If you are unable to open an MP4 file on our media player, try changing the video format. There are many good video converters available on the internet that can help you convert your MP4 to MP3, AVI, ...

The native file format for iPhone ringtones is M4R. In order to use MIDI ringtones on your iPhone, you must first convert them to M4R. You can use iTunes and rename the resulting audio file to achieve ...