[Coco] Using a coco modem with VOIP

[Dave Philipsen]

There are various codecs that certain devices support for VoIP and some are more lossy than others. It’s been a few years since I messed around with this stuff on my asterisk server but I think G.711 is a fairly high quality codec that requires around 85 kbps bandwidth. In order to make it work, though, both ends of the VoIP connection would have to support it. I’m guessing that SIP probably negotiates to find out the best protocol supported by both ends of the link before establishing a connection.

Dave

> On Nov 11, 2019, at 12:46 PM, William Astle <lost at l-w.ca> wrote:
> 
> On 2019-11-11 11:09 a.m., rietveld rietveld wrote:
>> Has anyone had any success using a dial up modem with a VOIP. I have not had any luck doing this using my magic jack. I would love to be able to save the long distance charges
> 
> I would be surprised if it works on VOIP connections at all. This is simply due to the lossy compression used to squeeze voice communications down minimal bandwidth. This pretty much destroys the fidelity of the modulation used by the modems. Also consider that if the effective bandwidth of a VOIP connection is 8kbps, then you can't get more than 8kbps data speed even with perfect data support over the connection, and once you add in the audio modulation, you lose a fair chunk of that.
> 
> (Arguably, VOIP connections destroy voice fidelity, too. I absolutely despise talking to people who are using VOIP connections most of the time due to the ridiculous amount of distortion that is often present.)
> 
> Now, an uncompressed or losslessly compressed VOIP connection would probably work. Or one that detected the modem handshake and adapted the compression algorithm to match.
> 
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