MPEG-4 Explained

MPEG-4 Explained

According to, Moving Picture Experts Group 4 (MPEG-4) or (MP4), introduced in late 1998, is the name of a group of audio and video coding standards as well as their related technology standardized by the MPEG group (Moving Picture Experts Group) of ISO / IEC. The main uses of the MPEG-4 standard are audiovisual media streams, CD distribution, two-way videophone transmission and television broadcasting.

MPEG-4 takes many of the features of MPEG-1 and MPEG-2 as well as other related standards, such as extended VRML (Virtual Reality Modeling Language) support for 3D viewing, object-oriented compound files (including audio objects, video and VRML), support for external Digital Rights management and various types of interactivity.

Most of the features that make up the MPEG-4 standard do not have to be available in all implementations, to the extent that full implementations of the MPEG-4 standard may not exist. To handle this variety, the standard includes the concept of profile and level, which allows defining specific sets of capabilities that can be implemented to meet particular objectives.

Differences between MPEG-3 and MPEG-4

In these times it is quite common to buy a portable music player, usually an mp3 or mp4, which puts us in a situation at least curious and that is that most people know perfectly well that an mp3 is an audio file, but the same does not happen when we refer to mp4, exactly what is mp4? What are the differences between these two formats?

Mp3 is developed by the German Fraunhofer Institute, which together with Thomson Multimedia control most of the patents for this format. We are facing a patented and licensed file system, in which royalties are collected every time there is profit motive in its use.

The system began to be developed in 1986 and in 1992 the Moving Pictures Expert Group (MPEG) approved its development and included the format as a standard in the MPEG-1 format under the name MPEG-1 Audio Layer III, later it would be expanded to be incorporated into the version 2.

The simplest explanation happens because the mp3 is compressed by eliminating sound frequencies that are not perceptible by the human ear, so we can compress a CD with an 11: 1 ratio, where a wav file of about 50 MB would occupy less than 5 MB maintaining a medium / high quality with the compression that most programs usually carry by default, 128 kbps at 44,100 Khz.

As a culturist and taking into account the relationship between audio and video, comment that there was an attempt to develop MPEG-3 that was originally intended for high-resolution television, but this was discarded because MPEG-2 continued to have a higher development.

At that time is when the leap to MPEG-4 is made, year 1998, this new development is more oriented to the distribution via web, videoconference, CD and television broadcasting. Part of the blame for the success of this format is Apple, having included it in the development of QuickTime; the most popular formats that use MPEG-4 are QuickTime mov and avi, generally Divx or Xvid.

And we come to MP4, Apple also influences the popularization of mp4 through the mp4a extension included iTunes and iPod, to differentiate it from MPEG-4. MPEG-4 is video with or without audio while MP4 can be audio, video and audio or only video, in addition to supporting images. Both extensions can be exchanged without problems, renaming an mp4a as mp4 or vice versa.

The MP4 format supports mp3, ACC and Apple Lossless audio, jpg and png images, MPEG, MPEG-4 video, and BT and XMT subtitles. The compression ratio is 16: 1 and they are self-executing files with which an audio file in mp4 comes to occupy more or less the same as an mp3 for having to include the player.

The greatest confusion that can arise in both formats is accompanied by the players, when the player for mp4 is developed it is decided to call it the same as the format in an attempt to position itself hierarchically above the mp3. If you see mp3 player and mp4 player you tend to think that the second is technically superior to the first, when this is not really the case, from what we have seen so far we can deduce that they are two different and differentiated things although they have some points in common.


  • Mp3 is CD-quality compressed audio.
  • Mp4 is a container format.
  • The mp4 offers a higher compression ratio.
  • The mp4 can also be video or images.

The mp4 is undoubtedly a more powerful format for capacity and possibilities, although when buying an mp3 or mp4 player we must pay special attention to the technical characteristics of the device and the supported playback formats since there are mp3 players that play video but it does not necessarily have to be mp4 and it is quite possible that they will try to sell it to us as such. On the contrary, an mp4 player should serve us to reproduce our mp3s, without problems since a priori it is a compatible and supported format.

This is, although it may not seem like it, a summary. With this we simply try to know a little more about these formats, in the links that are throughout the article you can access more detailed information on various aspects of some of the discussed formats. In any case, for more information, I would recommend looking at specialized sites or wikis since using search engines can become torture in that most of the results are usually from product sales sites or download pages.

Parts of MPEG-4

MPEG-4 is made up of several standards, called “parts,” including:

  • Part 1 (ISO / IEC 14496-1): Systems: Describes the synchronization and simultaneous transmission of audio and video.
  • Part 2 (ISO / IEC 14496-2): Visual: A compression codec for visual elements (video, textures, synthetic images, etc.). One of the many profiles defined in Part 2 is the Advanced Simple Profile (ASP).
  • Part 3 (ISO / IEC 14496-3): Audio: A set of compression codecs for encoding audio streams; they include variants of Advanced Audio Coding (AAC) as well as audio and speech coding tools.
  • Part 4 (ISO / IEC 14496-4): Conformity: Describes procedures to verify the conformity of other parts of the standard.
  • Part 5 (ISO / IEC 14496-5): Reference software: Consisting of software elements that demonstrate and clarify the other parts of the standard.
  • Part 6 (ISO / IEC 14496-6): Delivery Multimedia Integration Framework (DMIF).
  • Part 7 (ISO / IEC 14496-7): Optimized reference software: Contains examples on how to perform optimized implementations (for example, in relation to Part 5).
  • Part 8 (ISO / IEC 14496-8): Transport over IP networks: Specifies a method for transporting MPEG-4 content over IP networks.
  • Part 9 (ISO / IEC 14496-9): Reference hardware: Provides hardware designs that demonstrate implementations of other parts of the standard.
  • Part 10 (ISO / IEC 14496-10): Advanced Video Coding (AVC): A codec of video signals technically identical to the ITU-T H.264 standard.
  • Part 11 (ISO / IEC 14496-11): Scene description and application engine. BIFS.
  • Part 12 (ISO / IEC 14496-12): ISO-based format for audiovisual media: A file format for storing multimedia content.
  • Part 13 (ISO / IEC 14496-13): Extensions for the management and protection of Intellectual Property (IPMP).
  • Part 14 (ISO / IEC 14496-14): MPEG-4 file format: The designated container file format for MPEG-4 content; based on Part 12.
  • Part 15 (ISO / IEC 14496-15): AVC file format: For video storage Part 10, based on Part 12.
  • Part 16 (ISO / IEC 14496-16): Animation Framework eXtension (AFX).
  • Part 17 (ISO / IEC 14496-17): Subtitle format (in development – latest development in revision dated January 2005).
  • Part 18 (ISO / IEC 14496-18): Compression and streaming of typeface fonts (for OpenType fonts).
  • Part 19 (ISO / IEC 14496-19): Synthesized texture flows.
  • Part 20 (ISO / IEC 14496-20): Light scene rendering (LASeR).
  • Part 21 (ISO / IEC 14496-21): MPEG-J extension for rendering (in development – latest revision in January 2005).
  • Part 22 (ISO / IEC 14496-22): Open Font Format: open font format.
  • Part 23 (ISO / IEC 14496-23): Symbolic representation of music, SMR (Symbolic Music Representation).
  • Part 24 (ISO / IEC 14496-24): Interaction with the system and audio.
  • Part 25 (ISO / IEC 14496-25): 3D graphics compression model.
  • Part 26 (ISO / IEC 14496-26): Audio conformance.
  • Part 27 (ISO / IEC 14496-27): 3D graphics conformance.

It is also possible to define profiles at the part level, since an implementation of a part does not necessarily contain all of that part.

MPEG-1, MPEG-2, MPEG-7, and MPEG-21 are other groups of MPEG standards.