The 'Open with' option is automatically changed with my app when my app is installed

I am developing an Deskto开发者_JAVA百科p application which organizes and plays movie files. So, I have added the mp4, mov, avi, m4v (mp4, mov, avi, m4v extensions) as document type under Properties of my application target. The problem is that when the user installs my app in Applications folder of his system, the default option for opening the mp4 movie file changes to Voila from QuickTime Player automatically. The default option is nothing but the 'Open With' option provided in the Info window of a file. This happens for most of the users. Why is this happening? How do I solve this?

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