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

[Jeff LaCoursiere]

On Thu, 12 Nov 2009, Cary Fitch wrote:

> I am not sure what the problems are and the reasons for the basic 64K modems
> used in VOIP are.  I understand the compressed codecs that get the bandwidth
> down to 20-30 K.  And perhaps the 64K units give much better potential audio
> than you would get on a normal POTS line.
>
> But, as phone circuits VOIP/SIP doesn't seem to perform as well as plane old
> phones.
>
> Multiple transcodings cause issues.  Today a cell phone or a POTS line phone
> can send DTMF clearly enough to operate a credit card or other interactive
> tone based system at the far end.  With SIP it is sometimes "chancy".
>
> 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.
>
> Cary Fitch

Isn't that ulaw/alaw?

j

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