Re: VOIP codecs and interoperability (was "Re: my future telephones") [telecom]

On 8/26/2009 3:53 PM, Geoffrey Welsh wrote:
Thad Floryan wrote:
G.711 is supported by most VoIP providers.

VOIP noob question: if a VOIP provider is going to interoperate with an ILEC
(or other CLECs who have to interoperate with an ILEC), wouldn't the samples
have to be in G.711 format anyway? If so, wouldn't the question then be, do
we want to save on bandwidth over our 'internal' network and convert at the
interchange points, or to carry the data everywhere in that format for
convenience and give our customers the codec quality they've come to expect?

My experience with VoIP is limited to asterisk; I didn't buy the Ooma
thing last month (money is tight).

For the systems I've setup, a PRI is ordered and run from the CO to
the client site. Here in California it's basically fiber now to a
wiring closet, then wire to the server room computer which has a PCI
card (model number escapes me, it's been a few years) that is the
client's endpoint of the PRI. Think of the PRI as a T1. So, yes, G.711
is used for the interface to the PSTN.

Internally to the client, I don't specifically know if G.711 is being
used -- it's a function of which instruments are on the VoIP LAN.
Cisco 7960 VoIP phones are typically used and their voice quality is
excellent even using a headset plugged in their backs.

Asterisk voice mail is saved in several formats, one of which is PCM,
and that sort-of implies G.711.

Looking right now at my old AT&T 3B1 manuals and the Voice Power
manuals (noting I still have 3 functional systems), it looks like
G.711 but I don't specifically see that nomenclature. Audio is sampled
at 64 kbps and it's definitely claimed as µ-law with no compression in
the Voice Power Programmer Applications Reference manual.

Hmmm, haven't looked at these manuals in awhile, and it almost appears
one can create a miniature CO with the 3B1s and the Voice Power cards
(with up to 7 Voice Power cards per 3B1).

.

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