Overview
Vinyl emulation normally uses special vinyl records which are played on conventional turntables. The vinyl is a recording of analogue audio signals often referred to as timecode. The turntables' audio output - the timecode recording - is routed into an analog-to-digital converter, or ADC. This ADC may be a multi-channel soundcard or a dedicated external USB or firewire audio interface box, DJ controller device or compatible mixer (usually distributed with the software). The ADC sends digital time code information to the software, which then translates the signal into corresponding changes in the playback speed, direction and position of a digital audio file. The audio file will react as if were pressed directly onto the record. The manipulated audio output of the program is then sent back through the DAC or the computer's sound card, and can be routed into an audio mixer where it can be mixed like any other analog audio signal.
The result is digital audio playback that sounds like music manipulated by an analogue vinyl recording. However, there is always a short delay between the needle's reading of the time code and the software's playback of the audio. The delay time is treated as a figure of merit for vinyl emulation products. A shorter delay allows the DJ to have better response and control of the music and is usually not noticeable by the user or listener.
In some countries, for example Finland, a digital DJ license is required to legally play copyrighted music with vinyl emulation software.
Read more about this topic: Vinyl Emulation Software