set_sound_input_source − Selects the audio input source. Allegro game programming library.
#include <allegro.h>
int set_sound_input_source(int source);
Selects the audio input source. The parameter should be one of the values:
SOUND_INPUT_MIC
SOUND_INPUT_LINE
SOUND_INPUT_CD
The function returns zero on success, or -1 if the hardware does not provide an input select register (ie. you have no control over the input source).