MPEG Music Player Application Format
MPEG doc#: N7710
Author: S. Quackenbush
The Music Player Multi-Media Application Format (MAF) shows how to carry MPEG-1 Layer III (MP3) and MPEG-7 information (music and metadata) within the MPEG-4 framework. Moving MP3 into the MPEG-4 world supports, as a baseline, everything that users know and expect, but offers the capability to deliver a much richer music experiences with components of MPEG-4, MPEG-7 and MPEG-21 at its disposal.
We desire to provide the more modern frameworks provided by MPEG-4 and MPEG-21 to the pervasive world of MP3 music players. It is the hope new music players will adopt this specification so as to remain compatible with the widely deployed legacy MP3 infrastructure, while using this specification as a bridge to the more modern worlds of MPEG-4 and MPEG-21.
Overview of technology
This specification presents a simple architecture for constructing an annotated music library. It defines a process, based completely on MPEG-4 and MPEG-7 standardized modules, for importing MP3 encoded music files containing ID3 tags into this architecture. This is shown in the figure below.
ISO/IEC 11172-3 Layer III (“MP3”) specifies a music compression scheme that results in a sequence of bits, or a bitstream. In contrast, ISO/IEC 14496-3, MPEG-4 Audio, specifies a music compression scheme that results in a sequence of packets which can be stored directly into the MPEG-4 File Format, specified in ISO/IEC 14496-14.
The first module required in this architecture is a specification to translate an MP3 bitstream into a series of MP3 packets. This is accomplished by the MP3onMP4 formatter, specified in ISO/IEC 14496-3 / AMD 3. This formatter reads a standard MP3 file (i.e. a bitstream) and converts it to a series of packets (called access units in MPEG-4 terminology) that can be loaded into an MPEG-4 File.
Playback then consists of
- extracting the metadata from the MPEG-4 file and displaying it on a suitable visual interface,
- extracting the MP3onMP4 data from the MPEG-4 file, filtering it with very light-weight de-formatting operation, and playing it through a “classic” MP3 decoder.
- if desired, extracting the MPEG-7 metadata for display or use by the player application.
In practice, it may be that the MP3onMP4 data is played by an “MP3onMP4 decoder,” consisting of the concatenation of the MP3onMP4 deformatter and the MP3 decoder.
The Music Player MAF is aimed at the MP3 music player marketplace, both PC-based and portable devices, which currently support playback of MP3 encoded music, display of song-related metadata, and possibly JPEG album art. As a further step, it supports sufficient song-related meta data so as to permit higher-level functionalities such as music sorting, searching or playlist application.