PostScript (57 KB)
Word (14 KB)Stored File Format for MPEG-4 (Rev. 3.0)
Contribution M2873, 41st MPEG Meeting, Fribourg, Switzerland, October 1997
Introduction
This document specifies a file format that allows efficient streaming of a file, or, at the users choice, introduces various types of access data objects in the file. Random access as well as sequential segment-based data access to objects is supported. The different access modes allow users to balance hardware resources against efficient data access for a variety of media and applications. For stored file applications, in contrast with data streamed across a network, content made available in random access mass storage facilities (stored file) can provide additional functionality. In particular, taking advantage of the random access characteristics of the underlying physical medium, it can allow direct access to arbitrary points within the scene description or audiovisual object information. Beyond random access for playback purposes, such functionality is also useful in editing operations in which one wishes to, for instance, extract a particular elementary stream from a file.
The file format supports the following features:
The MPEG-4 file format is portable and independent of the platform or the storage media used (e.g., DVD or hard disk or CD-ROM). All the AV objects and BIFS information stored in an MPEG-4 file are encapsulated in adaptation layer (AL) PDUs or alternatively, a multiplex format such as FlexMux [1]. The file format specification enables the storage of multiplexed PDUs (MUX PDUs) that can be streamed directly over a network. In the following discussion, "stored file" refers to an MPEG-4 file that contains AL PDUs and a "streaming file" refers to a file that contains transport level PDUs or MUX PDUs. Here after the term PDU will be used to refer to MUX PDUs when referring streaming files and Access unit Layer PDUs (AL-PDUs) when referring to stored files. Explicit reference to the type of PDUs in question is made when necessary.