al_set_mixer_postprocess_callback - Man Page

#include <allegro5/allegro_audio.h>

bool al_set_mixer_postprocess_callback(ALLEGRO_MIXER *mixer,
   void (*pp_callback)(void *buf, unsigned int samples, void *data),
   void *pp_callback_userdata)

Sets a post-processing filter function that’s called after the attached streams have been mixed. The buffer’s format will be whatever the mixer was created with. The sample count and user-data pointer is also passed.