[asterisk-users] How can I improve call quality?

Gordon Henderson gordon+asterisk at drogon.net
Mon Apr 23 02:56:02 MST 2007

On Mon, 23 Apr 2007, Adrian Marsh wrote:

> So which is the best quality?
> Gradwells www site lists g711u and g729a, but we currently use ulaw/alaw
> with them too..

ulaw is g711u ...

g711 (u or a), or ulaw or alaw which are the same things will give you the 
best audio quality, but it's not better than a perfect copper-wires 
telephone line because that's what BT (& others) use internally inside 
their digital networks.

So if you have the bandwidth, you'll never get better audio quality than 

But if you're bandwidth starved then you may have no choice to use a 
compressing codec in which case, it's a trade-off between CPU power 
required to encode/decode the audio data vs. speech quality. You can get 
some fantastic compressions, but then you end up sounding like a dalek...

The difficulty is when you have packet loss - in this case, which codec 
gives the best results when it loses a packet or 2...

I wish I knew the answer to that last one... I've used g711 over a lossy 
wifi connection and it's been acceptable to me, but maybe not to others!


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