MPEG-4 Systems Research Articles

A memory-based architecture for MPEG2 system protocol LSIs

This paper proposes a memory-based architecture implementing the MPEG2 system protocol large scale integrations (LSIs), and demonstrates its flexibility and performance. The memory-based architecture implements the full functionality of the MPEG2 system protocol for both multiplexing and demultiplexing MPEG2-encoded streams. It consists of a core central processing unit, memories, and dedicated application-specific hardware. It is designed and optimized by hardware/software codesign techniques. The LSI's provide sufficient performance and flexibility for real-time application of the MPEG2 system protocol. They were fabricated with 0.5 /spl mu/m CMOS embedded gate array process technology. They are now in use on MPEG2 codec systems for several multimedia communication and storage services.

Real-time interactive MPEG-4 system encoder using a cluster of workstations

MPEG-4 currently being finalized by the Moving Pictures Experts Group of the ISO is a multimedia standard, MPEG-4 aims to support content-based coding of audio, text, image, and video (synthetic and natural) data, multiplexing of coded data, as well as composition and representation of audiovisual scenes. One of the most critical components of an MPEG-4 environment is the system encoder. An MPEG-4 scene may contain several audio and video objects, images, and text, each of which must be encoded individually and then multiplexed to form the system bitstream. Due to its flexible features, object-based nature, and provision for user interaction, MPEG-4 encoder is highly suitable for a software-based implementation. A full-scale software-based MPEG-J system encoder with real-time encoding speed is a nontrivial task and requires massive computation. We have built such an encoder using a cluster of workstations collectively working as a virtual parallel machine. Parallel processing of MPEG-4 encoder needs to be carried out carefully as objects may appear or disappear dynamically in a scene. In addition, objects may be synchronized with each other. User interactions may also prohibit a straightforward parallelization. We propose a modeling methodology that captures the spatio-temporal relationship between various objects and user interaction. We then propose a number of scheduling algorithms that periodically allocate MPEG-4 objects to multiple workstations ensuring load balancing and synchronization requirements among multiple objects. Each scheduling algorithm has its own performance and complexity characteristics. The experimental results, while showing real-time encoding rates, exhibit tradeoffs between load balancing, scheduling overhead cost, and global performance.

An efficient multiplex architecture for mobile MPEG-4 systems

This paper describes a multiplex architecture for mobile multimedia applications which has been considered as the underlying multiplex system in the MPEG-4 standardization effort (MPEG-4: Coding of audio-visual objects, standardization project of the ISO/IEC JTC1/SC29/WG11). Multimedia information consists of several different kinds of information which differ widely in their requirements on Quality of Service (QoS). The generic data services in today's mobile networks are not designed to comply with these QoS requirements. On the other hand, future object-based multimedia systems (e.g. MPEG-4) will use a multitude of simultaneous data streams. Many of these will have similar requirements on transmission. The proposed multiplexing architecture consists of two layers. One layer serves to bundle elementary data streams of similar QoS requirements, resulting in a small number of data streams with differing QoS requirements. The other layer serves to provide appropriate error protection for each of these streams and to form a single data stream which can be transmitted over an error prone link. Thus multiplexing overhead is minimized while error protection is adapted to the requirements of the individual elementary streams. It is argued that the lower layers dealing with protection and the error-resilient multiplex of the protected streams should be included in the network in order to avoid the problems of end-to-end error control. The system described can thus help to obtain highly efficient multimedia communication with future mobile networks.

Optimal memory organization for scalable texture codecs in MPEG-4

This paper addresses the problem of minimizing memory size and memory accesses in multiresolution texture coding architectures for discrete cosine transform (DCT) and wavelet-based schemes used, for example, in virtual-world walk-throughs or facial animation scenes of an MPEG-4 system. The problem of minimizing the memory cost is important since memory accesses, memory bandwidth limitations, and in general the correct handling of the data flows have become the true critical issues in designing high-speed and low-power video-processing architectures and in efficiently using multimedia processors. For instance, the straightforward implementation of a multiresolution texture codec typically needs an extra memory buffer of the same size as the image to be encoded/decoded. We propose a new calculation schedule that reduces this buffer memory size with up to two orders of magnitude, while still ensuring a number of external (off-chip) memory accesses that is very close to the theoretical minimum. The analysis is generic and is therefore useful for both wavelet and multiresolution DCT codecs.

Timestamping schemes for MPEG-2 systems layer and their effect on receiver clock recovery

We propose and analyze several strategies for performing timestamping of an MPEG-2 Transport Stream transmitted over a packet-switched network using the PCR-unaware encapsulation scheme, and analyze their effect on the quality of the recovered clock at the MPEG-2 Systems decoder. When the timestamping scheme is based on a timer with a fixed period, the PCR values in the packet stream may switch polarity deterministically, at a frequency determined by the timer period and the transport rate of the MPEG signal. This, in turn, can degrade the duality of the recovered clock at the receiver beyond acceptable limits. We consider three timestamping schemes for solving this problem: (1) selecting a deterministic timer period to avoid the phase difference in PCR values altogether, (2) fine-tuning the deterministic timer period to maximize the frequency of PCR polarity changes, and (3) selecting the timer period randomly to eliminate the deterministic PCR polarity changes. For the case of deterministic timer period, we derive the frequency of the PCR polarity changes as a function of the timer period and the transport rate, and use it to find ranges of the timer period for acceptable quality of the recovered clock. We also analyze a random timestamping procedure based on a random telegraph process and obtain lower bounds on the rate of PCR polarity changes such that the recovered clock does not violate the PAL/NTSC clock specifications. The analytical results are verified by simulations with both synthetic and actual MPEG-2 Transport Streams sent to a simulation model of an MPEG-2 Systems decoder.

A client/server application as an example for MPEG-4 systems

One of the most important standardization efforts in the broad field of audio-visual coding is MPEG-4 which introduces objects as smallest accessible units inside frames. This conceptual step forward led to completely new possibilities for applications using content-based scalability or content-based interactivity. When MPEG-4 started in 1994 it was no more than an ambitious vision. Then, in March 1998, it received the status of the final committee draft of an international standard and it is certainly a milestone in realizing second-generation audio-visual communication systems. In this paper, we give a brief introduction to MPEG-4 systems terminology and discuss the set-up procedure of an application using MPEG-4 systems. We present a prototype implementation of a video-on-demand application that enables distributed event handling of object-related events created by a user. Our system consists of a client/server architecture, where the client side handles events like zooming or moving single video objects at presentation time, while the server side manages user control concerning the quality of a lossy encoding of the single video objects. The system is introduced by means of OMT diagrams, status diagrams and block diagrams.

Jitter smoothing and traffic modeling for MPEG-2 video transport over ATM networks

In this article, we study how to deal with jitter when a variable-bit-rate (VBR) MPEG-2 video is delivered through asynchronous transfer mode (ATM) networks. First, the MPEG-2 system and its timing model are reviewed and difficulties introduced by ATM cell delay jitter are elucidated. Second, approaches to smoothing network jitter for both constant-bit-rate and VBR traffic are reviewed. A novel approach to modeling the end-to-end MPEG-2 packet generation and arrival process in the presence of network jitter is next presented. Based on this model, the buffer behavior of the MPEG-2 transport stream system target decoder is simulated. Simulation results show that jitter significantly affects the required decoder buffer size and packet loss ratio. © 1998 John Wiley & Sons, Inc. Int J Imaging Syst Technol, 9, 332–339, 1998

End-to-end modeling and simulation of MPEG-2 transport streams over ATM networks with jitter

The operation of MPEG-2 systems is modeled and simulated when an MPEG-2 transport stream is delivered through an ATM network with jitter. End-to-end packet-based analysis is performed for delivery of MPEG-2 transport streams over ATM networks. A novel approach to analyzing the decoder buffer behaviour in the presence of network jitter is presented. The probability density function of the interarrival time of the ATM adaptation layer 5 (AAL5) protocol data unit (PDU) is derived from an MPEG-2 video source model and an ATM network jitter model. Based on a real-time decoding requirement of the MPEG-2 transport stream (TS) system target decoder (T-STD), the decoder buffer behaviour is simulated. In this simulation, the packets' arrivals follow the derived probability density function of the AAL5 PDU interarrival time. The modeling and simulation results show the interactions among packet loss ratio, decoder buffer size, and network jitter level. We found that jitter affects decoder buffer size and packet loss ratio in a significant way.

Design and implementation of an MPEG-2 transport stream multiplexer for HDTV satellite broadcasting

This paper describes the design and implementation of an HDTV program multiplexer which is based on MPEG-2 systems specifications for satellite broadcasting. We have developed an MPEG-2 TS compliant multiplexer with special considerations for timing and synchronization. In particular, we introduce a scheduling algorithm, which use the monitoring information of the buffers of T-STD as one of scheduling factors. We have also implemented a software simulator and used it for efficient verification of MPEG-2 compliance from an early design stage.

The MPEG-4 systems and description languages: A way ahead in audio visual information representation

Abstract The state of the standardization of the Systems part of ISO/IEC JTC1/SC29/WG11 (MPEG-4 Systems) as specified early 1997 is presented. First, a rationale and the architecture of the complete Systems are described. Based on the rapid technological advances in software and in hardware, the MPEG-4 Systems provides for a framework for the integration of natural and synthetic streamed and synchronised media. The different fields of interest in Systems are then developed from the description of audiovisual scenes to the definition of the multiplex. The programmability of the standard is described for composition and decompression and the language adopted by MPEG-4 on purpose of syntax description is fully detailed. Finally, a conclusion and the future evolutions of the specifications are presented.

Step to creation

The state of the standardization of the Systems part of ISO/IEC JTC1/SC29/WG11 (MPEG-4 Systems) as specified early 1997 is presented. First, a rationale and the architecture of the complete Systems are described. Based on the rapid technological advances in software and in hardware, the MPEG-4 Systems provides for a framework for the integration of natural and synthetic streamed and synchronised media. The different fields of interest in Systems are then developed from the description of audiovisual scenes to the definition of the multiplex. The programmability of the standard is described for composition and decompression and the language adopted by MPEG-4 on purpose of syntax description is fully detailed. Finally, a conclusion and the future evolutions of the specifications are presented.

A rational approach to testing MPEG-2

Any complex electronic communication system presents a variety of challenges during design, installation, and operation. In MPEG-2 systems, problems usually show up in two areas: testing and interoperability. Test procedures put together without adequate understanding of the hierarchical nature of the MPEG-2 transport stream may allot too much time to the scrutiny of less important parameters, while possibly allowing more important ones to escape notice. Interoperability problems may arise not only from obvious physical incompatibilities, like mismatched connectors, but also from more subtle discrepancies, like inconsistent uses of reserved packet-identification values. The paper provides a feel for the sorts of problems routinely encountered in MPEG-2 transmission systems and supply some practical guidelines on test methodology. Because transport operation-but not physical interconnection-is specified by MPEG-2 for decoders, issues relating to the connection of systems and testing devices must be explored. Some typical problems in a sample application, satellite news gathering, are examined as well.

マルチメディアを目指すＭＰＥＧ‐４標準化動向 ＭＰＥＧ‐４システム

マルチメディアを目指すＭＰＥＧ‐４標準化動向 ＭＰＥＧ‐４システム

Design and implementation of MPEG-2/DVB scrambler unit and VLSI chip

This paper describes the MPEG-2/DVB scrambler unit (DVB-SU) and VLSI chip developed for ETRI's conditional access system (CAS) for a digital broadcasting system. The DVB-SU is designed and implemented based on an ASIC, FPGAs and a DSP. The ASIC, compliant with the EP-DVB common scrambling specification, is a 128-pin MQFP type and operates with a 50 MHz system clock; it has features of flexible conditional access handling and interfaces with a commercial MPEG-2 multiplexer in compliance with the MPEG-2 system specification (ISO/IEC 13818). It has been integrated as a part of a conditional access sub-system for a digital broadcasting system and conforms so that it meets all the initial objectives and performance requirements.

Demultiplexer IC for MPEG2 transport streams

The MPEG2 systems was adopted as an international standard that specifies the multiplexed structure for combining audio and video data and a means of representing the timing information needed to replay synchronized sequences in real-time. This paper describes an integrated circuit developed to demultiplex desired programmes carried in an MPEG2 compatible transport stream. Up to nine simultaneous PIDs (packet identifiers) can be processed by the IC. The The MPEG2 demultiplexer is a fully static CMOS integrated circuit realized as an 0.8 /spl mu/m gate array.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

MPEG-2 SystemsのISDBへの適用の検討 : コンシューマエレクトロニクス,放送方式

MPEG-2 SystemsのISDBへの適用の検討 : コンシューマエレクトロニクス,放送方式