[Asterisk-Users] A software FAX modem

[Steve Underwood]

Steven Critchfield wrote:

> [...]
>
>Now I just wish it was robust enough to work over my IAX connection
>without problem. I'm sure it is the GSM compression that is biting it.
>I'll run some more tests and then maybe I'll move it to a machine
>located in the same rack as my phone gateway machine. At that time, it
>shouldn't be a big deal for me to use G711 for the transport. I'm just
>wary of putting it on my production switch at this moment. 
>  
>
Any compression below G.711 will screw most modems. GSM certainly will. 
If you use G,711 you still need to beware of any data slips. Even a 
single sample hop will kill a modem faster than 1200bps. They encode 
data as phase, and the phase will jump irrecoverably with even a single 
sample of slip.

Regards,
Steve