DVD Video: A Primer For Educators
- By Sandra Benedetto
For creation, playback, and storage of high-quality educational content, from video and audio to graphics and animation, nothing beats the DVD-Video format.
The latest buzzword in disc technology is DVD. DVD technology was announced in 1995, and as with most new technologies, it arrived amidst a flurry of excitement and promises for the future of communication. DVD was going to revolutionize the multimedia industry.
It is true: DVD is a major step forward in optical disc technology. It can address technology needs that neither laser disc nor CD-ROM alone could fully meet. Now that DVD movie discs and home entertainment DVD players have been available for more than a year and the initial media hype about the technology has subsided, we can begin to examine its benefits for teaching and learning.
DVD offers the ability to combine the best of laser disc and CD-ROM programs, creating a multimedia platform that can deliver high-quality, full-motion video and an on-screen user interface for interactive navigation and branching. With these features, educators can use either a DVD-Video player or a DVD-ROM computer system as tools for providing group or individual instruction.
What Is DVD?
Originally, DVD was an abbreviation for "Digital Videodisc." However, many data formats, not only video, can be stored on a DVD disc, so some folks started calling it "Digital Versatile Disc." But the Digital Versatile Disc name didn't take hold, and a fair amount of confusion ensued from the use of both terms to describe the same entity. Now, most people simply refer to DVD as DVD.
A DVD disc is often compared to a compact disc, because it has the same physical size and appearance. However, although a CD can store many different kinds of mediatext, graphics, photos, animations, and audioin a "read only" format, with a storage capacity of only 650 megabytes, a CD cannot store or play video. By contrast, a DVD disc can hold two sides of information, each side containing two layers of data. A single-sided disc holds up to 4.7 Gbytes of information, enough for a full-length movie (one Gbyte equals one billion bytes). A single-sided disc with two layers can hold up to 8.5 Gbytes. The same holds true for the second side, resulting in a 17.0 Gbytes total capacity on one disc. DVD discs can be manufactured in any of the side/layer combinations. Each type of disc has been given a particular classification:
DVD Class Side/Layer Capacity
- DVD 5 Single-Sided/Single-Layer 4.7 Gbytes
- DVD 9 Single-Sided/Dual-Layer 8.5 Gbytes
- DVD 10 Double-Sided/Single-Layer 9.4 Gbytes
- DVD 18 Double-Sided/Dual-Layer 17.0 Gbytes
The DVD Forum, an international association of hardware manufacturers, software firms, and other users of the DVD format, categorizes DVD discs into five formats: DVD-Video, DVD-ROM, DVD-R, DVD-RAM, and DVD-Audio. The format of each disc describes how information is stored and which type of hardware system must be used to play it. A familiar analogy is the comparison between CD-Audio and CD-ROM discs; both utilize the same type of physical disc but each contains different data formats and is played back on different types of hardware systems.
The two most important DVD formats for education are DVD-Video and DVD-ROM because these are the types of discs that will be created by publishers to deliver educational content to schools, universities, and libraries.
DVD Disc Format Application
- DVD-Video Interactive or linear video programs
- DVD-ROM Multimedia programs or data storageof any type; requires a computer
- DVD-R Record-once format used in developing DVD-Video or DVD-ROM programs
- DVD-RAM Re-recordable format, used as a computer peripheral to store files
- DVD-Audio Audio-only format; specifications still in development
The DVD Video Format
The DVD-Video format allows developers of video-rich, educational material to create highly interactive multimedia programs. Like laser disc, DVD-Video allows the user to quickly search for and play back specific segments in the video program. DVD-Video also offers many more capabilities ideal for classroom use.
A single-sided, single-layer DVD-Video disc can hold more than two hours of high-quality, digital video, as opposed to 30 minutes of analog video on a CAV (constant angular velocity) laser disc, or 60 minutes on a CLV (constant linear velocity) laser disc. With CAV, the disc rotates at a constant speed regardless of what area is being accessed. With CLV, the disc rotates faster for inner tracks because less data can fit there.
DVD d'es not have these limitations. However, the exact amount of video that can be stored on a DVD disc depends on the level of MPEG2 compression applied when encoding the video as digital data. Usually, no more than two hours of compressed video is a good rule of thumb in order to maintain a high-quality picture. Many feature films available on DVD are single-sided, single-layer discs.
DVD-Video discs can contain up to eight, high-quality audio tracks. Such flexibility not only allows for multiple languages on the same disc, but also offers the opportunity to create audio narration for different grade levels, or a special video-description audio track for blind and visually impaired students. If the producer chooses, a special staff development track can be added to guide the teacher and provide tips on how to use the program in the classroom.
Buttons and Program Branching
Multimedia or interactive video programs that employ graphical user interface designs with on-screen buttons usually require some kind of computer control. CD-ROMs and laser discs require a computer to manage user selections and to execute branching instructions.
With DVD-Video, graphics or text buttons can be displayed within the video material on the video monitor, allowing the teacher to select a particular lesson from a list of menu options, have students answer multiple-choice questions, or quickly navigate through the program content. A computer is not needed to control the program because the DVD player has the built-in processing power and intelligence to execute the interactive branching instructions contained in the program on the disc. All DVD-Video players support interactive buttons and branching. Buttons are selected with a remote control unit or, on some players, with a mouse that can be directly connected to the player.
Sub-Pictures and Multi-Angles
Sub-pictures and multi-angles are two additional capabilities that can be creatively applied to reinforce the established pedagogy and extend the instructional design of the DVD video program.
The sub-picture feature allows the instructional designer to add text and graphics that display over the video and that can be turned on and off by the teacher or student. Text can be displayed in multiple languages and can sub-title or annotate the video content. Graphics can be used to highlight specific action on the screen, such as the precise moment a cell divides or exactly when a reaction takes place in a science experiment.
While DVD supports traditional closed captioning for deaf and hearing-impaired viewers, sub-pictures can also be employed to further extend accessibility to the video material. On a DVD, 32 sub-picture channels are available for a variety of text and graphics displays.
The multi-angles feature allows up to nine parallel video paths to be embedded in the video program, allowing for multiple angles that the user can choose among while using the disc. This capability is often described as a way to include alternate camera angles or add "out-takes" in special DVD editions of feature films. To date, few DVD video titles utilize multiple angles, which require additional video recording, production, and editing. However, the possibilities for teaching high-level skills and procedural training are great.
The functions and features in the DVD-Video format can strengthen and expand the instructional effectiveness and classroom utilization of a video program. Together, a DVD-Video disc and a player can provide a highly interactive video platform for use in the classroom.
Playing DVD Video
All DVD-Video discs can be played on all DVD-Video players. Players are directly connected to a video monitor or television, as one would connect a laser disc player or VCR to a television. The teacher or student can control the video and navigate through the program with a remote control unit or mouse. While a computer can be connected to some DVD-Video players, a computer is not required for a teacher to present an interactive video lesson.
Several DVD-Video players that are specially designed for education and classroom use support all of the standard DVD-Video functions described above and, depending on the player and manufacturer, add other capabilities. Additional features may include: a serial interface port for connection to a computer (similar to laser disc players), bar-code control, mouse support for on-screen button selection, and graphics tools and keyboard support so that the teacher can draw or type text over the video.
DVD-Video and DVD-ROM are two separate formats. Yet, just as CD-Audio discs can be played on CD-ROM computer systems, DVD-Video discs can also be played on DVD-ROM computer systems and can further extend the use of the program in the classroom.
In order to play a DVD-Video disc, the computer should be a 166 MHz processor (higher is better) and must be equipped with a DVD-ROM drive, an MPEG2 video decoder card or software decoder, and special software that emulates a DVD-Video player. The Digital-Video format includes a Content Scrambling System to prevent users from copying discs. This means that DVD-ROM players require a software or hardware upgrade to decode and play the encrypted discs. The emulation software is usually bundled with the decoder software or hardware.
Such a computer configuration will allow playback of DVD-Video discs and supports all interactive functions, including buttons, sub-pictures, and multi-angles. Many computer manufacturers are now shipping DVD-ROM systems.
It's important to note that DVD-ROM discs cannot be played on DVD-Video players. A DVD-Video player is a dedicated machine designed to play discs that contain specially formatted DVD-Video files. A DVD-ROM, on the other hand, can contain multimedia files, DVD-Video files, graphics, text, or any other type of data. Therefore, a properly configured computer with the appropriate software is required in order to read files from a DVD-ROM disc.
DVD Technology Adoption
DVD-Video offers additional features to the instructional designer that can be applied or not applied, based on the educational objectives of the program. And the simple configuration of a player, disc, and video monitor can be a highly interactive platform that d'es not require a computer and is easy to use by both teachers and students.
Since DVD is a new technology, there are few titles presently available that address core curriculum areas and are designed for classroom use. However, over the coming year, the DVD-Video title library will begin to grow as educators and educational publishers become more familiar with the instructional benefits of the technology.
When laser disc and CD-ROM were first introduced, content publishers and hardware manufacturers worked together to develop key titles for education. Most likely, the same situation will occur with DVD. As with any new technology, it will require the right balance of hardware and software availability in order to create the right business and market climate to deliver DVD technology to education.
There is no question that DVD-Video has the potential to be an effective, exciting teaching and learning tool. It's only a matter of time before it reaches its potential.