Electronic skip protection
Buffer system preventing audio skip in portable CD and MD players.
Electronic skip protection is a data buffer system used in some portable compact disc players and all MiniDisc units. It prevents audio disruption when the disc cannot be read due to movement. The system became notable for enabling portable CD playback in moving environments.
Technology
When electronic skip protection is active, the disc is read at a fixed read speed (CAV) and content is buffered, optionally with ADPCM compression, into RAM. Audio is read from RAM, decompressed if needed, and sent to the digital-to-analog converter. If reading is interrupted, the player uses stored data while tracking finds the prior passage. An alternative method rotates the disc at variable (CLV) speed, slightly faster than normal, with the same buffering approach.
History
The technology emerged around 1995 as a smaller alternative to bulky rubber shock absorbers used in portable players, reducing the size of players designed for cars. Small rubber shock absorbers remained in use but were less effective than larger pre-1995 ones. Initially, buffering lasted 3 seconds; by 2006, it ranged from 10 seconds to skip-free. All MiniDisc decks and portables buffered at least 10 seconds from the format's 1992 introduction, with larger buffers by 2006. Flash-based MP3 players and smartphones later replaced CD for portable use, eliminating the need for skip protection.
Attributes
The system provides interruption-free playback despite movement or jolts. Trade-offs include possible audio quality degradation in systems using compression, and reduced battery life due to the memory buffer's power draw. This battery impact was especially pronounced in players from 1992 to 1997, with reductions up to fifty percent when skip protection was enabled. Players from 1997 onward used more power-efficient technology, lessening this drawback.
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