I want to dial-up through VoIP. Yes, I know that it's almost impossible. I have heard that softmodems use software for DSP, but I guess the code its hardware specific. If I only could isolate the code that makes the modem signal I could use it on my project. Anyone ever heard about a library that would fullfill my needs?
PS: iaxmodem only modulates fax signals.
Most telephone audio codecs compress the data using perceptual coding. This coding can not reproduce all frequencies of the source at the target, as it omits the ones that are irrelevant. Therfore you can not use a data encoding that encodes binary data into audio frequencies (like a modem does) with GSM or VoIP.
Besides that: having VoIP means having an IP connection, so why not transfer the data via IP (if it needs to be secure via a VPN instead of trying to use a modem over VoIP?
I'm not sure if this will help you, but take a look at the Dialogic SDK and it's API manuals.
I've been doing some work on a Dialogic voice/fax board, and on one of the machines that I'm using I've set up the SDK but without having a board installed (they're pretty expensive).
I've noticed that on this machine, since I don't have the board installed, it's provided me with a softIP virtual-hardware board, managed by their software.
I haven't played with the VoIP stuff myself, but it might provide some of what you need.
Here's a screenshot.
Downloading and installing the SDK is free, though when you enter your details they will probably give you a call and try to sell you a board.
