How does CD scratching work?

Question

For e.g. Pioneer CDJ, Denon, Technics

Answer 1

the cd deck loads a portion, if not all of the cd track in to memory. the audio is then played from the memory and is manipulated by controls which basically emulate a DJ table to a point. then through the wonderful magic that is digital audio processing, the computer is able to simulate the scratching effects according to the input of the scratching pad.

AnalogX wrote a program a couple of years back that lets you scratch using a wave file and your mouse by dragging the waveform...it's very similar to what the CD scratching decks do with hardware. best of all, it's free and still available: http://www.analogx.com/contents/download/audio/scratch.htm

Answer 2

Scartch CD decks basically work by doing the following :

Due to the tehnical specification of the CD format, it's not possible to physically manipulate the data in real time (ie change play direction or scratch). It takes too long for the disc to spin round to the same location and for the lasers to pick up the right point to start reading from again.

To get round this the song is loaded into a temporary memory location called a buffer. This is why it takes a cd deck a few seconds before playback begins, it needs time to read the start of the track.
The player can then read from pretty much any part of it's internal memory almost instantly. This is all a cue or loop button is...a link to a memory location.

The wheel controller on the top controls the position of the playback counter. When you drag or spin the wheel you are instructing the player to move to the previous or next frame.

Answer 3

Well here's the shore version ....It takes the information on a cd and basically breaks it down into sections that can be controlled manually. This feature on new DJ CD players is to emulate scratching vinyl. Some will argue that it does not sound the same as vinyl though. For instant a vinyl turntable has an audible start and stop effect when you start and stop the record. Some DJ CD players have a release and a brake control to simulate this feature. But DJ CD players have come along way and seem to be the popular trend among DJ's.