[ltp] VOIP

[James Knott]

perley@adelphia.net wrote:
>>You may experience quality degradation calling "minor" markets where
>>there is no PSTN gateway...for example when I call New Zealand, the
>>closest gateway is Taiwan, and the call is then passed on to a cheap
>>Taiwanese LD company who probably compresses the hell out of it and
>>sends it to NZ...so I get up to a three second delay.
> 
> 
> The main cause of degredation is not that the Taiwanese LD uses excessive compression as that the signal is getting at least 2 generations of compress-decompress-recompress.. each generation likely set at an "acceptable" quality, but add them together and you sound like you are underwater.
> 
> I've been hearing that a lot on radio/TV news lately with voice from remote correspondants in Iraq etc... pocket voice recorder played back through wireless (satellite?) phone, LD circuit, stored compressed on the network's computer.. THere's 4 generations.
> 
> 

Then there's the packetizing delay, that can interfere with 
conversations.  For an example of the delay, use a digital cell phone, 
to call someone nearby on another digital cell phone.  Listen for the 
time delay, between the direct sound and that carried through the phone.