When I create a file in which I have synchronized audio and video , running the swf is desynchronized me

I need to create files in wich audio and video are perfectly synchronized . The problem is that when I export and run them, they are out of sync . Maybe it's a problem with my computer, or maybe the graphics card, or simply the sotware.

This is my PC :

Inte Core i5-3337U CPU 1.80 GHz , 6 GB RAM , Nvidia GeForce GT 740M .

Thank you.