[asterisk-users] "POTS 4K linear codec"

[Benny Amorsen]

"Cary Fitch" <caryf at usawide.net> writes:

> Is there a plain 64K codec that would simply pass through the SIP server and
> be handed off to a PRI or phone co. trunk on a T1 on the other side of the
> SIP server?  Digital 64K telco sounds very good as a phone conversation.

You can't get a guaranteed bit-for-bit identical stream through SIP/RTP
or IAX. You can pick the same codecs as the PSTN uses (Alaw or ulaw,
depending on country), but jitter and packet loss still makes things
like DTMF or fax/modem unreliable. For DTMF it is better to signal that
in RTP or SIP, for fax you want T.38, and for modems you need incense
and strange rites at midnight.


/Benny