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Glossary Of DVD Terms

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Aberration: Variations in focus of a laser beam spot, resulting in the beam of light being diffused at different points, is called an aberration. These aberrations, caused by a lens or variations in substrate density, can create focusing errors in the laser pick-up. The thinner 0.6mm substrate utilized on DVD discs significantly reduces aberrations of the laser spot pick-up, improving accuracy in a high density environment.
Aperture: Aperture is the opening or width of a lens.
Anamorphic: The process of compressing wide screen images, 1.78:1 or greater, to fit into the bandwidth of a standard 1.33:1 television signal. The images are then expanded for viewing in their original format on a widescreen display device. 

Do you want to know more?  Jump to an article on "Aspect Ratio."

Angles: Scenes that make up a movie may be shot from multiple camera angles, each providing a unique perspective of the program. DVD will allow, at the director's discretion, up to nine different camera angles to be recorded on a disc, enabling the viewer to select the angle they desire. This option will add interactivity to movies, sporting events and instructional videos.
Artifacts: Flaws in the video image that lessen the picture quality and were not present in the original material.
Aspect Ratio: The relationship between width and height of a television set. Current television products feature a 4:3 aspect ratio. DVD will off 4:3, letterbox and 16:9 aspect ratios. 

Do you want to know more?   Jump to an article on "Aspect Ratio."

Audio Streams: DVD - Has the ability to hold a maximum of eight audio streams on a single disc. This enhanced capacity allows Hollywood Studios to include up to eight different language tracks providing added versatility in multi-language applications.
Average Bit Rate: A Bit is a single binary unit. This is the smallest unit of information that the processor can handle. Bit rate refers to the speed at which the processor can read and process data from the disc. The average bit rate is the average of a variable bit rate system. DVD utilizes a variable bit rate to better allocate storage capacity on a disc.


Bitmap: A format for storing still graphic images. In DVDs, bitmaps are used for menus and overlays.
Bit Rate: The rate at which digital information is presented or encoded. Since there is room for only so many bits on a DVD, the bit rate can vary. The rate is kept lower for simpler sequences so that extra space will be available for more complex ones.
Blocking: A visible artifact of digital compression in which blocky rectangular areas appear in the picture due to the way an image's pixels are organized.
Bonded Disc: DVD Video Discs are 1.2mm thick consisting of two 0.6mm layers permanently bonded together. This procedure produces a disc that is more resistant to warpage and offers improved tilt margins. It also enables a software content provider the capability to utilize both sides of the DVD disc.

Do you want to know more?  Jump to "Inside a DVD."

Buffer: An integrated circuit that temporarily stores information prior to processing. Images are retrieved from a DVD disc in packets referred to as groups of pictures (GOP) that are assembled in the buffer. The buffer assembles entire picture data and then releases it for processing.


Caption: Text that appears on screen during a program, such as foreign language subtitles.
Cell: A point on a DVD where a chapter stop has been created, allowing the viewer to jump instantly to that spot.
Channel: One section of an audio track, usually carrying the sound for one speaker.
Chapter: Also known as a "part of the title," a point on a DVD that the viewer can instantly jump to, like a track on a CD.
Chroma: The color part of a video signal, as well as a description of how intense the color is in a given frame.
Closed Caption: A caption that is only visible when particularly requested, as opposed to "open captions," which are a permanent part of the picture image.
Coaxial Cable: A two-conductor cable with a hot center wire and a neutral shield wire running along the same axis. Used to link a television to a DVD player or to provide cable TV access.
Codec: Any form of encoding and decoding a signal
Colorist: The responsible for the look of a title when it is mastered to video, including adjusting not only the color and contrast, but also occasionally the framing of the image (also called a telecine colorist).
Component Format: A method of transferring color video through three wires, ensuring that the color signals don't interfere with one another.
Component Video: A video system in which colors are transferred through three individual wires, so that the color signals don't interfere with one another. Most television sets are now equipped to receive a component signal, which offers higher quality pictures than composite video.
Composite Video: A video system in which three colors are transferred over one wire. NTSC (the pre-digital television standard in the United States) and PAL (the European television standard) are examples of composite video, which offers a lower quality picture than component video.
Compression: Any method of reducing the amount of space needed to record or transmit information. In DVDs, video is compressed using a process called variable bit rate encoding, which allots a changing number of bits to enhance resolution in a given scene. Scenes with lots of light or little action require less hits than dark scenes or those with lots of action.


D/A Converter Sampling Rate: As with computers, processor speed in a DVD player directly effects the picture quality. The D/A Converter speed allows for a more accurate and detailed reading of the DVD disc.
Data Reduction: Digital video that has not been compressed carries more picture information than is necessary to produce a quality image. Digitized video identifies the precise brightness and color of each pixel. It is not necessary to assign this large amount of storage space to each pixel since common picture elements can be grouped together and represented by smaller segments of code. This is the basis of MPEG-2. For example, the picture elements of a static image do not need to be stored as new information over and over to create successive frames. Through the use of I-frames, a reference frame that appears once every fifteen frames, bi-directional B- frames, and P-frames, predictive frames that fill in the information between the I-frames, the amount of data storage necessary to reproduce high quality moving images is greatly reduced.
Data Stream: The constant stream of information being fed to the decoder. This stream contains all information needed to decode and view the image.
Decode: To take compressed, encoded sources and turn them into a data stream that can be played back by another device. (Decoder: the machine that can do so).
Decoder: A circuit that determines the content of a given instruction and performs digital to analog conversion of picture and sound elements.
Digital: A recording technique in which sounds and/or images are converted into groups of electronic bits for storage. The groups of bits are retrieved electronically, by a laser, as a series of ones and zeroes. This binary code is converted into the audio and video images to be displayed.
Digital Comb Filter: Chrominance and Luminance signals are converted to a digital medium prior to separation and 2H delay. This process provides enhanced color purity and reduced dot crawl. Vertical and diagonal correction performed in a digital medium provides highly accurate Chrominance and Luminance signal separation.
Digital Compression Any algorithm that reduces the storage space required to record or transmit information. MPEG and JPEG are both digital compression schemes.
Dolby Digital Sound (AC-3): AC-3 provides six separate discrete audio channels: left, right and center front, right and left surround and a low frequency woofer as a listener option. Dolby AC-3 is the first perceptual coding scheme designed specifically to code multichannel digital audio. It divides sizes optimized with respect to the frequency selectivity of human hearing. This makes it possible to sharply filter coding noise and reduce data consumption while delivering dynamic theater quality sound. Unlike Dolby surround, AC-3 is entirely discrete and features five full frequency (20-20KHz) channels and one low frequency effects i.e.: subwoofer (20-120Hz) channel. DVD players with AC-3 audio will still be compatible with Pro-Logic surround and two channel stereo systems.

Do you want to know more?  Jump to "Types of Digital Audio."

Dolby Digital Surround: Perceptual encoding data reduction system that provides 5 discreet full range (20-20khz) channels (L-C-R-LS-RS) and a dedicated low frequency effects channel replicates the Theater experience in the home.

Do you want to know more?  Jump to "Types of Digital Audio."

Dolby Pro Logic: An audio coding system that allows four channels of sound to be encoded into two channels (stereo) and then decoded back into four channels (left, center, right and surround). The extra center channel enables Dolby Pro Logic to reproduce sound more fully than Dolby Surround, though still not as richly as Dolby Digital.
DTS-CD: DTS markets a line of compact discs featuring music remastered to play on 5.1 surround sound systems
DVD: A CD-sized optical disc that can store from 4.7 to 17 gigabytes of digital information.
DVD-5: Single-sided/Single-layer type with 4.7 GB storage capability.

Do you want to know more?  Jump to "Inside a DVD."

DVD-9: Single-sided/Dual-layer type DVD with 8.5 GB storage capability.

Do you want to know more?  Jump to "Inside a DVD."

DVD-10: Double-sided/Single-layer type DVD with 9.4 GB storage capability.

Do you want to know more?  Jump to "Inside a DVD."

DVD-18: Double-sided/Dual-layer type DVD with 17 GB storage capability.

Do you want to know more?  Jump to "Inside a DVD."

DVD-R: A recordable DVD that can be recorded on only once.
DVD-RAM: A recordable DVD that can be recorded on more than once.
Dolby Digital Surround Sound Left and Right Rear Channel information is decoded and processed following specific delay and frequency response parameters to provide a dramatic environment of sound that envelopes you from all directions.

Do you want to know more?  Jump to "Types of Digital Audio."

Dot Pitch Refers to the distance between like (i.e., red to red/ green to green/ blue to blue) phosphors on the florescent panel. A narrower dot pitch (i.e., a lower number) will reproduce finer detail on the screen resulting in a more resolvable picture.
DSP Digital Signal Processing. This circuit allows you to shape your home audio environment to duplicate what you are watching on the screen. Options include: Theater, Stadium, Nightclub and Concert Hall. Selected models include rear speakers powered by independent amplifiers providing a four channel environment.
dts: An audio format like Dolby. DTS has its own six-channel (5.1) encode/decode system for movie theaters and also sells a line of DVD videos and DVD-Audio titles that use its compression technique. Audio track DTS, however, requires almost four times as much space on a DVD disc than a Dolby track. DTS will only play in 5.1-channel sound on a system that has a DTS decoder.


Encode: To convert a signal from one form to another, such as analog to digital. (Encoder: Any device that compresses a signal for audio or video and outputs a digital signal. Encoders can be either software- or hardware-based.
Encoder: The real time MPEG-2 processor that converts digital studio masters into a digital tape formatted for DVD replication. Toshiba, a supplier of real time encoders to Hollywood, was also the first company to develop commercially available MPEG-2 chip sets.
Error Correction: The digital circuit used to correct errors when retrieving and decoding information from a disc.


File System: How data is organized in digital playback systems.
Frame: The basic unit of video (or film). One single still image that, when played in rapid succession with other frames, creates the illusion of motion.
Frame Doubling: Method of doubling the vertical lines present in a given frame, which allows for better resolution
Frame Rate: The number of frames that appear on screen per second. In film (in the United States), the frame rate is 24 frames per second; in U.S. video, the frame rate is 30 frames per second; in European film and video, the frame rate is 25 frames per second.
Frequency: Number of cycles per second in an electronic signal, measured in Hertz (Hz).


Gigabyte: A gigabyte represents one billion bytes of information. A byte is a grouping of binary codes, often shorter than a word, that are processed together by a CPU. Eight bits equals one byte. Single layer DVD discs will store up to 4.7 Gigabytes on a single side. Dual layer disc will store a maximum of 8.5 gigabytes on a single side.
Glitch: DVD - A general term for any noticeable error that is seen or heard.
GOP Abbreviation for Group of Pictures.


HD Video: High-definition video, currently the highest quality version of digital video. There is some debate about exactly what constitutes high-definition. It has either 720 lines of resolution (scanned progressively in one pass from top to bottom--referred to as 720P) or 1,080 lines of resolution (scanned twice from top to bottom, with the resulting two fields interlaced into one frame--referred to as 1080I).
HDTV: High-definition television, the highest quality version of digital television. ABC considers HDTV to be 720 lines progressive, while CBS and NBC prefer 1,080 lines interlaced.


I-frame: These frames, that generally occur twice during every 30 frames of digital information, depending on the completion of the picture, work to reduce data by providing a full frame reference of the video image. The I-frames identify the entire background and are the initial reference frames for bi-directional and P-frames.
Interlace: To scan a frame from top to bottom in two passes (first even lines, then odd ones). They are then interlaced into a single frame. The method used in nearly all television monitors now on the market.
Interleave: Arrangement of digital data in alternating packets of information.
Interpolate: Creating new pixels, lines or frames by averaging information from those on either side of a given pixel, line or frame.
Intraframe: Information about a frame of video that does not rely on information from other frames.
ITU-R BT.601: The international standard for studio digital video sampling, as designated by the International Telecommunications Union, Radiocommunications Sector.


Jewel Box: A plastic storage case for a DVD or a CD.
Jump: Another form of audio, or video interruption.  This is when the DVD player 'jumps' ahead.  It could be as short as a millisecond, or as long as an entire scene.


Kbps: Thousands of bits per second.
Keyframe: A video picture that contains all the information about the image (intraframe information), rather than just the difference between it and another image.
kHz: A measure of frequency, equal to 1,000 cycles per second.
Kilobyte (KB): A measure of data storage, equal to 1,024 bytes.


Laserdisc: A precursor to DVD, an analog video format stored on a 12-inch disc, with either analog or digital sound.
Letterbox: Format in which black stripes at the top and bottom of a television screen make up the difference in size between the aspect ratio of the program being shown and that of the video screen. (Movies shown on 4X3 televisions are sometimes letterboxed to preserve the original widescreen aspect ratio.)
Line Doubler: A processor that doubles the number of lines on screen, making the scan lines smaller and, therefore, less visible and resulting in better video resolution.


Macrovision: An antipiracy system that degrades a video signal and makes it unwatchable if it is recorded and played back.
Matrix Surround System: A surround sound system, such as Dolby Pro Logic or Dolby Surround in which two sound channels hold more than two encoded channels of sound and are then decoded upon presentation.
Megabits per Second: A megabit contains one million bits. Megabits per second is a measurement of processing speed broken down to the smallest binary digit, a bit.
Meridian Lossless Packing: An audio coding system by Meridian Associates that compresses sound information so that it can be relayed more efficiently yet still recovered exactly as it was before compression with no loss of fidelity. This is known as "lossless" compression, as opposed to "lossy" compression in which some information is irretrievably lost during the encoding/decoding process
Modulation: In DVD, signal modulation refers to the process by which the bits representing user data are converted to the modulation refers to the process by which the bits representing user data are converted to the modulation code bits recorded on the disc. This process increases reading accuracy and reduces crosstalk between primary signal information and tracking servo mechanism pits on the disc. DVD utilizes an eight-to-sixteen modulation system that creates a slightly larger buffer between streams of digital information ensuring a high measure of accuracy in signal processing.
Moire: A ring-like artifact in composite analog video
MPAA: Acronym for Motion Picture Association of America. MPAA is the film industry group that determines suitable ratings for individual movies. With multi-story capability, DVD players may have the ability to select and black out undesired material. For example: Parents can view the "R" version of a movie and select a "PG" version for their children.
MPEG-1: An improved form of digital signal compression developed by the Moving Pictures Expert Group, a division of ISO (International Standards Organization). This system achieves a frame rate of 30 per second, with more than a 6:1 compression ratio. MPEG-a achieves approximately one forth the resolution of broadcast television. The system is too slow for processing high quality images.
MPEG-2: Acronym for Moving Picture Experts Group, a joint committee responsible for developing digital video compression.  MPEG-2 delivers 30 frames of video playback per second with a variable compression ration as high as 200:1. Broadcast quality video can be achieved with a 30:1 compression ratio. MPEG-2 will also support MPEG-1 playback. MPEG-2 works by removing redundant signal information during compression and reassembles this data during playback through the use of I-frames, B-frames and P-frames. MPEG-2 is utilized for DVD, HDTV and DBS video.
Multi-Angle: The multi-angle function allows viewers to select from up to nine alternate perspectives that can be recorded on a DVD should the director feel the additional views are of value.
Multi-Language: This feature allows up to eight different audio tracks to be mastered on a single Digital Video Disc. The user than can select the language track that suits their preferences.
Multimedia: A combination of media used for entertainment, education and communication. For computing, DVD can afford the user the flexibility to merge text, graphics and full motion video to create high quality, effective presentations.
Multiplexer: A system that combines multiple data streams into one, as when compressed audio and video are joined into a single data stream during DVD authoring.


Nanometer: Measurement equal to one-billionth of a meter. The shorter wavelength thinner beam red laser incorporated in DVD players measures 650 nanometers compared to 780 nanometers for a conventional CD player laser.
NTSC: The National Television System Committee.  The body responsible for the color television broadcast standards in North America.
Non-Interlaced: See Progressive Scan
Numerical Aperture: The number representing the lens aperture of a laser pick-up device. An increased numerical aperture, 0.6 on a DVD player, allows for finer track pitch, pit length and pitch width necessary for the increased storage capacity of a DVD. Thinner substrates which diffuses less light, allow a laser with an increased aperture to be utilized while still maintaining high reading accuracy.


Overscan: Areas at the edges of a television tube that are covered to conceal any video distortion.


P-frame: As a part of MPEG-2 decoding, P-frames are constructed by analyzing previous frames and estimating where objects will be in the next frame. The ability to predict where static and moving object will appear in successive frames provides superior adaptivity to motion in the picture. P-frames take up the least possible amount of bandwidth in transmission.
Packetization: Binary Codes, read from the DVD disc, instead of being transported as a constant stream of information, is transported as packets representing individual tasks to be completed by the DVD player. This is done to achieve the most accurate data processing possible.
PAL: European Video Standard
Pan & Scan This represents full screen DVD video, in the same aspect ratio as you would expect to see on any normal TV channel.
Panavision: Theatrical screen ratio of 2.35:1 filmed on 35mm film stocks utilizing anamorphic lenses.

Do you want to know more?   Jump to an article on "Aspect Ratio."

Passive Matrix: A flat-panel display made up of a grid of wires running horizontally and vertically with an LCD at every intersection. Each LCD represents one pixel and restricts the amount of light passing through and appearing on screen at that point. Less expensive than active matrix technology, but not quite at the same level in terms of visual quality.
PCI (Presentation Control Index): DVD feature that specifies how the program will be presented, with categories such as aspect ratio, multiangle, etc.
PCM: An uncompressed digital code that conveys an analog audio signal. Used on CDs, laserdiscs and some DVDs

Do you want to know more?  Jump to "Types of Digital Audio."

Pits and Lands: Short for picture element, pixels are the points of light that make up a video image. Each pixel has four components (red, green, blue and a transparent alpha channel) that combine to make one point.
Pixel: The shape of the pixel in a particular monitor. In computer monitors, they’re square, while in video monitors they’re rectangular.
Pixel Format: The shape of the pixel in a particular monitor. In computer monitors, they’re square, while in video monitors they’re rectangular.
Pixel Frequency: How many pixels appear on screen per second (the width of the screen in pixels, times the height in lines, times the number of frames per second). The greater the pixel frequency, the better the video resolution.
Progressive Scan: Scanning a frame from the top to bottom of the frame, taking each line in turn. The standard technology for computer monitors.



Raster Scan: The constant scanning of the horizontal lines on a video monitor that, when seen as a whole, creates the on-screen images.
Rastering: Converting a digital bit stream to black, white or 16 shades of gray that make up a picture.
Regional Encoding: A form of encryption on a DVD.  There are 6 regions throughout the world.  DVD's that are coded from outside your region may not play on your machine.

Do you want to know more?  Jump to the "DVD Regional Coding."

Resolution: Number of pixels (digital formats) or horizontal lines (analog formats) that can be displayed on screen in a particular format. The higher the resolution, the sharper the picture
RSDL: Reverse Spiral, Dual Layer.  This form of DVD construction allows for 8.5 GB of data to be stored on a single side.  During the layer change the picture may pause slightly.

Do you want to know more?  Jump to "Inside a DVD."

RSPC-Reed Soloman Product Code: Error correction method used in DVD system. This process, developed by MIT mathematicians in 1960 and enhanced by Toshiba, compensates for gaps in digital information that can be caused by imperfections or scratches in the substrate of the DVD maintaining picture and sound quality. this is the type of system used in magnetic and optical storage systems and allows for more flexibility as the DVD system develops. The advanced RSPC error correction system utilized in DVD is 6 times as robust as a conventional compact disc.


Scanning: The process through which a video image is displayed on a monitor. The pixels that make up the video image are arranged on screen in horizontal scan lines; an electronic signal travels left to right along each scan line, from the top line to the bottom, eventually creating the on-screen image.
SD Alliance: Original group of 29 hardware and software companies involved in the development of standard of the DVD system.
Skip: DVD - An interruption in video or sound.  This can be due to physical imperfections in the DVD, or hardware problems.
Standard CD Capacity: Standard CD's can hold approximately 75 minutes, or approximately 0.67 GB of recorded information. The 4.7 GB DVD can hold as much as seven times as much information as a standard audio CD.
Storage Capacity: Limit to the amount of information that can be recorded on any recording medium. In DVD, this varies from 4.7GB on a DVD-5 disc to 17GB on a DVD-18 disc.
Substrate: Polycarbonate material that encases and protects the stamped information on a disc. On a DVD, the utilization of two bonded substrates, measuring 0.6mm each, significantly reduces the distance between the surface of the disc and the pits on the disc that hold information when compared to that of conventional CD/CD-ROM media. Reduction in the thickness of the disc substrate, achieved through disc bonding is an important component in achieving the increased storage capacity and improved tilt margins of DVDs. This thinner substrate diffuses and refracts less light from the laser pick-up, and results in greater reading accuracy by the laser. Besides improving tilt margins, bonded substrates strengthen the disc, prevent warping and make the disc more resilient to changes in temperature and humidity.

Do you want to know more?  Jump to "Inside a DVD."

S-Video Inputs: Use of Separated (S) Video input for playback  reduces dot crowl in the picture, providing sharper edge detail.


Telecine: The transfer of film to video (also, the machine used in the process). As a film image goes through telecine, its color, contrast and sometimes aspect ratio are adjusted by the telecine colorist.
THX: A program run by Lucasfilm that ensures certain minimum standards are being met in the presentation of moving pictures, regarding sound and picture. THX establishes certain criteria, then licenses devices (processors, amplifiers, speaker systems and so on) that meet those guidelines.
Tilt Margin: The amount of variation in the laser focus, cased by the physical characteristics of a disc, that can be accommodated while maintaining signal integrity is referred to as the Tilt Margin. The 0.6mm substrate of a DVD diffuses less of the laser's focus than does a conventional CD's 1.2mm substrate, resulting in a more accurate beam spot. The bonded substrates of a DVD reduces warpage and further improves tilt margins.
Tracking: Tracking is important for the most accurate reading of the information being retrieved from a disc. Located on a DVD disc is tracking and A/V data. The laser reads the primary information that represents the audio and video signals to be displayed, as well as pits on either side of the main track which serve to provide tracking information. The information they return to the pick-up keeps the main beam spot aimed at the correct track on the disc, resulting in accurate retrieval of digital information.



Variable Bit Rate: The flow of data, or bit rate, of a DVD is variable depending on the complexity of the signal being processed. A detailed, rapidly moving scene with multiple picture elements would require a high bit rate, while a static image with little detail would receive far fewer bits. This advance in processing, a part of the MPEG-2 system, uses bits more efficiently, allocating storage capacity according to the requirement of the signal. Because disc space is limited and increased data storage is critical for quality improvements, it is important to vary the bit rate in order to allocate space in the most efficient manner.


Weave: Up-and-down or side-to-side motion of an image, originating from a lack of stability in the original film. It can be tracked digitally and eliminated, so that the image appears stable.





16:9 New digital television monitors are much wider than are the nearly square television monitors that have been standard since the beginning of television. Instead of the width-to-height ratio being 4:3, as before, new digital sets have an aspect ratio of 16:9, allowing them to show movies in a form much closer to that seen in theaters.




3-2 Pull-down: This process which converts the 24 frames per second found on film, to the 30 frames per second necessary for display as NTSC video, is achieved in the DVD player. In analog formats, such as videotape, 3-2 Pull-down is achieved as part of the film to video transfer. DVD players eliminate the need for this extra step in video mastering by accomplishing 3:2 pull-down in the microprocessor. Besides reducing the data storage requirements, this process also offers future opportunities in development of multi-scan, high resolution displays.


4:2 Ratio: Signifies over sampling frequencies for Y (X4) R-Y (X2) B-Y (X2) utilized in digital component video. DVD, Betacam D1 and other studio masters utilize 4:22 over-sampling. DSS utilizes 4:1:1 over sampling.
4:3 Ratio: This represents full screen DVD video, in the same aspect ratio as you would expect to see on any normal TV channel.





Note: Some of the definitions on this page were taken directly from Toshiba's DVD Glossary page, DVD Angle and some were taken directly from Ultimate Home Theater's Glossary.





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