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A skip occurs when a phonograph (gramophone), cassette tape or compact disc player malfunctions or is disturbed so as to play incorrectly, causing a break in sound or a jump to another part of the recording.
Vinyl records are easily scratched and vinyl readily acquires a static charge, attracting dust that is difficult to remove completely. Dust and scratches cause audio clicks and pops and, in extreme cases, they can cause the needle (stylus) to skip over a series of grooves, or worse yet, cause the needle to skip backwards, creating an unintentional locked groove that repeats the same 1.8 seconds (at 33⅓ RPM) or 1.3 seconds (at 45 RPM) of track over and over again. Locked grooves are not uncommon and are even heard occasionally in broadcasts. The locked groove gave rise to the expression "broken record" referring to someone who continually repeats the same statement with little if any variation.
A skip or jump is when the laser of a CD player cannot read the faulty groove or block of data. Skips are usually caused by marks blocking the path of the beam to the disc, e.g. a finger mark, hair, dirt in general, or a scratch. Since the read mechanism has very little contact with the disc's surface and the data itself is not on the outer layer of the disc, the blockage is not a physical issue as with a record, but rather reflective.
Early CD players were very basic in nature. A laser tracks the blocks of data from the centre of the disc outwards, while the disc itself revolves at a variable speed between a starting speed of 495 RPM, and a minimum finishing speed of 212 RPM. Generally, one cycle constitutes one block of data. If there is a faulty block of data, the player may do one of the following:
A player may utilise one or more of these techniques, depending on how faulty the data is. In the case of severe, irrecoverable damage to the data, the player may try to rescan the disc to relocate its position. In this case, the machine may make a series of audible chirping noises as the laser is moving from the faulty block to the data information area and back again.
When CD players began their induction into battery-powered portable machines and vehicles, a skip could happen even for simple movement such as walking, vehicles jerking etc. Therefore a strategy was needed to try to prevent this. When certain techniques were tested and failed, the most successful and popular method to date was to spin the disc faster in order to read a chunk of the data into memory while playing. This meant that the player itself could concentrate on reading while the software controlling the buffers and memory distribution could also act as the audio feed. In the case of a minor error, the disc's rotation would again speed up to facilitate several attempts to read the data. A technique was also developed for testing data to prevent severe skipping. These two techniques were largely successful, unless of course the data was damaged beyond repair, in which case the audio may stop, or skip as before.
In a computer, a CD-ROM drive is governed by the program controlling it. In most cases, the BIOS has rudimentary access to the drive for boot purposes, while operating systems usually come bundled with their own drivers. The drive itself has very little instruction, apart from direct instructions, such as spin up, read data etc.
When playing a CD in the computer, the media player of choice is giving instructions to the CD drive, whether through the operating system's drivers or by accessing the device's low-level interface itself. Usually, similar to modern players, the media player will be reading audio into memory for later playback, especially given the extreme speeds used by CD-ROM drives in order to access raw data on other discs. Because of this, if there is a fault during playback, the player will already be performing a checksum to verify the data read is correct. If it is wrong, the audio is usually stopped, depending on the player.
Cassette tape players can cause skips when the tape being played is worn or in some other way damaged. Since the tape is rolled into a reel, it depends on how the tape runs across the roll as to how the skip affects playback. Indeed, some early artists such as the Beatles deliberately rearranged the tape reels in order to produce loops used in their recordings.
Electronic media on a computer can often skip. Such media may include compressed and uncompressed audio, and video containing audio. Generally this cannot happen to music instructive files such as MIDI or MOD files, however depending on the circumstance single notes may become "jammed", when the note off message is not received by the playback device.
Computer skips can be caused by lack of available RAM or processing power, damaged storage mediums (CD, hard drive etc.), a crash in the playback software, or a corrupted, incomplete or damaged audio file. Depending on the player and the operating system, a skip usually consists of a 50MS, 300MS, 500MS or a one-second loop, depending on the size or length of the chunk of data that is currently loaded into memory.
Compact Disc skipping is prevalent in glitch music.
The compact disc (CD) is a digital optical disc data storage format that was co-developed by Philips and Sony to store and play digital audio recordings. In August 1982, the first compact disc was manufactured. It was then released in October 1982 in Japan and branded as Digital Audio Compact Disc. It was released on March 2, 1983 in North America and Europe.
CD-R is a digital optical disc storage format. A CD-R disc is a compact disc that can be written once and read arbitrarily many times.
Disk storage is a general category of storage mechanisms where data is recorded by various electronic, magnetic, optical, or mechanical changes to a surface layer of one or more rotating disks. A disk drive is a device implementing such a storage mechanism. Notable types are the hard disk drive (HDD) containing a non-removable disk, the floppy disk drive (FDD) and its removable floppy disk, and various optical disc drives (ODD) and associated optical disc media.
An optical disc is a flat, usually disc-shaped object that stores information in the form of physical variations on its surface that can be read with the aid of a beam of light. Optical discs can be reflective, where the light source and detector are on the same side of the disc, or transmissive, where light shines through the disc to the be detected on the other side.
Video CD is a home video format and the first format for distributing films on standard 120 mm (4.7 in) optical discs. The format was widely adopted in Southeast Asia, South Asia, China, Hong Kong, Central Asia and the Middle East, superseding the VHS and Betamax systems in the regions until DVD-Video finally became affordable in the first decade of the 21st century.
A CD player is an electronic device that plays audio compact discs, which are a digital optical disc data storage format. CD players were first sold to consumers in 1982. CDs typically contain recordings of audio material such as music or audiobooks. CD players may be part of home stereo systems, car audio systems, personal computers, or portable CD players such as CD boomboxes. Most CD players produce an output signal via a headphone jack or RCA jacks. To use a CD player in a home stereo system, the user connects an RCA cable from the RCA jacks to a hi-fi and loudspeakers for listening to music. To listen to music using a CD player with a headphone output jack, the user plugs headphones or earphones into the headphone jack.
Mastering, a form of audio post production, is the process of preparing and transferring recorded audio from a source containing the final mix to a data storage device, the source from which all copies will be produced. In recent years digital masters have become usual, although analog masters—such as audio tapes—are still being used by the manufacturing industry, particularly by a few engineers who specialize in analog mastering.
The LaserDisc (LD) is a home video format and the first commercial optical disc storage medium, initially licensed, sold and marketed as MCA DiscoVision in the United States in 1978. Its diameter typically spans 30 cm (12 in). Unlike most optical-disc standards, LaserDisc is not fully digital, and instead requires the use of analog video signals.
In computing, an optical disc drive is a disc drive that uses laser light or electromagnetic waves within or near the visible light spectrum as part of the process of reading or writing data to or from optical discs. Some drives can only read from certain discs, but recent drives can both read and record, also called burners or writers. Compact discs, DVDs, and Blu-ray discs are common types of optical media which can be read and recorded by such drives.
The Capacitance Electronic Disc (CED) is an analog video disc playback system developed by Radio Corporation of America (RCA), in which video and audio could be played back on a TV set using a special stylus and high-density groove system similar to phonograph records.
In optical storage, constant linear velocity (CLV) is a qualifier for the rated speed of an optical disc drive, and may also be applied to the writing speed of recordable discs. CLV implies that the angular velocity varies during an operation, as contrasted with CAV modes. The concept of constant linear velocity was patented in 1886 by phonograph pioneers Chichester Bell and Charles Tainter.
Copy Control was the generic name of a copy prevention system, used from 2001 until 2006 on several digital audio disc releases by EMI Group and Sony BMG Music Entertainment in several regions. It should not be confused with the CopyControl computer software copy protection system introduced by Microcosm Ltd in 1989.
CD/DVD copy protection is a blanket term for various methods of copy protection for CDs and DVDs. Such methods include DRM, CD-checks, Dummy Files, illegal tables of contents, over-sizing or over-burning the CD, physical errors and bad sectors. Many protection schemes rely on breaking compliance with CD and DVD standards, leading to playback problems on some devices.
In computing, data recovery is a process of retrieving deleted, inaccessible, lost, corrupted, damaged, or formatted data from secondary storage, removable media or files, when the data stored in them cannot be accessed in a usual way. The data is most often salvaged from storage media such as internal or external hard disk drives (HDDs), solid-state drives (SSDs), USB flash drives, magnetic tapes, CDs, DVDs, RAID subsystems, and other electronic devices. Recovery may be required due to physical damage to the storage devices or logical damage to the file system that prevents it from being mounted by the host operating system (OS).
Disc rot is the tendency of CD, DVD, or other optical discs to become unreadable because of chemical deterioration. The causes include oxidation of the reflective layer, reactions with contaminants, ultra-violet light damage, and de-bonding of the adhesive used to adhere the layers of the disc together.
Compact disc manufacturing is the process by which commercial compact discs (CDs) are replicated in mass quantities using a master version created from a source recording. This may be either in audio form (CD-DA) or data form (CD-ROM). This process is used in the mastering of read-only compact discs. DVDs and Blu-rays use similar methods.
Record restoration, a particular kind of audio restoration, is the process of converting the analog signal stored on gramophone records into digital audio files that can then be edited with computer software and eventually stored on a hard-drive, recorded to digital tape, or burned to a CD or DVD. The process may be divided into several separate steps performed in the following order:
The preservation of optical media is essential because it is a resource in libraries, and stores audio, video, and computer data to be accessed by patrons. While optical discs are generally more reliable and durable than older media types, environmental conditions and/or poor handling can result in lost information.
A CD-ROM is a type of read-only memory consisting of a pre-pressed optical compact disc that contains data. Computers can read—but not write or erase—CD-ROMs. Some CDs, called enhanced CDs, hold both computer data and audio with the latter capable of being played on a CD player, while data is only usable on a computer.
LV-ROM is an optical disc format developed by Philips Electronics to integrate analog video and computer software for interactive multimedia. The LV-ROM is a specialized variation of the CAV Laserdisc. LV-ROM is an initialism for "LaserVision Read-Only Memory".