Different/Unrecognized content type returned for the audio file

We are facing a problem of wrong content type returned when accessing the uploaded file. We are trying to play the audio file in iOS SDK, expected content-type is audio/mp4 where as dreamfactory returns audio/x-m4a which is an unknown content-type for iOS SDK.

How to solve the problem? There can be a solution we think of, writing a Pre-Script to change the content-type of the file requested, but not sure HOW?

If anyone can put us in right direction it will be very helpful.