19.3. spandsp

Initially, the only way to handle faxing in Asterisk was through the spandsp library. spandsp provides a multitude of Digital Signal Processing (DSP) capabilities, but in this context all we are interested in is its fax functionality.

Asterisk has the hooks built in to make use of spandsp, but due to incompatible licenses, the spandsp libraries must be downloaded and compiled separately from Asterisk. Also, since spandsp was not written only for Asterisk, it will not assume that it is being installed for Asterisk. This means that a few extra steps will be required to ensure Asterisk can use spandsp.