poor Call Quality

[davegravy]

I'm experiencing poor (tinny-sounding) VOIP call quality. Internal calls suffer the same problem, so I've ruled out my VSP as the cause. The problem is also independent of softphone client and choice of protocol (IAX/SIP).  Any ideas what the culprit could be?

Could this be related to the fact that my home network is completely wireless after the core?

[colinjones]

try different codecs/bitrates in the configuration....

[tschak909]

What setup are you using as far as phones? are you using simplephones? If so, PLEASE get a Phoenix Solo USB microphone.

-Thom

[davegravy]

The codec my VSP suggests and the codec I'm using is u-law. I understand it's the best (provided you have the bandwidth which I certainly do...or should) and I understand the bitrate is fixed at 64kbps or thereabouts.

I have set [disallow=all] and [allow=u-law] for all extensions and protocols. Asterisk CLI verifies that u-law is being used exclusively.

I am testing as follows:

Call between two internal extensions, one is an iPhone with Siax (IAX) using internal wifi network, the other is a PC with Voiper softphone (IAX). I am listening from the PC via ipod headphones, while my girlfriend talks into the iphone. The call quality is exactly the same tinny sounding quality as I get when I make external calls through my unlimitel IAX trunk.

Does anyone else have this problem?  I understand I should be able to get landline quality or better but this is far from that.

[wierdbeard65]

Call quality issues with VoIP are almost always down to network issues. Having said that, they are oftem intermittant in nature. Bandwidth problems show up as packet loss, which sounds "crackly" (Anything over 1% packet loss is considered unacceptable, which is why so many commercial VoIP installs have problems, the data guys say the network is "good" at 5% loss!!) unless you use packet loss concealment, which makes the audio sound robotic at high levels.

Pay a visit to www.voiptroubleshooter.com. There are a lot of sample wav files there which demonstrate particular issues and explain what to do to fix them.

HTH

[davegravy]

Didn't realize VOIP was so sensitive. I read at some point that linuxmce has a QOS feature to prioritize voice data, but I just did some research on my aging wireless access point and it seems to be missing any such features. Will be interesting to see if there's any improvement using wired LAN only.

[tschak909]

Dude, I should _SMACK YOU HARD_ for doing all wireless inside the LMCE network. This works okay for orbiters and certain other devices, BUT DON'T DO THIS FOR YOUR VOIP TRAFFIC!

-Thom

[dlewis]

I would bet you'll get a lot of improvement over LAN.

[colinjones]

if you must use wireless, then you must have a dedicated access point and setup QoS for all the voice traffic. Voice traffic is "real time" traffic transmitted using UDP which means that if a packet is lost or delayed in transmission, it is simply dropped as there is no time to retransmit the data (the time to play the "sound" it represents has past!) which means you immediately hear the effects of traffic congestion.

You need to have a wired NIC on the internal interface of your Core, connected to a switch that does some form of QoS, then an access point connected to that, that also does QoS. Once QoS is configured, you will at least then stand a chance that other internal network traffic may not kill your VoIP traffic. Also try different codecs. I got my SIP wireless handset working quite well even under network traffic loads... but don't expect it to be bullet proof!

[davegravy]

Thanks guys. I don't expect it to be immune to high network traffic, but expect it to perform well under low load which is how I've been testing it.

What about a wireless router that has QOS? I was thinking of replacing my existing access point with a Linksys wrt310n running DD-WRT.