The development of an integrated audiovisual coding standard: MPEG

These days companies from many industry segments are moving towards the adoption of digital technology for upgrading existing or introducing new services. This unstoppable movement prompted by technological progress could have produced the digital replica of the existing incompatible systems put in place in the analog world. It is the merit of MPEG to have provided an integrated audiovisual coding standard to implement this epochal conversion from one technology to another while supporting a universal syntax representing audiovisual information that makes the standard usable for a variety of interoperable applications. The paper presents the approach followed in the development of the MPEG-1 and MPEG-2 standards and explains some of the basic technical elements. An overview of the current MPEG work is also given     

MPEG-4 multimedia for our time

The MPEG-4 standard explores every possibility of the digital environment. Recorded images and sounds co-exist with their computer-generated counterparts, a new language for sound promises compact-disk quality at extremely low data rates; and the multimedia content could even adjust itself to suit the transmission rate and quality. Possibly the greatest of the advances made by MPEG-4 is that viewers and listeners need no longer be passive. The height of “interactivity” in audiovisual systems today is the users ability merely to stop or start a video in progress. MPEG-4 is completely different: it allows the user to interact with objects within the scene, whether they derive from so-called real sources, such as moving video, or from synthetic sources, such as computer-aided design output or computer-generated cartoons. Authors of content can give users the power to modify scenes by deleting, adding, or repositioning objects, or to alter the behavior of the objects. Perhaps the most immediate need for MPEG-4 is defensive. It supplies tools with which to create uniform (and top-quality) audio and video encoders and decoders on the Internet, preempting what may become an unmanageable tangle of proprietary formats. In addition to the Internet, the standard is also designed for low bit-rate communications devices, which are usually wireless     

Tests on MPEG-4 audio codec proposals

During December 1995, subjective tests were carried out by members of the Moving Picture Experts Group (MPEG, ISO/JTC1/SC29/WG11) to select the proposed technology for inclusion in the audio part of the new MPEG-4 standard. The new standard addresses coding for more than just the functionality of data rate compression. Material coded at very low bit-rates is also included. Thus, different testing methodologies were applied, according to ITU-R Rec. BS 1116 for a bit-rate of 64 kbit/s per channel and according to ITU-T Rec. P.80 for lower bit-rates or functionalities other than data rate compression. Proposals were subjectively tested for coding efficiency, error resilience, scalability and speed change: a subset of the MPEG-4 ‘functionalities’. This paper describes how two different evaluation methods were used and adjusted to fit the different testing requirements. This first major effort to test coding schemes at low bit-rates proved successful. Based on the test results, decisions for MPEG-4 technology were made.

This was the first opportunity for MPEG members to carry out tests on the submitted functionalities. In the process, much was learnt. As a result, some suggestions are made to improve the way new functionalities can be subjectively evaluated.     

MPEG-4: Why,what, how and when?

The MPEG-4 Version 1 standard has been recently finalized. Since MPEG-4 adopted an object-based audiovisual representation model with hyperlinking and interaction capabilities and supports both natural and synthetic content, it is expected that this standard will become the information coding playground for future multimedia applications. This paper intends to give an overview on the MPEG-4 motivations, objectives, achievements, process and workplan, providing a stimulating starting point for more detailed reading.     

基于MPEG-4的数字监控系统

介绍了一种基于MPEG-4的数字监控系统的系统构成和软件实现方法。该系统采用MPEG-4标准压缩方法,比较其他压缩方法其压缩比更大。通过对MPEG压缩原理的分析,比较了MPEG-1、MPEG-2和MPEG-4三种标准,说明MPEG-4采用视频对象VO的概念进行编码,更适合远程数字监控。     

ATSC Video and Audio Coding

In recent decades, digital video and audio coding technologies have helped revolutionize the ways we create, deliver, and consume audiovisual content. This is exemplified by digital television (DTV), which is emerging as a captivating new program and data broadcasting service. This paper provides an overview of the video and audio coding subsystems of the Advanced Television Systems Committee (ATSC) DTV standard. We first review the motivation for data compression in digital broadcasting. The MPEG-2 video and AC-3 audio compression algorithms are described, with emphasis on basic concepts, system features, and coding performance. Next-generation video and audio codecs currently under consideration for advanced services are also presented.     

Error concealment algorithms for robust decoding of MPEG compressed video

This paper provides some research results on the topic of error resilience for robust decoding of MPEG (Moving Picture Experts Group) compressed video. It introduces and characterizes the performance of a general class of error concealment algorithms. Such receiver-based error concealment techniques are essential for many practical video transmission scenarios such as terrestrial HDTV broadcasting, packet network based teleconferencing/multimedia, and digital SDTV/HDTV delivery via ATM (asynchronous transfer mode). Error concealment is intended to ameliorate the impact of channel impairments (i.e., bit-errors in noisy channels, or cell-loss in ATM networks) by utilizing available picture redundancy to provide a subjectively acceptable rendition of affected picture regions. The concealment process must be supported by an appropriate transport format which helps to identify image pixel regions which correspond to lost or damaged data. Once the image regions (i.e., macroblocks, slices, etc.) to be concealed are identified, a combination of spatial and temporal replacement techniques may be applied to fill in lost picture elements. A specific class of spatio-temporal error concealment algorithms for MPEG video is described and alternative realizations are compared via detailed end-to-end simulations for both one- or two-tier transmission media. Several algorithm enhancements based on directional interpolation, ‘I-picture motion vectors’, and use of MPEG-2 ‘scalability’ features are also presented. In each case, achievable performance improvements are estimated via simulation. Overall, these results demonstrate that the proposed class of error concealment algorithms provides significant robustness for MPEG video delivery in the presence of channel impairments, permitting useful operation at ATM cell-loss rates in the region of 10⁻⁴ to 10⁻³ and 10⁻² to 10⁻¹ for one- and two-tier transmission scenarios, respectively.     

A perspective: the role of identifiers in managing and protectingintellectual property in the digital age

There is an essential need for the owners of intellectual property rights to be able to identify uniquely the creative components which make up digitized multimedia content. The relationship between these identifiers and the “well-formed” metadata which describe them is critical to the successful management of rights in an electronic trading environment. By persistently associating creation identifiers with digital content, rights holders will effectively be able to licence, monitor, and track the usage of rights across digital networks. Within the evolution of the MPEG-4 standard, representatives of rights holders from across the creative industries worked with technologists to devise an effective solution for managing creation identifiers and their associated metadata within MPEG-4 objects. This was achieved in such a manner that the identifiers will continue to be associated with content that is manipulated and edited. In addition, through the valuable contribution of leading watermarking and encryption specialists, the MPEG-4 standard will contain an interface for applying intellectual property management and protection (IPMP) systems. These IPMP systems can be applied to MPEG-4 software and hardware devices that manage the delivery of copyright content to prevent unauthorized copying, the removal of identifiers, and therefore control and restrict fraudulent use. This paper describes and documents these issues which rights holders have worked collectively to address within the evolving MPEG-4 standard     

MPEG: a technological basis for multimedia applications

The Moving Picture Experts Group was established in 1988 in the framework of the Joint ISO/IEC Technical Committee (JTC 1) on Information Technology. They were given the mandate to develop standards for coded representation of moving pictures, associated audio, and their combination when used for storage and retrieval on digital storage media (DSM). In April 1990 they became Working Group 11 of JTC 1/SC 2, then in November 1991, WG 11 of JTC 1/SC 29. The three original work items of the group-coding up to 1.5, 10, and 40 Mbps-were nicknamed MPEG-1, -2 and -3, respectively. The group dropped the MPEG3 work item in July 1992 when it became apparent that the functionalities supported by the MPEG-2 requirements made it redundant. The current MPEG-4 work item, first proposed in May 1991 and approved in July 1993, targets audiovisual coding at very low bit-rates     

An experimental determination of the ambipolar diffusion coefficient in germanium

A method for determining the ambipolar diffusion length and thereby the ambipolar diffusion coefficient in elemental semiconductors is presented. The method, a modification of the standard travelling light spot measurement, is applicable over the entire range of resistivity. The steady-state three-dimensional continuity equation, is solved for the excess carrier concentration in a rectangular bar specimen partially illuminated on one surface with short wavelength light. Computer calculations of the average excess carrier concentration profile along the length of the rectangular bar are given. An experimental technique, which satisfies the conditions imposed on the continuity equation, is described. The feasibility of the technique was checked using n-type germanium. It was empirically established that the bulk relation L = √ Dτ remains valid when surface recombination is present if the diffusion length L is replaced by an ‘effective’ diffusion length and the lifetime τ by an ‘effective’ lifetime. From experimental measurements of L_eff by the technique introduced, and τ_eff by the photoconductivity decay method, the ambipolar diffusion coefficient can be determined.     

基于MPEG-4视频标准数字视频录像机的设计与实现

国内外许多公司都在开发有关MPEG-4视频标准的产品,最具代表意义的即是数字视频录像机(DVR)。为了缩短开发周期,这里介绍基于嵌入式Linux操作系统,应用专用音视频编解码芯片AT2042实现数字视频录像机功能,该系统实现MPEG-4视频标准高级框架的编解码器,并在此基础上添加数字硬盘的功能,例如编码存储、解码播放、快进、快退和暂停等功能。最后给出系统的实际运行的测试结果。该系统已实现对视频数据的编、解码,且实现MPEG-4/MPEG-2/MPEG-1 H.263视频标准,并已成为成型产品推向市场。     

MPEG digital audio coding

The Moving Pictures Expert Group (MPEG) within the International Organization of Standardization (ISO) has developed a series of audio-visual standards known as MFEG-1 and MPEG-2. These audio-coding standards are the first international standards in the field of high-quality digital audio compression. MPEG-1 covers coding of stereophonic audio signals at high sampling rates aiming at transparent quality, whereas MPEG-2 also offers stereophonic audio coding at lower sampling rates. In addition, MPEG-2 introduces multichannel coding with and without backwards compatibility to MPEG-1 to provide an improved acoustical image for audio-only applications and for enhanced television and video-conferencing systems. MPEG-2 audio coding without backwards compatibility, called IMPEG-2 Advanced Audio Coding (AAC), offers the highest compression rates. Typical application areas for MPEG-based digital audio are in the fields of audio production, program distribution and exchange, digital sound broadcasting, digital storage, and various multimedia applications. We describe in some detail the key technologies and main features of MPEG-1 and MPEG-2 audio coders. We also present the MPEG-4 standard and discuss some of the typical applications for MPEG audio compression     

TIRAMISU: A novel approach to content representation and key management for seamless super-distribution of protected media

Media delivery over heterogeneous networks requires both flexible representation and robust protection of content. This paper provides details on the framework for audiovisual content creation, delivery, consumption and protection as conceived within the IST project The Innovative Rights and Access Management Interplatform SolUtion. The proposed framework is based on the emerging MPEG-21 standard for multimedia content delivery and consumption and at the same time it complements it in several aspects, most notably by fully specifying a digital rights management (DRM) scheme. Central to the described framework is a novel key management system, relying on smartcards, which addresses many issues that previously blocked wider adoption of DRM: obtrusiveness of the DRM technology perceived by the end-user, flexibility in licence formulation and adequate level of trust as requested by content owners.     

Fast MPEG-4 Motion Estimation: Processor Based and Flexible VLSI Implementations

MPEG-4 is a new multimedia standard combining interactivity, object-based natural and synthetic digital video, audio and computer-graphics. For the implementation of the video part of the MPEG-4 standard a high degree of flexibility is required, where the motion estimation requires the highest part of the computational power. Therefore, in this paper fast algorithms for MPEG-4 motion estimation are evaluated in terms of visual quality and computational power requirements for processor based implementations. Due to the object-based nature of MPEG-4 also new VLSI architectures for MPEG-4 motion estimation are required. Therefore known motion estimation architectures are evaluated on their capability of being modified for MPEG-4 support. Based on this evaluation a new dedicated, but flexible MPEG-4 motion estimation architecture targeted for low-power handheld applications is presented, which resulted to be advantageous to processor based implementations by magnitudes of order.     

Broadband and digital ‘content’ in the EU-25: Recent trends and challenges

This paper focuses on recent trends and issues in the EU-25 countries related to one key broadband application area: digital media ‘content’ applications. It draws upon recently completed research addressing current and future uses and applications of broadband in the EU-25 area.

The paper presents key findings from the BEACON project concerning the broadband content trends and issues in the EU-25 countries. First, the paper briefly considers recent literature on broadband and digital media innovations as well as the policy context in Europe, which has an important influence on framing supports for innovation in content and digital media. Next, it addresses a number of key issues that impact upon the creation of content services. These include the high cost of content production and the difficulty of forming attractive business cases given the uncertainties related to user demand, and the IPR and copyright regimes. It will also consider users’ patterns of engagement with broadband content and emerging user applications. Next, the paper discusses whether broadband is reaching a ‘tipping point’, whereby broadband access is becoming the norm and in the next five years we will see the emergence of innovative, dynamic content services. The paper considers whether recent moves by three sets of significant actors (media corporations, the advertising sector, and EC regulators) could be early signs of a tipping point in favour of the creation of and more focused support for broadband content services.     

Chiariglione and the birth of MPEG

Leonardo Chiariglione, the father of the Moving Pictures Experts Group and the driving force behind its standards for digitized video is now pushing a standard for Internet images manipulable by the user. As first conceived, MPEG-2 was to standardize the digital coding of interlaced TV pictures (in which a field made up of every other scan line is followed by another field consisting of the remaining scan lines). The coding was to occur at about 10 Mb/s, and standard digital television was the main goal. Then MPEG-3 was to formulate coding standards for pictures at 40 Mb/s, with a view to HDTV. The current effort of the Moving Pictures Experts Group, MPEG-4, is geared to digital coding at low bit-rates and was at first conceived rather vaguely in a multimedia context     

MPEG digital video-coding standards

The efficient digital representation of image and video signals has been the subject of considerable research over the past 20 years. Digital video-coding technology has developed into a mature field and products have been developed that are targeted for a wide range of emerging applications, such as video on demand, digital TV/HDTV broadcasting, and multimedia image/video database services. With the increased commercial interest in video communications, the need for international image- and video-compression standards arose. To meet this need, the Moving Picture Experts Group (MPEG) was formed to develop coding standards. MPEG-1 and MPEG-2 video-coding standards have attracted much attention worldwide, with an increasing number of very large scale integration (VLSI) and software implementations of these standards becoming commercially available. MPEG-4, the most recent MPEG standard that is still under development, is targeted for future content-based multimedia applications. We provide an overview of the MPEG video-coding algorithms and standards and their role in video communications. We review the basic concepts and techniques that are relevant in the context of the MPEG video-compression standards and outline MPEG-1 and MPEG-2 video-coding algorithms. The specific properties of the standards related to their applications are presented, and the basic elements of the forthcoming MPEG-4 standard are also described. We also discuss the performance of the standards and their success in the market place