For those new to the laser video and audio medium, the language and terms used by experienced veterans can often be foreign and difficult to understand. Listed Below are some of the most commonly used terms, along with a description, definition, and explanation of each.
The Starship Industries Laser Disc Glossary was originally published in Starship's August, 1985 Laser Disc catalog. Since then, we've made additions and changes to bring the glossary up to date. We invite our readers to make suggestions for further additions, and corrections. Please E-mail your comments to: firstname.lastname@example.org
What makes the "CX" system unique is it's ability to reduce noise while still
making it possible for
non-CX users to enjoy the recording with a minimum of side effects. This
compatibility comes from
not stressing any specific frequencies during encoding or decoding. The
compression process is
limited to the upper portion of the volume levels. While this gives non-CX users
a greater degree of
realism, it creates the one weakness in the system by requiring EXACTING
calibration of play back
expander circuits to match the compression levels. A mis-match will cause gain
they should not occur and the end result may be a "pumping" of the volume
xxxxxxxxxxxxxxxxxxxxxxxx *printer 27,87*DISH WARP --------- SEE: WARP, CONE *printer 27,87*DOLBY AUDIO NOISE REDUCTION --------------------------- Dolby noise reduction refers to three different audio noise reduction systems under patent by Dolby Labs. The use of the trade name "Dolby" does not, however, guarantee that a given product displaying the name will contain an audio noise reduction system. SEE: DOLBY SURROUND MATRIX *printer 27,87*DOLBY SURROUND MATRIX --------------------- Also known as Dolby "MP" matrix, this is Dolby's trade mark for their system of recording and decoding "Surround Sound Matrix" stereo. The use of the trade name "Dolby" in this application does NOT in any way guarantee the presence of an audio noise reduction system, although the Dolby standard does in theory call for noise reduction to be used in the rear channel in the recording process. The Dolby name also does not indicate any kind of general patent ownership of the basic phase matrix process that makes surround sound possible. To this end, any company can offer a decoder that provides accurate channel separation without displaying the Dolby trade name on their product. SEE: SURROUND SOUND MATRIX *printer 27,87*DROPOUTS -------- A "Dropout" is an interuption or unrecoverable loss of recorded information for a specific period of time. Dropouts in laser video discs are caused by the blocking of or physical damage to the recorded "pits" in the disc. A single dropout will appear as a bright speckle in a dark frame, or as a black mark in a light background. The number of Dropouts in a single frame is often called the "dropout count". The specific time period for each given dropout can be referred as the "dropout time constant" or "dropout frequency". The time period of a dropout will dictate the horizontal width of the visible noise spot. Together, the "dropout count" and "dropout time constant" values can be used as truly objective standards for judging disc quality. Example: A good quality disc should average no more than 5 dropouts per frame with an average time constant no greater than that value which would produce 2 horizontal lines of resolution, (about 1/8" width on a 25" TV screen). *printer 27,87*ECCENTRIC TRACKING ERROR ------------------------ Caused by an out of center spindle hole, eccentric tracking error can cause skipping, "laser lock", and is usually accompanied by a loud rapping noise coming from inside the player. Eccentric tracking error may also cause crosstalk at beginning of the disc, particularly on solid state players. *printer 27,87*FISH NET EFFECT --------------- SEE: RESOLUTION *printer 27,87*GRAIN ----- SEE: RESOLUTION *printer 27,87*HELICOPTOR AUDIO NOISE ---------------------- "Helicopter" audio noise is the continuous rapid bursting of noise caused by a limited area of data loss or "dropouts" on the laser disc. The noise burst effect is created when the "good" and "bad" areas of the disc alternate across the laser pickup as the disc turns. The defect was named "helicopter" because of its characteristic chopping sound. SEE: DROPOUTS *printer 27,87*GLOSSARY GLOSSARY ______________________________________________________________________________ *printer 27,87*LASER LOCK ---------- This term refers to a laser disc defect that causes the player to "stick" or "jam" on a single track or group of tracks. On a CAV format disc, the problem will look almost like a perfect freeze frame, but with a loud howling sound from both audio channels. On a CLV disc, the picture will jump or roll with part of two or more frames repeating over and over again. In some cases, when a group of tracks are involved, a short repeating sequence will be produced. Laser Lock can be caused by flaws in the disc data and reflective coating, or by finger prints, glue, or other opaque substance on the face of the disc. Cleaning the disc will often cure the laser lock problem. *printer 27,87*LASER ROT --------- The term "Laser Rot" was first coined by one of our customers who discovered that a favorite disc which when new originally tested "good" was showing video noise and dropouts upon playback at a later date. Over the past year, we have received additional reported cases of disc deterioration, as well as confirmed findings in the private collections owned by the folks here at Starship. Needless to say, we were rather concerned to think that this product, which in Pioneer's LD-700 brochure was touted to "last forever", could indeed suffer short term loss of data while on the shelf. After much research, including contacts with all three major manufacturers of laser discs in the United States, we are happy to report that the manufacturing faults causing "laser rot" have been found and most of the discs now on dealer's shelves should be considered "safe". The exact cause of disc data loss seems to come from the bonding agent used to hold the two sides of the disc together and how the adhesive is applied. One source reported that timing was critical in pressing the two sides of the disc together, while another indicated traces of sulfur being found in the aluminum coating on a sample test case. The trick seems to be to make a good bond without allowing the glue and its reactive curing agents to break through the reflective layer of aluminum. Reported solutions to "laser rot" include applying a thicker layer of aluminum, the use of less reactive adhesives, and greater care in the assembly of the disc to keep the amount of curing agents trapped between the two sides to a minimum. This leaves only the problem of what to do with the limited number of potentially defective discs already in the market and on consumer's shelves. While Pioneer has recalled most inventories from each studio for quality checks, there have not been any bulletins issued to date on how dealers are to respond to consumer complaints. Most affected are customers who may believe they have no recourse because of the published 10 day warranty in Pioneer's catalog. Pioneer has indicated to us, however, that they will respond with replacement or refund to a consumer who contacts the company directly with a defective disc. To receive a return authorization from Pioneer, write or call: Pioneer Video, Attn: Customer Service, 4880 Rosecrans Avenue, Hawthorne, Ca, 90250 Telephone: 213-679-8141 or 800-421-1404 *printer 27,87*LETTER BOX ---------- A process by which wide screen motion pictures are transferred to the more square shaped television screen. In "letter box", the video transfer camera is adjusted to view the entire wide screen motion picture image. The result is a television picture with solid bars across the top and bottom of the screen. The solid bars give the image the look of being in a "letter box". While this procedure discards some of the available video resolution, the original framing and full content of the motion picture is presented without any adjustments or changes to make it fit on the home television screen. SEE: ASPECT RATIO; PAN & SCAN *printer 27,87*LINEAR TRACKING ERROR --------------------- This kind of tracking error is produced when the player is unable to lock into the encoded timing information on the disc. This can be caused by an uneven or "nonlinear" track progression that exceeds the player's tracking ability. In audio tape, this is the equilevent to flutter in the sound caused by changes in the machine's transport speed. In laser video discs, linear tracking error can produce bands of rainbow color bars across the picture. In severe cases, color and sound may be lost entirely. *printer 27,87*MATTE FINISH QUALITY -------------------- SEE: RESOLUTION *printer 27,87*MONITOR ------- A special television set that allows connections directly to the video *printer 27,87*GLOSSARY GLOSSARY ______________________________________________________________________________ circuits so the operator can bypass the tuner's electronics when viewing laser video discs, video tapes, or any other video source offering a direct video output. Using direct video connections can improve picture quality and resolution as compared with connections through the tuner. SEE: RESOLUTION *printer 27,87*PAN & SCAN ----------- A process by which wide screen motion pictures are transferred to the more square shaped television screen. In "Pan & Scan", the video transfer camera moves across the viewing field of the motion picture in an attempt to keep pace with the activity in the scene. While some of the original film content is lost to the television viewer, the process maintains a full viewing screen without loss of available video resolution. SEE: ASPECT RATIO; LETTER BOX *printer 27,87*RESOLUTION --------- The measurement of detail or clarity in a photographic or video image. In video, resolution is measured by the number of times light and dark shades can be produced across the face of the screen. Because all televisions in the United States use 525 scan lines to produce a frame of video, the real consideration in measuring video resolution is to observe just how many times light and dark changes can be produced in EACH horizontal scan line. Such a measurement is called "horizontal resolution". Broadcast television offers between 330 and 370 lines of horizontal resolution, depending on the quality of the receiver or tuner used. A Laser video signal fed directly into the video inputs of a monitor can offer over 400 lines. Unfortunately, many laser discs are recorded using master sources way below the 400 line potential of the system. The result can be a picture that lacks detail or clarity. Engineers can try to compensate for the loss of clarity by amplifying that part of the video signal which contains the detail information. The result, however, may also be an increase in background video noise, producing an image that looks like it was transferred through a fish net. Photographic studios use this same effect when making matte finish photographs. The grain of the matte finish print tends to hide flaws, and give the illusion of greater detail than really exists. The terms "fish net effect" and "matte finish quality" are often used to describe laser video disc releases that were produced from poor resolution masters. Although such discs may be considered below the laser system's potential, they are not considered as individual defects by the manufacturer or retailer, and may not be returned under warranty. *printer 27,87*ROLLING NOISE BARS ------------------ This term refers to horizontal bands of video noise that travel (or roll) up or down the screen when playing a CLV format disc. Usually, rolling noise bars are accompanied by a rapid bursting of audio noise, and are caused by a limited area of data loss or "dropouts" on the laser disc. In a CAV format disc, the noise appears as stationary bands across the screen. SEE: DROPOUTS; HELICOPTER AUDIO NOISE *printer 27,87*SAMPLING RATE ------------- This term refers to digital recording techniques. The sampling rate is the number of times per second the computer "looks" at the volume or amplitude of the signal being recorded and assigns that specific "sample" a digital number. This number (or byte) details the volume or amplitude of the signal at that given instant in time. To be able to reassemble the original signal with acceptable accuracy, the sampling rate must be at least twice the highest frequency contained in the program signal being recorded. EXAMPLE: The highest frequency in audio is 20,000 cycles per second. Most digital audio recording systems operate with a sampling rate between 41,000 to 45,000 samples per second. SEE: BIT; BYTE *printer 27,87*SNOW ---- SEE: CONFETTI; DROPOUTS; VIDEO NOISE *printer 27,87*SQ QUADRAPHONIC MATRIX ---------------------- Owned by CBS records as a trademark, "SQ" stands for Stereo Quadraphonic. The "SQ" system uses a phase matrix to encode two rear channels onto the primary front left and right channels. Rear channel information is mixed into the two front channels with equal levels applied to both. Channel separation is created by shifting the phase between the two signals applied to the primary left and right tracks. One rear channel is shifted to lead by 90 degrees, the other lags by 90 degrees. The net phase for a rear mono output is 180 degrees. This makes SQ somewhat compatible with Surround Sound matrix used on motion *printer 27,87*GLOSSARY GLOSSARY ______________________________________________________________________________ pictures, with the only problem being the 90 degree angles putting some information in the rear that really should not be there. When it comes to SQ recordings, some still remain on the market, although there are not any plans to offer new releases at this time. *printer 27,87*SURROUND SOUND MATRIX --------------------- The "Surround Sound Matrix" is a phase matrix system for encoding center front and rear channels into a conventional 2 channel (left & right) medium. Surround Sound's main use is in the mastering of multi-channel motion picture sound tracks. The vast majority of all matrix audio releases available today use the Surround Sound system. Surround Sound consists of a single rear channel which is shifted 180 degrees and then mixed back onto the primary left and right tracks with equal level to both. A fourth channel in the front center can also be derived to help control the volume of the movie dialog in relation to music and special effects. Depending on the manufacturer or patent holder, a Surround Sound decoder may also include a delay line as well as noise reduction on the rear channel. While these options may be desirable, they are not required to produce accurate channel separation, and in some cases may actually reduce the overall quality of the rear output signal.
VIDEO NOISE ----------- Any kind of additional noise, distortion, or loss of image quality beyond what was already contained in the original master film, tape, or live performance. When applied to defining defective laser discs or equipment, video noise is only that noise, distortion, or loss of image quality that can be found beyond what is already contained in the original master tape or film. Example: A bad film splice or scratch would NOT be considered a laser disc defect. SEE: AUDIO NOISE *printer 27,87*WARP, "POTATO CHIP" ------------------- Named for its classic "potato chip" shape, this kind of laser disc warp is most often caused from poor storage that allows the disc to lean to one side or another. The force of gravity causes the disc to sag across a single axis through the center. When viewed on edge, it looks like someone tried to wrap the disc around a large tree trunk. This kind of warp can create a real tracking problem as the focusing lens must bob up and down twice for each turn of the disc. For 1,800 RPM, this means 3,600 moves per minute! In most cases, the player must rely on the quality and focusing ability of the laser light to deal with this problem. This is one of the reasons why many of the older "Discovision" CAV format discs will play on a tube player but will skip when using the longer wavelength light of solid state players. *printer 27,87*WARP, CONE ---------- A "cone warp" or "dish warp" in a laser disc, when viewed on edge, exists when the center of the disc is higher (or lower) than the outside rim. In a simple cone warp, the given warpage curve measured from the center to the rim is the disc is the same from any point around the outside rim. The result is tracking error that is uniform for each turn of the disc. Any compensation required to correct for the error can be made very slowly as the laser approaches the increased warpage toward the outside rim of the disc. In all solid state players, this is done by a separate "tilt servo" in the focusing system. In a properly adjusted tube player, the shorter wave length of the tube laser light (as compared to solid state lasers) will allow for up to 1/8" downward or upward warp from the center before performance quality is affected. In most cases, Cone warped laser discs can be "repaired" by applying gentle continuous pressure to return the disc to a flat condition. One favorite method uses a dinner plate and a soda bottle: Rest the disc on the plate so that the warp of the disc is high at the center and low at the outside edge. With the lip of the plate supporting the outside edge of the disc, place the soda bottle on top of center hole to force the disc to curve back to the desired direction. Allow to stand for a few days and the results should be permanent. (Footnote: We recommend using a full 16 ounce container for the soda bottle.) *printer 27,87*WARP, DOWNWARD -------------- Warpage that causes the laser disc to curve closer to the focusing lens. SEE: WARP, CONE *printer 27,87*WARP, UPWARD ------------ Warpage that causes the laser disc to curve away from the focusing lens. SEE: WARP, CONE