Abstract
This paper addresses source clock recovery in ATM networks for real-time services which require a timing relation between source and destination. A detailed jitter analysis is performed for the synchronous methods, from which a simple design approach is suggested for the clock recovery system. A new timing information transport protocol is proposed for constant bit rate and variable bit rate real-time services, leading to a unified ATM Adaptation Layer for both types of services. The method presented is called Generic Synchronous Technique (GST) and exhibits the following properties: (a) good control on its parameters to satisfy jitter objectives;(b) decoupling between timing and service information; (c) efficient coding leading to reduced overhead; (d) good transmission error immunity and (e) simple implementation. As a case study, it is shown that GST provides adequate clock recovery for MPEG video signals, in the most stringent case when the reconstructed system clock is used to derive a chrominance sub-carrier for use in composite video.

Abstract
Today's available solutions for the production of digitally compressed TV programmes require successive decoding and re-coding operations due both to the multiplicity of digital formats currently in use for signal acquisition and to technology limitations. This has the consequence of increasing the production costs and of reducing the overall signal quality. The ability of using compression also at the production stage will contribute to improve the overall signal quality and to reduce storage requirements and associated costs. The ATLANTIC project (ACTS 078) is developing a digital studio for the production of TV programmes using the MPEG2 format throughout the entire process, from the input of the studio to final programme distribution. EXPO'98, the next international exposition to be held in Lisbon, has been identified as an ideal showcase for audio-visual services developed by ACTS projects. The ATLANTIC project will provide basic infrastructures and technology for compressed-based TV programme production and distribution of audio-visual information and entertainment services for the entire EXPO site. This paper describes the studio reference model of the ATLANTIC project and the role ATLANTIC will be playing within the planned demonstrations of ACTS projects at EXPO'98.

Abstract
An efficient algorithm for dynamically multiplexing MPEG2 encoded video sources is presented. Sources are grouped into classes regarding different combined levels of spatial detail and amount of movement. Simulations were performed using different associations of sources belonging to distinct classes, different bit rates and GOP structures. The implications associated to a real implementation are analysed and a modular architecture is proposed. Simulation results are presented and discussed, showing that sequences with higher spatial detail and motion are those which exhibit the higher quality improvements.

Abstract
Like many other subjects, SDL is embroiled in the fusion of the Telecom and Information systems worlds. This represents a shift from the predominant use of SDL in relatively closed Telecom areas to the more and more widely used open distributed processing environments. ACTS project AC227, SCREEN, is working to improve the creation of distributed telematic services. This paper presents some of the issues and challenges that these new environments present to SDL language, and the rationale for combing SDL with OMT and the targeting to CORBA compliant environments.

Abstract
We present an integrated approach (practices) to object-oriented, distributed, application development that covers all phases of software development: requirements capture, analysis, design (structural and behavioural), simulation and targeting to CORBA-based distributed processing environments. We focus on a code generation strategy that addresses and supports all phases of the practices. We highlight code generation objectives including support for multiple paths through the practices, reuse of existing tool-sets and support for traceability. We describe one path in more detail and present an example of design OMT to SDL translation based on labelling in OMT. We describe two development environments used in the project and analyse them with respect to their support for our code generation objectives. Our tool adaptation work is addressing identified weaknesses. This includes an SDL to Java/CORBA code generator, the generation of CORBA-to-SDL-mapping C++ wrappers for C code generated by existing tools and the use of CORBA to integrate development tools and support traceability.

Abstract
The detection and location of faulty passive components is crucial in testing printed circuit boards. This issue is one of the objectives to be satisfied by the development of a mixed-signal test bus standard - IEEE P1149.4 - now on the final phase of evaluation. In this paper a method is presented that enables electronic in-circuit testing for presence and value of passive components, based on the use of analogue boundary modules like those developed under P1149.4, but making use of the positive power supply rail as an analogue test line. This method allows saving one analogue test line while profiting from the eventual presence of current sensors inserted for power supply current monitoring.