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At present, only files that are in the Windows Media (.wmv) file format may be added to your playlist. Other file types such as .mpg, .mpeg, and .avi cannot be added to the playlist. Additionally, the files must be provided by AOL. Files provided through other services cannot be added to the playlist. Clear your browser's cache
MPEG-4 files with audio and video generally use the standard .mp4 extension. Audio-only MPEG-4 files generally have a .m4a extension. This is especially true of unprotected content. MPEG-4 files with audio streams encrypted by FairPlay digital rights management as were sold through the iTunes Store use the .m4p extension.
MPEG-4 is a group of international standards for the compression of digital audio and visual data, multimedia systems, and file storage formats. It was originally introduced in late 1998 as a group of audio and video coding formats and related technology agreed upon by the ISO/IEC Moving Picture Experts Group (MPEG) (ISO/IEC JTC 1/SC29/WG11) under the formal standard ISO/IEC 14496 – Coding ...
In contrast to that, some very general-purpose container types like AVI (.avi) and QuickTime (.mov) can contain video and audio in almost any format, and have file extensions named after the container type, making it very hard for the end user to use the file extension to derive which codec or program to use to play the files.
The 'Music' category is merely a guideline on commercialized uses of a particular format, not a technical assessment of its capabilities. For example, MP3 and AAC dominate the personal audio market in terms of market share, though many other formats are comparably well suited to fill this role from a purely technical standpoint.
The MP4 file format known as "version 1" was published in 2001 as ISO/IEC 14496-1:2001, as revision of the MPEG-4 Part 1: Systems. [14] [15] [16] In 2003, the first version of the MP4 file format was revised and replaced by MPEG-4 Part 14: MP4 file format (ISO/IEC 14496-14:2003), commonly known as MPEG-4 file format "version 2". [17]
As such, the user normally doesn't have a raw AAC file, but instead has a .m4a audio file, which is a MPEG-4 Part 14 container containing AAC-encoded audio. The container also contains metadata such as title and other tags, and perhaps an index for fast seeking. [2] A notable exception is MP3 files, which are raw audio coding without a ...
MPEG-4 Audio includes a system for handling a diverse group of audio formats in a uniform manner. Each format is assigned a unique Audio Object Type to represent it. [18] [19] Object Type is used to distinguish between different coding methods. It directly determines the MPEG-4 tool subset required to decode a specific object.