Wannabe Rep: 0 Joined: 13 Dec 2006 Posts: 25 OFFLINE | Here , I would like to introduce some knowledge about MP4 , if u are interested in this area, this must be very useful to u,
Within the ISO/IEC 14496 MPEG-4 standard there are several parts that define file formats for the storage of time-based media (such as audio, video etc.). They are all based and derived from the ISO Base Media File Format, which is a structural, media-independent definition that is also published as part of the JPEG 2000 family of standards.
The MP4 file format defines the storage of MPEG-4 audio, scenes and multimedia content using the ISO Base Media File Format. The AVC File Format defines the storage for the Advanced Video Coding (ISO/IEC 14496-10/AVC) standard data within files of the ISO Base Media File Format family.
MP4 File Format
MP4 files are generally used to contain MPEG-4 media, including not only MPEG-4 audio and/or video, but also MPEG-4 presentations. When a complete or partial presentation is stored in an MP4 file, there are specific structures that document that presentation.
MPEG-4 presentations are scenes, described by the scene language MPEG-4 BIFS. Within those scenes media objects can be placed; these media objects might be audio, video, or entire sub-scenes.
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ok, let’s continue the media objects mentioned above, each object is described by an object descriptor, and within the object descriptor the streams that make up that object are described. The entire scene is described by an initial object descriptor (IOD). This is stored in a special box within the movie atom in MP4 files. The scene and the object descriptors it uses are stored in tracks ¡ª a scene track, and an object descriptor track; for files that comprise a full MPEG-4 presentation this IOD and these two tracks are required.
MPEG-21 File Format
As described above, the general meta-box can be used at the file level to contain a description and its associated or included data. This structure is used for MPEG-21 files. A file-level meta-box is used to hold an MPEG-21 Digital Item Declaration (DID), The meta-box also contains a list of attached resources; which may have local names, and may be located within the same file or in another file.
Last edited 11 Jan 2007 03:53 am by codecrob |
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