dtj v05-02 1993

This document is Volume 5, Number 2 of the Digital Technical Journal, published in Spring 1993. It is primarily dedicated to two main themes: Multimedia and Application Control.

Multimedia Section: The journal's multimedia focus addresses the challenges and solutions for handling large, time-sensitive digital audio and video data within computer systems and networks.

• Video Rendering: Discusses fundamental methods for generating high-quality, device-dependent pixel data from device-independent image data, emphasizing fast, simple, and inexpensive techniques like multilevel dithering (including the "void-and-cluster" method) and color space conversion.
• Software Motion Pictures (SMP): Presents a software-only approach for playing digital video on desktop systems without specialized hardware. It details a compression algorithm designed for rapid decompression, addressing integration with existing window systems and portability across various platforms.
• Digital Audio Compression: Surveys techniques for compressing digital audio signals, ranging from simpler methods like μ-law and ADPCM to more sophisticated ones like MPEG/Audio, explaining the trade-offs in complexity, quality, and compression ratios. It also touches upon real-time software implementations and psychoacoustic masking.
• The Megadoc Image Document Management System: Describes a system for large-scale electronic document management, focusing on the use of write-once optical (WORM) disks, its UNIX file system interface, storage manager, and application framework (RetrievAll) to efficiently store and retrieve image documents.
• The Design of Multimedia Object Support in DEC Rdb: Details the enhancements made to Digital's relational database (DEC Rdb) to support the storage and indexing of multimedia objects (Binary Large Objects, or BLOBs). It addresses performance and capacity challenges related to optical disk integration and transaction recovery for such large data types.
• DECspin: A Networked Desktop Videoconferencing Application: Introduces a real-time desktop videoconferencing application that transmits digitized audio and video data over standard LANs and WANs. A key aspect is its ability to manage network congestion and synchronize audio and video by dynamically adjusting video frame rates.
• LAN Addressing for Digital Video Data: Focuses on the efficient allocation of multicast addresses for transmitting digital video data over local area networks (LANs), proposing a dynamic allocation method from a finite pool of addresses to optimize network usage for multiple viewers.

Application Control Section: This part highlights Digital's Application Control Architecture (ACA), an implementation of the Object Management Group's (OMG) Common Object Request Broker Architecture (CORBA) specification, as a core technology for application integration.

• CASE Integration Using ACA Services: Explains how ACA Services addresses challenges in integrating diverse, distributed, and multi-vendor Computer-Aided Software Engineering (CASE) applications. It covers modeling applications, data, and operations to enable seamless interaction and work flow management.
• DEC @aGlance—Integration of Desktop Tools and Manufacturing Process Information Systems: Showcases a practical application of ACA Services for integrating desktop analytical tools (like spreadsheets) with real-time and historical data from complex manufacturing process control systems, providing simplified, interactive access to plant data for engineers.

In summary, the journal explores cutting-edge developments in multimedia technologies, from foundational rendering and compression algorithms to complex networked applications and large-scale data management within databases. Concurrently, it delves into robust application integration strategies using object-oriented architectures like ACA Services, demonstrating their utility in diverse computing environments such as CASE and industrial process control.