MP4, a shortened name for MPEG-4 Part 14, is a multimedia container format standard specified as a part of MPEG-4. It is most commonly used to store digital video and digital audio streams, as well as other data such as subtitles and still images. Like most modern container formats, it allows streaming over the Internet. The official filename extension for MPEG-4 Part 14 files is MP4, thus the container format is often referred to simply as MP4.
Since MP4 is getting more and more popular, despite containing both audio and video, has a very small file size and can be sent over the internet at great speed. The file can be watched in perfect quality immediately upon receiving. it is quite common to people who use the latest iPod, iPhone and PSP. An MP4 file uses separate compression schemes for audio and video. Video is compressed using the MPEG-4 encoding algorithm, while the audio is compressed using the AAC compression format. But since MP4 is a container format, it can also contain an MPEG-2 AAC or an MP3 bit stream. These different formats are given in the header of an MP4 file, specifying the exact object types in the container.
Although MP4 is the most widely-used video format and accepted by most applications and devices, it is sometimes not recognized by these apps/devices such as iMovie. That's because MP4 is a container format which may include the video/audio codec not supported by the apps/devices. You'll need to either convert it to the accetped formats like MOV or install the codec plug-in. Know More>>