1.1.1 Overview of MPEG-4 Audio
This part of ISO/IEC 14496 (MPEG-4 Audio) is a new kind of audio standard that integrates many different types of audio coding: natural sound with synthetic sound, low bitrate delivery with high-quality delivery, speech with music, complex soundtracks with simple ones, and traditional content with interactive and virtual-reality content. By standardizing individually sophisticated coding tools as well as a novel, flexible framework for audio synchronization, mixing, and downloaded post-production, the developers of the MPEG-4 Audio standard have created new technology for a new, interactive world of digital audio.
MPEG-4, unlike previous audio standards created by ISO/IEC and other groups, does not target a single application such as real-time telephony or high-quality audio compression. Rather, MPEG-4 Audio is a standard that applies to every application requiring the use of advanced sound compression, synthesis, manipulation, or playback. The subparts that follow specify the state-of-the-art coding tools in several domains; however, MPEG-4 Audio is more than just the sum of its parts. As the tools described here are integrated with the rest of the MPEG-4
standard, exciting new possibilities for object-based audio coding, interactive presentation, dynamic soundtracks,
and other sorts of new media, are enabled.
Since a single set of tools is used to cover the needs of a broad range of applications, interoperabilityis a natural feature of systems that depend on the MPEG-4 Audio standard. A system that uses a particular coder.for example, a real-time voice communication system making use of the MPEG-4 speech coding toolset.can easily share data and development tools with other systems, even in different domains, that use the same tool.for example, a voicemail indexing and retrieval system making use of MPEG-4 speech coding. A multimedia terminal
that can decode the Main Profile of MPEG-4 Audio has audio capabilities that cover the entire spectrum of audio functionality available today and in the future.
The remainder of this clause gives a more detailed overview of the capabilities and functioning of MPEG-4 Audio.
First, a discussion of concepts that have changed since the MPEG-2 audio standards is presented; then, the MPEG-4 Audio toolset is outlined.
