Videoconferencing & Broadcast Television
by Farhad Saba, Ph. D.

Broadcast television is the oldest and the most common means of video production and distribution.

Since the 1940's, educational television has been used by educators and trainers in a variety of disciplines to reach learners. With the advent of telecommunication satellites, corporations and institutions of higher education have increasingly turned to broadcast television for videoconferencing as well.

Educators and trainers generally use two types of equipment to produce video programs for broadcast television. They either use a small format video system, or a television studio.

Small Format Television

In its most simple configuration a video system consists of the following components:

• video camera,
• video recorder,
• video monitor,
• tripod and dolly,
• microphone, and
• earphones.

The function of a video camera is to change the light captured by its lens to an electric signal. The camera lens focuses the light and dark parts of an image on a photosensitive plate or an imaging device (e.g., a picture tube ). The photosensitive plate emits electrons in proportion to the amount of light hitting its surface. An electron gun scans the surface of the plate and shoots off the remaining electrons from the plate's surface. The electrons are collected, turned into a signal, and sent to the monitor and the recorder.

In the monitor the same process is repeated in reverse. The electron gun scans the surface of the picture tube. The picture tube's surface is treated with phosphorous; when it receives electrons it glows in proportion to the number of electrons received, and a picture is formed on the screen.

In the recorder the electric signal from the camera is received at two video heads, which create a magnetic field (some VCRs are equipped with four video heads for longer play time and special effects). This magnetic field rearranges the tiny particles of iron oxide on the surface of the tape, thus recording the image on its surface. When the tape is played back, the video heads "read" the tape and emit a signal which travels to the monitor for viewing. The camera is placed on a tripod to make it stable during shooting. Often the tripod is placed on a dolly, a three-wheeled base, which facilitates camera maneuverability.

The function of the microphone is to change sound waves into an electric signal. There is a plate (or a similar component) inside most microphones that vibrates as it is hit by sound waves. The plate's vibration changes the magnetic field of an electric circuit surrounding it. This signal is passed through the microphone cable to the video recorder and is recorded on the audio track of the video tape and/or is sent to the speaker of the monitor.

The audio and video processes were oversimplified here to provide a basic understanding of how they work.

Video Cameras

Video cameras can be classified by the size and type of their imaging device, the quality of their image, and their price. Another useful way to categorize them is by their application, which subsumes the other classifications:

* Broadcast quality cameras produce a high quality color video image, just like what you see on your screen at home. They have three pick-up tubes for the three primary colors (red, blue and green) and range from $7,000.00 to $100.000.00 in price. These cameras are used for a variety of production purposes in the broadcast industry. Portable models are used for news gathering and documentary production. More expensive and larger cameras are used for studio production and the telecast of dramas, games, variety shows, news, sports and educational programs.

* Industrial quality cameras produce a good quality color video image that may not be acceptable for broadcast purposes, but is adequate for the majority of instructional, training and corporate communication video productions. These cameras may have three tubes, in which case their price ranges from $3,000.00 to $8,000.00, or they may have a single tube with a price range of $1,200.00 to $3,000.00.

* Home quality cameras very often have only a single tube and generally cost under a thousand dollars. Their color image is adequate for making "home movies," but does not have the resolution required for the production of good quality instructional and training programs.

Until a few years ago video camera technology remained the same: cameras used a pick up tube as their imaging device. New video cameras, however use a component called a charged coupled device (CCD) for imaging. CCD technology has made the manufacture of smaller, lighter and less expensive cameras possible.

* Hi 8 camcorders are an example of such high quality, small, and relatively low-cost systems. Not only do they combine a camera and a recorder in one unit, but they reproduce a high quality image on tape that is only 8 mm wide. The cost of these camcorders ranges from $1200.00 to $3000.00.

Video Recorders

Video recorders are often classified according to the width of the tape they take and the technique they use for recording and playback, hence, 1/2 inch VHS (Video Home System ), 1 inch C format, Betamax , etc. Programs recorded in each format can be played back only on the same format, therefore, 1/2 inch VHS is not compatible with Betamax or 1 inch C format.

* 1 Inch C Format recorders are very expensive ($10,000.00 to $50,000.00) and are primarily used by broadcasters who have to adhere to technical standards set for them by the Federal Communications Commission (FCC). This format is useful to educators and trainers only if they wish to produce a program for broadcast or for transfer to videodisc.

* 3/4" U has emerged as the most widely used video cassette recording format in business and education. Many public schools and institutions of higher education use this format for production and distribution of their programs. The price of recording equipment in this format ranges between $3,000.00 to $5,000.00, and is considerably higher than the VHS and Beta formats. The price of tape for this format is about $50 for an hour of recording. These recorders use only one speed. Used with a broadcast quality camera, they reproduce an acceptable image for broadcast purposes; they also come in light models for field production and remote broadcasts.

* VHS and Betamax recorders are less expensive, ($300.00 to $3,000.00) and lighter than 3/4" U format, but they cannot reproduce an image as sharp and as stable as the 3/4" U recorders. Nevertheless, they have found many users in corporate communication departments, schools and universities. At the outset, Betamax was manufactured only by Sony and its popularity did not increase as much as the VHS format. All other manufacturers made VHS type recorders, which have rapidly gained the number two position in popularity after 3/4" U among video users. Beta and VHS cassette tapes are also much less expensive than 3/4" U cassettes ($6), and they can be recorded in three speeds, providing longer recording and playback time. Standard play (SP) speed, however, is recommended for professional use. This speed on a VHS tape will provide 2 hours of recording time (1 hour for Beta).

Video Monitors

Video monitors are most often classified by the size of their screen (e.g. 10", 13" 26"). Generally, the bigger the screen, the higher the price. They range in price from several hundred dollars to more than a thousand dollars. Video monitors can reproduce the image they receive, either directly from a camera or from a videotape recorder. Some monitors do not have a speaker, so they cannot reproduce sound. Monitors are used in small format productions for previewing a take as it is being recorded, or after it has been recorded.

Video Editing &
Post Production Equipment

Video editing equipment can be as simple as a playback unit (source deck), a recorder (editor deck), an edit control unit, and two video monitors. While editing, you select a segment you have previously recorded on your video tape (the source tape), and literally duplicate that segment onto a blank tape (which will become your edited master). The edit control unit allows you to select precise points on your source tape and the edited master tape, and then transfer audio and video segments from the source tape to the edited master tape without a glitch between two shots. Simple editing systems for 3/4"U format cost between $10,000.00 to $15,000.00. The cost of editing equipment is lower for VHS or Beta equipment; in these formats an editing system can be purchased from $6000.00 to $10,000.00.

A simple editing system can be gradually augmented with additional components to provide more flexibility to the post-production process. For example, with the addition of a video switcher, additional video sources (such as a microcomputer or a video camera) can also be fed into the editor deck. This enables the editor to use graphics generated in a microcomputer for titles, credits and other purposes. Most microcomputers, however, do not produce a signal compatible with the standard video signal. Therefore, their output should be processed through an adapter card, often called a NTSC (National Television Standard Committee) card. These cards are available for most microcomputers; their cost ranges from $1000.00 to $3000.00.

Through a switcher, a video camera can also feed additional video segments, such as the image of a conventional graphic, or the image of a three dimensional model or even a "live" announcer to the editor deck. With the use of a switcher the editor can produce a fairly complex and sophisticated video program. To further develop the post-production facility, a time-base-corrector (TBC) can be added to the system. The function of a TBC is to synchronize the various video sources fed into the switcher. TBCs can stabilize the video output of a switcher and solve many post-production problems. But they are expensive and only facilities with a healthy budget can afford them. The price of a TBC ranges from $8000.00 to $20,000.00.

To add music or "voice-over" narration onto an edited master requires that an audio mixer, a microphone, and at least one audio playback unit (e.g., a compact disc player) be added to the post production facility. Another way of adding sound to an edited master tape is to take the tape to an audio studio that is equipped with a video recorder and add the desired audio segments.

A new and exciting development in video post-production is the advent of digital editing equipment. Also known as non-linear editing systems or tapeless editing systems, they allow you to digitize your video segments and save them on a computer disc as files. Software specially produced for these systems then allows you to choose among different file segments or different files, and edit them together. Transitions from one scene to another scene are also software driven and can be handled in a variety of ways such as wipes, dissolves, mosaics, etc. with little effort. Graphics and special effects are built-in, so titles, credits, and captions can be produced and incorporated on the same system. Once you are done with the editing process, you can "print" your edited version to a tape for distribution and viewing purposes.

Studio Equipment

Studio video equipment is expensive and usually requires a professional crew who have had extensive training and experience in the production of video programs. A video studio, however is a very flexible environment for video production and allows the producer/director to produce a professional program. Most video studios consist of a sound stage (or studio floor) and a control room.

The sound stage is equipped with at least two (usually three) broadcast quality television cameras, a light grid and lighting instruments, boom stands, and other types of stands for microphones. The control room is equipped with a video switcher, an audio control board, a light control board, several monitors for each video source (such as the cameras), camera control units, electronic measuring and monitoring instruments (e.g., vector scopes and waveform monitors), audio recorders and playback units (audio cassette recorders, turntables, etc.), a character generator (or a computer for graphics), and many other types of electronic equipment to enhance and control the audio and video signals.

In a studio production, each piece of equipment is run by a professional crew member. The director issues commands from the control room via an internal communication system (intercom) to the crew on the studio floor or in the control room. These commands can only be heard by the crew via their head sets and do not interfere with the flow of the program being taped or telecast. The commands are formal and specific and allow the camera personnel, audio personnel and the rest of the crew to follow the "show" as it progresses on the studio floor. Audio and video signals in a studio production are often recorded on a 1 inch tape and edited after the production is completed.

Talkback Systems

The most commonly used talkback system in one-way video, two-way audio distance education systems is the ordinary telephone. With an 800 number, students can call in questions to the live studio experts at no charge to them. Recently, educational broadcasters have also added fax machines to provide "talkback" capability to their systems. Those who have access to the Internet, also, use this international telecommunication system for receiving questions from their audience.