Information technology MPEG strides forward
with ISO/IEC 14496-2 (MPEG-4, Video)
By Dr. Leonardo Chiariglione,
Telecom Italia Lab, Italy
With the rapid convergence of technologies employed by telecommunications, computer and TV/film industries, there was an ever-increasing need to standardize algorithms and tools for coding and flexible representation of audio-visual data to meet the challenges of future multimedia applications.
ISO/IEC 14496-2, Information technology Coding of audiovisual objects Part 2 : Visual, also known as MPEG-4 Video, was developed in response to the growing need for a coding method that can facilitate access to visual objects in natural and synthetic moving pictures and associated natural or synthetic sound for various applications such as digital storage media, internet, various forms of wired or wireless communication.
This means that motion video can be manipulated as a form of computer data and can be stored on various storage media, transmitted and received over existing and future networks and distributed on existing and future broadcast channels.
In particular ISO/IEC 14496-2 (MPEG-4) addresses the need for Universal accessibility and robustness in error-prone environments Multimedia audio-visual data need to be transmitted and accessed in heterogeneous network environments, possibly under severe error conditions (e.g. mobile channels). Although the MPEG-4 standards is network (physical-layer) independent in nature, the algorithms and tools for coding audio-visual data have been designed with awareness of network peculiarities.
· High interactive functionality Multimedia applications call for extended interactive functionalities to assist the users needs. In particular the flexible, highly interactive access to and manipulation of audio-visual data are of prime importance. It is independent in nature, the algorithms and tools for coding audio-visual data have been designed with awareness of network peculiarities.
· High interactive functionality Multimedia applications call for extended interactive functionalities to assist the users needs. In particular the flexible, highly interactive access to and manipulation of audio-visual data are of prime importance. It is envisioned that in addition to conventional playback of audio and video sequences the user needs to access content of audio-visual data to present and manipulate/store the data in a highly flexible way.
· Coding of natural and synthetic data Next generation processors will enable Multimedia terminals to present sample-based audio and pixel-based video together with synthetic audio/speech and video in a highly flexible way. MPEG-4 assists the efficient and flexible coding and representation of both natural (sample-based) as well as synthetic data.
· Compression efficiency For the storage and transmission of audio-visual data, a high coding efficiency, meaning a good quality of the reconstructed data, is required. Improved coding efficiency, in particular at very low bit rates below 64 kbits/s, continues to be an important functionality that is supported by the MPEG-4 video standard. The applications of ISO/IEC 14496 cover, but are not limited to, internet multimedia (IMM), interactive video games (IVG), interpersonal communications such as videoconferencing (IPC), interactive storage media (ISM), multimedia mailing (MMM), networked database services (NDB), remote emergency systems (RES), remote video surveillance (RVS), wireless multimedia (WMM) and multimedia, in general.
MPEG-1 A generic standard
The MPEG group was established in January 1988 as an Experts Group of ISO/IEC JTC 1/SC 2/WG 8. In 1991 it became WG 11 of the newly-established ISO/IEC JTC 1/SC 29. In November 1992 MPEG produced MPEG-1 (ISO/IEC 11173), its first standard, a complete digital audio-visual solution for interactive
video and digital audio broadcasting.
MPEG-1 is intended to be generic, independent of a particular application and therefore comprises mainly a toolbox. It is up to the user to decide which tools to select to suit the particular applications envisaged. The bitrates involved were about 1.5 Mbit/s for audio and video together and about 256 kbit/s for audio only. Two years later MPEG produced MPEG-2 (ISO/IEC 13818), its second standard, a complete digital audio-visual solution for broadcasting and interactive video.
The video coding scheme used in MPEG-2 is again generic and similar to the one of MPEG-1, however with further refinements (such as the introduction of scalability ) and special consideration of interlaced sources. These two standards have offered new opportunities to the manufacturing and service provisioning industries worldwide and have created businesses worth several hundred billion USD.
The bitrate range below 1 Mbit/s was not specifically addressed by MPEG-1 and MPEG-2. Still the ability to send video over low bitrate channels was clearly a need felt by the industry. High-quality video coding at bitrates as low as 10 kbit/s was the goal when the MPEG-4 Video project was established. Version 1 of MPEG-4 was approved in October 1998 and version 2 in December 1999.
MPEG-4 a standard whose implementation could be software
Unlike MPEG-1 and MPEG-2, designed and, at least in the first phase, implemented as traditional hardware solutions, MPEG-4 was conceived as a standard whose implementation could be software.
This explains why part 5 of ISO/IEC 14496, a reference software implementation of the standard, has the same normative value as the other traditional textual parts of the standard. Also the development of the reference software followed closely the spirit, if not the letter, of open source software projects. Indeed, the reference software is posted on the ISO web site for users to download. There is one condition, though, and that is that the software can only be used for implementations that conform to the relevant parts of ISO/IEC
14496. The other is a warning, viz. that use of the software may infringe patent rights of third parties.
This last point, an accepted fact for those operating in ISO and IEC, provides an opportunity to explain a major feature of MPEG standards. Ever since people in the late 1960s realized the eventual benefits of digitally compressed audio and video, the number of R&D projects in this area has been counted by the tens of thousands with a corresponding number of patents applied and, in many cases, granted. Even though the validity of the first patents has now expired, it is a fact that it is virtually impossible today to develop an audio or video coding standard with a reasonable performance that does not require the use of one or, more likely, several patents.
The establishment of a patent pool
Setting aside MPEG-1, it is known that the number of patents required for implementing MPEG-2 is of the order of 100. This complex patent situation was resolved, at the initiative of interested parties, with the establishment of a patent pool. For MPEG-4, a standard designed to be generic and hence usable by a large number of industries, no such spontaneous movement was possible. Therefore a group of interested companies from a multiplicity of industries established the so-called MPEG-4 Industry Forum (www.m4if.org). In this Forum a Call for Patent Holders was made with the suggestion to potential Patent Holders to have their patents reviewed by a patent attorney.
This is where the role of M4IF stopped. Patent Holders then have then independently established a patent pool for MPEG-4 Video Simple and Core Profiles. This has recently published their licensing policy.
MPEG-4 Video is being used in a number of environments. The most prominent is for mobile communication applicable to the so-called 2.5 G, a data transmission known with the name of Generalised Packet Radio System (GPRS) and to 3G or Universal Mobile Telecommunication System (UMTS). The second is to further compress movie files (themselves compressed using MPEG-2) so that they can fit in a single CD-ROM. The third is for video streaming over the Internet. More application domain will open up with the exploitation of other features of MPEG-4.
MPEG (pronounced M-peg), which stands for Moving Picture Experts Group, is the name of a family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. MPEG is a working group within ISO/IEC in charge of the development of international standards for compression, decompression, processing and coded representation of moving pictures, audio and their combination. Within MPEG, the MPEG Video Group has the mandate to develop and standardize video coding tools and algorithms. The MPEG group meetings are usually attended by over 300 experts from some 20 countries (Asia, Australia, North America, Europe). The MPEG video group successfully completed and released the MPEG-1 video coding standard in 1992, the MPEG-2 video coding standard in 1994 and the MPEG-4 video coding standard in 1998. Three amendments to MPEG-4 Video have been published in 1999 and 2001.