Technology Showcase: Video Over IP
Nov 1, 2008 12:00 PM, By Jay Ankeney
The latest hardware-based technology simplifies video distribution.
To show how far the Internet has progressed, consider that in the March 1946 issue of Astounding Science Fiction magazine, Murray Leinster described its basic concept with humor and foresight in a sci-fi story called “A Logic Named Joe.” Its plot involves a “logic” (personal computer) who scrambles “the tank” (precursor to the World Wide Web), which creates chaos by flooding the system with an overload of unfiltered information. Of course, back then, the whole idea of PCs and the Internet were mere figments of the imagination. Today, they are cornerstones of our daily existence.
The Internet is so ubiquitous that everyone is using Internet Protocol (IP) intuitively to distribute text and files; although few bother to understand how it functions. In recent years, however, the potential of using IP to also send the larger throughput requirements of video to multiple recipients has begun to permeate the corporate and institutional community as an increasingly viable alternative to the current Asynchronous Transfer Mode (ATM).
The difference is significant. ATM creates a virtual circuit before the data exchange begins that is based on standards created in the mid '80s by the International Telecommunications Union and augmented, starting in 1991, by the ATM Forum (now merged into the IP/MPLS Forum). It is a core protocol used in the Synchronous Optical Networking/Synchronous Digital Hierarchy (SONET/SDH) backbone of the public switched telephone network run by telcos. Therefore, you have to pay for it.
IP, on the other hand, sends information in packets over the free public Internet or a relatively inexpensive private intranet, and therein lies both the advantage and the challenge. IP had many fathers, but a significant milestone was a paper published in May 1974 by Vinton G. Cerf and Robert E. Kahn titled “A Protocol for Packet Network Interconnection.” Cerf and Kahn laid out a methodology for sharing information over a network in the form of packets or datagrams. This was later divided into an architecture consisting of a transmission control program at the connection-oriented layer and the Internet protocol at the internetworking layer. Hence, the term “TCP/IP,” or its more formal moniker, the “Internet Protocol Suite,” which separated the concept of the network from its physical implementation.
This makes the distribution of digital video to multiple recipients vastly simpler than during the days when RF-modulated analog video directed through routing switchers was the only practical option to a patch panel. Back then, every input and output required its own matrixed switch, but with an IP-based system, you only have to provide the specific number of encoders and decoders needed for each stream. If you need to add an additional source, just add an additional encoder.
Although massive amounts of information can be distributed quickly and easily to anyone with enough bandwidth accessing a local area network (LAN), wide area network (WAN), or the Internet (a network of networks sometimes referred to as “the cloud”), essential to the success of TCP/IP is that the material is being sent in packets. This is very efficient as long as the packets arrive in time and in their proper order. If they don't, the audio/video information can be out of sync and, in the worst case, garbled. Keeping all that content together over a closed, internal IP network is fairly straightforward as long as professional encoders and decoders are implemented and the system's capabilities are not exceeded. To achieve an acceptable quality of service (QoS) while sending all of those packets over the public Internet, some kind of buffering is required to maintain proper order in the parade of packets.
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