Enabling technology and real-life applications of video over fiber using IP
Pete Ianace Intelect Network Technologies
Internet-based videoconferencing services supported by fiber networks are now in use at several locations, thanks to new compression techniques.
Not long ago, communications managers who wanted to deliver videoconferencing services to their corporation had one option: Integrated Services Digital Network (ISDN). More recently, much has been said about adding video traffic to installed fiber-optic wide-area or local-area networks (WANs/LANs). Internet Protocol (IP) is the preferred transmission vehicle for that video traffic.
Most communications managers now struggle to differentiate between the viability of IP-based video and blue-sky predictions. While there are various methods to deliver videoconferencing services, there is an underlying technology that makes videoconferencing over IP possible and practical in several applications. A wide range of videoconferencing systems are available (see Table), however, the focus here will be on personal computer-based systems, or "desktop systems," designed for individual use. Desktop videoconferencing systems typically range from $500 to $4000 each.
ISDN, frame relay, and IP
The global telecommunications industry developed ISDN as an international standard for transmitting voice, video, and data over a digital line. Developed subsequently, broadband ISDN was designed to boost transmission speeds to rates that could facilitate the delivery of broadband services. For videoconferencing systems based on the pervasive H.320 standard, ISDN is the ideal communications vehicle because it offers a steady, constant bit rate. H.320 today is an extremely well-accepted videoconferencing standard. Most vendors` videoconferencing systems are H.320-compliant.
The industry developed two protocols to support ISDN-based videoconferencing. The H.261 and H.263 protocols were intended to provide high compression rates while conserving bandwidth using ISDN lines over WANs. These protocols conserve bandwidth, which is an important advantage, but they also compromise picture quality. Images lose detail and contain visible pixelization. Marked blurring occurs when the H.261 or H.263 video contains intense motion.
ISDN-based videoconferencing has disadvantages as well. ISDN service is not universally available. When the service is offered, it is expensive and consumes bandwidth.
Due to the drawbacks of ISDN, H.261, and H.263, increasing attention is being given to the idea of multiplexing video and data traffic across a frame-relay backbone. Traffic can be transmitted one of two ways--packaged as frame-relay frames or sent as IP packets. Both approaches are cost-effective methods of transmitting video communications, especially when compared with ISDN-based videoconferencing. But either approach will fail if the supporting network is not designed, implemented, and operated appropriately. For many communications managers, the threat of unreliable service is enough that they choose not to deploy videoconferencing over their existing networks.
In reality, the rewards are great and the risks minimal when sending video over IP. The option of sending video as IP packets is particularly appealing because it gives communications managers flexibility and lets them conserve that precious corporate resource: bandwidth. The key is whether the underlying IP network is reliable, as is the case with the IP-based videoconferencing applications described here. IP-based videoconferencing systems that use the new H.323 protocol are particularly efficient in their use of bandwidth. H.323 is the newest international telecommunications standard for videoconferencing over LANs. H.323-based systems also give end-user organizations unprecedented flexibility in mixing systems from many vendors.
Therefore, before adding videoconferencing services to an existing WAN or LAN, the communications manager should feel confident that the IP network can meet the end-user organization`s quality-of-service requirements.
An old timer new to imaging
Three compression algorithms are commonly used in IP-based image processing: MPEG, JPEG, and Wavelet. The first two algorithms use a compression method known as discrete cosine transform (DCT). MPEG is designed to transmit sequences of images such as video, while JPEG transmits still images. Both DCT algorithms function by representing an image`s details in mathematical terms. A less detailed image has fewer terms than a very detailed image.
The point of using any compression algorithm is that images will transfer faster or consume less storage space if they are compressed. Thus, the goal when using MPEG or JPEG is to achieve a high compression ratio. MPEG often works very well, but if the image is compressed too quickly, disturbing artifacts appear. Artifacts are undesirable flickers or shadows on an image that are visible to the human eye.
Both MPEG and JPEG algorithms demand more processing power to encode than to decode. This means that MPEG compression encoders are expensive--often costing thousands of dollars--while MPEG-based decoders cost less than $100.
The alternative Wavelet algorithm has increased in popularity because of its resistance to artifacts and its comparatively low cost. Based on century-old mathematical theories, the first modern application of the Wavelet algorithm was in geophysics in the mid-1980s. Next, the technique was adopted for use in applied mathematics and theoretical physics. By the end of the last decade, the telecommunications industry began to apply Wavelet to signal and image processing. In the past five years, Wavelet`s use in image processing has exploded, partly due to the introduction of low-cost Wavelet-based encoder/decoder chips. Wavelet is now deployed in videoconferencing systems, video editing, and high-quality medical images such as magnetic resonance imaging (MRI) systems.
The Wavelet compression technique requires the same processing power whether it is encoding or decoding--a noticeable advantage over the DCT algorithms. In addition, Wavelet delivers television-quality pictures while using the same amount or less bandwidth than MPEG.
A further advantage of Wavelet is its scaleability. If the end-user organization is running low on bandwidth, the user of a Wavelet-based videoconferencing system can choose to send images at a lower frame rate and with greater compression. This selection can be made without compromising image quality. On the other hand, if image quality is of prime concern--such as in medical applications--images can be sent with less compression and at higher frame rates.
Furthermore, the Wavelet technique allows images to be manipulated so they are enhanced for videoconferencing. The algorithm offers biorthogonal wavelet transform, which is a special filtering and coding mechanism that produces a highly detailed image. This detailed image can be compressed in such a way that softened artifacts result, which are less noticeable to the human eye than artifacts produced with the MPEG algorithm.
Wavelet allows the transformed image to be manipulated further to enhance its suitability for videoconferencing. Compression is implemented nearly without loss; good compression is achieved at either a constant quality or bit rate; and high-quality scaled images can be created without computational overhead. Finally, Wavelet creates an error-resilient compressed bit stream, which occurs because each transformed block of the image contains information about the whole image.
For these reasons, it makes sense to select Wavelet as the video-compression algorithm for a videoconferencing system that will communicate using IP. Most LANs today accommodate IP, including networks based on Ethernet, T1/E1, frame relay, Asynchronous Transfer Mode (ATM), and Synchronous Optical Network protocols. Intelect Network Technologies, for example, selected the Wavelet compression technique as the most reliable method of providing high-quality images from a desktop-based videoconferencing system.
From Texas to Alaska
Let`s look at two applications of Wavelet-based videoconferencing systems that transmit over IP:
An advertising production services company uses videoconferencing to involve clients in the creative process, enhance client relationships, improve quality control, and reduce travel costs.
An energy pipeline operation videotapes repair and maintenance work and broadcasts to locations several hundreds of miles away. The application reduces travel time for technicians to monitor repair work done at remote sites.
In the first application, Laser Tech Color (Irving, TX), an advertising product services company, selected a Wavelet-based videoconferencing system that operates over IP as a core technology to communicate with its clients. Laser Tech supplies outsourced digital prepress and asset management services to advertising agencies, consumer product and packaging companies, and retail advertisers.
Before selecting the IP-based desktop videoconferencing system, Laser Tech evaluated a number of alternatives. The company wanted a videoconferencing system that could support multiple-party conferences from a personal computer. Laser Tech also wanted videoconferencing systems that could communicate over the Internet and that complied with the emerging H.323 video standard.
Laser Tech uses videoconferencing now to involve clients in creative campaigns from conception to implementation. Previously, Laser Tech sent creative work to out-of- town clients via courier or with an account team, which involved considerable travel costs. Now, six or more people confer on a videoconference, which has improved communications and cut expenses.
The videoconferencing system electronically sends files over the Internet from Laser Tech`s LAN to the client`s LAN without any compromise in image quality. The videoconferencing system also uses document cameras if a situation calls for a fine level of detail.
Any client with an IP address can tie into Laser Tech`s digital workflow, but communications over the network are carefully secured. The network is supported by an ATM communications backbone.
Before selecting the IP-based videoconferencing system, Laser Tech considered installing private telecommunications networks so that it could collaborate with clients. The cost would have been prohibitive.
Laser Tech clients welcome the chance to be more involved in the creative process, and they like to see visual images of the agency`s work, according to company president Damien Gough. "The videoconferencing system also helps us turn concepts into digital images faster and put the right products in front of clients more quickly," he says.
In a second application of Wavelet-based videoconferencing, video systems operate over the fiber lines that are part of an Alaskan energy pipeline in what may be best described as a repair and maintenance application (see Figure). Video images of routine maintenance work done on the pipeline are transmitted to locations hundreds of miles away. The videotaped repair and maintenance work eliminates the need for a field technician to travel to these remote sites that are difficult to access, particularly in the winter.
Equipment that is tied into the fiber network includes pump stations, metering stations, marine terminals, and regenerator sites. Three separate OC-3 (155-Mbit/sec) networks are tied together in WANs.
When the advantages of a Wavelet-based videoconferencing system that uses IP to communicate are understood, the choice for the communications manager is clear. If the end-user organization needs a cost-effective, scaleable, and flexible method to deliver high-quality video services, IP-based video is a reasonable way to go. u
Pete Ianace is president and chief executive of Intelect Network Technologies (Richardson, TX).