Jane C. Blake,
This issue of the Digital Technical Journal features papers on multimedia
technologies and applications, and on uses of the Application Control
Architecture (ACA), Digital's implementation of the Object Management
Group's CORBA specification.
The high quality of today's television, film, and sound recordings have set
expectations for computer-based multimedia; we expect high-quality images,
fast response times, good quality audio, availability - including network
transmission, and all at "reasonable" cost. Bob Ulichney has written
about video image-rendering methods that are in fact fast, simple, and
inexpensive to implement. He reviews a color rendering system and compares
techniques that address the problem of insufficient colors for displaying
video images. Dithering is one of these techniques, and he describes a new
algorithm which provides good quality color and high-speed image rendering.
The dithering algorithm is utilized in Software Motion Pictures. SMP is a
method for generating digital video on desktop systems without the need for
expensive decompression hardware. Burkhard Neidecker-Lutz and Bob Ulichney
discuss issues encountered in designing portable video compression software
to display digital video on a range of display types. SMP has been ported
to Alpha AXP, Sun, IBM, Hewlett-Packard, and Microsoft platforms.
Digitized data - video or audio - must be compressed for efficient storage
and transmission. Davis Pan surveys audio compression techniques, beginning
with analog-to-digital conversion and data compression. He then discusses
the Motion Picture Experts audio algorithm and the interesting problem of
developing a real-time software implementation of this algorithm.
Even compressed, digitized data takes up tremendous amounts of storage
space. A relational database can not only store this data but provide
fast retrieval. Mark Riley, Jay Feenan, John Janosik, and T.K. Rengarajan
describe DEC Rdb enhancements that support multimedia objects, i.e., text,
still frame images, compound documents, and large binary objects.
Managing image documents is the subject of a paper by Jan te Kiefte, Bob
Hasenaar, Joop Mevius, and Theo van Hunnik. Megadoc is a hardware and
software framework for building customized image management applications
quickly and at low cost. They describe the UNIX file system interface to
WORM drives, a storage manager, and an image application framework.
Distributing multimedia over a network presents both engineering challenges
and opportunities for applications. DECspin is a real-time, desktop
videoconferencing application that operates over LANs or WANs, using
TCP/IP or DECnet protocols. Larry and Ricky Palmer present an overview
of the DECspin graphical interface. They then address network issues of
real-time conferencing on non-real-time networks and a solution to network
The transmission of full-motion video programs to multiple users requires
adaptations in many parts of a client-server, LAN environment. Peter
Hayden's paper focuses on the specific problem of efficient allocation of
network addresses for the transmission of digital video data on a LAN. He
reviews alternatives and describes a technique for the dynamic allocation
of multicast addresses.
The common theme of two final papers is ACA Services, Digital's
implementation of the OMG's Common Object Request Broker Architecture. Paul
Patrick has written an instructive paper on CASE environment development
utilizing ACA. Assuming a multivendor, distributed environment, he
discusses modeling of applications, data, and operations; application
interfacing; and environment management.
DEC @aGlance software is an implementation of ACA that supports the
integration of manufacturing process information systems. David Ascher
differentiates between generic integration software and @aGlance,
and describes how ACA is used to integrate independently developed
The editors thank John Morse, engineering manager, Corporate Research, and
Mary Ann Slavin, engineering manager, ACA, for their help in preparing this