Multimedia Communications

Increasing competition and relentless pressure to develop more products in less time with fewer resources is placing renewed emphasis on information flow and ultimately on network architectures and networking capabilities. If you are an engineer, the impact of teleconferencing technologies is likely to affect you in one or two ways:

1. If you are designing multimedia peripherals, hardware or software, whether PC-based or not, then the design considerations for audio and video enabled peripherals could be fundamental to your work.
2. All engineers in general should be prepared for the new era of multimedia communications and the ability this will bring to make team meetings more productive and less intrusive.

The evolving norm for multimedia communications among technical professionals is to share data while having a voice call. But many opt for video as well, since it adds a personal touch to the conference and can make a conference call seem more like a "meeting." Desktop systems allow remote users to share CAD files as well as other office documents created in spreadsheets, word processors, presentation packages, etc. It is only a small paradigm shift to use the computer this way, and replace hardcopy handouts, faxed presentations, or FedEx packages to give meeting attendees information in advance of or simultaneous with, a working session.

Perhaps even more compelling is today's interest in using computer and videoconferencing technology to perform remote presentations. The concept is to take the combination of human interaction and slide shows or even streaming video clips, and combine these into a presentation which can be viewed by participants in the same meeting room as well as by those sitting in a distance conference room, connected by phone lines and by the Web.

In the early 1980s, group videoconferencing systems cost hundreds of thousands of dollars and were totally proprietary. Each vendor used his own compression algorithms. Communications between equipment from different vendors was generally impossible. But by the early 1990s, acquisition prices had fallen to the tens of thousands of dollars, while the systems themselves were able to provide superior audio and video quality on pipelines of 768 kbps and even 384 kbps, thereby reducing the cost of using the system. In December, 1990, the ITU published its first international standard for videotelephony, H.320, a recommendation which solved the interoperability problem. H.320 was demanded by customers, adopted by vendors, and the group market began to flourish.

The videoconferencing industry took a sharp evolutionary turn in the early 1990s, when some vendors recognized that PC's were an ideal platform for building low-cost, high performance videoconferencing systems. By 1994, several companies had introduced add-on videoconferencing kits for the PC that cost around $6000, and the desktop videoconferencing industry was born, positioning itself to ride on the convergence of personal computers, communications, and consumer electronics. Relentless efforts to lower costs have had dramatic impact. Today, ISDN-based (H.320) desktop kits are widely available for under $1500, and POTS-based (H.324) kits with street prices of $250 and below are common.

ISDN conferencing products today have blurred desktop vs. group product category distinctions based on video performance, communications needs, and prices. The real distinction today is based on intended usage. Desktop systems are largely intended for personal use. Group systems tend to be more formal, and use higher end group-oriented cameras and sound systems.

The next phase of the desktop market is now beginning to take shape, as videoconferencing standards for LAN-based communications (H.323) are solidifying, bringing interoperability, ease-of-use, robust designs, and network management capabilities to the pipeline that is already installed in most offices—the corporate LAN. The world is becoming IP-centric, Internet-focused, and videoconferencing is moving accordingly.

• Standards
  The history of multimedia communications is written in the technology of video and audio compression. Many techniques have been developed to squeeze a river of data down to a soda straw of bandwidth. Today, systems level implementers have to live within the constraints of standards-based compression algorithms, since standards are the foundation for interoperability, which in the communications field, is absolutely necessary. Technology challenges here involve implementation of standards, especially optimizing the software to run on common host CPU chips, and the development of special accelerator silicon which not only speeds up the compression process, but also offloads the host for other applications.
  
  
• Bandwidth
  Another technology challenge involves bandwidth provisioning and designing networks for reduced latency. Raw bandwidth always helps. On the WAN, you can buy ISDN services ranging from dedicated 128 kbps to 1920 kbps, and pay as you go. On the LAN, 10 Mbps is available, but is shared by all the users on the segment. So adding lots of conferencing users poses the threat of bringing down the data network. Users should be looking to a migration from 10 Mbps Ethernet to 100 Mbps Ethernet, and from a shared hub architecture to a switched network.
  
  
• Latency
  Latency is another issue, and one that has come to the forefront as multimedia conferencing moves to packet-switched networks. End-to-end latency is the sum of all delays in the system, the endpoints doing compression/decompression, the switches, and the routers doing store-and-forward messaging. End-to-end performance on the LAN is the primary determinant of user satisfaction. Dedicated videoconferencing hardware (rather than host-based for audio/video compression has tremendous benefits on the LAN not only because the higher performance reduces delay, but also because the system can handle faster bitstreams, yielding higher video quality, without burdening the host workstation. Today, many network protocols such as RTP and RTCP are intended to reduce latency on IP-based networks.
  
  
• Price
  A few years ago, $50,000 for a videoconferencing system was not out of the ordinary. Today, a very nice conference room system can be purchased for under $8K, and a $1500 ISDN videoconferencing kit added on to a $1500 desktop computer makes for a very effective personal conferencing system. The industry continues to ride the price/performance curve of the electronics industry. Prices, which continue to fall, are largely a second rate concern today.
  
  
• Performance
  Quality of audio and video are always disappointing to those who are used to TV-quality images and sound. However, audio and video quality are much better than they were a few years ago, due to more horsepower (MIPS) which can be thrown at the problem, as well as to advanced algorithms. The conferencing market today has two segments here, consumer and business. Consumer products are generally price driven, but businesses need a minimum level of quality in order to conduct effective meetings. Like pricing, the performance metric improves continuously. Performance also relates to ease-of-use and ease-of-installation.
  
  
• Plumbing
  Plumbing refers to the ability to conference on pipelines that are readily available. And to use standards-based products on whatever pipeline is available. Most North American homes today have analog phone services; which most corporate offices have proprietary PBX connections and TCP/IP Ethernet connections. In many areas of Europe and Japan, residences are equipped with ISDN phone services. Until 1995 however, teleconferencing standards existed only for the ISDN network. Today, standards exist for all the important pipelines, and products are now coming to market that address this opportunity.
  
  Since mid-1997, with the adoption of the ITU's H.323, which establishes standards for IP-based conferencing, there has been an explosion in interest in using IP LANs as the "plumbing" to connect multimedia conferencing stations. Unlike ISDN, IP is already installed in most corporate offices. And many companies have already established extensive IP data networks to connect far flung facilities. Furthermore, IP is the technology understructure of the Internet and corporate intranets. Vendors, in turn, are reacting with the rapid announcement of IP and H.323-based products for the desktop, for the network manager, for the communications closet, and for the carrier/service provider.
  
  Network managers and network users alike are well advised to pay attention to H.323, the new standard for IP-based videoconferencing and IP-telephony or voice-over-IP (VoIP). Like all ITU recommendations, H.323 sets standards for audio and video compression, and for call setup and control. But H.323 also includes several sections key to network managers. For example, H.323 defines a hardware or software device known as an MCU to enable conferences with more than two people; it also defines a gatekeeper function. Gatekeepers handle bandwidth management, authentication, and other policies that prevent the network from being abused. While gatekeepers manage LAN usage, gateways are the critical component for tying the LAN to the WAN (and to the Internet) and managing bandwidth across this function. Good gateways provide the intelligence at this critical intersection to make the LAN/WAN connection appear seamless.
  
  
• Interoperability and Connectivity
  With the adoption of standards, the videoconferencing industry is now moving beyond standards, to the issues of interoperability and connectivity. These are really the benefits that the user is looking for. An industry group, the International Multimedia Teleconferencing Consortium (IMTC), has taken the intent of the ITU a step further, by creating an industry forum for ensuring that vendors' interpretations of the standards result in products that work together as planned. Standards from the ITU, together with interoperability testing by the IMTC, set the foundations for vendor-to-vendor interoperability, making it possible for the network manager to purchase products and the user to "place the call" without worrying about possible incompatibilities between components.