MP4 and M4A and how to convert it

MP4 is the short form of the multimedia format MPEG-4 Part 14. It can be used to store digital audio files, digital video files, subtitles and still images. A device that is able to play .mp4 files is named MP4 Player.

The .mp4 format is nearly similar to Quick Player’s .mov format, but supports other MPEG features. Since MPEG-4 internet users all over the world are confused. The word .mp4 was first used by Apple. The problem since MPEG is, that people do not know, what an .mp4 file contains. As they knew an MP3 file could contain either audio or video streams, it wasn’t that clear with .mp4. This container format may also hold images or subtitles. Matter of fact Apple started popularizing the word .m4a, for audio/video content.

Since then everybody could figure out, a .m4a file, contains audio or video, while a .mp4 file could also hold subtitles and still images. Because there is no difference between the file format of both .mp4 and .m4a, most players should be able playing their audio/video content without problems. Audio only files are normaly encoded as a .m4a file. ITune’s DRM audio streams use the .m4p extension. Audio books and podcast files can contain .m4a, but use the .m4b extension more often.

A simplified version of .mp4 is used by 3G mobile phones.

This data can be embedded in a MPEG-4 Part 14 file:

Video: MPEG-4 Part 10, MPEG-4 Part 2, MPEG-1

Audio: AAC, MP3 MPEG-4 Part 3, MP2, MPEG-1 Audio Layer 1, CELP, TwinVQ, SAOL

Subtitles: MPEG-4 Timed Text

Nero’s use of DVD subtitles (Vobsub) are not a part of the MPEG-4 file format standard, even though they are sometimes used in MP4 files. That means, some programs are not supporting them.

At last: .mp4 files are usually used for the iTunes DRM copy protectet content. M4A in the standard for iTunes DRM-free, unprotected content.

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