MPEG-4 Part 14

Icon of a VLC MP4 File

MPEG-4 Part 14 (not to be confused with MP4 player) is a container format specified as part of the ISO/IEC international MPEG-4 standard. It is used to store the audiovisual formats specified by ISO/IEC and the MPEG group (Moving Picture Experts Group) as well as other available audiovisual formats. It is typically used to store data in computer files, to transmit audiovisual streams, and probably in many other ways.

Technical characteristics

The AAC format corresponds to the international standard "ISO/IEC 13818-7" as an extension of MPEG-2: a standard created by MPEG (Moving Pictures Expert Group). The algorithm it uses to compress the files performs better than MP3, and produces better quality for small files compared to those encoded in mp3. The mp4 requires less system resources to encode and decode. Files compressed with this format are ultimately smaller than MP3 files of equivalent quality. In turn, the equivalent file encoded with matroska and OGG vorbis is lighter than that encoded in m4a (mp4).

The encoding method adapts the number of bits used per second to encode audio data using "variable bit rate encoding" (VBR), depending on the complexity of the audio transmission at any given time.

Unlike the maximum two channels (stereo) that the MP3 format can support, AAC formats allow polyphonic sounds with a maximum of 48 channels. The AAC format also offers sample rates that range from 8 Hz to 96 kHz as opposed to mp3 rates that range from 16 to 48 kHz.

General information

Like the MP3 format, the AAC format applies a form of compression that reduces some of the audio data, called "lossy compression". This means that some of the audio data, for example frequencies inaudible to humans, is removed so that a greater degree of file size reduction can be achieved, even though that resulting file sounds the same as the original, in the original. practice.

MPEG-4 Part 14 are AAC files that have the extension.mp4 (for MPEG-4), m4a (for MPEG-4 Audio) or m4p, for protected MPEG-4. "M4A" (although originally M4A was the name used only for sound files) or MP4 file format, formally ISO/IEC 14496-14:2003, is a standard Media Container format. Better known as M4A by the extensions.m4a and.m4p. Not to be confused with MP4 player. It is a container format specified as part of the IEC standard. It is used to store the audiovisual formats specified by ISO/IEC and the MPEG group (Moving Picture Experts Group) as well as other available audiovisual formats. It is typically used to store data in computer files, to transmit audiovisual streams, and probably in many other ways.

Commonly used for combining digital audio and digital video content, especially those defined by MPEG, but can also be used to combine many more types of media content, such as multiple audio, videos, subtitles, and still or stained images variable rate or variable bit rate, variable sample rate, you can also mix different advanced content officially called "Rich Media" o “BIFS”, with 2D and 3D animated graphics, user interactivity, DVD menus.

These types of content cannot be combined with AVI, with and all AVI being a more popular container, being older and more widespread among users. Like most modern formats, MPEG-4 allows streaming over the Internet. A separate reference track is used to include streaming information in the file. The ".m4a" has been popularized by Apple, who pioneered the use of the ".m4a" in your "iTunes" to distinguish between audio and video MPEG-4 files (M4A and M4V respectively). Although at first M4A was the name used only for sound files, this name became popular because it was used by the Apple company for its products in the Ipod, Iphone line... Currently, most of the software that supports the MPEG-4 standard plays files with the ".m4a" extension. Most ".m4a" available have been created using the AAC format, but other files in formats such as Apple Lossless and ".mp3" can be included in a ".m4a" file.

You can usually safely change the extension of audio files to ".mp4" to ".m4a" and vice versa, but not ".mp3" since in order to be reproduced in an audio player, it must necessarily have the capacity to decode the format that is contained in the ".mp4" which is generally encoded in MPEG-4 AAC and incompatible with MPEG-1 Layer 3 encoding and decoding for ".mp3".

MPEG-4 is a series of international video, audio, and data standards and codecs created especially for the web. It is made up of a series of compression algorithms that encode data, audio and video, optimizing their storage, encoding and distribution quality over networks. With today's cameras, it is integrated, captured and encoded in a single action, which optimizes the user's potential to broadcast.

*.mp4 allows streaming over the Internet. It also allows sending combinations of audio, video and coordinated text streams in a consolidated way. The starting point for this format was Apple's QuickTime file format. Currently *.mp4 has been enriched in many different ways so that it could no longer be said that they are the same format.

*.mp4 is often used as an alternative to *.mp3 on iPod and iTunes. The quality of the AAC codec that is stored in *.mp4 is higher than that of MPEG-1 Audio Layer 3, but its use is currently not as wide as that of *.mp3.

It stands to reason that files compressed with the MPEG-4 Part 14 format would ultimately be larger than equivalent Matroska and OGG Vorbis-encoded files of equivalent quality. In addition to the technical evolution produced until the appearance of the matroska format, for example, or the advantages of each of the coding systems, it must be added that these alternative formats do not need to include identification data for copyright validation in their resulting file.

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Compatibility

It is possible to send almost any type of data inside *.mp4 files via so-called private streams, but the recommended formats, for compatibility reasons, are::

• Video: MPEG-4, MPEG-2 and MPEG-1
• Audio: MPEG-4 AAC, MP3, MP2, MPEG-1 Part 3, MPEG-2 Part 3, CELP (voice), TwinVQ (very low bit rates), SAOL (midi)
• Images: JPEG, PNG
• Subtitles: MPEG-4 Timed Text, or text format xmt/bt (means subtitles have to be translated into xmt/bt)
• Systems: Allows animation, interactivity and DVD-style menus

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

• .mp4: Official extension for audio, video and advanced content (see below)
• .m4a: Only for audio files; files can be renamed as .mp4but not all experts recommend this.
• .m4p: FairPlay protected files
• .m4v: only video (sometimes used for mpeg-4 video streams not specified in the format definition)
• .3gp,.3g2: used by 3G mobile phone, can also store content not directly specified in the definition of .mp4 (H.263, AMR, TX3G)

The Ogg Vorbis format is not compatible with the MP3 format, but it is compatible with MPEG-4 Part 14. This means that the user has to use an audio player that supports the format or install a specific codec to play the files. ogg vorbis files. The main difference between MPEG-4 Part 14 and Ogg Vorbis is that the MPEG-4 Part 14 format was designed to safeguard the rights of copyright owners and prevent illegal distribution of their content. The m4a audio format MPEG-4 Part 14 of AAC, unlike the OGG format, allows to legally include copyright protection, those unauthorized audio files that have copy protection will not work in any AAC-type player. For example, the m4a files for iPod in the iTunes software, although compatible for playing on the Nintendo DSi, are not allowed to play, because it is unauthorized.

However, an increasing number of audio programs can play Ogg Vorbis files, and most current MP3 playback hardware devices support this format.