The role of computer Technology in broadcasting.

Television got its start in the late 19^th century as a mechanical scanning system. An invention by Paul Nipkow in 1884 was the basis of a working mechanical TV system by the 1920's. A rotating wheel and mask, through which a bright light was shone, modulated a photocell. This information was transmitted. At the receiving end the information modulated a bright light which shone through a corresponding wheel that the viewer sat in front of. The received images were small and jerky, the result of a low frame rate. (Usually 5 to 10 per second, compared to our current system of 30 per second.)

Reference: PBS crash course in DTV

At this time all equipment utilized vacuum tubes as their amplifying devices. Although they are still used today in some applications such as high-powered stages in Television transmitters, they presented many challenges to the designers of electronic equipment. The invention of the transistor by Bell labs in 1947 changed that. Suddenly engineers had an amplifier that was inexpensive, small and gave off very little heat.

Reference: PBS A History of the transistor

The CBS Television network was the first to develop a practical color TV system, but it was incompatible with the existing system. RCA developed a system that was compatible with the present system and it was adopted by the NTSC in 1953. This set of technical standards is the basis for today's Television Signal, which is rather unusual, given the rapid pace of electronic technology.

Reference: PBS A History of TV

In the late fifties and early sixties the transistor evolved and the integrated circuit was developed. An IC consisted of many transistors and often other components in one small package. The first to receive a patent on the IC was Robert Noyce and the Fairchild Company. Noyce later went on to found the Intel Corp and oversee the invention of the Microprocessor. Mr. Noyce was married to well known Maine Philanthropist Betty Noyce.

Reference: PBS A History of the Integrated Circuit

In the mid 1970's the digital time base corrector was developed. This was made possible due to the speed of IC's that had been developed, largely for and by the computer industry. This device samples the video, digitizes it and stores it in IC memory. Later it can be read out at some other rate, either faster or slower to achieve synchronization. The TBC or frame store made possible and legal the use of comparatively inexpensive cassette based tape recording formats. This spelled the end for the 16 mm film machines used for electronic news gathering (ENG) Nearly all stations went to the Umatic format for ENG. These machines were the basis for the VHS type machines that is so common today.

Ref: K. Blair Benson, Television Engineering Handbook, 1986

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In 1979, the Japanese demonstrated a high definition system that was implemented in the early eighties. Designed mainly for production, and to be transferred to film for theatre viewing it had about twice the picture detail of the NTSC system. As the system was analog it consumed a lot of bandwidth and could not be broadcast in the allotted television channel. One scheme used for over the air broadcast was for the base information to be transmitted in the conventional manner and the high definition information was transmitted using a satellite system. At the receive site it was spliced into a single picture. This was not the most practical system, but was workable given the current technology.

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Digital video effects started to become common in the late seventies and early eighties. These special effects, often overused, allowed the producer to make the video, flip, turn, squeeze, etc. Other production tools include paint systems that electronically simulate the effects of paint on a canvas, allowing the operator to alter a scene. Animation and Character generators, all based on computers became commonplace. At this time most of this equipment, though based on computers was dedicated to a single task and usually used a proprietary operating system and hardware.

Ref: K. Blair Benson, Television Engineering Handbook, 1986

McGraw-Hill Book Company

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This began to change in the mid/late eighties as nearly off the shelf Personal computers were sold, perhaps with the addition of a specific I/O (in-out) board that could perform sophisticated operations, previously only possible with a room full of dedicated equipment. The Video Toaster based on the Commodore computer is one such example.

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Also prevalent in the eighties decade was the development of the Very Large Scale Integrated Circuit. (VLSI) This is defined as an IC with the equivalent of about 300,000 transistors. At this point in time we are somewhere in the vicinity of several million transistors in the largest IC's. The result of this is more powerful, less expensive components.

Ref: K. Blair Benson, Television Engineering Handbook, 1986

McGraw-Hill Book Company

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Non Linear Editors (NLE) became available in or around 1993. They are used to edit and assemble television programs and so named because no longer was it necessary to build a program or story in a linear fashion. The hard drive storage that these editors used meant that the program did not have be assembled in any particular order. The video and audio is digitized, compressed and stored on a hard drive. Again, this piece of equipment replaced racks of equipment. The first machines were usually based on an off the shelf Apple computer with a video capture card and software written for this application. The same machine could be used for traditional PC tasks, such as word processing or spreadsheets. These machines are very practical at this point. Video uses a lot of bandwidth so it's almost a necessity that the machines use some sort of compression to reduce storage requirements. Most use a compression ratio between 4:1 and 2:1, which is the ratio of the data rate before and after compression. These machines have few shortcomings, but among them is the fact that many effects are not done in real time. As the hardware capacity increases, this will improve.

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Digital Television Broadcasting

As mentioned earlier, the NTSC system is approaching 50 years old. Many digital and computer systems have been built around it, but the technological backbone is ancient. This will soon change as the Federal Government has mandated that all Television stations must convert to digital broadcasting by 2002. (Actually non-profit PBS stations have until 2003.) This mandate was due in part to the desire to balance the federal budget by auctioning off radio frequency spectrum that will become available when the digital conversion is complete. All stations must continue broadcasting their NTSC signal until 2006 or longer if enough people haven't purchased the new digital sets or converter boxes.

Any station that hasn't converted by 2006 will have to cease operations.

The new format will bring many improvements to television. The most obvious is the new wide screen format and high definition. DTV will have up to 4 times the picture detail of our current system. Also the ability to broadcast up to four different programs at once (although not at the highest quality) and 5 channel digital sound. The capacity to deliver large amounts of data to a computer or to enhance a program you are viewing is within the capacity of the system. Although the system has not been designed for true interactivity the possibility does exist for its implementation at some date, especially in a closed system such as cable.

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The conversion of our television system to high definition and digital will allow us to fit the signal in our existing 6Mhz allocation. Only now do we have the technology to allow us to do this, using data compression. The data delivery rate transmitted will be around 19 million bits per second and will use a form of data compression called MPEG-2. MPEG-2 works by throwing away unneeded information and analyzing elements of motion and detail. For example, in a scene change, often much of the information is the same and can be reused. MPEG-2 is already in use by computer DVD video disks and direct broadcast satellite services.

Reference: PBS A History of TV

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The computer industry continues to drive the technological advances in many fields. In the beginning Television and Computers were totally separate fields but they have converged to the point that advances in Broadcasting don’t happen until the appropriate computer technology is developed.

Daniel R. Works

August 20^th, 1999