Skip (audio playback)

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 Compact Disc 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 constituted 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.

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Wikipedia