al_identify_video_f - Allegro 5 API

       Tries  to  guess the video file type of the open ALLEGRO_FILE by reading the first few bytes.  By default
       Allegro cannot recognize any file types, but calling al_init_video_addon(3alleg5) will add  detection  of
       the types it can read.

       Returns  a pointer to a static string with a file extension for the type, including the leading dot.  For
       example “.ogv”.  Returns NULL if the video type cannot be determined.

       al_identify_video_f - Allegro 5 API

al_init_video_addon(3alleg5), al_identify_video(3alleg5)

Allegro reference manual                                                            al_identify_video_f(3alleg5)

       5.2.8

              #include <allegro5/allegro_video.h>

              char const *al_identify_video_f(ALLEGRO_FILE *fp)