MP4 is an ISO standard developed by Moving Picture Experts Group or MPEG. MP4 is also known as MPEG 4 AVC or advanced video coding. MP4 is getting more and more popular. In fact, it is now very popular to people who use the latest iPod players and PSP owners.

Just like how MP3s work by compressing music and audio files without affecting the audio quality, MP4 files are compressed video files.  This new technology is going to make video files decrease in size so that they are easier to work with and support.

Here are some file extensions used on files that contain data in the *.mp4 format:

• .mp4: official extension, for audio, video and advanced content files
• .m4a: for audio-only files; can safely be renamed to *.mp4, though opinions differ on the wisdom of this.
• .m4p: FairPlay protected files
• .mp4v, .m4v: video-only (sometimes also used for raw mpeg-4 video streams not in the *.mp4 container format)
• .3gp, .3g2: used by 3G mobile phones, may also store content not specified directly in the *.mp4 specification (H.263, AMR, TX3G)

There are many players such as VLC Media Player, Amarok, Songbird etc which are compatible with MP4. Next time you decide to download your favorite movie or song, think of MP4!