After reading the forums on this matter, I have found the list of acceptable files in the function.php file. However, I am not sure this is what I should be doing. My plan is to add the 3gpp video to the list, but I don't know what to type. Also, those posts were mostly written by network admins. I don't know if I understood the other posts.
Would someone show me what to do with this section of the php file, or is this the wrong section or the wrong file?