MP4 files are some of the most commonly used file types for sharing audio and video files on the internet. M4A is a type of lossless audio file created by Apple that uses its Lossless Audio Codec to compress audio files without losing any of the audio information. These files are highly compatible with the popular media player iTunes. As far as the codecs, M4A files are basically MP4 files without the video track, which makes them similar enough to convert by simply changing the file extension.
Search your hard drive for the MP4 file that you would like to convert to M4A. Go to the folder where the file is stored.
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Right-click on the MP4 file. A menu of available actions will come up. Select "Rename" from the list. This will highlight the name of the file and make it editable.
Delete the MP4 file extension. The file extension is everything that appears after the dot in the file name.
Type "m4a" in the place of "mp4." Make sure you type the extension in all lowercase letters as file extensions are case-sensitive. Press "Enter" on your keyboard to save the change.
Confirm that you want to make the change. When you attempt to change a file extension, you will receive a popup warning that altering the extension may make the file not work properly. Click "Yes" to indicate that you want to make the change anyway.
Test the file. Simply double-click to begin playing. This will open the M4A file in your default media player.