How it works¶

Traditional “controller-based” modems generally used a microcontroller and a DSP to handle all aspects of modem communication on the device itself. Later, so-called “Winmodems” were introduced that allowed for field-programmable DSPs and moved the controller and other functionality into software running on the host PC. This was followed by “pure software” modems that moved DSP functionality to the host as well. The physical hardware of these softmodems was only used to connect to the phone network, and all processing was done in software.

D-Modem replaces a softmodem’s physical hardware with a SIP stack. Instead of passing audio to and from the software DSP over an analog phone line, audio travels via the RTP (or SRTP) media streams of a SIP VoIP call.