Mojo with Horan & Company, LLC wrote:
I've heard a MOS of 4.4 is ulaw/alaw, presumably like a local exchange
call through the pstn.
testyourvoip.com tells me that the highest score available with G.729
is 4.2, which is pretty darn close to 4.4.
Alaw and ulaw are about 4.4. ulaw on a robbed bit trunk is about 4.3.
G.729 is about 3.9. That doesn't sound like a big spread, but MOS tends
to bunch them together. G.729 at 3.9 is pretty reasonable, while
anything scoring 3.0 is bloody awful.
I don't know why I think this (or why I've heard it (or if it's
right)) but I think gsm is 3.8? Maybe someone can confirm or
disconfirm this. This kinda seems like the codec my long distance
calls go out on but I'm not really sure.
3.8 sounds about right.
http://www.testyourvoip.com/results.html?id=071GM0&result=0
(one of my more POOR results) approximates about 2.75 for 'tin cans
and string', 3.2 for a crummy cell phone call, about 3.9 for a decent
cell call, 4.4 or so for 'like calling next door', and the mystical
5.0 for 'better than being there'.
I wonder if 16kHz wideband codecs would bring our voice-carrying
experiences into the 5.0 range?
Much of the reason ulaw/alaw is way below 5.0 is due to bandwidth
limitations. 16kHz sampling gets much closer to 5.0 It takes more like
32kHz sampling to actually reach 5.0, though.
Steve
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