u-law, a-law verses G.723, G.729, GSM etc

William Muriithi william.muriithi-Re5JQEeQqe8AvxtiuMwx3w at public.gmane.org
Tue Dec 16 19:40:21 UTC 2008

Hi pals,

I am not sure if what I have in mind is correct and nothing picked up
by google seriously satisfied me and that is why I am posting this.

Its on VOIP. There is these compounding algorithms - according to
wikipedia, u-law and a-law. Then there is the voice compression
algorithms or codecs? I mean G.723, G.729, GSM to name a few.

Now I kind of know how they work but a little mixed up as to whether
they are inclusive, exclusive or just one thing with different names.

For example, G.711 is in some on line article also called u-law. This
is not a single incident and the whole business has made me feel

My take of it is this, when a call is received, its taken through
either u-law or a-law depending on geographical location. The
resulting audio signal is then taken again through the later group -
G.723 or GSM. The result is then packed as an IP packet and delivered
to destination where the reverse happen. Now, is this the correct or I
could as well be smoking pot?

audio <-> a-law <-> G.723 <-----------------> G.723 <-> a-law <->

Ah, now I even noticed something else. Someone could call from Canada
- read a-law to UK where u-law is used. Now that would result to using
one algorithm for compressing and another for expanding and I do not
believe the result would be intelligible. Someone please educate me


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