How to Convert M4V to MP4
Things You'll Need
Instructions
1Download and install OJOsoft Total Video Converter (see Resources), which will allow you to convert M4V into MP4.
2
Load the M4V file that you want to convert by clicking the "Browse" button on the right-hand side of the input text box and choosing the file from your file viewfinder.
3
Select the output format you want to convert the file into. Choose the "To MP4" button located across the top of the application.
4
Select the MP4 profile. There is a drop-down menu named "MP4 Profile" where you can select various quality settings. Higher-quality videos will take longer to convert, however.
5
Convert the file by pressing the "Convert" button located in the right-hand side of the application.
Source...